ferroui-build 0.3.0

//! ferroui-build
//!
//! Build-script support: compiles the markup documents of a crate to Rust
//! source and embeds its assets (docs/porting/xaml.md, section 9.6). The
//! counterpart of the build tasks of the upstream project
//! (`CompileXamlTask` with `XamlCompilerTaskExecutor`, and
//! `GenerateResourcesTask`), which run after the compiler and rewrite the
//! assembly; a Rust crate has no such step, so the build script of the crate
//! runs before the compiler and writes source the crate includes.
//!
//! ```ignore
//! // build.rs
//! fn main() {
//!     ferroui_controls::register_types();           // the types the documents name
//!     ferroui_build::Build::from_env()
//!         .assembly(&ASSEMBLY)                      // the assembly of the crate
//!         .embed_assets(&["Assets"])
//!         .compile_xaml()                           // every *.xaml of the crate
//!         .run();
//! }
//!
//! // lib.rs
//! ferroui_markup_xaml::include_compiled_xaml!();    // pub mod compiled_xaml, pub mod compiled_markup
//! pub fn register_types() { /* .. */ compiled_markup::register(); }
//! ```
//!
//! # What a run does, in order
//!
//! 1. Reads the `.xamlmeta` of every crate the crate depends on directly
//!    (`DEP_<CRATE>_XAML_XAMLMETA`, which Cargo sets from the `links` key and
//!    the `cargo::metadata=xamlmeta=<path>` line of that crate) and,
//!    transitively, the files they name: the compiled documents an include of
//!    a document of another crate is linked to.
//! 2. Compiles each group of documents as upstream compiles the documents of
//!    an assembly (parse, transform, group transformers, emit) and writes
//!    `$OUT_DIR/xaml/<module>.rs` with its position map.
//! 3. Lists the assets, leaving out the documents it compiled (upstream
//!    removes a compiled resource from the assembly).
//! 4. Writes `$OUT_DIR/<crate>.xamlmeta` (the compiled documents of the
//!    crate, and the paths of the files of step 1) and
//!    `$OUT_DIR/xaml/mod.rs` (the modules of the groups, the asset table, the
//!    loader table of the crate and `register()`).
//! 5. Prints the `cargo::` lines: `rerun-if-changed` for every input,
//!    `metadata=xamlmeta=<path>` for the crates that depend on this one, and
//!    `rustc-env=FERROUI_XAMLMETA=<path>` for the crate itself.
//!
//! Every document is compiled before the run fails: each error is printed as
//! a `cargo::error=` line, and the script exits with a failure once.
//!
//! # Diagnostics
//!
//! What the compiler reports has the code of upstream's build task
//! (`FerroXamlDiagnosticCodes`) and, where it is known, the document and the
//! position: `Views/Main.xaml(12,8): warning FRN2208: ..`. A diagnostic of the
//! transform goes through the filter of upstream's task
//! ([`xaml_compiler_diagnostics_filter`]): the EditorConfig files of the build
//! ([`Build::analyzer_config_files`]) state its severity by its code, and
//! [`Build::warnings_as_errors`] makes every warning that is left an error. A
//! warning is a `cargo::warning=` line; an error fails the build: a group that
//! does not transform (`FRN2000`, once for the group, or the diagnostics of the
//! transform that say why), a document the emitter refuses (`FRN3000`, with the
//! document and the node), a class no load by URI can create (`FRN3001`, a
//! warning).
//!
//! # Where the type metadata comes from
//!
//! A build compiles against the type models of the crates
//! ([`TypeSystem::Model`], the next section): this crate links the compiler
//! (the transform and the emitter of Rust source) and the base crate, and
//! neither the XAML runtime library nor the controls, so a build script that
//! uses it builds none of them for the host.
//!
//! The other host is the feature `runtime-host` ([`TypeSystem::Runtime`]): the
//! compiler transforms a document against the run-time type system, the
//! types, properties and constructors the crates registered in the process
//! (`register_types()` of each). A build script that enables it takes the crates
//! whose types its documents name as build dependencies and registers them
//! before it calls [`Build::run`], and it starts whatever application
//! services the transform of its documents needs. Two consequences:
//!
//! - those crates are built for the host as well as for the target (once
//!   more when the two differ or their features do);
//! - a build script cannot link the crate it builds, so it cannot compile a
//!   document that names a type of that crate: neither the document of a
//!   class of the crate (`x:Class`) nor a document that uses one of its
//!   types. Such a document is generated by a test of the crate and checked
//!   in (`rust_emitter::generate_class_file`); its loader table and its
//!   `.xamlmeta` join the ones of the build through [`Build::loader`] and
//!   [`Build::checked_in_metadata`].
//!
//! The feature links the XAML runtime library and, through it, the controls. No
//! crate of the repository enables it.
//!
//! # The build-time type model
//!
//! The way out of both consequences is xaml.md 9.5: the types read from the
//! sources instead of the process. With [`Build::type_system`] and
//! [`TypeSystem::Model`] a build scans the crate, reads the type models of
//! the crates it depends on from their `.xamlmeta` (the framework crates
//! export theirs from their own build scripts) and compiles every group
//! against the type system over those models: the build script registers
//! nothing, needs no crate for its types, and compiles the documents of the
//! classes of the crate it builds ([`XamlGroup::class_document`]). The
//! run-time type system stays the value of a build that does not state one, and
//! is an error of the build without the feature `runtime-host`.
//!
//! ```ignore
//! // build.rs
//! fn main() {
//!     ferroui_build::Build::from_env()
//!         .type_system(ferroui_build::TypeSystem::Model)   // the assembly is the one the sources state
//!         .compile_group(XamlGroup::new("compiled_xaml").documents(DOCUMENTS))
//!         .compile_group(XamlGroup::new("compiled_main_window").documents(VIEWS).class_document("MainWindow.xaml"))
//!         .run();
//! }
//! ```
//!
//! What is here:
//!
//! - [`model`], [`scanner`], [`model_set`], [`call_forms`], [`export`]: the
//!   type model of a crate and its file (the `.xamlmeta` of format 2), the
//!   source scanner that fills it, the models of several crates read together,
//!   the call form of every declared member, and the export of a model from a
//!   build script. They are the crate `ferroui-build-scan`, which links
//!   nothing of the framework so that the framework crates can scan
//!   themselves with it, exported here under the names they had in this crate;
//! - [`Build::export_metadata`]: the scan of the crate, with the models of
//!   its dependencies, written into its `.xamlmeta`;
//! - [`type_system`]: the type system of the compiler over the models
//!   (`ModelTypeSystem`, xaml.md 9.5.5), with the closed table of runtime
//!   library types it shares with the run-time type system, and what the
//!   models state for the emitter (`ModelEmitTypes`, xaml.md 9.5.12).
//!
//! What a build against the models does not have yet: the compile-time value
//! parser of the run-time host (text a type refuses is found when the document
//! is built, not when it is compiled), and a position map for the file of a
//! class.
//!
//! ```ignore
//! // build.rs of a crate that declares types and has no documents
//! fn main() {
//!     ferroui_build::Build::from_env().export_metadata().run();
//! }
//! ```
//!
//! # A crate with checked-in compiled markup
//!
//! A crate that keeps all of its compiled markup checked in (the two themes)
//! does not need this crate: its build script prints the line of step 5 for
//! its checked-in file, and its manifest has the `links` key.
//!
//! ```ignore
//! println!("cargo::metadata=xamlmeta={}/compiled_xaml.xamlmeta", env!("CARGO_MANIFEST_DIR"));
//! ```

#![forbid(unsafe_code)]

pub mod deterministic_id_generator;
mod diagnostics;
// The model, the scanner and the export are the crate the framework crates scan themselves
// with (`ferroui-build-scan`, which links nothing of the framework); they are exported
// here under the names they had in this crate.
pub use ferroui_build_scan::{call_forms, export, model, model_set, scanner};
pub mod type_system;
pub mod xaml_compiler_diagnostics_filter;

use std::env;
use std::fs;
use std::path::{Path, PathBuf};
use std::rc::Rc;
use std::time::Instant;

use ferroui_base::metadata::MarkupAssembly;
use xamlx::type_system::IXamlTypeSystem;

use crate::export::ScanReport;
use crate::model::AssemblyModel;
use crate::model_set::ModelSet;
use crate::scanner::{scan_crate, Scan, ScanOptions, Severity};
use crate::type_system::{ModelEmitTypes, ModelTypeSystem};
pub use ferroui_markup_xaml_loader::rust_emitter::ClassConstructor;
use crate::xaml_compiler_diagnostics_filter::XamlCompilerDiagnosticsFilter;
use ferroui_markup_xaml_loader::compiler_extensions::FerroXamlDiagnosticCodes;
use ferroui_markup_xaml_loader::rust_emitter::{
    class_document_group, class_of_document, generate_class_file_with, generate_file_with, rust_string_literal, ClassGroup, CompiledMarkupTypeSystem,
    EmitterHost, TransformOptions, XamlMetadata, CLASS_GROUP_NOT_TRANSFORMED, GROUP_NOT_TRANSFORMED,
};

/// The name of the module of the default group ([`Build::compile_xaml`]).
pub const DEFAULT_MODULE: &str = "compiled_xaml";

/// The environment variable the build sets for the crate: the path of its `.xamlmeta`
/// (`env!("FERROUI_XAMLMETA")`).
pub const XAMLMETA_VARIABLE: &str = "FERROUI_XAMLMETA";

/// A group of documents that are compiled together into one module: the group
/// transformers see every document of it, so includes between them are linked, as
/// upstream compiles the documents of an assembly.
pub struct XamlGroup {
    module: String,
    documents: Option<Vec<(String, String)>>,
    create_source_info: Option<bool>,
    exported: bool,
    class_document: Option<String>,
    constructor: Option<ClassConstructor>,
}

/// The type system the documents of a build are compiled against ([`Build::type_system`]).
#[derive(Clone, Copy, Debug, Default, PartialEq, Eq)]
pub enum TypeSystem {
    /// The run-time type system: the types the build script registered in its process. The
    /// script links the crates whose types its documents name, and cannot compile a
    /// document that names a type of the crate it builds. Only with the feature
    /// `runtime-host` of this crate, which links the XAML runtime library and the
    /// controls; without it a build that compiles documents against this type system
    /// fails with an error that says so.
    #[default]
    Runtime,
    /// The build-time type system over the type models (docs/porting/xaml.md, 9.5): the
    /// model of the crate, scanned from its sources, and the models of the crates it
    /// depends on, read from their `.xamlmeta`. The script links no crate for its types
    /// and compiles the documents of the classes of the crate ([`XamlGroup::class_document`]).
    Model,
}

impl XamlGroup {
    /// A group whose generated file is the body of the module `module` of the crate
    /// root. Without [`documents`](Self::documents) the group is every `.xaml` file
    /// below the XAML root of the build.
    pub fn new(module: &str) -> Self {
        Self { module: module.to_string(), documents: None, create_source_info: None, exported: true, class_document: None, constructor: None }
    }

    /// Makes the group the group of a class of the crate: `name` (its path below the root
    /// URI of the assembly) is the document of the class its root names with `x:Class`,
    /// and the group is that document with every document of the group it includes,
    /// directly or not. The generated file is the file of the class
    /// (`rust_emitter::generate_class_file`): `populate`, which the constructor of the
    /// class calls, the build functions of the included documents and the loader table.
    /// Its module is declared at the crate root like the module of any group
    /// (`crate::<module>::populate`).
    ///
    /// Only with [`TypeSystem::Model`]: the class is a type of the crate being built.
    pub fn class_document(mut self, name: &str) -> Self {
        self.class_document = Some(name.to_string());
        self
    }

    /// The constructor the loader table creates the class of a class group with. Without
    /// the call the compiler picks it as upstream's does: a public parameterless
    /// constructor, else a public constructor that takes the service provider.
    pub fn constructor(mut self, constructor: ClassConstructor) -> Self {
        self.constructor = Some(constructor);
        self
    }

    /// The documents of the group, by their path below the root URI of the assembly
    /// (`Views/Main.xaml`), in the order they are compiled. The build script states the
    /// files they come from with [`Build::input`].
    pub fn documents(mut self, documents: &[(&str, &str)]) -> Self {
        self.documents = Some(documents.iter().map(|(name, xaml)| (name.to_string(), xaml.to_string())).collect());
        self
    }

    /// Whether the documents are compiled with source information (`CreateSourceInfo`);
    /// without the call, as the assembly states it.
    pub fn create_source_info(mut self, value: bool) -> Self {
        self.create_source_info = Some(value);
        self
    }

    /// Keeps the group out of the loader table and of the `.xamlmeta` of the crate: its
    /// documents are reached by their build functions only (a second compilation of
    /// documents another group registers, as a test compiles them).
    pub fn internal(mut self) -> Self {
        self.exported = false;
        self
    }
}

pub use ferroui_build_scan::export::Outcome;

/// The build of the markup of a crate; see the crate documentation.
pub struct Build {
    manifest_dir: PathBuf,
    out_dir: PathBuf,
    crate_name: String,
    assembly: Option<&'static MarkupAssembly>,
    xaml_root: PathBuf,
    groups: Vec<XamlGroup>,
    asset_directories: Vec<String>,
    loaders: Vec<String>,
    checked_in_metadata: Vec<PathBuf>,
    inputs: Vec<PathBuf>,
    dependencies: Vec<PathBuf>,
    export_metadata: bool,
    source_root: Option<PathBuf>,
    type_system: TypeSystem,
    default_compile_bindings: bool,
    analyzer_config_files: Vec<PathBuf>,
    warnings_as_errors: bool,
}

impl Build {
    /// The build of the crate whose build script is running: `CARGO_MANIFEST_DIR`,
    /// `OUT_DIR`, `CARGO_PKG_NAME`, and the `.xamlmeta` of every direct dependency
    /// (`DEP_<CRATE>_XAML_XAMLMETA`), in the order of the names of the variables.
    ///
    /// # Panics
    /// Panics outside a build script (a variable Cargo sets is missing).
    pub fn from_env() -> Self {
        let variable = |name: &str| env::var_os(name).unwrap_or_else(|| panic!("{name} is not set: not a build script"));
        Self::new(
            PathBuf::from(variable("CARGO_MANIFEST_DIR")),
            PathBuf::from(variable("OUT_DIR")),
            &variable("CARGO_PKG_NAME").to_string_lossy(),
            ferroui_build_scan::export::dependencies_from_env(),
        )
    }

    /// The build of the package `package_name` in `manifest_dir`, writing below `out_dir`,
    /// with the `.xamlmeta` files of its direct dependencies.
    pub fn new(manifest_dir: PathBuf, out_dir: PathBuf, package_name: &str, dependencies: Vec<PathBuf>) -> Self {
        Self {
            manifest_dir,
            out_dir,
            crate_name: package_name.replace('-', "_"),
            assembly: None,
            xaml_root: PathBuf::new(),
            groups: Vec::new(),
            asset_directories: Vec::new(),
            loaders: Vec::new(),
            checked_in_metadata: Vec::new(),
            inputs: Vec::new(),
            dependencies,
            export_metadata: false,
            source_root: None,
            type_system: TypeSystem::Runtime,
            default_compile_bindings: false,
            analyzer_config_files: Vec::new(),
            warnings_as_errors: false,
        }
    }

    /// The type system the documents are compiled against; [`TypeSystem::Runtime`] without
    /// the call.
    ///
    /// With [`TypeSystem::Model`] the build scans the sources of the crate (as
    /// [`export_metadata`](Self::export_metadata) does, and writes the model the same
    /// way), reads the models of the crates it depends on from their `.xamlmeta`, and
    /// compiles every group against the type system over those models. The build script
    /// registers nothing and needs no [`assembly`](Self::assembly): the assembly is the
    /// `MarkupAssembly` the sources state. A document the models cannot answer a question
    /// of the emitter for is an error of the build that names the document and the
    /// question; it is never compiled from a guess.
    pub fn type_system(mut self, type_system: TypeSystem) -> Self {
        self.type_system = type_system;
        self
    }

    /// Whether `{Binding}` is a compiled binding in a document that does not say otherwise
    /// (`x:CompileBindings`): the `DefaultCompileBindings` of upstream's build task. Not
    /// without the call.
    pub fn default_compile_bindings(mut self, value: bool) -> Self {
        self.default_compile_bindings = value;
        self
    }

    /// The EditorConfig files of the build, relative to the crate directory (the
    /// `AnalyzerConfigFiles` of upstream's build task): an entry
    /// `ferro_xaml_diagnostic.<code>.severity = <severity>` states the severity a diagnostic
    /// of the markup compiler with that code is reported with (`error`, `warning`,
    /// `default`; anything else silences it). A file that does not exist is skipped; the
    /// build runs again when one changes.
    pub fn analyzer_config_files(mut self, files: &[&str]) -> Self {
        self.analyzer_config_files.extend(files.iter().map(|file| self.manifest_dir.join(file)));
        self
    }

    /// Reports every warning of the markup compiler as an error of the build (the
    /// `TreatWarningsAsErrors` upstream leaves to the build system), after the severities
    /// of the EditorConfig files: a warning a file silences stays silent. Every document is
    /// still compiled before the build fails.
    pub fn warnings_as_errors(mut self, value: bool) -> Self {
        self.warnings_as_errors = value;
        self
    }

    /// Scans the sources of the crate and writes its type model into its `.xamlmeta`
    /// (format 2: the model next to the compiled documents), which the crates that depend
    /// on this one read as they read its documents (xaml.md 9.6.3). The scan reads the
    /// models of the dependencies of the crate first, so that what the crate names of
    /// theirs is resolved ([`ScanOptions::dependencies`]).
    ///
    /// The sources are read as files: nothing of the crate is linked, and a crate that
    /// only exports its model needs no [`assembly`](Self::assembly) (the scan reads the
    /// `MarkupAssembly` the sources state; a crate without one is the assembly named after
    /// the crate). What the scanner cannot read of a declaration is a `cargo::warning=`
    /// line and does not fail the build.
    pub fn export_metadata(mut self) -> Self {
        self.export_metadata = true;
        self
    }

    /// The root file of the sources of the crate, relative to the crate directory, for
    /// [`export_metadata`](Self::export_metadata). Without the call: `src/lib.rs`, else
    /// `lib.rs`, else `src/main.rs`.
    pub fn source_root(mut self, file: &str) -> Self {
        self.source_root = Some(PathBuf::from(file));
        self
    }

    /// The scan of the sources of the crate, with the models of its dependencies.
    fn scan(&self, dependencies: Vec<AssemblyModel>) -> Result<Scan, String> {
        let root = ferroui_build_scan::export::source_root(&self.manifest_dir, self.source_root.as_deref())?;
        let mut options = ScanOptions::new(&self.crate_name, root).with_dependencies(dependencies);
        options.assembly_name = self.assembly.map(|assembly| assembly.name.to_string());
        Ok(scan_crate(&options))
    }

    /// The assembly of the crate: its name is the host of the URIs of its documents and
    /// assets, and its metadata the default of `CreateSourceInfo`. The same value the
    /// crate registers in its `register_types()`.
    pub fn assembly(mut self, assembly: &'static MarkupAssembly) -> Self {
        self.assembly = Some(assembly);
        self
    }

    /// The directory, relative to the crate directory, below which the documents of a
    /// group without stated documents are found. The crate directory by default.
    pub fn xaml_root(mut self, directory: &str) -> Self {
        self.xaml_root = PathBuf::from(directory);
        self
    }

    /// A file, relative to the crate directory, the build reads through the build
    /// script (a file the script includes): the build runs again when it changes.
    pub fn input(mut self, path: &str) -> Self {
        self.inputs.push(self.manifest_dir.join(path));
        self
    }

    /// Embeds every file below the directories (relative to the crate directory) as an
    /// asset of the crate, by its path below the crate directory, except the documents
    /// the build compiles.
    pub fn embed_assets(mut self, directories: &[&str]) -> Self {
        self.asset_directories.extend(directories.iter().map(|directory| directory.to_string()));
        self
    }

    /// Compiles every `.xaml` file below the XAML root as the group
    /// [`DEFAULT_MODULE`].
    pub fn compile_xaml(self) -> Self {
        self.compile_group(XamlGroup::new(DEFAULT_MODULE))
    }

    /// Compiles a group of documents.
    pub fn compile_group(mut self, group: XamlGroup) -> Self {
        self.groups.push(group);
        self
    }

    /// The loader table of a checked-in generated file of the crate, by the path of its
    /// `try_load` (`crate::compiled_main_window::try_load`): the table of the crate asks
    /// it first, in the order of the calls.
    pub fn loader(mut self, path: &str) -> Self {
        self.loaders.push(path.to_string());
        self
    }

    /// The `.xamlmeta` of a checked-in generated file of the crate, relative to the crate
    /// directory: its documents are added to the `.xamlmeta` of the crate.
    pub fn checked_in_metadata(mut self, path: &str) -> Self {
        self.checked_in_metadata.push(self.manifest_dir.join(path));
        self
    }

    /// Runs the build and prints its lines for Cargo. On an error every error is printed
    /// and the process exits with a failure.
    pub fn run(self) {
        let outcome = self.execute();
        for line in &outcome.lines {
            println!("{line}");
        }
        if !outcome.errors.is_empty() {
            for error in &outcome.errors {
                eprintln!("error: {error}");
                println!("cargo::error={error}");
            }
            std::process::exit(1);
        }
    }

    /// Runs the build and returns what [`run`](Self::run) prints.
    pub fn execute(self) -> Outcome {
        let mut lines = Vec::new();
        let mut errors = Vec::new();
        let rerun = |lines: &mut Vec<String>, path: &Path| lines.push(format!("cargo::rerun-if-changed={}", path.display()));
        rerun(&mut lines, &self.manifest_dir.join("build.rs"));
        rerun(&mut lines, &self.manifest_dir.join("Cargo.toml"));
        for input in &self.inputs {
            rerun(&mut lines, input);
        }
        let on_models = self.type_system == TypeSystem::Model;
        // The documents are compiled against the assembly the crate registers; a build
        // that reads the type model of the crate reads the assembly from the sources.
        if self.assembly.is_none() && !on_models && (!self.export_metadata || !self.groups.is_empty()) {
            errors.push("the assembly of the crate is not stated (Build::assembly)".to_string());
            return Outcome { lines, errors };
        }
        // The run-time type system is in the build only with the feature that links it.
        if !on_models && !self.groups.is_empty() && !cfg!(feature = "runtime-host") {
            errors.push(
                "the documents are compiled against the type models (Build::type_system(TypeSystem::Model)): the run-time type system is the feature `runtime-host` of ferroui-build, which links the XAML runtime library and the controls"
                    .to_string(),
            );
            return Outcome { lines, errors };
        }

        // 1. The compiled markup and the type models of the dependencies.
        let mut report = ScanReport { crate_name: self.crate_name.clone(), ..ScanReport::default() };
        let started = Instant::now();
        let (models, dependency_files) = match ModelSet::read(&self.dependencies) {
            Ok(read) => read,
            Err(error) => {
                errors.push(format!("the .xamlmeta of a dependency cannot be read: {error}"));
                return Outcome { lines, errors };
            }
        };
        report.read_dependencies = started.elapsed();
        report.dependency_files = dependency_files.len();
        report.dependency_models = models.len();
        for file in &dependency_files {
            rerun(&mut lines, file);
        }
        let dependencies: Vec<XamlMetadata> = models.iter().map(AssemblyModel::metadata).collect();

        // The type model of the crate, from its sources.
        let scanned = self.export_metadata || on_models;
        let mut model: Option<AssemblyModel> = None;
        // The models the documents are compiled against: the ones of the dependencies, then
        // the one of the crate.
        let mut compiled_against: Vec<AssemblyModel> = Vec::new();
        if scanned {
            if on_models {
                compiled_against = models.clone();
            }
            let started = Instant::now();
            match self.scan(models) {
                Ok(scan) => {
                    report.scanned(&scan, started.elapsed());
                    for file in &scan.files {
                        rerun(&mut lines, &file.path);
                    }
                    for diagnostic in scan.diagnostics_of(Severity::Error) {
                        lines.push(format!("cargo::warning={diagnostic}"));
                    }
                    model = Some(scan.model);
                }
                Err(error) => {
                    errors.push(error);
                    return Outcome { lines, errors };
                }
            }
        }
        let assembly_name: String = match (self.assembly, &model) {
            (Some(assembly), _) => assembly.name.to_string(),
            (None, Some(model)) if !model.name.is_empty() => model.name.clone(),
            // A crate that states no assembly is the assembly named after the crate, as
            // the type systems name it.
            (None, _) => self.crate_name.clone(),
        };
        // Whether source information is on for the assembly, as the configuration of the
        // run-time loader reads it from the metadata of the assembly.
        let assembly_source_info = model.as_ref().is_some_and(|model| {
            model.metadata.iter().find(|(key, _)| key == ferroui_build_scan::CREATE_SOURCE_INFO).is_some_and(|(_, value)| value.trim().eq_ignore_ascii_case("true"))
        });

        // The type system of the build.
        let mut model_host: Option<(Rc<dyn IXamlTypeSystem>, Rc<dyn IXamlTypeSystem>, ModelEmitTypes)> = None;
        if on_models {
            if let Some(model) = &model {
                let mut own = model.clone();
                own.name = assembly_name.clone();
                compiled_against.push(own);
            }
            let system = ModelTypeSystem::new(compiled_against);
            // No class is one "with markup of its own" for a build: that states which
            // classes the run-time loader populates, and a class whose document is compiled
            // populates itself from its compiled markup.
            let types = ModelEmitTypes::new(system.clone(), Vec::new());
            // The compiled documents of the dependencies are part of the type system, as
            // they are for the run-time host (`EmitterHost::runtime`).
            let type_system = match dependencies.is_empty() {
                true => Ok(system.as_type_system()),
                false => CompiledMarkupTypeSystem::new(system.as_type_system(), &dependencies).map(|wrapped| wrapped as Rc<dyn IXamlTypeSystem>),
            };
            match type_system {
                Ok(type_system) => model_host = Some((type_system, system.as_type_system(), types)),
                Err(error) => {
                    errors.push(format!("the compiled markup of a dependency cannot be read against the type models: {}", error.message()));
                    return Outcome { lines, errors };
                }
            }
        } else if let Some(assembly) = self.assembly {
            #[cfg(feature = "runtime-host")]
            runtime_host::register(assembly);
            #[cfg(not(feature = "runtime-host"))]
            let _ = assembly;
        }

        // 2. The groups.
        for file in &self.analyzer_config_files {
            rerun(&mut lines, file);
        }
        let diagnostics = diagnostics::Diagnostics::new(
            XamlCompilerDiagnosticsFilter::new(Some(self.analyzer_config_files.clone())),
            self.warnings_as_errors,
        );
        let xaml_directory = self.out_dir.join("xaml");
        let root_uri = format!("ferres://{assembly_name}/");
        let mut metadata = XamlMetadata {
            name: assembly_name.clone(),
            crate_name: self.crate_name.clone(),
            documents: Vec::new(),
            dependencies: self.dependencies.iter().map(|path| path.display().to_string()).collect(),
        };
        let mut modules: Vec<Module> = Vec::new();
        let mut compiled_documents: Vec<String> = Vec::new();
        for group in &self.groups {
            if self.assembly.is_none() && !on_models {
                break;
            }
            if modules.iter().any(|module| module.name == group.module) {
                errors.push(format!("two groups have the module `{}`", group.module));
                continue;
            }
            let documents = match &group.documents {
                Some(documents) => documents.clone(),
                None => {
                    let root = self.manifest_dir.join(&self.xaml_root);
                    rerun(&mut lines, &root);
                    let mut files = Vec::new();
                    if let Err(error) = collect(&self.manifest_dir, &root, &mut files) {
                        errors.push(error);
                    }
                    let mut documents = Vec::with_capacity(files.len());
                    for (rooted, path) in files {
                        if !path.extension().is_some_and(|extension| extension == "xaml") {
                            continue;
                        }
                        match fs::read_to_string(&path) {
                            Ok(text) => documents.push((rooted.trim_start_matches('/').to_string(), text)),
                            Err(error) => errors.push(format!("{}: {error}", path.display())),
                        }
                    }
                    documents
                }
            };
            let borrowed: Vec<(&str, &str)> = documents.iter().map(|(name, xaml)| (name.as_str(), xaml.as_str())).collect();
            let path = xaml_directory.join(format!("{}.rs", group.module));
            let module_path = format!("::{}::{}", self.crate_name, group.module);

            // The group of a class of the crate.
            if let Some(class_document) = &group.class_document {
                let Some((type_system, models, types)) = &model_host else {
                    errors.push(diagnostics::error(
                        FerroXamlDiagnosticCodes::TRANSFORM_ERROR,
                        class_document,
                        "the document of a class of the crate is compiled against the type models only (Build::type_system(TypeSystem::Model)): a build script cannot link the crate it builds",
                    ));
                    continue;
                };
                let host = EmitterHost { type_system: type_system.clone(), types, parsers: Vec::new() };
                let options = TransformOptions {
                    local_assembly: Some(assembly_name.clone()),
                    create_source_info: group.create_source_info.unwrap_or(assembly_source_info),
                    use_compiled_bindings_by_default: self.default_compile_bindings,
                    diagnostic_handler: Some(diagnostics.handler()),
                    design_mode: false,
                };
                let compiled = class_group(&host, &**models, &root_uri, &borrowed, class_document, group.constructor, &module_path, &options);
                let reported_errors = diagnostics.report(&mut lines, &mut errors);
                match compiled {
                    Ok(file) => {
                        // Upstream's `XamlLoaderUnreachable`, a warning the filter decides on.
                        for warning in &file.warnings {
                            diagnostics.warning(FerroXamlDiagnosticCodes::XAML_LOADER_UNREACHABLE, class_document, warning, &mut lines, &mut errors);
                        }
                        write_if_changed(&path, &file.source, &mut errors);
                        let class_metadata = file.metadata(&[]);
                        if group.exported {
                            compiled_documents.extend(class_metadata.documents.iter().filter_map(|document| document_path(&document.uri)));
                            metadata.documents.extend(class_metadata.documents);
                        }
                    }
                    // The class is not found, or its group does not transform: an error of the
                    // transform, which the diagnostics of the transform reported if they
                    // have it. Anything else is a document the emitter refuses.
                    Err(ClassGroupError::Transform(reason)) => {
                        if !reported_errors {
                            errors.push(diagnostics::error(FerroXamlDiagnosticCodes::TRANSFORM_ERROR, class_document, &reason));
                        }
                    }
                    Err(ClassGroupError::Emit(reasons)) => errors.extend(reasons.lines().map(|reason| {
                        // A reason names its document when it is not the document of the class.
                        let (document, reason) = borrowed
                            .iter()
                            .find_map(|(name, _)| reason.strip_prefix(*name).and_then(|rest| rest.strip_prefix(": ")).map(|rest| (*name, rest)))
                            .unwrap_or((class_document.as_str(), reason));
                        diagnostics::error(FerroXamlDiagnosticCodes::EMIT_ERROR, document, reason)
                    })),
                }
                modules.push(Module { name: group.module.clone(), path, exported: group.exported, file: true });
                continue;
            }

            let file = match &model_host {
                Some((type_system, _, types)) => {
                    let host = EmitterHost { type_system: type_system.clone(), types, parsers: Vec::new() };
                    let options = TransformOptions {
                        local_assembly: Some(assembly_name.clone()),
                        create_source_info: group.create_source_info.unwrap_or(assembly_source_info),
                        use_compiled_bindings_by_default: self.default_compile_bindings,
                        diagnostic_handler: Some(diagnostics.handler()),
                        design_mode: false,
                    };
                    generate_file_with(&host, &assembly_name, &root_uri, &borrowed, &options)
                }
                #[cfg(feature = "runtime-host")]
                None => {
                    let Some(assembly) = self.assembly else { break };
                    runtime_host::generate_file(assembly, &root_uri, &borrowed, group.create_source_info, self.default_compile_bindings, &dependencies)
                }
                // Reported before the groups: without the feature no group is compiled
                // against the run-time type system.
                #[cfg(not(feature = "runtime-host"))]
                None => break,
            };
            let reported_errors = diagnostics.report(&mut lines, &mut errors);
            // A group that does not transform is one error of the transform, which the
            // diagnostics of the transform reported if they have it; a document the emitter
            // refuses is an error of the emit, each with its document.
            let mut group_reported = reported_errors;
            for (name, reason) in &file.documents {
                let Some(reason) = reason else { continue };
                let reason = reason.replace(['\r', '\n'], " ");
                match reason.starts_with(GROUP_NOT_TRANSFORMED) {
                    true if group_reported => {}
                    true => {
                        group_reported = true;
                        errors.push(diagnostics::error(FerroXamlDiagnosticCodes::TRANSFORM_ERROR, &format!("the group `{}`", group.module), &reason));
                    }
                    false => errors.push(diagnostics::error(FerroXamlDiagnosticCodes::EMIT_ERROR, name, &reason)),
                }
            }
            write_if_changed(&path, &file.source, &mut errors);
            write_if_changed(&xaml_directory.join(format!("{}.map.json", group.module)), &file.position_map, &mut errors);
            if group.exported {
                metadata.documents.extend(file.metadata(&self.crate_name, &module_path, &[]).documents);
                compiled_documents.extend(documents.iter().map(|(name, _)| format!("/{name}")));
            }
            modules.push(Module { name: group.module.clone(), path, exported: group.exported, file: false });
        }
        for path in &self.checked_in_metadata {
            rerun(&mut lines, path);
            let read = fs::read_to_string(path).map_err(|error| error.to_string()).and_then(|text| XamlMetadata::parse(&text));
            match read {
                Ok(read) if read.name == assembly_name => metadata.documents.extend(read.documents),
                Ok(read) => errors.push(format!(
                    "{}: the file describes the assembly `{}`, the crate is `{}`",
                    path.display(),
                    read.name,
                    assembly_name
                )),
                Err(error) => errors.push(format!("{}: {error}", path.display())),
            }
        }

        // 3. The assets.
        let mut assets: Vec<(String, PathBuf)> = Vec::new();
        for directory in &self.asset_directories {
            let directory = self.manifest_dir.join(directory);
            rerun(&mut lines, &directory);
            if let Err(error) = collect(&self.manifest_dir, &directory, &mut assets) {
                errors.push(error);
            }
        }
        assets.retain(|(rooted, _)| !compiled_documents.contains(rooted));
        assets.sort();
        assets.dedup();

        if !errors.is_empty() {
            return Outcome { lines, errors };
        }

        // 4. The `.xamlmeta` (with the type model of the crate, when it was scanned) and
        // the file the crate includes.
        let metadata_path = self.out_dir.join(format!("{}.xamlmeta", self.crate_name));
        let metadata_text = match model {
            Some(mut model) => {
                model.name = metadata.name;
                model.crate_name = metadata.crate_name;
                model.documents = metadata.documents;
                model.dependencies = metadata.dependencies;
                model.to_json()
            }
            None => metadata.to_json(),
        };
        let started = Instant::now();
        report.model_bytes = metadata_text.len();
        match ferroui_build_scan::export::write_if_changed(&metadata_path, &metadata_text) {
            Ok(written) => report.model_written = written,
            Err(error) => errors.push(error),
        }
        report.write = started.elapsed();
        // What the scan cost, for whoever judges it (`export::ScanReport`).
        if scanned {
            if let Err(error) = report.write(&self.out_dir) {
                errors.push(error);
            }
        }
        // A crate that only exports its model includes nothing.
        if self.assembly.is_some() || !self.groups.is_empty() || !self.asset_directories.is_empty() {
            let text = crate_file(&assembly_name, &modules, &self.loaders, &assets);
            write_if_changed(&xaml_directory.join("mod.rs"), &text, &mut errors);
        }
        if !errors.is_empty() {
            return Outcome { lines, errors };
        }

        // 5. For the dependents, and for the crate itself.
        lines.push(format!("cargo::metadata=xamlmeta={}", metadata_path.display()));
        lines.push(format!("cargo::rustc-env={XAMLMETA_VARIABLE}={}", metadata_path.display()));
        Outcome { lines, errors }
    }
}

/// The run-time host of the compiler: the documents are compiled against the types the
/// build script registered in its process. With the feature `runtime-host`, which links
/// the XAML runtime library and, through it, the controls.
#[cfg(feature = "runtime-host")]
mod runtime_host {
    use ferroui_base::metadata::MarkupAssembly;
    use ferroui_markup_xaml::RuntimeXamlLoaderConfiguration;
    use ferroui_markup_xaml_loader::rust_emitter::{GeneratedFile, XamlMetadata};
    use ferroui_markup_xaml_loader::FerroRuntimeXamlLoader;

    /// Makes the assembly of the crate and the runtime library known to the compiler.
    pub(super) fn register(assembly: &'static MarkupAssembly) {
        // The compiler resolves the assembly of the crate and the types of the runtime
        // library; every other type is the build script's to register.
        ferroui_markup_xaml::register_types();
        MarkupAssembly::register(assembly);
        // Makes the assembly known to the asset loader, as the `register_types()` of the
        // crate does: the host of the emitter in the tests of a crate runs with it.
        ferroui_base::platform::register_assets(assembly.name, &[]);
        FerroRuntimeXamlLoader::register();
    }

    /// The generated file of a group, with the configuration of the run-time loader.
    pub(super) fn generate_file(
        assembly: &'static MarkupAssembly,
        root_uri: &str,
        documents: &[(&str, &str)],
        create_source_info: Option<bool>,
        default_compile_bindings: bool,
        dependencies: &[XamlMetadata],
    ) -> GeneratedFile {
        let mut configuration = RuntimeXamlLoaderConfiguration::new();
        configuration.local_assembly = Some(assembly);
        configuration.use_compiled_bindings_by_default = default_compile_bindings;
        if let Some(create_source_info) = create_source_info {
            configuration.set_create_source_info(create_source_info);
        }
        ferroui_markup_xaml_loader::rust_emitter::generate_file(assembly.name, root_uri, documents, &configuration, dependencies)
    }
}

/// The module of a group in the file the crate includes.
struct Module {
    name: String,
    /// The generated file.
    path: PathBuf,
    /// Whether the loader table of the crate asks the table of the module.
    exported: bool,
    /// Whether the generated file is a module file of its own (the file of a class, which
    /// starts with attributes of the module) and not the body of a module.
    file: bool,
}

/// The rooted path (`/Folder/Style.xaml`) of the document with the URI `uri`.
fn document_path(uri: &str) -> Option<String> {
    let rest = uri.split_once("://")?.1;
    rest.find('/').map(|separator| rest[separator..].to_string())
}

/// The file of the class whose document is `class_document`, among the documents of its
/// crate: the class is the type the models have for the `x:Class` of the document, and
/// the group is the document with the documents it includes.
#[allow(clippy::too_many_arguments)]
fn class_group(
    host: &EmitterHost<'_>,
    models: &dyn IXamlTypeSystem,
    root_uri: &str,
    documents: &[(&str, &str)],
    class_document: &str,
    constructor: Option<ClassConstructor>,
    module_path: &str,
    options: &TransformOptions,
) -> Result<ferroui_markup_xaml_loader::rust_emitter::ClassFile, ClassGroupError> {
    let group = class_document_group(root_uri, documents, class_document).map_err(ClassGroupError::Transform)?;
    let class_name = class_of_document(&group[0].1)
        .map_err(ClassGroupError::Transform)?
        .ok_or_else(|| ClassGroupError::Transform("the document names no class (`x:Class`)".to_string()))?;
    let class = models.find_type(&class_name).ok_or_else(|| {
        ClassGroupError::Transform(format!(
            "the type models have no type `{class_name}`, which the document names with `x:Class`: the class is not declared in the sources of the crate, or its declaration is not read"
        ))
    })?;
    generate_class_file_with(host, &ClassGroup { class, documents: &group, constructor, module_path }, options).map_err(|reasons| {
        match reasons.strip_prefix(CLASS_GROUP_NOT_TRANSFORMED) {
            Some(_) => ClassGroupError::Transform(reasons),
            None => ClassGroupError::Emit(reasons),
        }
    })
}

/// Why the file of a class is not generated.
enum ClassGroupError {
    /// The group of the class is not found or does not transform (upstream's
    /// `TransformError`).
    Transform(String),
    /// Documents the emitter refuses, one reason per line (upstream's `EmitError`).
    Emit(String),
}

/// Compiles every `.xaml` file of the crate whose build script is running
/// (`Build::from_env().assembly(assembly).compile_xaml().run()`).
pub fn compile_xaml(assembly: &'static MarkupAssembly) {
    Build::from_env().assembly(assembly).compile_xaml().run();
}

/// Embeds the files below `directories` as the assets of the crate whose build script
/// is running (`Build::from_env().assembly(assembly).embed_assets(directories).run()`).
pub fn embed_assets(assembly: &'static MarkupAssembly, directories: &[&str]) {
    Build::from_env().assembly(assembly).embed_assets(directories).run();
}

/// Scans the sources of the crate whose build script is running and exports its type
/// model (`Build::from_env().export_metadata().run()`).
pub fn export_metadata() {
    Build::from_env().export_metadata().run();
}

/// Every file below `directory`, with its rooted path below `root` (`/Assets/a.png`),
/// in the order of the names. Directories whose name starts with a dot and the
/// directory `target` of `root` are skipped.
fn collect(root: &Path, directory: &Path, found: &mut Vec<(String, PathBuf)>) -> Result<(), String> {
    let entries = fs::read_dir(directory).map_err(|error| format!("{}: {error}", directory.display()))?;
    let mut paths = Vec::new();
    for entry in entries {
        paths.push(entry.map_err(|error| format!("{}: {error}", directory.display()))?.path());
    }
    paths.sort();
    for path in paths {
        let name = path.file_name().map(|name| name.to_string_lossy().into_owned()).unwrap_or_default();
        if path.is_dir() {
            if !name.starts_with('.') && !(directory == root && name == "target") {
                collect(root, &path, found)?;
            }
            continue;
        }
        let relative = path.strip_prefix(root).map_err(|_| format!("{} is not below {}", path.display(), root.display()))?;
        let parts: Vec<String> = relative.components().map(|part| part.as_os_str().to_string_lossy().into_owned()).collect();
        found.push((format!("/{}", parts.join("/")), path));
    }
    Ok(())
}

/// Writes `text` to `path` unless the file holds it already, so that a build that
/// changed nothing does not make the compiler run again.
fn write_if_changed(path: &Path, text: &str, errors: &mut Vec<String>) {
    if let Err(error) = ferroui_build_scan::export::write_if_changed(path, text) {
        errors.push(error);
    }
}

/// The text of `$OUT_DIR/xaml/mod.rs`, which `include_compiled_xaml!()` includes at the
/// root of the crate: the module of every group, and the module `compiled_markup`
/// with the asset table, the loader table of the crate (the checked-in tables, then
/// the groups, in order) and `register()`.
fn crate_file(assembly_name: &str, modules: &[Module], loaders: &[String], assets: &[(String, PathBuf)]) -> String {
    let mut text = String::new();
    text.push_str("// @generated by ferroui-build (Build::run). Do not edit.\n");
    for Module { name: module, path, file, .. } in modules {
        text.push('\n');
        text.push_str(&format!("/// The compiled documents of the group `{module}`.\n"));
        text.push_str("#[doc(hidden)]\n");
        text.push_str("#[rustfmt::skip]\n");
        if *file {
            // The file of a class is a module file: it starts with attributes of the module.
            text.push_str(&format!("#[path = {}]\n", rust_string_literal(&path.display().to_string())));
            text.push_str(&format!("pub mod {module};\n"));
            continue;
        }
        // A document that is not public (`x:ClassModifier`) and that the documents of its
        // group only merge has a build function nothing calls: its content is in theirs.
        text.push_str("#[allow(dead_code)]\n");
        text.push_str(&format!("pub mod {module} {{\n"));
        text.push_str(&format!("    include!({});\n", rust_string_literal(&path.display().to_string())));
        text.push_str("}\n");
    }
    text.push('\n');
    text.push_str("/// The compiled markup and the embedded assets of the crate.\n");
    text.push_str("#[doc(hidden)]\n");
    text.push_str("#[rustfmt::skip]\n");
    text.push_str("pub mod compiled_markup {\n");
    text.push_str("    /// The assembly of the crate.\n");
    text.push_str(&format!("    pub const ASSEMBLY_NAME: &str = {};\n", rust_string_literal(assembly_name)));
    text.push('\n');
    text.push_str("    /// The embedded assets of the crate, by rooted path.\n");
    text.push_str("    pub static ASSETS: &[(&str, &[u8])] = &[\n");
    for (rooted, path) in assets {
        text.push_str(&format!(
            "        ({}, include_bytes!({})),\n",
            rust_string_literal(rooted),
            rust_string_literal(&path.display().to_string())
        ));
    }
    text.push_str("    ];\n");
    text.push('\n');
    text.push_str("    /// The loader of the compiled markup of the crate: the object of the document with the URI\n");
    text.push_str("    /// `uri`, from the first table that has it; `Ok(None)` if none has.\n");
    text.push_str("    #[allow(unused_variables)]\n");
    text.push_str("    pub fn try_load(\n");
    text.push_str("        service_provider: ::core::option::Option<&::std::rc::Rc<dyn ::ferroui_base::metadata::IServiceProvider>>,\n");
    text.push_str("        uri: &str,\n");
    text.push_str("    ) -> ::core::result::Result<::core::option::Option<::ferroui_base::BoxedValue>, ::ferroui_markup_xaml::XamlLoadException> {\n");
    let tables = loaders
        .iter()
        .cloned()
        .chain(modules.iter().filter(|module| module.exported).map(|module| format!("super::{}::try_load", module.name)));
    for table in tables {
        text.push_str(&format!("        if let ::core::option::Option::Some(loaded) = {table}(service_provider, uri)? {{\n"));
        text.push_str("            return ::core::result::Result::Ok(::core::option::Option::Some(loaded));\n");
        text.push_str("        }\n");
    }
    text.push_str("        ::core::result::Result::Ok(::core::option::Option::None)\n");
    text.push_str("    }\n");
    text.push('\n');
    text.push_str("    /// Registers the assets and the compiled markup of the crate. The assembly is made known\n");
    text.push_str("    /// to the asset loader even without assets: a load by URI asks it for the assembly of the\n");
    text.push_str("    /// document.\n");
    text.push_str("    pub fn register() {\n");
    text.push_str("        ::ferroui_base::platform::register_assets(ASSEMBLY_NAME, ASSETS);\n");
    text.push_str("        ::ferroui_markup_xaml::FerroXamlLoader::register_compiled_xaml(ASSEMBLY_NAME, try_load);\n");
    text.push_str("    }\n");
    text.push_str("}\n");
    text
}

#[cfg(test)]
mod tests {
    use super::*;

    /// Not from upstream: the file a crate includes names the generated files, chains the
    /// loader tables (the checked-in ones first, a group that is not exported not at all)
    /// and registers the assets with the table.
    #[test]
    fn crate_file_declares_the_modules_and_the_loader_table() {
        let module = |name: &str, exported: bool, file: bool| Module { name: name.to_string(), path: PathBuf::from(format!("/out/xaml/{name}.rs")), exported, file };
        let modules = vec![module("compiled_xaml", true, false), module("compiled_xaml_source_info", false, false), module("compiled_main_window", true, true)];
        let assets = vec![("/Assets/a.png".to_string(), PathBuf::from("/crate/Assets/a.png"))];
        let text = crate_file("Tests", &modules, &["crate::compiled_main::try_load".to_string()], &assets);
        assert!(text.contains("pub mod compiled_xaml {\n    include!(\"/out/xaml/compiled_xaml.rs\");\n}\n"), "{text}");
        assert!(text.contains("pub mod compiled_xaml_source_info {\n"), "{text}");
        assert!(text.contains("    pub const ASSEMBLY_NAME: &str = \"Tests\";\n"), "{text}");
        assert!(text.contains("        (\"/Assets/a.png\", include_bytes!(\"/crate/Assets/a.png\")),\n"), "{text}");
        let checked_in = text.find("= crate::compiled_main::try_load(service_provider, uri)?").expect("the checked-in table");
        let group = text.find("= super::compiled_xaml::try_load(service_provider, uri)?").expect("the table of the group");
        assert!(checked_in < group, "{text}");
        assert!(!text.contains("super::compiled_xaml_source_info::try_load"), "{text}");
        // The file of a class is a module file of its own.
        assert!(text.contains("#[path = \"/out/xaml/compiled_main_window.rs\"]\npub mod compiled_main_window;\n"), "{text}");
        assert!(text.contains("= super::compiled_main_window::try_load(service_provider, uri)?"), "{text}");
    }

    /// Not from upstream: `export_metadata()` scans the sources of the crate, writes its
    /// type model into its `.xamlmeta` and names every file it read; the build of a crate
    /// that depends on it reads that file and resolves against the model in it.
    #[test]
    fn export_metadata_writes_the_model_and_reads_the_models_of_the_dependencies() {
        let fixtures = Path::new(env!("CARGO_MANIFEST_DIR")).with_file_name("FerroUI.Build.Scan").join("tests").join("fixtures");
        let out = env::temp_dir().join(format!("ferroui-build-export-{}", std::process::id()));
        let first = Build::new(fixtures.join("scanner"), out.join("fixture"), "fixture", Vec::new()).source_root("lib.rs").export_metadata().execute();
        assert_eq!(first.errors, Vec::<String>::new());
        let fixture_file = out.join("fixture").join("fixture.xamlmeta");
        assert!(first.lines.contains(&format!("cargo::metadata=xamlmeta={}", fixture_file.display())), "{:?}", first.lines);
        let border = fixtures.join("scanner").join("controls").join("border.rs");
        assert!(first.lines.contains(&format!("cargo::rerun-if-changed={}", border.display())), "{:?}", first.lines);
        // What the scanner does not read is a warning of the build.
        assert!(first.lines.iter().any(|line| line.starts_with("cargo::warning=") && line.contains("error FRN9010")), "{:?}", first.lines);
        let text = fs::read_to_string(&fixture_file).expect("the .xamlmeta of the fixture");
        let model = AssemblyModel::parse(&text).expect("a file of format 2");
        assert_eq!((model.name.as_str(), model.crate_name.as_str()), ("Fixture", "fixture"));
        assert!(model.find_type("Fixture.Controls.Border").is_some() && !model.exports.is_empty());
        assert!(model.documents.is_empty() && model.dependencies.is_empty());
        assert_eq!(XamlMetadata::parse(&text).map(|metadata| metadata.name), Ok("Fixture".to_string()));
        assert!(!out.join("fixture").join("xaml").join("mod.rs").exists(), "a crate that only exports its model includes nothing");

        let second = Build::new(fixtures.join("dependent"), out.join("dependent"), "dependent", vec![fixture_file.clone()]).export_metadata().execute();
        assert_eq!(second.errors, Vec::<String>::new());
        assert!(second.lines.contains(&format!("cargo::rerun-if-changed={}", fixture_file.display())), "{:?}", second.lines);
        let text = fs::read_to_string(out.join("dependent").join("dependent.xamlmeta")).expect("the .xamlmeta of the dependent crate");
        let model = AssemblyModel::parse(&text).expect("a file of format 2");
        assert_eq!((model.name.as_str(), model.crate_name.as_str()), ("dependent", "dependent"));
        assert_eq!(model.dependencies, [fixture_file.display().to_string()]);
        let card = model.find_type("Card").expect("the class of the dependent crate");
        assert_eq!(card.registered[0].name.as_deref(), Some("Background"));
        assert_eq!(card.base.as_ref().map(|base| base.text.as_str()), Some("::fixture::controls::border::Border"));
        // The models are read back as a set, the dependency through the file that names it.
        let (models, files) = ModelSet::read(&[out.join("dependent").join("dependent.xamlmeta")]).expect("the two files");
        assert_eq!(models.iter().map(|model| model.name.as_str()).collect::<Vec<_>>(), ["dependent", "Fixture"]);
        assert_eq!(files.len(), 2);

        let missing = Build::new(fixtures.join("dependent"), out.join("missing"), "dependent", Vec::new()).source_root("main.rs").export_metadata().execute();
        assert_eq!(missing.errors.len(), 1, "{:?}", missing.errors);
        assert!(missing.errors[0].ends_with("main.rs, is not a file"), "{:?}", missing.errors);
        let _ = fs::remove_dir_all(&out);
    }

    /// Not from upstream: the two texts of the base crate the scanner states itself, because
    /// the crate it is in cannot link the base crate, are the ones of the base crate.
    #[test]
    fn texts_the_scanner_states_are_the_ones_of_the_base_crate() {
        assert_eq!(ferroui_build_scan::FERRO_XML_NAMESPACE, ferroui_base::metadata::FERRO_XML_NAMESPACE);
        assert_eq!(ferroui_build_scan::CREATE_SOURCE_INFO, MarkupAssembly::CREATE_SOURCE_INFO);
        assert_eq!(ferroui_build_scan::USE_COMPILED_BINDINGS_BY_DEFAULT, MarkupAssembly::USE_COMPILED_BINDINGS_BY_DEFAULT);
    }

    /// Not from upstream: against the type models a build reads the assembly from the
    /// sources and compiles the document of a class of the crate; what the models do not
    /// have is an error that names the document. The fixture declares no framework type,
    /// so the group does not get as far as a transform here: the include fixture
    /// (`tests/XamlIncludeFixture`) is the build that compiles.
    #[test]
    fn class_document_is_compiled_against_the_models_only() {
        let fixtures = Path::new(env!("CARGO_MANIFEST_DIR")).with_file_name("FerroUI.Build.Scan").join("tests").join("fixtures");
        let out = env::temp_dir().join(format!("ferroui-build-class-{}", std::process::id()));
        let document = "<Border xmlns='https://github.com/ferroui' xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml' x:Class='Fixture.Missing'/>";
        let group = || XamlGroup::new("compiled_border").documents(&[("Border.xaml", document)]).class_document("Border.xaml");
        let build = |name: &str| Build::new(fixtures.join("scanner"), out.join(name), "fixture", Vec::new()).source_root("lib.rs");

        let on_models = build("models").type_system(TypeSystem::Model).compile_group(group()).execute();
        assert_eq!(on_models.errors.len(), 1, "{:?}", on_models.errors);
        assert!(
            on_models.errors[0].starts_with("Border.xaml: error FRN2000: the type models have no type `Fixture.Missing`, which the document names with `x:Class`"),
            "{:?}",
            on_models.errors
        );
        // The sources were scanned: the files are inputs of the build.
        let border = fixtures.join("scanner").join("controls").join("border.rs");
        assert!(on_models.lines.contains(&format!("cargo::rerun-if-changed={}", border.display())), "{:?}", on_models.lines);

        // Against the run-time type system the document of a class is not compiled; without
        // the feature that links that type system no document is.
        static ASSEMBLY: MarkupAssembly =
            MarkupAssembly { name: "Fixture", crate_name: "fixture", xmlns_definitions: &[], xmlns_prefixes: &[], metadata: &[] };
        let at_run_time = build("runtime").assembly(&ASSEMBLY).compile_group(group()).execute();
        assert_eq!(at_run_time.errors.len(), 1, "{:?}", at_run_time.errors);
        let expected = match cfg!(feature = "runtime-host") {
            true => "Border.xaml: error FRN2000: the document of a class of the crate is compiled against the type models only",
            false => "the documents are compiled against the type models (Build::type_system(TypeSystem::Model)): the run-time type system is the feature `runtime-host`",
        };
        assert!(at_run_time.errors[0].starts_with(expected), "{:?}", at_run_time.errors);
        let _ = fs::remove_dir_all(&out);
    }

    /// Not from upstream: a build without an assembly reports it, with the lines that make
    /// Cargo run the script again.
    #[test]
    fn build_without_an_assembly_is_an_error() {
        let outcome = Build::new(PathBuf::from("/crate"), PathBuf::from("/out"), "my-crate", Vec::new()).compile_xaml().execute();
        assert_eq!(outcome.errors, ["the assembly of the crate is not stated (Build::assembly)"]);
        assert_eq!(outcome.lines, ["cargo::rerun-if-changed=/crate/build.rs", "cargo::rerun-if-changed=/crate/Cargo.toml"]);
    }
}