alba_core/

model.rs

//! The typed project model that `alba-core` evaluates a Beamfile's AST
//! into: [`Project`], its [`Beam`]s, and the small value types they carry.
//!
//! Scope boundary: a [`Beam`]'s `needs` list is converted straight from
//! the AST's `BeamRef`s (namespaced by [`crate::loader::load_project`]
//! when it came from an `import`) without validating that the referenced
//! beam actually exists — that is [`crate::validate_graph`]'s job, not
//! this module's.

use std::path::PathBuf;

use alba_syntax::{Span, Spanned, StringTemplate};

use crate::eval::Scope;

/// Identifies which source file a [`Beam`] or [`crate::CoreError`] came
/// from, for pointing diagnostics at the right source text. Assigned by
/// [`crate::loader::load_project`] (the root file is always `SourceId(0)`,
/// each import gets the next one in load order) and resolvable back to a
/// path and source text via [`crate::loader::SourceMap::get`].
/// `load_str`'s single-file loading always produces `SourceId(0)`.
#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, Default)]
pub struct SourceId(pub usize);

/// A fully namespaced beam identifier, e.g. `"api:build"` for a beam
/// imported under the alias `api`, `"api:db:migrate"` for one imported
/// transitively through a chain of aliases, or `"build"` for a local one.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct BeamId(pub String);

/// How a beam's commands run.
#[derive(Debug, Clone, PartialEq)]
pub enum ExecutorKind {
    /// The default, when a beam declares no `executor` field at all.
    /// Which shell implementation actually runs a beam is the engine's
    /// concern, not this model's.
    Shell,
    /// `executor system_shell`: the host shell, the per-beam opt-out from
    /// the embedded shell.
    SystemShell,
    /// `executor docker { image "..." volumes [...] workdir "..." }`: the
    /// engine runs this beam's commands inside a container built from
    /// `image`, with `volumes` bind-mounted (`host:container` each) and
    /// `workdir` as the container's working directory when set.
    Docker {
        image: String,
        volumes: Vec<String>,
        workdir: Option<String>,
    },
    /// `executor <name> { ... }` for any name that is not `shell`,
    /// `system_shell`, or `docker`. Not an error: `name` is resolved at
    /// plan time to an external `alba-executor-<name>` binary on the
    /// `PATH`, and `options` is handed to it verbatim.
    Plugin {
        name: String,
        options: Vec<(String, OptionValue)>,
    },
}

/// The value half of an executor option, once rendered (its `{expr}`
/// interpolation resolved, for the `Str`/`List` cases) at load time. Mirrors
/// [`alba_syntax::ExecutorOptionValue`], minus the interpolation itself.
#[derive(Debug, Clone, PartialEq)]
pub enum OptionValue {
    Str(String),
    Bool(bool),
    List(Vec<String>),
}

/// A value produced by evaluating an [`alba_syntax::Expr`]: either of the
/// DSL's two runtime types.
#[derive(Debug, Clone, PartialEq)]
pub enum Value {
    Str(String),
    Bool(bool),
}

impl Value {
    /// A short, human-readable name for this value's type, for error
    /// messages ("expected a boolean, found a string").
    pub(crate) fn type_name(&self) -> &'static str {
        match self {
            Value::Str(_) => "a string",
            Value::Bool(_) => "a boolean",
        }
    }

    /// This value as it appears when interpolated into a template:
    /// strings verbatim, booleans as `true`/`false`.
    pub(crate) fn as_display(&self) -> &str {
        match self {
            Value::Str(s) => s.as_str(),
            Value::Bool(true) => "true",
            Value::Bool(false) => "false",
        }
    }
}

/// A single beam: the unit of work produced by evaluating a `beam { ... }`
/// declaration.
///
/// Load-time vs. schedule-time rendering: `description`, `inputs`,
/// `outputs`, `cwd`, and the executor's options are rendered once, at load
/// time, into plain values — referencing a beam parameter there is a load
/// error. `run` and `env` are kept as [`StringTemplate`]s and rendered at
/// schedule time (via [`crate::render_template`]), once the beam's
/// parameters are bound into a [`Scope`] built from [`Beam::scope`] via
/// [`Scope::with_params`].
#[derive(Debug, Clone)]
pub struct Beam {
    pub id: BeamId,
    pub description: Option<String>,
    /// Each entry keeps the span of the reference that produced it, so a
    /// `needs` entry that does not resolve is underlined exactly, rather
    /// than the whole beam declaration containing it.
    pub needs: Vec<Spanned<BeamId>>,
    pub params: Vec<String>,
    /// Evaluated but inert in this crate: the cache (out of scope here) is
    /// the only intended consumer.
    pub inputs: Vec<String>,
    pub outputs: Vec<String>,
    pub run: Vec<StringTemplate>,
    pub env: Vec<(String, StringTemplate)>,
    pub cwd: Option<String>,
    pub executor: ExecutorKind,
    pub allow_failure: bool,
    /// The directory of the defining Beamfile, used as the `cwd` base.
    /// Always absolute for a project built by `crate::loader::load_project`
    /// (it derives this via `std::path::absolute`, not the file's
    /// possibly-relative path, so it stays correct even if the process's
    /// current directory changes between loading and running) — except for
    /// `load_str`'s single-file front door, which has no real file on disk
    /// to resolve against and uses `"."` (see its doc comment).
    pub dir: PathBuf,
    pub span: Span,
    /// Which source file this beam was defined in, for diagnostics.
    pub source: SourceId,
    /// The defining file's evaluated file-level `let` bindings. The
    /// engine composes this with the beam's own parameter values at
    /// schedule time — `beam.scope.with_params(&beam.params, &args)` —
    /// before rendering `run`/`env`.
    pub scope: Scope,
}

/// A git hook bound to a beam: `hook pre-commit { beam check }`. Only the
/// root Beamfile's hooks make it here; an import's are ignored, as its
/// `default` is.
#[derive(Debug, Clone, PartialEq)]
pub struct Hook {
    /// The git hook name (`pre-commit`), already checked against
    /// [`crate::git::KNOWN_HOOKS`].
    pub name: String,
    /// The beam the hook runs, with the span of the reference that named
    /// it, for pointing at an unresolved one.
    pub beam: Spanned<BeamId>,
    /// How many arguments git passes to this hook; the beam may declare at
    /// most that many parameters.
    pub arity: usize,
    pub span: Span,
    pub source: SourceId,
}

/// A fully evaluated Beamfile (single-file loading only; see the module
/// doc comment): every beam it declares, and which one runs by default.
#[derive(Debug, Clone)]
pub struct Project {
    pub beams: Vec<Beam>,
    /// The beam a bare `alba` runs, with the span of the `default`
    /// declaration that named it — [`crate::validate_graph`] checks it
    /// resolves and points at that span when it does not.
    pub default: Option<Spanned<BeamId>>,
    /// The root Beamfile's hook declarations, in source order.
    pub hooks: Vec<Hook>,
}