fallow_graph/resolve/

types.rs

//! Type definitions and constants for import resolution.

use std::path::{Path, PathBuf};
use std::sync::{Arc, Mutex};

use dashmap::DashMap;
use oxc_resolver::Resolver;
use rustc_hash::{FxBuildHasher, FxHashMap, FxHashSet};
use serde_json::Value;

use fallow_config::TsconfigOutputMap;
use fallow_types::discover::FileId;

/// Result of resolving an import specifier.
#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
pub enum ResolveResult {
    /// Resolved to a file within the project.
    InternalModule(FileId),
    /// Resolved from a CommonJS `require()` to a file within the project.
    CommonJsInternalModule(FileId),
    /// Resolved to a project file through a framework convention auto-import.
    SyntheticAutoImport(FileId),
    /// Resolved to a workspace or self package source file while preserving
    /// dependency usage for package accounting.
    InternalPackageModule {
        /// Internal source file reached by the package map.
        file_id: FileId,
        /// Package name that was used in the import specifier.
        package_name: String,
    },
    /// Resolved from a CommonJS `require()` to workspace or self-package source.
    CommonJsInternalPackageModule {
        /// Internal source file reached by the package map.
        file_id: FileId,
        /// Package name used in the require specifier.
        package_name: String,
    },
    /// Resolved to a file outside the project (`node_modules`, `.json`, etc.).
    ExternalFile(PathBuf),
    /// Bare specifier — an npm package.
    NpmPackage(String),
    /// Bare npm package referenced through CommonJS `require()`.
    CommonJsNpmPackage(String),
    /// Could not resolve.
    Unresolvable(String),
}

impl ResolveResult {
    /// Return the target file for any project-internal result.
    #[must_use]
    pub const fn internal_file_id(&self) -> Option<FileId> {
        match self {
            Self::InternalModule(file_id)
            | Self::CommonJsInternalModule(file_id)
            | Self::SyntheticAutoImport(file_id)
            | Self::InternalPackageModule { file_id, .. }
            | Self::CommonJsInternalPackageModule { file_id, .. } => Some(*file_id),
            Self::ExternalFile(_)
            | Self::NpmPackage(_)
            | Self::CommonJsNpmPackage(_)
            | Self::Unresolvable(_) => None,
        }
    }

    /// Return whether this edge was synthesized from framework auto-import conventions.
    #[must_use]
    pub const fn is_synthetic_auto_import(&self) -> bool {
        matches!(self, Self::SyntheticAutoImport(_))
    }

    /// Return whether this edge originated from CommonJS `require()`.
    #[must_use]
    pub const fn is_commonjs_require(&self) -> bool {
        matches!(
            self,
            Self::CommonJsInternalModule(_)
                | Self::CommonJsInternalPackageModule { .. }
                | Self::CommonJsNpmPackage(_)
        )
    }

    /// Return whether this target is an unresolved bare package edge.
    #[must_use]
    pub const fn is_bare_package(&self) -> bool {
        matches!(self, Self::NpmPackage(_) | Self::CommonJsNpmPackage(_))
    }

    /// Retain CommonJS provenance on targets that can participate in upgrades.
    #[must_use]
    pub fn into_commonjs_require(self) -> Self {
        match self {
            Self::InternalModule(file_id) => Self::CommonJsInternalModule(file_id),
            Self::InternalPackageModule {
                file_id,
                package_name,
            } => Self::CommonJsInternalPackageModule {
                file_id,
                package_name,
            },
            Self::NpmPackage(package_name) => Self::CommonJsNpmPackage(package_name),
            other => other,
        }
    }

    /// Remove CommonJS provenance while preserving the resolved destination.
    #[must_use]
    pub fn into_es_module(self) -> Self {
        match self {
            Self::CommonJsInternalModule(file_id) => Self::InternalModule(file_id),
            Self::CommonJsInternalPackageModule {
                file_id,
                package_name,
            } => Self::InternalPackageModule {
                file_id,
                package_name,
            },
            Self::CommonJsNpmPackage(package_name) => Self::NpmPackage(package_name),
            other => other,
        }
    }

    /// Return the package name that should receive dependency usage credit.
    #[must_use]
    pub fn package_usage_name(&self) -> Option<&str> {
        match self {
            Self::InternalPackageModule { package_name, .. }
            | Self::CommonJsInternalPackageModule { package_name, .. }
            | Self::NpmPackage(package_name)
            | Self::CommonJsNpmPackage(package_name) => Some(package_name),
            Self::InternalModule(_)
            | Self::CommonJsInternalModule(_)
            | Self::SyntheticAutoImport(_)
            | Self::ExternalFile(_)
            | Self::Unresolvable(_) => None,
        }
    }
}

/// Resolver output for one extracted project.
#[derive(Debug, Default)]
pub struct ResolvedProject {
    /// Modules with every ordinary import and re-export resolved.
    pub modules: Vec<ResolvedModule>,
    /// Proven test-time replacements whose targets resolve inside the project.
    pub replaced_module_targets: Vec<ResolvedReplacedModuleTarget>,
    /// Deterministic work counts of the resolution that built this project.
    /// Zero for a project restored from the graph cache.
    pub work: super::ResolveWork,
}

/// One project-internal module replacement resolved from its declaring source file.
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct ResolvedReplacedModuleTarget {
    /// File that declares the replacement fact.
    pub source_file: FileId,
    /// Project file replaced for this source's test-root traversal.
    pub target_file: FileId,
}

/// A resolved import with its target.
#[derive(Debug, Clone)]
pub struct ResolvedImport {
    /// The original import information.
    pub info: fallow_types::extract::ImportInfo,
    /// Where the import resolved to.
    pub target: ResolveResult,
}

/// A resolved re-export with its target.
#[derive(Debug, Clone)]
pub struct ResolvedReExport {
    /// The original re-export information.
    pub info: fallow_types::extract::ReExportInfo,
    /// Where the re-export source resolved to.
    pub target: ResolveResult,
}

/// Any source-bearing module edge that resolves one literal specifier.
pub enum ResolvedSourceEdge<'a> {
    /// Static or literal dynamic import edge.
    Import(&'a ResolvedImport),
    /// Re-export source edge.
    ReExport(&'a ResolvedReExport),
}

impl<'a> ResolvedSourceEdge<'a> {
    /// Return the original source specifier.
    #[must_use]
    pub fn source_specifier(&self) -> &'a str {
        match self {
            Self::Import(import) => &import.info.source,
            Self::ReExport(re_export) => &re_export.info.source,
        }
    }

    /// Return the resolved target.
    #[must_use]
    pub const fn target(&self) -> &'a ResolveResult {
        match self {
            Self::Import(import) => &import.target,
            Self::ReExport(re_export) => &re_export.target,
        }
    }

    /// Return whether this edge is type-only.
    #[must_use]
    pub const fn is_type_only(&self) -> bool {
        match self {
            Self::Import(import) => import.info.is_type_only,
            Self::ReExport(re_export) => re_export.info.is_type_only,
        }
    }

    /// Return the span of the full import or re-export declaration.
    #[must_use]
    pub const fn span(&self) -> oxc_span::Span {
        match self {
            Self::Import(import) => import.info.span,
            Self::ReExport(re_export) => re_export.info.span,
        }
    }

    /// Return the source literal span when the extractor has one.
    #[must_use]
    pub const fn source_span(&self) -> oxc_span::Span {
        match self {
            Self::Import(import) => import.info.source_span,
            Self::ReExport(re_export) => re_export.info.source_span,
        }
    }

    /// Return the span of the enclosing statement.
    ///
    /// Imports do not record a statement span, so their per-binding
    /// declaration span is the closest available statement anchor.
    #[must_use]
    pub const fn statement_span(&self) -> oxc_span::Span {
        match self {
            Self::Import(import) => import.info.span,
            Self::ReExport(re_export) => re_export.info.statement_span,
        }
    }
}

/// Fully resolved module with all imports mapped to targets.
///
/// The `Arc<[T]>` fields are refcounted views of the same allocations owned by
/// the source [`fallow_types::extract::ModuleInfo`], not copies; see the note
/// on that struct.
#[derive(Debug)]
pub struct ResolvedModule {
    /// Unique file identifier.
    pub file_id: FileId,
    /// Absolute path to the module file.
    pub path: PathBuf,
    /// All export declarations in this module.
    pub exports: Arc<[fallow_types::extract::ExportInfo]>,
    /// All re-exports with resolved targets.
    pub re_exports: Vec<ResolvedReExport>,
    /// All static imports with resolved targets.
    pub resolved_imports: Vec<ResolvedImport>,
    /// All dynamic imports with resolved targets.
    pub resolved_dynamic_imports: Vec<ResolvedImport>,
    /// Dynamic import patterns and their matched target files.
    pub resolved_dynamic_patterns: Vec<(fallow_types::extract::DynamicImportPattern, Vec<FileId>)>,
    /// Static member accesses (e.g., `Status.Active`).
    pub member_accesses: Arc<[fallow_types::extract::MemberAccess]>,
    /// Typed semantic facts produced by extraction for cross-layer analysis.
    pub semantic_facts: Arc<[fallow_types::extract::SemanticFact]>,
    /// Identifiers used as whole objects (Object.values, for..in, spread, etc.).
    pub whole_object_uses: Arc<[String]>,
    /// Whether this module uses `CommonJS` exports.
    pub has_cjs_exports: bool,
    /// Whether this module declares at least one Angular `@Component({
    /// templateUrl: ... })` decorator. Mirrors `ModuleInfo.has_angular_component_template_url`;
    /// see that field for the contract this gate enforces.
    pub has_angular_component_template_url: bool,
    /// Local names of import bindings that are never referenced in this file.
    pub unused_import_bindings: FxHashSet<String>,
    /// Local import bindings referenced from type positions.
    pub type_referenced_import_bindings: Vec<String>,
    /// Local import bindings referenced from runtime/value positions.
    pub value_referenced_import_bindings: Vec<String>,
    /// Namespace-import aliases re-exported through an object literal.
    /// See `fallow_types::extract::NamespaceObjectAlias` for the shape.
    pub namespace_object_aliases: Vec<fallow_types::extract::NamespaceObjectAlias>,
    /// Exported free-function factories that provably return one class instance.
    /// See `fallow_types::extract::FactoryReturnExport` and issue #1441 (Part A).
    pub exported_factory_returns: Arc<[fallow_types::extract::FactoryReturnExport]>,
    /// Object-literal factory-return shapes (`export function createUi() {
    /// return { orders: factory.ordersPage } }`), threaded from `ModuleInfo` for
    /// the analyze-layer member-crediting join. See issue #1858.
    pub exported_factory_return_object_shapes:
        Arc<[fallow_types::extract::FactoryReturnObjectShapeExport]>,
    /// Named-type property types declared by this module's top-level interfaces
    /// and type-literal aliases. See `fallow_types::extract::TypeMemberTypeEntry`
    /// and issue #1785.
    pub type_member_types: Arc<[fallow_types::extract::TypeMemberTypeEntry]>,
    /// Unresolved bare specifiers whose package `exports` entry names only
    /// paths that do not exist, in specifier order. The resolver records the
    /// paths so that the unresolved-import check can test them against the
    /// ignore rules of the repository. No edge points at these paths.
    pub missing_export_targets: Vec<MissingExportTarget>,
}

/// The missing paths that the `exports` map of a project package names for
/// one unresolved bare specifier.
#[derive(Debug, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
pub struct MissingExportTarget {
    /// The import specifier, for example `store/enums`.
    pub specifier: String,
    /// The absolute paths that the matched `exports` entry names.
    pub paths: Vec<PathBuf>,
}

impl Default for ResolvedModule {
    fn default() -> Self {
        Self {
            file_id: FileId(0),
            path: PathBuf::new(),
            exports: Arc::default(),
            re_exports: vec![],
            resolved_imports: vec![],
            resolved_dynamic_imports: vec![],
            resolved_dynamic_patterns: vec![],
            member_accesses: Arc::default(),
            semantic_facts: Arc::default(),
            whole_object_uses: Arc::default(),
            has_cjs_exports: false,
            has_angular_component_template_url: false,
            unused_import_bindings: FxHashSet::default(),
            type_referenced_import_bindings: vec![],
            value_referenced_import_bindings: vec![],
            namespace_object_aliases: vec![],
            exported_factory_returns: Arc::default(),
            exported_factory_return_object_shapes: Arc::default(),
            type_member_types: Arc::default(),
            missing_export_targets: vec![],
        }
    }
}

impl ResolvedModule {
    /// Iterate over all concrete resolved imports in source order buckets.
    ///
    /// Includes static `import`/`require` edges and literal dynamic `import()`
    /// edges. Dynamic import patterns are intentionally excluded because they
    /// resolve to sets of files rather than single import specifiers.
    pub fn all_resolved_imports(&self) -> impl Iterator<Item = &ResolvedImport> {
        self.resolved_imports
            .iter()
            .chain(self.resolved_dynamic_imports.iter())
    }

    /// Iterate over every literal source edge that has one resolved target.
    ///
    /// Includes static imports, literal dynamic imports, and re-export sources.
    /// Dynamic import patterns are excluded because they resolve to sets of
    /// files rather than single import specifiers.
    pub fn all_resolved_source_edges(&self) -> impl Iterator<Item = ResolvedSourceEdge<'_>> {
        self.resolved_imports
            .iter()
            .map(ResolvedSourceEdge::Import)
            .chain(
                self.resolved_dynamic_imports
                    .iter()
                    .map(ResolvedSourceEdge::Import),
            )
            .chain(self.re_exports.iter().map(ResolvedSourceEdge::ReExport))
    }
}

/// Shared context for resolving import specifiers.
///
/// Groups the immutable lookup tables and caches that are shared across all
/// `resolve_specifier` calls within a single `resolve_all_imports` invocation.
pub(super) struct ResolveContext<'a> {
    /// The oxc_resolver instance (configured once, shared across threads).
    pub resolver: &'a Resolver,
    /// Script and JSON extension inference, with explicit asset targets intact.
    /// Shares the broad resolver's filesystem and PnP cache.
    pub script_resolver: &'a Resolver,
    /// CSS-only resolver with package.json `sass` and `style` conditions enabled.
    /// Used only for stylesheet package subpaths so JS/TS imports do not
    /// accidentally prefer CSS export branches.
    pub style_resolver: &'a Resolver,
    /// Ordered extension list used by the resolver.
    pub extensions: &'a [String],
    /// Canonical path → FileId lookup (raw paths when root is canonical).
    pub path_to_id: &'a FxHashMap<&'a Path, FileId>,
    /// Raw (non-canonical) path → FileId lookup.
    pub raw_path_to_id: &'a FxHashMap<&'a Path, FileId>,
    /// Workspace name → canonical root path.
    pub workspace_roots: &'a FxHashMap<&'a str, &'a Path>,
    /// Package manifests for the root package and workspace packages.
    pub package_manifests: &'a [PackageManifestInfo],
    /// Whether any package scope declared a Deno import map; false skips map
    /// lookup per import.
    pub has_deno_import_maps: bool,
    /// Ordered package condition names matching the resolver configuration.
    pub condition_names: &'a [String],
    /// Plugin-provided path aliases (prefix, replacement).
    pub path_aliases: &'a [(String, String)],
    /// Absolute directories to search when resolving bare SCSS/Sass
    /// `@import` / `@use` specifiers. Populated from Angular's
    /// `stylePreprocessorOptions.includePaths` and equivalent settings.
    pub scss_include_paths: &'a [PathBuf],
    /// Static directory URL mappings from framework config.
    /// Each tuple is `(absolute_source_dir, normalized_url_mount)`.
    pub static_dir_mappings: &'a [(PathBuf, String)],
    /// Mounts a framework serves for the whole project, reachable from any HTML
    /// document, unlike `static_dir_mappings`, which stays scoped to the tool
    /// whose config declared it.
    pub framework_static_dir_mappings: &'a [(PathBuf, String)],
    /// Project root directory.
    pub root: &'a Path,
    /// Lazy canonical path → FileId fallback for intra-project symlinks.
    /// Only initialized on first miss when root is canonical. `None` when
    /// path_to_id already uses canonical paths (root is not canonical).
    pub canonical_fallback: Option<&'a CanonicalFallback<'a>>,
    /// Dedup set for broken-tsconfig warnings. Emits one `tracing::warn!`
    /// per unique error message instead of spamming the log with one
    /// warning per affected file. Shared across all parallel resolver
    /// threads via `Mutex`. Empty and unused when no tsconfig errors occur.
    pub tsconfig_warned: &'a Mutex<FxHashSet<String>>,
    /// Per-analysis cache for local tsconfig discovery and JSON parsing.
    /// Import resolution calls these fallbacks for every unresolved or
    /// tsconfig-poisoned specifier, so keeping it session-local avoids
    /// repeated filesystem work without risking stale data across runs.
    pub tsconfig_cache: &'a TsconfigCache,
    /// Per-analysis cache of `dunce::canonicalize` results keyed by resolved
    /// path. Every import resolving to a `node_modules` / output-dir / symlinked
    /// target is realpath'd during classification, and the same package path is
    /// re-canonicalized for every file that imports the package. The result is a
    /// pure function of the path's on-disk state (constant within a run), so the
    /// cache is session-local for watch-mode safety.
    pub canonicalize_cache: &'a CanonicalizeCache,
}

/// Session-local cache of `dunce::canonicalize` results keyed by input path.
#[derive(Default)]
pub(super) struct CanonicalizeCache {
    map: DashMap<PathBuf, Option<PathBuf>, FxBuildHasher>,
}

impl CanonicalizeCache {
    /// Return the cached `dunce::canonicalize(path)` outcome, computing it on
    /// first miss. `None` (a path that fails to canonicalize) is cached too so a
    /// repeated probe of the same missing path does not re-issue the syscall.
    pub fn get(&self, path: &Path) -> Option<PathBuf> {
        if let Some(value) = self.map.get(path) {
            return value.clone();
        }
        let value = dunce::canonicalize(path).ok();
        self.map.insert(path.to_path_buf(), value.clone());
        value
    }

    /// Number of distinct paths this cache canonicalized. Two threads that
    /// miss the same path at once can both call the filesystem, so this is the
    /// work the run needs, not an exact syscall count.
    pub fn distinct_paths(&self) -> usize {
        self.map.len()
    }
}

/// Session-local cache for tsconfig helper lookups used during import resolution.
#[derive(Default)]
pub(super) struct TsconfigCache {
    json: DashMap<PathBuf, Option<Arc<Value>>, FxBuildHasher>,
    chains: DashMap<PathBuf, Arc<[PathBuf]>, FxBuildHasher>,
    output_maps: DashMap<PathBuf, Arc<TsconfigOutputMap>, FxBuildHasher>,
}

impl TsconfigCache {
    /// Return a cached parsed tsconfig JSON value, loading it on first miss.
    ///
    /// Handing back an [`Arc`] rather than a clone matters: a tsconfig chain is
    /// walked several times per import specifier, and deep-copying every parsed
    /// document on each hop dominated resolution on large project-reference
    /// graphs.
    pub fn json(
        &self,
        path: &Path,
        load: impl FnOnce(&Path) -> Option<Value>,
    ) -> Option<Arc<Value>> {
        if let Some(value) = self.json.get(path) {
            return value.clone();
        }

        let value = load(path).map(Arc::new);
        self.json.insert(path.to_path_buf(), value.clone());
        value
    }

    /// Return the cached tsconfig chain for a source file, if one exists.
    pub fn chain(&self, from_file: &Path) -> Option<Arc<[PathBuf]>> {
        self.chains.get(from_file).map(|entry| Arc::clone(&entry))
    }

    /// Store the computed tsconfig chain for a source file.
    pub fn store_chain(&self, from_file: &Path, chain: Arc<[PathBuf]>) {
        self.chains.insert(from_file.to_path_buf(), chain);
    }

    /// Return the output-to-source map of a package root, building it on
    /// first miss. Each package root reads its tsconfig files once per run.
    pub fn output_map(&self, package_root: &Path) -> Arc<TsconfigOutputMap> {
        if let Some(map) = self.output_maps.get(package_root) {
            return Arc::clone(&map);
        }
        let map = Arc::new(TsconfigOutputMap::from_project(package_root));
        self.output_maps
            .insert(package_root.to_path_buf(), Arc::clone(&map));
        map
    }
}

/// Package manifest data used by source fallbacks.
#[derive(Debug, Clone)]
pub(super) struct PackageManifestInfo {
    /// Package root path as discovered from the workspace tree.
    pub root: PathBuf,
    /// Canonical package root path for node_modules symlink comparisons.
    pub canonical_root: PathBuf,
    /// Parsed package name.
    pub name: Option<String>,
    /// Parsed package.json fields.
    pub package_json: fallow_config::PackageJson,
    /// Effective Deno import map for this package scope.
    pub deno_import_map: Vec<DenoImportMapEntry>,
}

/// One effective Deno import-map entry with the directory that declared it.
#[derive(Debug, Clone)]
pub(super) struct DenoImportMapEntry {
    pub key: String,
    pub target: String,
    pub declaring_dir: PathBuf,
}

/// Thread-safe lazy canonical path index, built on first access.
pub(super) struct CanonicalFallback<'a> {
    files: &'a [fallow_types::discover::DiscoveredFile],
    map: std::sync::OnceLock<FxHashMap<std::path::PathBuf, FileId>>,
}

impl<'a> CanonicalFallback<'a> {
    pub const fn new(files: &'a [fallow_types::discover::DiscoveredFile]) -> Self {
        Self {
            files,
            map: std::sync::OnceLock::new(),
        }
    }

    /// Look up a canonical path, lazily building the index on first call.
    pub fn get(&self, canonical: &Path) -> Option<FileId> {
        let map = self.map.get_or_init(|| {
            super::work::note_canonicalize(self.files.len() as u64);
            tracing::debug!(
                "intra-project symlinks detected, building canonical path index ({} files)",
                self.files.len()
            );
            self.files
                .iter()
                .filter_map(|f| {
                    dunce::canonicalize(&f.path)
                        .ok()
                        .map(|canonical| (canonical, f.id))
                })
                .collect()
        });
        map.get(canonical).copied()
    }
}

#[cfg(all(test, not(miri)))]
mod tests {
    use super::*;
    use fallow_types::discover::DiscoveredFile;

    #[test]
    fn canonical_fallback_returns_none_for_empty_files() {
        let files: Vec<DiscoveredFile> = vec![];
        let fallback = CanonicalFallback::new(&files);
        assert!(fallback.get(Path::new("/nonexistent")).is_none());
    }

    #[test]
    fn canonical_fallback_finds_existing_file() {
        let temp = std::env::temp_dir().join("fallow-test-canonical-fallback");
        let _ = std::fs::create_dir_all(&temp);
        let test_file = temp.join("test.ts");
        std::fs::write(&test_file, "").unwrap();

        let files = vec![DiscoveredFile {
            id: FileId(42),
            path: test_file.clone(),
            size_bytes: 0,
        }];
        let fallback = CanonicalFallback::new(&files);

        let canonical = dunce::canonicalize(&test_file).unwrap();
        assert_eq!(fallback.get(&canonical), Some(FileId(42)));

        assert_eq!(fallback.get(&canonical), Some(FileId(42)));

        let _ = std::fs::remove_dir_all(&temp);
    }

    #[test]
    fn canonical_fallback_returns_none_for_missing_path() {
        let temp = std::env::temp_dir().join("fallow-test-canonical-miss");
        let _ = std::fs::create_dir_all(&temp);
        let test_file = temp.join("exists.ts");
        std::fs::write(&test_file, "").unwrap();

        let files = vec![DiscoveredFile {
            id: FileId(1),
            path: test_file,
            size_bytes: 0,
        }];
        let fallback = CanonicalFallback::new(&files);
        assert!(fallback.get(Path::new("/nonexistent/file.ts")).is_none());

        let _ = std::fs::remove_dir_all(&temp);
    }

    #[test]
    fn tsconfig_cache_loads_once_and_shares_the_parsed_document() {
        let cache = TsconfigCache::default();
        let path = Path::new("/project/tsconfig.json");
        let loads = std::sync::atomic::AtomicUsize::new(0);
        let load = |_: &Path| {
            loads.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
            Some(serde_json::json!({ "compilerOptions": {} }))
        };

        let first = cache.json(path, load).unwrap();
        let second = cache.json(path, load).unwrap();

        assert_eq!(loads.load(std::sync::atomic::Ordering::SeqCst), 1);
        assert!(
            Arc::ptr_eq(&first, &second),
            "repeat reads must share one allocation rather than deep-copy"
        );
    }

    /// An unreadable tsconfig is cached as a miss so the read is not retried.
    #[test]
    fn tsconfig_cache_caches_a_failed_load() {
        let cache = TsconfigCache::default();
        let path = Path::new("/project/missing.json");
        let loads = std::sync::atomic::AtomicUsize::new(0);
        let load = |_: &Path| {
            loads.fetch_add(1, std::sync::atomic::Ordering::SeqCst);
            None
        };

        assert!(cache.json(path, load).is_none());
        assert!(cache.json(path, load).is_none());
        assert_eq!(loads.load(std::sync::atomic::Ordering::SeqCst), 1);
    }

    #[test]
    fn tsconfig_cache_round_trips_a_chain() {
        let cache = TsconfigCache::default();
        let from_file = Path::new("/project/src/index.ts");
        assert!(cache.chain(from_file).is_none());

        let chain: Arc<[PathBuf]> = vec![PathBuf::from("/project/tsconfig.json")].into();
        cache.store_chain(from_file, Arc::clone(&chain));

        assert!(Arc::ptr_eq(&cache.chain(from_file).unwrap(), &chain));
    }

    /// Both caches are read concurrently by rayon workers during resolution.
    #[test]
    fn tsconfig_cache_is_consistent_under_concurrent_access() {
        const THREADS: usize = 8;
        const PATHS: usize = 32;

        let cache = TsconfigCache::default();
        std::thread::scope(|scope| {
            for _ in 0..THREADS {
                scope.spawn(|| {
                    for index in 0..PATHS {
                        let path = PathBuf::from(format!("/project/{index}/tsconfig.json"));
                        let json = cache
                            .json(&path, |_| Some(serde_json::json!({ "index": index })))
                            .unwrap();
                        assert_eq!(json["index"], index);
                    }
                });
            }
        });
    }

    #[test]
    fn canonicalize_cache_returns_the_same_result_on_repeat_lookups() {
        let temp = tempfile::tempdir().expect("create temp dir");
        let file = temp.path().join("file.ts");
        std::fs::write(&file, "").unwrap();

        let cache = CanonicalizeCache::default();
        let expected = dunce::canonicalize(&file).ok();
        assert_eq!(cache.get(&file), expected);
        assert_eq!(cache.get(&file), expected);
        assert!(cache.get(&temp.path().join("missing.ts")).is_none());
    }

    #[test]
    fn commonjs_provenance_wraps_internal_and_bare_package_targets() {
        assert!(matches!(
            ResolveResult::InternalModule(FileId(4)).into_commonjs_require(),
            ResolveResult::CommonJsInternalModule(FileId(4))
        ));
        assert!(matches!(
            ResolveResult::InternalPackageModule {
                file_id: FileId(5),
                package_name: "pkg".to_string(),
            }
            .into_commonjs_require(),
            ResolveResult::CommonJsInternalPackageModule {
                file_id: FileId(5),
                package_name,
            } if package_name == "pkg"
        ));
        assert!(matches!(
            ResolveResult::NpmPackage("pkg".to_string()).into_commonjs_require(),
            ResolveResult::CommonJsNpmPackage(package_name) if package_name == "pkg"
        ));
    }
}

/// Known output directory names that may appear in exports map targets.
/// When an exports map points to `./dist/utils.js`, we try replacing these
/// prefixes with `src/` (the conventional source directory) to find the tracked
/// source file.
pub const OUTPUT_DIRS: &[&str] = &["dist", "build", "out", "esm", "cjs"];

/// Output directory names that map to `src/` only when the target is absent.
///
/// Many TypeScript libraries build `src/` into `lib/`, but older packages keep
/// hand-written source in `lib/`. Thus `lib` maps to `src/` only when the
/// `lib/` target is absent from the analyzed file set (for example in a fresh
/// clone before the build, or a gitignored build), and only for package
/// manifest targets. A `lib/` file in the file set always wins, and generic
/// relative imports never use this list.
pub const MISSING_ONLY_OUTPUT_DIRS: &[&str] = &["lib"];

/// Source extensions to try when mapping a built output file back to source.
pub const SOURCE_EXTS: &[&str] = &["ts", "tsx", "mts", "cts", "js", "jsx", "mjs", "cjs"];

/// React Native platform extension prefixes.
/// Metro resolves platform-specific files (e.g., `./foo` -> `./foo.web.tsx` on web).
pub const RN_PLATFORM_PREFIXES: &[&str] = &[".web", ".ios", ".android", ".native"];