feat: support tsconfig rootDirs (#885)

Boshen · Boshen · commit d205b70fbfde · 2025-12-03T12:02:15.000Z
closes #521
diff --git a/fixtures/tsconfig/cases/root-dirs-all-fail/src/index.ts b/fixtures/tsconfig/cases/root-dirs-all-fail/src/index.ts
@@ -0,0 +1 @@
+import {} from './nonexistent'
diff --git a/fixtures/tsconfig/cases/root-dirs-all-fail/tsconfig.json b/fixtures/tsconfig/cases/root-dirs-all-fail/tsconfig.json
@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "rootDirs": ["./src", "./generated"]
+  }
+}
diff --git a/fixtures/tsconfig/cases/root-dirs-multiple/generated/bar.ts b/fixtures/tsconfig/cases/root-dirs-multiple/generated/bar.ts
diff --git a/fixtures/tsconfig/cases/root-dirs-multiple/lib/baz.ts b/fixtures/tsconfig/cases/root-dirs-multiple/lib/baz.ts
diff --git a/fixtures/tsconfig/cases/root-dirs-multiple/src/index.ts b/fixtures/tsconfig/cases/root-dirs-multiple/src/index.ts
@@ -0,0 +1,2 @@
+import {} from './bar'
+import {} from './baz'
diff --git a/fixtures/tsconfig/cases/root-dirs-multiple/tsconfig.json b/fixtures/tsconfig/cases/root-dirs-multiple/tsconfig.json
@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "rootDirs": ["./src", "./generated", "./lib"]
+  }
+}
diff --git a/fixtures/tsconfig/cases/root-dirs-nested/src/foo.ts b/fixtures/tsconfig/cases/root-dirs-nested/src/foo.ts
diff --git a/fixtures/tsconfig/cases/root-dirs-nested/src/sub/foo.ts b/fixtures/tsconfig/cases/root-dirs-nested/src/sub/foo.ts
diff --git a/fixtures/tsconfig/cases/root-dirs-nested/src/sub/index.ts b/fixtures/tsconfig/cases/root-dirs-nested/src/sub/index.ts
@@ -0,0 +1 @@
+import {} from './foo'
diff --git a/fixtures/tsconfig/cases/root-dirs-nested/tsconfig.json b/fixtures/tsconfig/cases/root-dirs-nested/tsconfig.json
@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "rootDirs": ["./src", "./src/sub"]
+  }
+}
diff --git a/fixtures/tsconfig/cases/root-dirs-no-match/outside/foo.ts b/fixtures/tsconfig/cases/root-dirs-no-match/outside/foo.ts
diff --git a/fixtures/tsconfig/cases/root-dirs-no-match/src/index.ts b/fixtures/tsconfig/cases/root-dirs-no-match/src/index.ts
@@ -0,0 +1 @@
+import {} from '../outside/foo'
diff --git a/fixtures/tsconfig/cases/root-dirs-no-match/tsconfig.json b/fixtures/tsconfig/cases/root-dirs-no-match/tsconfig.json
@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "rootDirs": ["./src"]
+  }
+}
diff --git a/fixtures/tsconfig/cases/root-dirs-parent-dir/folder1/file1_1/index.ts b/fixtures/tsconfig/cases/root-dirs-parent-dir/folder1/file1_1/index.ts
@@ -0,0 +1 @@
+export {}
diff --git a/fixtures/tsconfig/cases/root-dirs-parent-dir/generated/folder2/file3.ts b/fixtures/tsconfig/cases/root-dirs-parent-dir/generated/folder2/file3.ts
@@ -0,0 +1 @@
+import {} from '../folder1/file1_1'
diff --git a/fixtures/tsconfig/cases/root-dirs-parent-dir/tsconfig.json b/fixtures/tsconfig/cases/root-dirs-parent-dir/tsconfig.json
@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "rootDirs": [".", "./generated"]
+  }
+}
diff --git a/fixtures/tsconfig/cases/root-dirs-parent-nav/folder1/file1.ts b/fixtures/tsconfig/cases/root-dirs-parent-nav/folder1/file1.ts
@@ -0,0 +1 @@
+export {}
diff --git a/fixtures/tsconfig/cases/root-dirs-parent-nav/generated/folder2/file3.ts b/fixtures/tsconfig/cases/root-dirs-parent-nav/generated/folder2/file3.ts
@@ -0,0 +1 @@
+import {} from '../folder1/file1'
diff --git a/fixtures/tsconfig/cases/root-dirs-parent-nav/tsconfig.json b/fixtures/tsconfig/cases/root-dirs-parent-nav/tsconfig.json
@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "rootDirs": [".", "./generated"]
+  }
+}
diff --git a/fixtures/tsconfig/cases/root-dirs-single/src/foo.ts b/fixtures/tsconfig/cases/root-dirs-single/src/foo.ts
@@ -0,0 +1 @@
+export {}
diff --git a/fixtures/tsconfig/cases/root-dirs-single/src/index.ts b/fixtures/tsconfig/cases/root-dirs-single/src/index.ts
@@ -0,0 +1 @@
+import {} from './foo'
diff --git a/fixtures/tsconfig/cases/root-dirs-single/tsconfig.json b/fixtures/tsconfig/cases/root-dirs-single/tsconfig.json
@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "rootDirs": ["./src"]
+  }
+}
diff --git a/fixtures/tsconfig/cases/root-dirs-trailing-slash/generated/foo.ts b/fixtures/tsconfig/cases/root-dirs-trailing-slash/generated/foo.ts
@@ -0,0 +1 @@
+export {}
diff --git a/fixtures/tsconfig/cases/root-dirs-trailing-slash/src/index.ts b/fixtures/tsconfig/cases/root-dirs-trailing-slash/src/index.ts
@@ -0,0 +1 @@
+import {} from './foo'
diff --git a/fixtures/tsconfig/cases/root-dirs-trailing-slash/tsconfig.json b/fixtures/tsconfig/cases/root-dirs-trailing-slash/tsconfig.json
@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "rootDirs": ["./src/", "./generated"]
+  }
+}
diff --git a/fixtures/tsconfig/cases/root-dirs/generated/foo.ts b/fixtures/tsconfig/cases/root-dirs/generated/foo.ts
diff --git a/fixtures/tsconfig/cases/root-dirs/src/index.ts b/fixtures/tsconfig/cases/root-dirs/src/index.ts
@@ -0,0 +1 @@
+import {} from './foo'
diff --git a/fixtures/tsconfig/cases/root-dirs/tsconfig.json b/fixtures/tsconfig/cases/root-dirs/tsconfig.json
@@ -0,0 +1,5 @@
+{
+  "compilerOptions": {
+    "rootDirs": ["./src", "./generated"]
+  }
+}
diff --git a/src/lib.rs b/src/lib.rs
@@ -370,7 +370,7 @@ impl<Fs: FileSystem> ResolverGeneric<Fs> {
         ctx: &mut Ctx,
     ) -> Result<CachedPath, ResolveError> {
         // tsconfig-paths
-        if let Some(path) = self.load_tsconfig_paths(cached_path, specifier, tsconfig)? {
+        if let Some(path) = self.load_tsconfig_paths(cached_path, specifier, tsconfig, ctx)? {
             return Ok(path);
         }
 
@@ -488,11 +488,10 @@ impl<Fs: FileSystem> ResolverGeneric<Fs> {
             c,
             Component::CurDir | Component::ParentDir | Component::Normal(_)
         )));
-        let cached_path = cached_path.normalize_with(specifier, self.cache.as_ref());
         // a. LOAD_AS_FILE(Y + X)
         // b. LOAD_AS_DIRECTORY(Y + X)
         if let Some(path) = self.load_as_file_or_directory(
-            &cached_path,
+            &cached_path.normalize_with(specifier, self.cache.as_ref()),
             // ensure resolve directory only when specifier is `.`
             if specifier == "." { "./" } else { specifier },
             tsconfig,
diff --git a/src/tests/mod.rs b/src/tests/mod.rs
@@ -30,6 +30,7 @@ mod tsconfig_discovery;
 mod tsconfig_extends;
 mod tsconfig_paths;
 mod tsconfig_project_references;
+mod tsconfig_root_dirs;
 #[cfg(target_os = "windows")]
 mod windows;
 
diff --git a/src/tests/tsconfig_root_dirs.rs b/src/tests/tsconfig_root_dirs.rs
@@ -0,0 +1,103 @@
+//! Tests for tsconfig root_dirs
+//!
+//! The rootDirs option allows mapping multiple source directories to a single
+//! output directory structure. This is commonly used in build systems where
+//! generated code and source code should appear to be in the same directory structure.
+//!
+//! TypeScript reference: https://www.typescriptlang.org/tsconfig#rootDirs
+
+use crate::{
+    ResolveError, ResolveOptions, Resolver, TsconfigDiscovery, TsconfigOptions, TsconfigReferences,
+};
+
+#[test]
+fn test() {
+    let f = super::fixture_root().join("tsconfig/cases");
+
+    #[rustfmt::skip]
+    let pass = [
+        // Test Case 1: Initial resolution succeeds
+        // Import ./foo from src/index.ts resolves to generated/foo.ts
+        (f.join("root-dirs"), "src/index.ts", "./foo", f.join("root-dirs/generated/foo.ts")),
+
+        // Test Case 2: Alternative rootDir succeeds
+        // Import ./bar from src/index.ts, bar doesn't exist in src/ but exists in generated/
+        (f.join("root-dirs-multiple"), "src/index.ts", "./bar", f.join("root-dirs-multiple/generated/bar.ts")),
+
+        // Test Case 3: Multiple alternatives - second alternative
+        // Import ./baz from src/index.ts, baz doesn't exist in src/ or generated/, but exists in lib/
+        (f.join("root-dirs-multiple"), "src/index.ts", "./baz", f.join("root-dirs-multiple/lib/baz.ts")),
+
+        // Test Case 4: Longest prefix match
+        // Import ./foo from src/sub/index.ts with nested rootDirs ["./src", "./src/sub"]
+        // Should match ./src/sub (longer prefix) and resolve to src/sub/foo.ts
+        (f.join("root-dirs-nested"), "src/sub/index.ts", "./foo", f.join("root-dirs-nested/src/sub/foo.ts")),
+
+        // Test Case 5: Directory resolution with rootDirs
+        // Resolving ./src/index from root directory
+        (f.join("root-dirs"), ".", "./src/index", f.join("root-dirs/src/index.ts")),
+
+        // Test Case 6: Parent directory navigation
+        // Import ../folder1/file1 from generated/folder2/file3.ts resolves to folder1/file1.ts
+        (f.join("root-dirs-parent-nav"), "generated/folder2/file3.ts", "../folder1/file1", f.join("root-dirs-parent-nav/folder1/file1.ts")),
+
+        // Test Case 7: Directory import with parent navigation
+        // Import ../folder1/file1_1 from generated/folder2/file3.ts resolves to folder1/file1_1/index.ts
+        (f.join("root-dirs-parent-dir"), "generated/folder2/file3.ts", "../folder1/file1_1", f.join("root-dirs-parent-dir/folder1/file1_1/index.ts")),
+
+        // Test Case 8: Single rootDir entry
+        // Verify that rootDirs works correctly with only one entry
+        (f.join("root-dirs-single"), "src/index.ts", "./foo", f.join("root-dirs-single/src/foo.ts")),
+
+        // Test Case 9: Trailing slash in rootDirs configuration
+        // Verify ./src/ works the same as ./src
+        (f.join("root-dirs-trailing-slash"), "src/index.ts", "./foo", f.join("root-dirs-trailing-slash/generated/foo.ts")),
+    ];
+
+    for (dir, from_path, request, expected) in pass {
+        let resolver = Resolver::new(ResolveOptions {
+            tsconfig: Some(TsconfigDiscovery::Manual(TsconfigOptions {
+                config_file: dir.join("tsconfig.json"),
+                references: TsconfigReferences::Auto,
+            })),
+            extensions: vec![".ts".into()],
+            ..ResolveOptions::default()
+        });
+        let path = dir.join(from_path);
+        let resolved_path = resolver.resolve(&path, request).map(|f| f.full_path());
+        assert_eq!(resolved_path, Ok(expected), "from {path:?} resolve {request}");
+    }
+
+    #[rustfmt::skip]
+    let fail = [
+        // Test Case 6: No rootDirs configured
+        // Without rootDirs, relative imports use normal resolution only
+        (f.join("index"), "src/index.ts", "./foo"),
+
+        // Test Case 7: All resolutions fail
+        // File doesn't exist in any rootDir
+        (f.join("root-dirs-all-fail"), "src/index.ts", "./nonexistent"),
+
+        // Test Case 8: No matching prefix
+        // Importing from root when rootDirs are "./src" and "./src/sub"
+        // The candidate doesn't match any rootDir prefix
+        (f.join("root-dirs-nested"), ".", "./nonexistent"),
+    ];
+
+    for (dir, from_path, request) in fail {
+        let resolver = Resolver::new(ResolveOptions {
+            tsconfig: Some(TsconfigDiscovery::Manual(TsconfigOptions {
+                config_file: dir.join("tsconfig.json"),
+                references: TsconfigReferences::Auto,
+            })),
+            extensions: vec![".ts".into()],
+            ..ResolveOptions::default()
+        });
+        let path = dir.join(from_path);
+        let resolved_path = resolver.resolve(&path, request);
+        assert!(
+            matches!(resolved_path, Err(ResolveError::NotFound(_))),
+            "expected NotFound error from {path:?} resolve {request}, got {resolved_path:?}"
+        );
+    }
+}
diff --git a/src/tsconfig.rs b/src/tsconfig.rs
@@ -285,6 +285,12 @@ impl TsConfig {
         {
             compiler_options.allow_js = Some(*allow_js);
         }
+
+        if compiler_options.root_dirs.is_none()
+            && let Some(root_dirs) = &tsconfig.compiler_options.root_dirs
+        {
+            compiler_options.root_dirs = Some(root_dirs.clone());
+        }
     }
     /// "Build" the root tsconfig, resolve:
     ///
@@ -326,6 +332,12 @@ impl TsConfig {
                 config_dir.join(stripped_path.trim_start_matches('/'));
         }
 
+        if let Some(root_dirs) = &mut self.compiler_options.root_dirs {
+            for root_dir in root_dirs.iter_mut() {
+                *root_dir = config_dir.normalize_with(&root_dir);
+            }
+        }
+
         if self.compiler_options.paths.is_some() {
             // Substitute template variable in `tsconfig.compilerOptions.paths`.
             for paths in self.compiler_options.paths.as_mut().unwrap().values_mut() {
@@ -483,6 +495,9 @@ pub struct CompilerOptions {
 
     /// <https://www.typescriptlang.org/tsconfig/#allowJs>
     pub allow_js: Option<bool>,
+
+    /// <https://www.typescriptlang.org/tsconfig/#rootDirs>
+    pub root_dirs: Option<Vec<PathBuf>>,
 }
 
 /// Value for the "extends" field.
diff --git a/src/tsconfig_resolver.rs b/src/tsconfig_resolver.rs
@@ -260,6 +260,7 @@ impl<Fs: FileSystem> ResolverGeneric<Fs> {
         cached_path: &CachedPath,
         specifier: &str,
         tsconfig: Option<&TsConfig>,
+        ctx: &mut Ctx,
     ) -> ResolveResult {
         if cached_path.inside_node_modules() {
             return Ok(None);
@@ -296,8 +297,69 @@ impl<Fs: FileSystem> ResolverGeneric<Fs> {
                 return Ok(Some(resolution));
             }
         }
+        if specifier.starts_with('.')
+            && let Some(path) =
+                self.load_tsconfig_root_dirs(cached_path, specifier, tsconfig, ctx)?
+        {
+            return Ok(Some(path));
+        }
         Ok(None)
     }
+
+    pub(crate) fn load_tsconfig_root_dirs(
+        &self,
+        cached_path: &CachedPath,
+        specifier: &str,
+        tsconfig: &TsConfig,
+        ctx: &mut Ctx,
+    ) -> ResolveResult {
+        debug_assert!(specifier.starts_with('.'));
+        debug_assert!(!cached_path.inside_node_modules());
+        let Some(root_dirs) = &tsconfig.compiler_options.root_dirs else { return Ok(None) };
+
+        // Use the containing directory, not the file itself
+        let containing_directory = if self.cache.is_dir(cached_path, ctx) {
+            cached_path.clone()
+        } else {
+            cached_path.parent(&self.cache).unwrap_or_else(|| cached_path.clone())
+        };
+        let candidate = containing_directory.normalize_with(specifier, &self.cache);
+        let mut matched_root_dir: Option<PathBuf> = None;
+        for root_dir in root_dirs {
+            let is_longest_matching_prefix = candidate.path().starts_with(root_dir)
+                && matched_root_dir
+                    .as_ref()
+                    .is_none_or(|prefix| prefix.as_os_str().len() < root_dir.as_os_str().len());
+            if is_longest_matching_prefix {
+                matched_root_dir.replace(root_dir.clone());
+            }
+        }
+        let Some(matched_root_dir) = matched_root_dir else {
+            return Ok(None);
+        };
+        if let Some(p) = self.load_as_file_or_directory(&candidate, ".", Some(tsconfig), ctx)? {
+            return Ok(Some(p));
+        }
+        // Defensive: This should never fail because we already verified the prefix match,
+        // but we handle it gracefully in case of unexpected path normalization edge cases.
+        let Ok(suffix) = candidate.path().strip_prefix(&matched_root_dir) else {
+            return Ok(None);
+        };
+        for root_dir in root_dirs {
+            if *root_dir == matched_root_dir {
+                continue;
+            }
+            let candidate = root_dir.normalize_with(suffix);
+            let cached_candidate = self.cache.value(&candidate);
+            if let Some(resolved) =
+                self.load_as_file_or_directory(&cached_candidate, ".", Some(tsconfig), ctx)?
+            {
+                return Ok(Some(resolved));
+            }
+        }
+        Ok(None)
+    }
+
     fn get_extended_tsconfig_path(
         &self,
         directory: &CachedPath,

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +{
 +  "compilerOptions": {
 +    "rootDirs": ["./src", "./generated"]
 +  }
 +}
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+import {} from './bar'`
	`2`	`+import {} from './baz'`