fix(tsconfig): dedupe project reference dependencies

Author: CPunisher

src/lib.rs

@@ -1578,6 +1578,7 @@ impl<Fs: FileSystem + Send + Sync> ResolverGeneric<Fs> {
       }
       let directory = tsconfig.directory().to_path_buf();
       let current_path = tsconfig.path.clone();
+      let mut flattened_reference_paths = FxHashSet::default();
       visited.insert(current_path.clone());
       for reference in &mut tsconfig.references {
         let reference_tsconfig_path = directory.normalize_with(&reference.path);
@@ -1618,10 +1619,19 @@ impl<Fs: FileSystem + Send + Sync> ResolverGeneric<Fs> {
             },
           )
           .await?;
-        TsConfig::extend_file_dependencies(
-          &mut tsconfig.file_dependencies,
-          &reference_tsconfig.file_dependencies,
-        );
+        tsconfig
+          .file_dependencies
+          .extend(reference_tsconfig.file_dependencies.iter().cloned());
+        for nested in &reference_tsconfig.flattened_references {
+          if flattened_reference_paths.insert(nested.path.clone()) {
+            tsconfig.flattened_references.push(Arc::clone(nested));
+          }
+        }
+        if flattened_reference_paths.insert(reference_tsconfig.path.clone()) {
+          tsconfig
+            .flattened_references
+            .push(Arc::clone(&reference_tsconfig));
+        }
         reference.tsconfig.replace(reference_tsconfig);
       }
       Ok(())

src/tests/tsconfig_project_references.rs

@@ -2,7 +2,7 @@
 
 use crate::{
   tsconfig::FileDependencies, ResolveContext, ResolveError, ResolveOptions, Resolver, ResolverPath,
-  TsConfig, TsconfigOptions, TsconfigReferences,
+  TsconfigOptions, TsconfigReferences,
 };
 
 #[test]
@@ -11,15 +11,15 @@ fn file_dependencies_are_deduplicated() {
   file_dependencies.insert("/repo/app/tsconfig.json".into());
   file_dependencies.insert("/repo/base.json".into());
 
-  let dependencies = [
+  let dependencies: FileDependencies = [
     "/repo/base.json".into(),
     "/repo/shared/tsconfig.json".into(),
     "/repo/shared/tsconfig.json".into(),
   ]
   .into_iter()
   .collect();
 
-  TsConfig::extend_file_dependencies(&mut file_dependencies, &dependencies);
+  file_dependencies.extend(dependencies.iter().cloned());
 
   assert_eq!(
     file_dependencies

src/tsconfig.rs

@@ -2,7 +2,7 @@ use std::{hash::BuildHasherDefault, sync::Arc};
 
 use camino::{Utf8Path, Utf8PathBuf};
 use indexmap::{IndexMap, IndexSet};
-use rustc_hash::{FxHashSet, FxHasher};
+use rustc_hash::FxHasher;
 use serde::Deserialize;
 
 use crate::path::PathUtil;
@@ -43,6 +43,10 @@ pub struct TsConfig {
   /// Bubbled up project references with a reference to their tsconfig.
   #[serde(default)]
   pub references: Vec<ProjectReference>,
+
+  /// Flattened transitive project references in resolution order.
+  #[serde(skip)]
+  pub(crate) flattened_references: Vec<Arc<TsConfig>>,
 }
 
 /// Compiler Options
@@ -158,52 +162,18 @@ impl TsConfig {
         .base_url
         .clone_from(&other_config.compiler_options.base_url);
     }
-    Self::extend_file_dependencies(&mut self.file_dependencies, &other_config.file_dependencies);
-  }
-
-  pub(crate) fn extend_file_dependencies(
-    file_dependencies: &mut FileDependencies,
-    dependencies: &FileDependencies,
-  ) {
-    file_dependencies.extend(dependencies.iter().cloned());
+    self
+      .file_dependencies
+      .extend(other_config.file_dependencies.iter().cloned());
   }
 
   pub fn resolve(&self, path: &Utf8Path, specifier: &str) -> Vec<Utf8PathBuf> {
-    let mut visited = FxHashSet::default();
-    if let Some(matched) = self.find_reference_paths(path, specifier, &mut visited) {
-      return matched;
-    }
-    self.resolve_path_alias(specifier)
-  }
-
-  // Walks `references` recursively, returning the nearest reference whose
-  // `base_path` contains `path`. Used to honor transitive project references
-  // (A → B → C): a file inside C should resolve via C's own `paths` even
-  // when the entry tsconfig is A and only B is listed directly in A's
-  // references. Matches `tsc`'s "nearest tsconfig wins" semantics.
-  fn find_reference_paths<'a>(
-    &'a self,
-    path: &Utf8Path,
-    specifier: &str,
-    visited: &mut FxHashSet<&'a Utf8Path>,
-  ) -> Option<Vec<Utf8PathBuf>> {
-    if !visited.insert(self.path.as_path()) {
-      return None;
-    }
-
-    for tsconfig in self
-      .references
-      .iter()
-      .filter_map(|reference| reference.tsconfig.as_ref())
-    {
-      if let Some(nested) = tsconfig.find_reference_paths(path, specifier, visited) {
-        return Some(nested);
-      }
+    for tsconfig in &self.flattened_references {
       if path.starts_with(tsconfig.base_path()) {
-        return Some(tsconfig.resolve_path_alias(specifier));
+        return tsconfig.resolve_path_alias(specifier);
       }
     }
-    None
+    self.resolve_path_alias(specifier)
   }
 
   // Copied from parcel