Improve case canonicalization performance (#2552)

Closes #2548

Co-authored-by: なつき <[email protected]>

Author: nex3

CHANGELOG.md

@@ -1,3 +1,8 @@
+## 1.86.1
+
+* Improve the performance of `file:` URL case canonicalization on Windows and
+  Mac OS.
+
 ## 1.86.0
 
 * Add support for `%` as an expression in its own right. It will still be parsed

lib/src/io.dart

@@ -30,9 +30,8 @@ String canonicalize(String path) => _couldBeCaseInsensitive
 
 /// Returns `path` with the case updated to match the path's case on disk.
 ///
-/// This only updates `path`'s basename. It always returns `path` as-is on
-/// operating systems other than Windows or Mac OS, since they almost never use
-/// case-insensitive filesystems.
+/// This always returns `path` as-is on operating systems other than Windows or
+/// Mac OS, since they almost never use case-insensitive filesystems.
 String _realCasePath(String path) {
   // TODO(nweiz): Use an SDK function for this when dart-lang/sdk#35370 and/or
   // nodejs/node#24942 are fixed, or at least use FFI functions.
@@ -47,14 +46,33 @@ String _realCasePath(String path) {
     }
   }
 
-  String helper(String path) {
+  String helper(String path, [String? realPath]) {
     var dirname = p.dirname(path);
     if (dirname == path) return path;
 
     return _realCaseCache.putIfAbsent(path, () {
+      // If the path isn't a symlink, we can use the libraries' `realpath()`
+      // functions to get its actual basename much more efficiently than listing
+      // all its siblings.
+      if (!linkExists(path)) {
+        // Don't recompute the real path if it was already computed for a child
+        // and we haven't seen any symlinks between that child and this directory.
+        String realPathNonNull;
+        try {
+          realPathNonNull = realPath ?? realpath(path);
+        } on FileSystemException {
+          // If we can't get the realpath, that probably means the file doesn't
+          // exist. Rather than throwing an error about symlink resolution,
+          // return the non-existent path and let it throw whatever use-time
+          // error it's going to throw.
+          return path;
+        }
+        return p.join(helper(dirname, p.dirname(realPathNonNull)),
+            p.basename(realPathNonNull));
+      }
+
       var realDirname = helper(dirname);
       var basename = p.basename(path);
-
       try {
         var matches = listDir(realDirname)
             .where(

lib/src/io/interface.dart

@@ -61,6 +61,9 @@ bool fileExists(String path) => throw '';
 /// Returns whether a dir at [path] exists.
 bool dirExists(String path) => throw '';
 
+/// Returns whether a symbolic link at [path] exists.
+bool linkExists(String path) => throw '';
+
 /// Ensures that a directory exists at [path], creating it and its ancestors if
 /// necessary.
 void ensureDir(String path) => throw '';
@@ -71,6 +74,10 @@ void ensureDir(String path) => throw '';
 /// beneath [path] as well.
 Iterable<String> listDir(String path, {bool recursive = false}) => throw '';
 
+/// Returns the resolved physical path of [path] on disk, with symbolic links
+/// resolved and with the same case as the physical file.
+String realpath(String path) => throw '';
+
 /// Returns the modification time of the file at [path].
 DateTime modificationTime(String path) => throw '';
 

lib/src/io/js.dart

@@ -181,6 +181,21 @@ bool dirExists(String path) {
   });
 }
 
+bool linkExists(String path) {
+  if (!isNodeJs) {
+    throw UnsupportedError("linkExists() is only supported on Node.js");
+  }
+  return _systemErrorToFileSystemException(() {
+    try {
+      return fs.lstatSync(path).isSymbolicLink();
+    } catch (error) {
+      var systemError = error as JsSystemError;
+      if (systemError.code == 'ENOENT') return false;
+      rethrow;
+    }
+  });
+}
+
 void ensureDir(String path) {
   if (!isNodeJs) {
     throw UnsupportedError("ensureDir() is only supported on Node.js");
@@ -220,6 +235,13 @@ Iterable<String> listDir(String path, {bool recursive = false}) {
   });
 }
 
+String realpath(String path) {
+  if (!isNodeJs) {
+    throw UnsupportedError("listDir() is only supported on Node.js");
+  }
+  return _systemErrorToFileSystemException(() => fs.realpathSync.native(path));
+}
+
 DateTime modificationTime(String path) {
   if (!isNodeJs) {
     throw UnsupportedError("modificationTime() is only supported on Node.js");

lib/src/io/vm.dart

@@ -80,6 +80,8 @@ bool fileExists(String path) => io.File(path).existsSync();
 
 bool dirExists(String path) => io.Directory(path).existsSync();
 
+bool linkExists(String path) => io.Link(path).existsSync();
+
 void ensureDir(String path) => io.Directory(path).createSync(recursive: true);
 
 Iterable<String> listDir(String path, {bool recursive = false}) =>
@@ -88,6 +90,9 @@ Iterable<String> listDir(String path, {bool recursive = false}) =>
         .whereType<io.File>()
         .map((entity) => entity.path);
 
+// The `File()` method works with directories as well.
+String realpath(String path) => io.File(path).resolveSymbolicLinksSync();
+
 DateTime modificationTime(String path) {
   var stat = io.FileStat.statSync(path);
   if (stat.type == io.FileSystemEntityType.notFound) {

lib/src/js/legacy.dart

@@ -473,10 +473,7 @@ RenderResult _newRenderResult(
   var end = DateTime.now();
 
   var css = result.css;
-  // TODO(nweiz): Get rid of this cast once pulyaevskiy/node-interop#109 is
-  // released.
-  // ignore: prefer_void_to_null
-  Uint8List? sourceMapBytes = undefined as Null;
+  Uint8List? sourceMapBytes = undefined;
   if (_enableSourceMaps(options)) {
     var sourceMapOption = options.sourceMap;
     var sourceMapPath =

pkg/sass-parser/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.4.17
+
+* No user-visible changes.
+
 ## 0.4.16
 
 * Use union types rather than base classes for Sass nodes wherever possible.

pkg/sass-parser/package.json

@@ -1,6 +1,6 @@
 {
   "name": "sass-parser",
-  "version": "0.4.16",
+  "version": "0.4.17",
   "description": "A PostCSS-compatible wrapper of the official Sass parser",
   "repository": "sass/sass",
   "author": "Google Inc.",

pkg/sass_api/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 15.3.1
+
+* No user-visible changes.
+
 ## 15.3.0
 
 * No user-visible changes.

pkg/sass_api/pubspec.yaml

@@ -2,15 +2,15 @@ name: sass_api
 # Note: Every time we add a new Sass AST node, we need to bump the *major*
 # version because it's a breaking change for anyone who's implementing the
 # visitor interface(s).
-version: 15.3.0
+version: 15.3.1
 description: Additional APIs for Dart Sass.
 homepage: https://github.com/sass/dart-sass
 
 environment:
   sdk: ">=3.6.0 <4.0.0"
 
 dependencies:
-  sass: 1.86.0
+  sass: 1.86.1
 
 dev_dependencies:
   dartdoc: ^8.0.14