From b3a68360a18b166bdc97d6a6a454cdd7a8191525 Mon Sep 17 00:00:00 2001
From: Pamela Lozano <pamelalozano16@gmail.com>
Date: Mon, 11 Dec 2023 16:15:35 -0800
Subject: [PATCH] Detect dependency loops in module migrator

---
 CHANGELOG.md                                  |  3 +++
 lib/src/migrators/module.dart                 | 22 +++++++++++++++++++
 pubspec.yaml                                  |  2 +-
 .../namespace_references/loop_error.hrx       | 21 ++++++++++++++++++
 4 files changed, 47 insertions(+), 1 deletion(-)
 create mode 100644 test/migrators/module/namespace_references/loop_error.hrx

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f2a876be..27bd1429 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,6 @@
+## 2.0.4
+* Detect dependency loops in module migrator fix.
+
 ## 2.0.3
 
 ### Module Migrator
diff --git a/lib/src/migrators/module.dart b/lib/src/migrators/module.dart
index e1afbf80..930f3f92 100644
--- a/lib/src/migrators/module.dart
+++ b/lib/src/migrators/module.dart
@@ -199,6 +199,21 @@ class _ModuleMigrationVisitor extends MigrationVisitor {
   /// The values of the --forward flag.
   final Set<ForwardType> forwards;
 
+  //  Maps direct and indirect dependencies to prevent any potential loops.
+  final Map<Uri, Uri> _dependencies = {};
+
+  void _addDependency(Uri source, Uri importedPath) {
+    if (_dependencies.containsKey(importedPath) &&
+        _dependencies[importedPath] == source) {
+      // Throw an error indicating a potential loop.
+      var sourceUrl = _absoluteUrlToDependency(source);
+      var importedPathUrl = _absoluteUrlToDependency(importedPath);
+      throw MigrationException(
+          'Dependency loop detected: ${sourceUrl.item1} -> ${importedPathUrl.item1}');
+    }
+    _dependencies[source] = importedPath;
+  }
+
   /// Constructs a new module migration visitor.
   ///
   /// [importCache] must be the same one used by [references].
@@ -1224,6 +1239,13 @@ class _ModuleMigrationVisitor extends MigrationVisitor {
     var url = declaration.sourceUrl;
     if (url == currentUrl) return null;
 
+    // Trace dependencies for loop detection.
+    try {
+      _addDependency(currentUrl, url);
+    } on Exception catch (e) {
+      throw MigrationSourceSpanException(e.toString(), declaration.member.span);
+    }
+
     // If we can load [declaration] from a library entrypoint URL, do so. Choose
     // the shortest one if there are multiple options.
     var libraryUrls = references.libraries[declaration];
diff --git a/pubspec.yaml b/pubspec.yaml
index df61c114..0b6ecd3e 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: sass_migrator
-version: 2.0.3
+version: 2.0.4
 description: A tool for running migrations on Sass files
 homepage: https://github.com/sass/migrator
 
diff --git a/test/migrators/module/namespace_references/loop_error.hrx b/test/migrators/module/namespace_references/loop_error.hrx
new file mode 100644
index 00000000..5895d3ff
--- /dev/null
+++ b/test/migrators/module/namespace_references/loop_error.hrx
@@ -0,0 +1,21 @@
+<==> arguments
+--migrate-deps
+
+<==> input/entrypoint.scss
+@import "ejemplo";
+$var: $value;
+
+<==> input/_ejemplo.scss
+$value: blue;
+a {
+  color: $var;
+}
+
+<==> error.txt
+Error: Error: Dependency loop detected: entrypoint -> ejemplo
+  ,
+1 | $value: blue;
+  | ^^^^^^^^^^^^
+  '
+  _ejemplo.scss 1:1  root stylesheet
+Migration failed!