fix(#995): preserve relative paths in source maps

Ffloriel · Ffloriel · commit 4f6c4d994e9e · 2026-01-24T14:54:37.000+01:00
diff --git a/packages/purgecss/__tests__/sourcemap.test.ts b/packages/purgecss/__tests__/sourcemap.test.ts
@@ -23,8 +23,61 @@ describe("source map option", () => {
       },
     });
 
+    // When from and to are the same file (no explicit to), the source is just the filename
     expect(resultsPurge[0].sourceMap).toContain(
-      'sources":["__tests__/test_examples/others/remove_unused.css"]',
+      'sources":["remove_unused.css"]',
     );
+    expect(resultsPurge[0].sourceMap).toContain('"file":"remove_unused.css"');
+  });
+
+  it("uses correct file field when 'to' option is specified", async () => {
+    const resultsPurge = await new PurgeCSS().purge({
+      content: [`${ROOT_TEST_EXAMPLES}others/remove_unused.js`],
+      css: [`${ROOT_TEST_EXAMPLES}others/remove_unused.css`],
+      sourceMap: {
+        inline: false,
+        to: "output.css",
+      },
+    });
+
+    // When 'to' is specified, the file field should match
+    expect(resultsPurge[0].sourceMap).toContain('"file":"output.css"');
+  });
+
+  it("preserves relative source paths from preprocessor source maps", async () => {
+    // This test simulates a CSS file compiled from Stylus with an inline source map
+    // The source map has a relative path "../stylus/styles.styl"
+    const resultsPurge = await new PurgeCSS().purge({
+      content: [`${ROOT_TEST_EXAMPLES}sourcemap/content.html`],
+      css: [`${ROOT_TEST_EXAMPLES}sourcemap/css/styles.css`],
+      sourceMap: true,
+    });
+
+    // Decode the inline source map from the output
+    const css = resultsPurge[0].css;
+    const match = css.match(
+      /sourceMappingURL=data:application\/json;base64,([A-Za-z0-9+/=]+)/,
+    );
+    expect(match).not.toBeNull();
+
+    const sourceMap = JSON.parse(Buffer.from(match![1], "base64").toString());
+
+    // The relative path "../stylus/styles.styl" should be preserved exactly
+    expect(sourceMap.sources).toContain("../stylus/styles.styl");
+  });
+
+  it("preserves relative source paths with inline: false", async () => {
+    const resultsPurge = await new PurgeCSS().purge({
+      content: [`${ROOT_TEST_EXAMPLES}sourcemap/content.html`],
+      css: [`${ROOT_TEST_EXAMPLES}sourcemap/css/styles.css`],
+      sourceMap: {
+        inline: false,
+      },
+    });
+
+    const sourceMap = JSON.parse(resultsPurge[0].sourceMap!);
+
+    // The relative path "../stylus/styles.styl" should be preserved exactly
+    expect(sourceMap.sources).toContain("../stylus/styles.styl");
   });
 });
diff --git a/packages/purgecss/__tests__/test_examples/sourcemap/content.html b/packages/purgecss/__tests__/test_examples/sourcemap/content.html
@@ -0,0 +1,5 @@
+<html>
+<body>
+  <div class="used-class">Hello</div>
+</body>
+</html>
diff --git a/packages/purgecss/__tests__/test_examples/sourcemap/css/styles.css b/packages/purgecss/__tests__/test_examples/sourcemap/css/styles.css
diff --git a/packages/purgecss/__tests__/test_examples/sourcemap/stylus/styles.styl b/packages/purgecss/__tests__/test_examples/sourcemap/stylus/styles.styl
@@ -0,0 +1,7 @@
+$primary-color = blue
+
+.used-class
+  color: $primary-color
+
+.unused-class
+  background: red
diff --git a/packages/purgecss/src/index.ts b/packages/purgecss/src/index.ts
@@ -676,9 +676,12 @@ class PurgeCSS {
       const postCSSResult = root.toResult({
         map: this.options.sourceMap,
         to:
-          typeof this.options.sourceMap === "object"
+          typeof this.options.sourceMap === "object" &&
+          this.options.sourceMap.to
             ? this.options.sourceMap.to
-            : undefined,
+            : isFromFile
+              ? option
+              : undefined,
       });
       const result: ResultPurge = {
         css: postCSSResult.toString(),

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +<html>
 +<body>
 +  <div class="used-class">Hello</div>
 +</body>
 +</html>