SCSS: resolve bare module imports on Windows (#245579)

src/services/cssNavigation.ts

@@ -399,8 +399,8 @@ export class CSSNavigation {
 				const documentFolderUri = dirname(documentUri);
 				const modulePath = await this.resolvePathToModule(moduleName, documentFolderUri, rootFolderUri);
 				if (modulePath) {
-					const pathWithinModule = ref.substring(moduleName.length + 1);
-					return joinPath(modulePath, pathWithinModule);
+					const remainder = ref.length > moduleName.length ? ref.slice(moduleName.length + 1) : ''; // skip the '/', bare import
+					return remainder ? joinPath(modulePath, remainder) : modulePath; // e.g. "@import 'bootstrap';"
 				}
 			}
 		}
@@ -422,7 +422,22 @@ export class CSSNavigation {
 			return this.mapReference(await this.resolveModuleReference(target, documentUri, documentContext), isRawLink);
 		}
 
-		const ref = await this.mapReference(documentContext.resolveReference(target, documentUri), isRawLink);
+		// Treat bare module names (“bootstrap/...”) like sass-loader does
+		const startsWithSchemeRegex = /^\w[\w\d+.-]:/;
+
+		const isBareImport = !target.startsWith('.')              // not ./ or ../
+		                  && !target.startsWith('/')              // not workspace-absolute
+		                  && !startsWithSchemeRegex.test(target); // not a scheme (file://, http://, etc.)
+
+		if (isBareImport) {
+		  const moduleRef = await this.mapReference(
+		        await this.resolveModuleReference(target, documentUri, documentContext),
+		        isRawLink);
+		  if (moduleRef) { return moduleRef; }
+		}
+
+		const ref = await this.mapReference(
+		        documentContext.resolveReference(target, documentUri), isRawLink);
 
 		// Following [less-loader](https://github.com/webpack-contrib/less-loader#imports)
 		// and [sass-loader's](https://github.com/webpack-contrib/sass-loader#resolving-import-at-rules)
@@ -589,4 +604,4 @@ export function getModuleNameFromPath(path: string) {
 	}
 	// Otherwise get until first instance of '/'
 	return path.substring(0, firstSlash);
-}
+}

src/test/scss/schemeImportLinks.test.ts

@@ -0,0 +1,46 @@
+import * as assert from 'assert';
+import { getSCSSLanguageService } from '../../scssLanguageService';
+import { TextDocument } from 'vscode-languageserver-textdocument';
+import { DocumentContext } from '../../cssLanguageTypes';
+
+function createDocument(contents: string, uri = 'file:///test.scss') {
+  return TextDocument.create(uri, 'scss', 0, contents);
+}
+
+const dummyContext: DocumentContext = {
+  resolveReference: (ref: string, _base: string) => ref
+};
+
+const ls = getSCSSLanguageService();
+
+async function getLinks(contents: string) {
+  const doc = createDocument(contents);
+  const stylesheet = ls.parseStylesheet(doc);
+  return ls.findDocumentLinks2(doc, stylesheet, dummyContext);
+}
+
+describe('SCSS Navigation – scheme URL imports', () => {
+  it('http scheme import is treated as absolute URL, not bare import', async () => {
+    const links = await getLinks(`@import "http://example.com/foo.css";`);
+    assert.strictEqual(links.length, 1);
+    assert.strictEqual(links[0].target, 'http://example.com/foo.css');
+  });
+
+  it('https scheme import is treated as absolute URL, not bare import', async () => {
+    const links = await getLinks(`@import "https://cdn.example.com/reset.css";`);
+    assert.strictEqual(links.length, 1);
+    assert.strictEqual(links[0].target, 'https://cdn.example.com/reset.css');
+  });
+
+  it('file scheme import is treated as absolute URL, not bare import', async () => {
+    const links = await getLinks(`@import "file:///Users/test/project/styles/base.scss";`);
+    assert.strictEqual(links.length, 1);
+    assert.strictEqual(links[0].target, 'file:///Users/test/project/styles/base.scss');
+  });
+
+  it('custom scheme import (vscode-resource) is treated as absolute URL, not bare import', async () => {
+    const links = await getLinks(`@import "vscode-resource://file/some.css";`);
+    assert.strictEqual(links.length, 1);
+    assert.strictEqual(links[0].target, 'vscode-resource://file/some.css');
+  });
+});

src/test/scss/scssNavigation-node-modules.test.ts

@@ -0,0 +1,18 @@
+import { assert } from 'chai';
+import { getSCSSLanguageService } from '../../cssLanguageService';
+import { TextDocument } from 'vscode-languageserver-textdocument';
+import { FileType, getNodeFSRequestService } from '../../nodeFs';
+import { URI } from 'vscode-uri'; 
+
+const ls = getSCSSLanguageService();
+const mockFS = getNodeFSRequestService();
+
+describe('SCSS link navigation – node_modules', () => {
+  it('resolves bootstrap path on Windows', async () => {
+    const doc = TextDocument.create('file:///c:/proj/app.scss', 'scss', 1,
+        "@import 'bootstrap/scss/variables';");
+    const links = await ls.findDocumentLinks2(doc, ls.parseStylesheet(doc), {}, mockFS);
+    const expected = URI.file('c:/proj/node_modules/bootstrap/scss/_variables.scss').toString();
+    assert.strictEqual(links[0].target, expected);       
+  });
+});