SCSS: resolve bare module imports on Windows (the sequel)

src/services/cssNavigation.ts

@@ -416,8 +416,8 @@ 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';"
 				}
 			}
 		}
@@ -439,7 +439,18 @@ 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
+		if (this.resolveModuleReferences && importIsBare(target)) {
+			const resolvedModuleRef = await this.resolveModuleReference(target, documentUri, documentContext);
+			const moduleRef = await this.mapReference(resolvedModuleRef, isRawLink);
+
+			if (moduleRef != null) {
+				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)
@@ -590,6 +601,12 @@ function toTwoDigitHex(n: number): string {
 	return r.length !== 2 ? '0' + r : r;
 }
 
+function importIsBare(target: string): boolean {
+	return !target.startsWith('.')              // not ./ or ../
+		&& !target.startsWith('/')              // not workspace-absolute
+		&& !startsWithSchemeRegex.test(target); // not a scheme (file://, http://, etc.)
+}
+
 export function getModuleNameFromPath(path: string) {
 	const firstSlash = path.indexOf('/');
 	if (firstSlash === -1) {

src/test/scss/scssNavigation.test.ts

@@ -6,7 +6,7 @@
 
 import * as nodes from '../../parser/cssNodes';
 import { assertSymbolsInScope, assertScopesAndSymbols, assertHighlights, assertColorSymbols, assertLinks, newRange, getTestResource, assertDocumentSymbols } from '../css/navigation.test';
-import { getSCSSLanguageService, DocumentLink, TextDocument, SymbolKind, LanguageSettings } from '../../cssLanguageService';
+import { getSCSSLanguageService, DocumentLink, TextDocument, SymbolKind, LanguageSettings, DocumentContext } from '../../cssLanguageService';
 import * as assert from 'assert';
 import * as path from 'path';
 import { URI } from 'vscode-uri';
@@ -20,11 +20,11 @@ function getSCSSLS() {
 function aliasSettings(): LanguageSettings {
 	return {
 		"importAliases": {
-				"@SassStylesheet": "/src/assets/styles.scss",
-				"@NoUnderscoreDir/": "/noUnderscore/",
-				"@UnderscoreDir/": "/underscore/",
-				"@BothDir/": "/both/",
-			}
+			"@SassStylesheet": "/src/assets/styles.scss",
+			"@NoUnderscoreDir/": "/noUnderscore/",
+			"@UnderscoreDir/": "/underscore/",
+			"@BothDir/": "/both/",
+		}
 	};
 }
 
@@ -57,6 +57,21 @@ async function assertNoDynamicLinks(docUri: string, input: string, extecedTarget
 
 }
 
+function createDocument(contents: string, uri = 'file:///test.scss') {
+	return TextDocument.create(uri, 'scss', 0, contents);
+}
+
+const dummyContext: DocumentContext = {
+	resolveReference: (ref: string, _base: string) => ref
+};
+
+async function getLinks(contents: string) {
+	const ls = getSCSSLS();
+	const doc = createDocument(contents);
+	const stylesheet = ls.parseStylesheet(doc);
+	return ls.findDocumentLinks2(doc, stylesheet, dummyContext);
+}
+
 suite('SCSS - Navigation', () => {
 
 	suite('Scopes and Symbols', () => {
@@ -353,4 +368,42 @@ suite('SCSS - Navigation', () => {
 		});
 	});
 
+	suite('URL Scheme Imports', () => {
+
+		test('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');
+		});
+
+		test('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');
+		});
+
+		test('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');
+		});
+
+		test('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');
+		});
+	});
+
+	suite('Bare Imports', () => {
+
+		test('resolves bare import path on Windows', async () => {
+			const ls = getSCSSLS();
+
+			const doc = TextDocument.create('file:///c:/proj/app.scss', 'scss', 1, "@import 'bootstrap/scss/variables';");
+			const links = await ls.findDocumentLinks2(doc, ls.parseStylesheet(doc), getDocumentContext('c:/proj'));
+			const expected = URI.file('c:/proj/node_modules/bootstrap/scss/_variables.scss').toString();
+			assert.strictEqual(links[0].target, expected);
+		});
+	});
 });