(fix) check path aliases

packages/language-server/src/plugins/typescript/module-loader.ts

@@ -67,6 +67,7 @@ export function createSvelteModuleLoader(
 ) {
     const svelteSys = createSvelteSys(getSnapshot);
     const moduleCache = new ModuleResolutionCache();
+    const pathAliases = getPathAliases(compilerOptions.paths);
 
     return {
         fileExists: svelteSys.fileExists,
@@ -98,7 +99,7 @@ export function createSvelteModuleLoader(
     ): ts.ResolvedModule | undefined {
         // In the normal case, delegate to ts.resolveModuleName.
         // In the relative-imported.svelte case, delegate to our own svelte module loader.
-        if (isAbsolute(name) || !isSvelteFilePath(name)) {
+        if (isAbsolutePath(name) || !isSvelteFilePath(name)) {
             return ts.resolveModuleName(name, containingFile, compilerOptions, ts.sys)
                 .resolvedModule;
         }
@@ -122,4 +123,17 @@ export function createSvelteModuleLoader(
         };
         return resolvedSvelteModule;
     }
+
+    function isAbsolutePath(path: string) {
+        return isAbsolute(path) && !pathAliases.some((p) => path.startsWith(p));
+    }
+
+    function getPathAliases(paths: ts.MapLike<string[]> | undefined) {
+        return Object.keys(paths || {}).map((key) => {
+            if (key.endsWith('*')) {
+                key = key.substr(0, key.length - 1);
+            }
+            return key;
+        });
+    }
 }

packages/language-server/test/plugins/typescript/module-loader.test.ts

@@ -23,7 +23,7 @@ describe('createSvelteModuleLoader', () => {
         const svelteSys = <any>'svelteSys';
         sinon.stub(svS, 'createSvelteSys').returns(svelteSys);
 
-        const compilerOptions: ts.CompilerOptions = { strict: true };
+        const compilerOptions: ts.CompilerOptions = { strict: true, paths: { '/@/*': [] } };
         const moduleResolver = createSvelteModuleLoader(getSvelteSnapshotStub, compilerOptions);
 
         return {
@@ -55,6 +55,26 @@ describe('createSvelteModuleLoader', () => {
         ]);
     });
 
+    it('uses tsSys for normal files part of TS aliases', async () => {
+        const resolvedModule: ts.ResolvedModuleFull = {
+            extension: ts.Extension.Ts,
+            resolvedFileName: 'filename.ts',
+        };
+        const { resolveStub, moduleResolver, compilerOptions } = setup(resolvedModule);
+        const result = moduleResolver.resolveModuleNames(
+            ['/@/normal'],
+            'C:/somerepo/somefile.svelte',
+        );
+
+        assert.deepStrictEqual(result, [resolvedModule]);
+        assert.deepStrictEqual(resolveStub.getCall(0).args, [
+            '/@/normal',
+            'C:/somerepo/somefile.svelte',
+            compilerOptions,
+            ts.sys,
+        ]);
+    });
+
     it('uses svelte module loader for virtual svelte files', async () => {
         const resolvedModule: ts.ResolvedModuleFull = {
             extension: ts.Extension.Ts,
@@ -87,6 +107,38 @@ describe('createSvelteModuleLoader', () => {
         assert.deepStrictEqual(getSvelteSnapshotStub.getCall(0).args, ['filename.svelte']);
     });
 
+    it('uses svelte module loader for virtual svelte files with TS path aliases', async () => {
+        const resolvedModule: ts.ResolvedModuleFull = {
+            extension: ts.Extension.Ts,
+            resolvedFileName: 'filename.svelte.ts',
+        };
+        const {
+            resolveStub,
+            svelteSys,
+            moduleResolver,
+            compilerOptions,
+            getSvelteSnapshotStub,
+        } = setup(resolvedModule);
+        const result = moduleResolver.resolveModuleNames(
+            ['/@/svelte.svelte'],
+            'C:/somerepo/somefile.svelte',
+        );
+
+        assert.deepStrictEqual(result, [
+            <ts.ResolvedModuleFull>{
+                extension: ts.Extension.Jsx,
+                resolvedFileName: 'filename.svelte',
+            },
+        ]);
+        assert.deepStrictEqual(resolveStub.getCall(0).args, [
+            '/@/svelte.svelte',
+            'C:/somerepo/somefile.svelte',
+            compilerOptions,
+            svelteSys,
+        ]);
+        assert.deepStrictEqual(getSvelteSnapshotStub.getCall(0).args, ['filename.svelte']);
+    });
+
     it('uses cache if module was already resolved before', async () => {
         const resolvedModule: ts.ResolvedModuleFull = {
             extension: ts.Extension.Ts,