(feat) resolve svelte.d.ts files first (#885)

Files ending with .svelte.d.ts are now resolved prior to a same file ending with .svelte . This enables library authors to ship type definitions of Svelte files next to their implementation.
#878

Author: dummdidumm

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

@@ -2,10 +2,8 @@ import ts from 'typescript';
 import {
     isVirtualSvelteFilePath,
     ensureRealSvelteFilePath,
-    isSvelteFilePath,
     getExtensionFromScriptKind
 } from './utils';
-import { isAbsolute } from 'path';
 import { DocumentSnapshot } from './DocumentSnapshot';
 import { createSvelteSys } from './svelte-sys';
 
@@ -67,7 +65,6 @@ export function createSvelteModuleLoader(
 ) {
     const svelteSys = createSvelteSys(getSnapshot);
     const moduleCache = new ModuleResolutionCache();
-    const pathAliases = getPathAliases(compilerOptions.paths);
 
     return {
         fileExists: svelteSys.fileExists,
@@ -97,24 +94,29 @@ export function createSvelteModuleLoader(
         name: string,
         containingFile: string
     ): 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 (isAbsolutePath(name) || !isSvelteFilePath(name)) {
-            return ts.resolveModuleName(name, containingFile, compilerOptions, ts.sys)
-                .resolvedModule;
+        // Delegate to the TS resolver first.
+        // If that does not bring up anything, try the Svelte Module loader
+        // which is able to deal with .svelte files.
+        const tsResolvedModule = ts.resolveModuleName(name, containingFile, compilerOptions, ts.sys)
+            .resolvedModule;
+        if (tsResolvedModule && !isVirtualSvelteFilePath(tsResolvedModule.resolvedFileName)) {
+            return tsResolvedModule;
         }
 
-        const tsResolvedModule = ts.resolveModuleName(
+        const svelteResolvedModule = ts.resolveModuleName(
             name,
             containingFile,
             compilerOptions,
             svelteSys
         ).resolvedModule;
-        if (!tsResolvedModule || !isVirtualSvelteFilePath(tsResolvedModule.resolvedFileName)) {
-            return tsResolvedModule;
+        if (
+            !svelteResolvedModule ||
+            !isVirtualSvelteFilePath(svelteResolvedModule.resolvedFileName)
+        ) {
+            return svelteResolvedModule;
         }
 
-        const resolvedFileName = ensureRealSvelteFilePath(tsResolvedModule.resolvedFileName);
+        const resolvedFileName = ensureRealSvelteFilePath(svelteResolvedModule.resolvedFileName);
         const snapshot = getSnapshot(resolvedFileName);
 
         const resolvedSvelteModule: ts.ResolvedModuleFull = {
@@ -123,17 +125,4 @@ 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

@@ -35,6 +35,10 @@ describe('createSvelteModuleLoader', () => {
         };
     }
 
+    function lastCall(stub: sinon.SinonStub<any[], any>) {
+        return stub.getCall(stub.getCalls().length - 1);
+    }
+
     it('uses tsSys for normal files', async () => {
         const resolvedModule: ts.ResolvedModuleFull = {
             extension: ts.Extension.Ts,
@@ -47,7 +51,7 @@ describe('createSvelteModuleLoader', () => {
         );
 
         assert.deepStrictEqual(result, [resolvedModule]);
-        assert.deepStrictEqual(resolveStub.getCall(0).args, [
+        assert.deepStrictEqual(lastCall(resolveStub).args, [
             './normal.ts',
             'C:/somerepo/somefile.svelte',
             compilerOptions,
@@ -67,14 +71,34 @@ describe('createSvelteModuleLoader', () => {
         );
 
         assert.deepStrictEqual(result, [resolvedModule]);
-        assert.deepStrictEqual(resolveStub.getCall(0).args, [
+        assert.deepStrictEqual(lastCall(resolveStub).args, [
             '/@/normal',
             'C:/somerepo/somefile.svelte',
             compilerOptions,
             ts.sys
         ]);
     });
 
+    it('uses tsSys for svelte.d.ts files', async () => {
+        const resolvedModule: ts.ResolvedModuleFull = {
+            extension: ts.Extension.Dts,
+            resolvedFileName: 'filename.d.ts'
+        };
+        const { resolveStub, moduleResolver, compilerOptions } = setup(resolvedModule);
+        const result = moduleResolver.resolveModuleNames(
+            ['./normal.ts'],
+            'C:/somerepo/somefile.svelte'
+        );
+
+        assert.deepStrictEqual(result, [resolvedModule]);
+        assert.deepStrictEqual(lastCall(resolveStub).args, [
+            './normal.ts',
+            '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,
@@ -98,13 +122,13 @@ describe('createSvelteModuleLoader', () => {
                 resolvedFileName: 'filename.svelte'
             }
         ]);
-        assert.deepStrictEqual(resolveStub.getCall(0).args, [
+        assert.deepStrictEqual(lastCall(resolveStub).args, [
             './svelte.svelte',
             'C:/somerepo/somefile.svelte',
             compilerOptions,
             svelteSys
         ]);
-        assert.deepStrictEqual(getSvelteSnapshotStub.getCall(0).args, ['filename.svelte']);
+        assert.deepStrictEqual(lastCall(getSvelteSnapshotStub).args, ['filename.svelte']);
     });
 
     it('uses svelte module loader for virtual svelte files with TS path aliases', async () => {
@@ -130,13 +154,13 @@ describe('createSvelteModuleLoader', () => {
                 resolvedFileName: 'filename.svelte'
             }
         ]);
-        assert.deepStrictEqual(resolveStub.getCall(0).args, [
+        assert.deepStrictEqual(lastCall(resolveStub).args, [
             '/@/svelte.svelte',
             'C:/somerepo/somefile.svelte',
             compilerOptions,
             svelteSys
         ]);
-        assert.deepStrictEqual(getSvelteSnapshotStub.getCall(0).args, ['filename.svelte']);
+        assert.deepStrictEqual(lastCall(getSvelteSnapshotStub).args, ['filename.svelte']);
     });
 
     it('uses cache if module was already resolved before', async () => {