use .d.svelte.ts for intercepting svelte files, which allows us to make ./foo.svelte make .svelte query before .svelte.ts

Author: dummdidumm

packages/language-server/package.json

@@ -10,7 +10,7 @@
         "./bin/server.js": "./bin/server.js"
     },
     "scripts": {
-        "test": "cross-env TS_NODE_TRANSPILE_ONLY=true mocha --require ts-node/register \"test/**/*.ts\" --exclude \"test/**/*.d.ts\"",
+        "test": "cross-env TS_NODE_TRANSPILE_ONLY=true mocha --require ts-node/register \"test/**/*.test.ts\"",
         "build": "tsc",
         "prepublishOnly": "npm run build",
         "watch": "tsc -w"

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

@@ -108,9 +108,6 @@ class ImpliedNodeFormatResolver {
         if (sourceFile) {
             this.cacheImpliedNodeFormat(sourceFile, compilerOptions);
             mode = ts.getModeForResolutionAtIndex(sourceFile, importIdxInFile, compilerOptions);
-            if (!mode && isSvelteFilePath(importPath)) {
-                mode = ts.ModuleKind.ESNext; // necessary for TS' module resolution to go into the right branches
-            }
         }
         return mode;
     }

packages/language-server/src/plugins/typescript/svelte-sys.ts

@@ -11,6 +11,17 @@ export function createSvelteSys(tsSystem: ts.System) {
     function svelteFileExists(path: string) {
         if (isVirtualSvelteFilePath(path)) {
             const sveltePath = toRealSvelteFilePath(path);
+
+            // First check if there's a `.svelte.d.ts` or `.d.svelte.ts` file, which should take precedence
+            const dtsPath = sveltePath.slice(0, -7) + '.svelte.d.ts';
+            const dtsPathExists = fileExistsCache.get(dtsPath) ?? tsSystem.fileExists(dtsPath);
+            fileExistsCache.set(dtsPath, dtsPathExists);
+            if (dtsPathExists) return false;
+
+            const svelteDtsPathExists = fileExistsCache.get(path) ?? tsSystem.fileExists(path);
+            fileExistsCache.set(path, svelteDtsPathExists);
+            if (svelteDtsPathExists) return false;
+
             const sveltePathExists =
                 fileExistsCache.get(sveltePath) ?? tsSystem.fileExists(sveltePath);
             fileExistsCache.set(sveltePath, sveltePathExists);
@@ -33,10 +44,11 @@ export function createSvelteSys(tsSystem: ts.System) {
         svelteFileExists,
         getRealSveltePathIfExists,
         fileExists(path: string) {
-            // We need to check both .svelte and .svelte.ts/js because that's how Svelte 5 will likely mark files with runes in them
+            // We need to check if this is a virtual svelte file
             const sveltePathExists = svelteFileExists(path);
-            const exists =
-                sveltePathExists || (fileExistsCache.get(path) ?? tsSystem.fileExists(path));
+            if (sveltePathExists) return true;
+
+            const exists = fileExistsCache.get(path) ?? tsSystem.fileExists(path);
             fileExistsCache.set(path, exists);
             return exists;
         },
@@ -66,7 +78,7 @@ export function createSvelteSys(tsSystem: ts.System) {
         const realpath = tsSystem.realpath;
         svelteSys.realpath = function (path) {
             if (svelteFileExists(path)) {
-                return realpath(toRealSvelteFilePath(path)) + '.ts';
+                return realpath(toRealSvelteFilePath(path));
             }
             return realpath(path);
         };

packages/language-server/src/plugins/typescript/utils.ts

@@ -70,21 +70,17 @@ export function isSvelteFilePath(filePath: string) {
 }
 
 export function isVirtualSvelteFilePath(filePath: string) {
-    return filePath.endsWith('.svelte.ts');
+    return filePath.endsWith('.d.svelte.ts');
 }
 
 export function toRealSvelteFilePath(filePath: string) {
-    filePath = filePath.slice(0, -'.ts'.length);
-    // When a .svelte file referenced inside an exports map of a package.json is tried to be resolved,
-    // TypeScript will probe for the file with a .d.svelte.ts extension.
-    if (filePath.endsWith('.d.svelte')) {
-        filePath = filePath.slice(0, -8) + 'svelte';
-    }
-    return filePath;
+    return filePath.slice(0, -11 /* 'd.svelte.ts'.length */) + 'svelte';
 }
 
-export function toVirtualSvelteFilePath(filePath: string) {
-    return filePath.endsWith('.ts') ? filePath : filePath + '.ts';
+export function toVirtualSvelteFilePath(svelteFilePath: string) {
+    return isVirtualSvelteFilePath(svelteFilePath)
+        ? svelteFilePath
+        : svelteFilePath.slice(0, -6 /* 'svelte'.length */) + 'd.svelte.ts';
 }
 
 export function ensureRealSvelteFilePath(filePath: string) {

packages/language-server/test/plugins/typescript/features/diagnostics/fixtures/import-precedence/a.svelte

@@ -0,0 +1,3 @@
+<script>
+    export let foo = true;
+</script>

packages/language-server/test/plugins/typescript/features/diagnostics/fixtures/import-precedence/a.svelte.d.ts

@@ -0,0 +1 @@
+export declare const a: boolean;

packages/language-server/test/plugins/typescript/features/diagnostics/fixtures/import-precedence/b.svelte

@@ -0,0 +1,3 @@
+<script>
+    export let foo = true;
+</script>

packages/language-server/test/plugins/typescript/features/diagnostics/fixtures/import-precedence/b.svelte.ts

@@ -0,0 +1 @@
+export const b = true;

packages/language-server/test/plugins/typescript/features/diagnostics/fixtures/import-precedence/c.d.svelte.ts

@@ -0,0 +1 @@
+export declare const c: boolean;

packages/language-server/test/plugins/typescript/features/diagnostics/fixtures/import-precedence/c.svelte

@@ -0,0 +1,3 @@
+<script>
+    export let foo = true;
+</script>