(perf) cache fileExists resolutions and path (#1325)

This make getCompletions perform many times faster, the bigger the project the more it benefits from the file exist cache. 
Computing path only once also helps a little overall as it's called quite often and url to path conversion is rather expensive.

Author: dummdidumm

packages/language-server/src/lib/documents/Document.ts

@@ -17,6 +17,11 @@ export class Document extends WritableDocument {
     configPromise: Promise<SvelteConfig | undefined>;
     config?: SvelteConfig;
     html!: HTMLDocument;
+    /**
+     * Compute and cache directly because of performance reasons
+     * and it will be called anyway.
+     */
+    private path = urlToPath(this.url);
 
     constructor(public url: string, public content: string) {
         super();
@@ -77,7 +82,7 @@ export class Document extends WritableDocument {
      * Returns the file path if the url scheme is file
      */
     getFilePath(): string | null {
-        return urlToPath(this.url);
+        return this.path;
     }
 
     /**

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

@@ -90,9 +90,14 @@ export function createSvelteModuleLoader(
         fileExists: svelteSys.fileExists,
         readFile: svelteSys.readFile,
         readDirectory: svelteSys.readDirectory,
-        deleteFromModuleCache: (path: string) => moduleCache.delete(path),
-        deleteUnresolvedResolutionsFromCache: (path: string) =>
-            moduleCache.deleteUnresolvedResolutionsFromCache(path),
+        deleteFromModuleCache: (path: string) => {
+            svelteSys.deleteFromCache(path);
+            moduleCache.delete(path);
+        },
+        deleteUnresolvedResolutionsFromCache: (path: string) => {
+            svelteSys.deleteFromCache(path);
+            moduleCache.deleteUnresolvedResolutionsFromCache(path);
+        },
         resolveModuleNames
     };
 

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

@@ -6,10 +6,15 @@ import { ensureRealSvelteFilePath, isVirtualSvelteFilePath, toRealSvelteFilePath
  * This should only be accessed by TS svelte module resolution.
  */
 export function createSvelteSys(getSnapshot: (fileName: string) => DocumentSnapshot) {
-    const svelteSys: ts.System = {
+    const fileExistsCache = new Map<string, boolean>();
+
+    const svelteSys: ts.System & { deleteFromCache: (path: string) => void } = {
         ...ts.sys,
         fileExists(path: string) {
-            return ts.sys.fileExists(ensureRealSvelteFilePath(path));
+            path = ensureRealSvelteFilePath(path);
+            const exists = fileExistsCache.get(path) ?? ts.sys.fileExists(path);
+            fileExistsCache.set(path, exists);
+            return exists;
         },
         readFile(path: string) {
             const snapshot = getSnapshot(path);
@@ -19,6 +24,13 @@ export function createSvelteSys(getSnapshot: (fileName: string) => DocumentSnaps
             const extensionsWithSvelte = (extensions ?? []).concat('.svelte');
 
             return ts.sys.readDirectory(path, extensionsWithSvelte, exclude, include, depth);
+        },
+        deleteFile(path) {
+            fileExistsCache.delete(ensureRealSvelteFilePath(path));
+            return ts.sys.deleteFile?.(path);
+        },
+        deleteFromCache(path) {
+            fileExistsCache.delete(ensureRealSvelteFilePath(path));
         }
     };