Move CachedOperation to a new file

extensions/ql-vscode/src/helpers.ts

@@ -584,77 +584,6 @@ export async function getPrimaryDbscheme(
   return dbscheme;
 }
 
-/**
- * A cached mapping from strings to value of type U.
- */
-export class CachedOperation<U> {
-  private readonly operation: (t: string, ...args: any[]) => Promise<U>;
-  private readonly cached: Map<string, U>;
-  private readonly lru: string[];
-  private readonly inProgressCallbacks: Map<
-    string,
-    Array<[(u: U) => void, (reason?: any) => void]>
-  >;
-
-  constructor(
-    operation: (t: string, ...args: any[]) => Promise<U>,
-    private cacheSize = 100,
-  ) {
-    this.operation = operation;
-    this.lru = [];
-    this.inProgressCallbacks = new Map<
-      string,
-      Array<[(u: U) => void, (reason?: any) => void]>
-    >();
-    this.cached = new Map<string, U>();
-  }
-
-  async get(t: string, ...args: any[]): Promise<U> {
-    // Try and retrieve from the cache
-    const fromCache = this.cached.get(t);
-    if (fromCache !== undefined) {
-      // Move to end of lru list
-      this.lru.push(
-        this.lru.splice(
-          this.lru.findIndex((v) => v === t),
-          1,
-        )[0],
-      );
-      return fromCache;
-    }
-    // Otherwise check if in progress
-    const inProgressCallback = this.inProgressCallbacks.get(t);
-    if (inProgressCallback !== undefined) {
-      // If so wait for it to resolve
-      return await new Promise((resolve, reject) => {
-        inProgressCallback.push([resolve, reject]);
-      });
-    }
-
-    // Otherwise compute the new value, but leave a callback to allow sharing work
-    const callbacks: Array<[(u: U) => void, (reason?: any) => void]> = [];
-    this.inProgressCallbacks.set(t, callbacks);
-    try {
-      const result = await this.operation(t, ...args);
-      callbacks.forEach((f) => f[0](result));
-      this.inProgressCallbacks.delete(t);
-      if (this.lru.length > this.cacheSize) {
-        const toRemove = this.lru.shift()!;
-        this.cached.delete(toRemove);
-      }
-      this.lru.push(t);
-      this.cached.set(t, result);
-      return result;
-    } catch (e) {
-      // Rethrow error on all callbacks
-      callbacks.forEach((f) => f[1](e));
-      throw e;
-    } finally {
-      this.inProgressCallbacks.delete(t);
-    }
-  }
-}
-
 /**
  * The following functions al heuristically determine metadata about databases.
  */

extensions/ql-vscode/src/language-support/contextual/template-provider.ts

@@ -17,7 +17,7 @@ import {
 } from "../../common/vscode/archive-filesystem-provider";
 import { CodeQLCliServer } from "../../codeql-cli/cli";
 import { DatabaseManager } from "../../databases/local-databases";
-import { CachedOperation } from "../../helpers";
+import { CachedOperation } from "../../pure/cached-operation";
 import { ProgressCallback, withProgress } from "../../common/vscode/progress";
 import { KeyType } from "./key-type";
 import {

extensions/ql-vscode/src/pure/cached-operation.ts

@@ -0,0 +1,70 @@
+/**
+ * A cached mapping from strings to value of type U.
+ */
+export class CachedOperation<U> {
+  private readonly operation: (t: string, ...args: any[]) => Promise<U>;
+  private readonly cached: Map<string, U>;
+  private readonly lru: string[];
+  private readonly inProgressCallbacks: Map<
+    string,
+    Array<[(u: U) => void, (reason?: any) => void]>
+  >;
+
+  constructor(
+    operation: (t: string, ...args: any[]) => Promise<U>,
+    private cacheSize = 100,
+  ) {
+    this.operation = operation;
+    this.lru = [];
+    this.inProgressCallbacks = new Map<
+      string,
+      Array<[(u: U) => void, (reason?: any) => void]>
+    >();
+    this.cached = new Map<string, U>();
+  }
+
+  async get(t: string, ...args: any[]): Promise<U> {
+    // Try and retrieve from the cache
+    const fromCache = this.cached.get(t);
+    if (fromCache !== undefined) {
+      // Move to end of lru list
+      this.lru.push(
+        this.lru.splice(
+          this.lru.findIndex((v) => v === t),
+          1,
+        )[0],
+      );
+      return fromCache;
+    }
+    // Otherwise check if in progress
+    const inProgressCallback = this.inProgressCallbacks.get(t);
+    if (inProgressCallback !== undefined) {
+      // If so wait for it to resolve
+      return await new Promise((resolve, reject) => {
+        inProgressCallback.push([resolve, reject]);
+      });
+    }
+
+    // Otherwise compute the new value, but leave a callback to allow sharing work
+    const callbacks: Array<[(u: U) => void, (reason?: any) => void]> = [];
+    this.inProgressCallbacks.set(t, callbacks);
+    try {
+      const result = await this.operation(t, ...args);
+      callbacks.forEach((f) => f[0](result));
+      this.inProgressCallbacks.delete(t);
+      if (this.lru.length > this.cacheSize) {
+        const toRemove = this.lru.shift()!;
+        this.cached.delete(toRemove);
+      }
+      this.lru.push(t);
+      this.cached.set(t, result);
+      return result;
+    } catch (e) {
+      // Rethrow error on all callbacks
+      callbacks.forEach((f) => f[1](e));
+      throw e;
+    } finally {
+      this.inProgressCallbacks.delete(t);
+    }
+  }
+}