Add "CodeQL: Trim Cache" using new mode parameter of evaluation/clearCache

extensions/ql-vscode/package.json

@@ -728,6 +728,10 @@
         "command": "codeQL.clearCache",
         "title": "CodeQL: Clear Cache"
       },
+      {
+        "command": "codeQL.trimCache",
+        "title": "CodeQL: Trim Cache"
+      },
       {
         "command": "codeQL.installPackDependencies",
         "title": "CodeQL: Install Pack Dependencies"

extensions/ql-vscode/src/common/commands.ts

@@ -208,6 +208,7 @@ export type LocalDatabasesCommands = {
   "codeQL.chooseDatabaseGithub": () => Promise<void>;
   "codeQL.upgradeCurrentDatabase": () => Promise<void>;
   "codeQL.clearCache": () => Promise<void>;
+  "codeQL.trimCache": () => Promise<void>;
 
   // Explorer context menu
   "codeQL.setCurrentDatabase": (uri: Uri) => Promise<void>;

extensions/ql-vscode/src/databases/local-databases-ui.ts

@@ -251,7 +251,8 @@ export class DatabaseUI extends DisposableObject {
         this.handleSetDefaultTourDatabase.bind(this),
       "codeQL.upgradeCurrentDatabase":
         this.handleUpgradeCurrentDatabase.bind(this),
-      "codeQL.clearCache": this.handleClearCache.bind(this),
+      "codeQL.clearCache": this.handleClearCache.bind(this, "clear"),
+      "codeQL.trimCache": this.handleClearCache.bind(this, "trim"),
       "codeQLDatabases.chooseDatabaseFolder":
         this.handleChooseDatabaseFolder.bind(this),
       "codeQLDatabases.chooseDatabaseArchive":
@@ -684,7 +685,7 @@ export class DatabaseUI extends DisposableObject {
     );
   }
 
-  private async handleClearCache(): Promise<void> {
+  private async handleClearCache(mode: "trim" | "clear"): Promise<void> {
     return withProgress(
       async (_progress, token) => {
         if (
@@ -694,6 +695,7 @@ export class DatabaseUI extends DisposableObject {
           await this.queryServer.clearCacheInDatabase(
             this.databaseManager.currentDatabaseItem,
             token,
+            mode,
           );
         }
       },

extensions/ql-vscode/src/query-server/new-messages.ts

@@ -29,6 +29,35 @@ export interface ClearCacheParams {
    * Whether the cache should actually be cleared.
    */
   dryRun: boolean;
+  /**
+   * The mode to use when trimming the disk cache.
+   */
+  mode?: CacheTrimmingMode;
+}
+
+export type CacheTrimmingMode = number;
+/**
+ * The mode to use when trimming the disk cache. This namespace is intentionally not an enum, see
+ * "for the sake of extensibility" comment above.
+ */
+// eslint-disable-next-line @typescript-eslint/no-namespace
+export namespace CacheTrimmingMode {
+  /** The entire cache is deleted unconditionally. */
+  export const BRUTAL = 0;
+  /** Only `cached` predicates are kept. */
+  export const NORMAL = 1;
+  /**
+   * Trim the cache down to the configured size, but *within* this limit keep anything that
+   * appears to be even possibly potentially useful in the future.
+   */
+  export const LIGHT = 2;
+  /**
+   * As {@link LIGHT}, but only if the *currently active* backend has written anything to
+   * the cache in its lifetime. (Thus it doesn't make much sense to specify this in a stand-alone
+   * CLI invocation, but we do it as a separate operation before shutting down a query server,
+   * because it can then have its own timeout).
+   */
+  export const GENTLE = 3;
 }
 
 /**

extensions/ql-vscode/src/query-server/new-query-runner.ts

@@ -7,6 +7,7 @@ import { DatabaseItem } from "../databases/local-databases";
 import {
   clearCache,
   ClearCacheParams,
+  CacheTrimmingMode,
   clearPackCache,
   deregisterDatabases,
   registerDatabases,
@@ -57,15 +58,20 @@ export class NewQueryRunner extends QueryRunner {
   async clearCacheInDatabase(
     dbItem: DatabaseItem,
     token: CancellationToken,
+    mode: "trim" | "clear",
   ): Promise<void> {
     if (dbItem.contents === undefined) {
-      throw new Error("Can't clear the cache in an invalid database.");
+      throw new Error(`Can't ${mode} the cache in an invalid database.`);
     }
 
     const db = dbItem.databaseUri.fsPath;
     const params: ClearCacheParams = {
       dryRun: false,
       db,
+      mode: {
+        trim: CacheTrimmingMode.NORMAL,
+        clear: CacheTrimmingMode.BRUTAL,
+      }[mode],
     };
     await this.qs.sendRequest(clearCache, params, token);
   }

extensions/ql-vscode/src/query-server/query-runner.ts

@@ -65,6 +65,7 @@ export abstract class QueryRunner {
   abstract clearCacheInDatabase(
     dbItem: DatabaseItem,
     token: CancellationToken,
+    mode: "trim" | "clear",
   ): Promise<void>;
 
   /**