Improve startup time (#1465)

* ArchiveFileSystem: Only parse zips once

* CLIServer: Only get version once

Author: Alexander Eyers-Taylor

extensions/ql-vscode/src/archive-filesystem-provider.ts

@@ -167,21 +167,26 @@ type Archive = {
   dirMap: DirectoryHierarchyMap;
 };
 
+async function parse_zip(zipPath: string): Promise<Archive> {
+  if (!await fs.pathExists(zipPath))
+    throw vscode.FileSystemError.FileNotFound(zipPath);
+  const archive: Archive = { unzipped: await unzipper.Open.file(zipPath), dirMap: new Map };
+  archive.unzipped.files.forEach(f => { ensureFile(archive.dirMap, path.resolve('/', f.path)); });
+  return archive;
+}
+
 export class ArchiveFileSystemProvider implements vscode.FileSystemProvider {
   private readOnlyError = vscode.FileSystemError.NoPermissions('write operation attempted, but source archive filesystem is readonly');
-  private archives: Map<string, Archive> = new Map;
+  private archives: Map<string, Promise<Archive>> = new Map;
 
   private async getArchive(zipPath: string): Promise<Archive> {
     if (!this.archives.has(zipPath)) {
-      if (!await fs.pathExists(zipPath))
-        throw vscode.FileSystemError.FileNotFound(zipPath);
-      const archive: Archive = { unzipped: await unzipper.Open.file(zipPath), dirMap: new Map };
-      archive.unzipped.files.forEach(f => { ensureFile(archive.dirMap, path.resolve('/', f.path)); });
-      this.archives.set(zipPath, archive);
+      this.archives.set(zipPath, parse_zip(zipPath));
     }
-    return this.archives.get(zipPath)!;
+    return await this.archives.get(zipPath)!;
   }
 
+
   root = new Directory('');
 
   // metadata

extensions/ql-vscode/src/cli.ts

@@ -168,7 +168,7 @@ export class CodeQLCliServer implements Disposable {
   nullBuffer: Buffer;
 
   /** Version of current cli, lazily computed by the `getVersion()` method */
-  private _version: SemVer | undefined;
+  private _version: Promise<SemVer> | undefined;
 
   /**
    * The languages supported by the current version of the CLI, computed by `getSupportedLanguages()`.
@@ -985,13 +985,13 @@ export class CodeQLCliServer implements Disposable {
 
   public async getVersion() {
     if (!this._version) {
-      this._version = await this.refreshVersion();
+      this._version = this.refreshVersion();
       // this._version is only undefined upon config change, so we reset CLI-based context key only when necessary.
       await commands.executeCommand(
         'setContext', 'codeql.supportsEvalLog', await this.cliConstraints.supportsPerQueryEvalLog()
       );
     }
-    return this._version;
+    return await this._version;
   }
 
   private async refreshVersion() {