Use QueryLanguage type for representing query languages

This will make both the `askForLanguage` and `findLanguage` functions
return a `QueryLanguage` instead of a `string`. This will make it harder
to make mistakes when using these functions.

There are also some other changes with regards to `QueryLanguage` such
that we never need to use `as QueryLanguage` explicitly anymore, except
for the new `isQueryLanguage` function. The only remaining place that I
know of where we're using a `string` to represent the `QueryLanguage`
is in a database item's language, but this is harder to change and may
be relied upon by language authors.

extensions/ql-vscode/src/data-extensions-editor/external-api-usage-query.ts

@@ -4,6 +4,7 @@ import { writeFile } from "fs-extra";
 import { dump as dumpYaml } from "js-yaml";
 import {
   getOnDiskWorkspaceFolders,
+  isQueryLanguage,
   showAndLogExceptionWithTelemetry,
 } from "../helpers";
 import { TeeLogger } from "../common";
@@ -15,7 +16,6 @@ import { fetchExternalApiQueries } from "./queries";
 import { QueryResultType } from "../pure/new-messages";
 import { join } from "path";
 import { redactableError } from "../pure/errors";
-import { QueryLanguage } from "../common/query-language";
 
 export type RunQueryOptions = {
   cliServer: Pick<CodeQLCliServer, "resolveQlpacks">;
@@ -41,7 +41,14 @@ export async function runQuery({
   // For a reference of what this should do in the future, see the previous implementation in
   // https://github.com/github/vscode-codeql/blob/089d3566ef0bc67d9b7cc66e8fd6740b31c1c0b0/extensions/ql-vscode/src/data-extensions-editor/external-api-usage-query.ts#L33-L72
 
-  const query = fetchExternalApiQueries[databaseItem.language as QueryLanguage];
+  if (!isQueryLanguage(databaseItem.language)) {
+    void showAndLogExceptionWithTelemetry(
+      redactableError`Unsupported database language ${databaseItem.language}`,
+    );
+    return;
+  }
+
+  const query = fetchExternalApiQueries[databaseItem.language];
   if (!query) {
     void showAndLogExceptionWithTelemetry(
       redactableError`No external API usage query found for language ${databaseItem.language}`,

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

@@ -12,6 +12,7 @@ import {
   isFolderAlreadyInWorkspace,
   getFirstWorkspaceFolder,
   showNeverAskAgainDialog,
+  isQueryLanguage,
 } from "../helpers";
 import { ProgressCallback, withProgress } from "../common/vscode/progress";
 import {
@@ -32,7 +33,6 @@ import {
   setAutogenerateQlPacks,
 } from "../config";
 import { QlPackGenerator } from "../qlpack-generator";
-import { QueryLanguage } from "../common/query-language";
 import { App } from "../common/app";
 import { existsSync } from "fs";
 
@@ -739,6 +739,13 @@ export class DatabaseManager extends DisposableObject {
       return;
     }
 
+    if (!isQueryLanguage(databaseItem.language)) {
+      void this.logger.log(
+        "Could not create skeleton QL pack because the selected database's language is not supported.",
+      );
+      return;
+    }
+
     const firstWorkspaceFolder = getFirstWorkspaceFolder();
     const folderName = `codeql-custom-queries-${databaseItem.language}`;
 
@@ -769,7 +776,7 @@ export class DatabaseManager extends DisposableObject {
     try {
       const qlPackGenerator = new QlPackGenerator(
         folderName,
-        databaseItem.language as QueryLanguage,
+        databaseItem.language,
         this.cli,
         firstWorkspaceFolder,
       );

extensions/ql-vscode/src/helpers.ts

@@ -25,7 +25,7 @@ import { QueryMetadata } from "./pure/interface-types";
 import { telemetryListener } from "./telemetry";
 import { RedactableError } from "./pure/errors";
 import { getQlPackPath } from "./pure/ql";
-import { dbSchemeToLanguage } from "./common/query-language";
+import { dbSchemeToLanguage, QueryLanguage } from "./common/query-language";
 import { isCodespacesTemplate } from "./config";
 import { AppCommandManager } from "./common/commands";
 
@@ -726,6 +726,10 @@ export async function isLikelyDbLanguageFolder(dbPath: string) {
   );
 }
 
+export function isQueryLanguage(language: string): language is QueryLanguage {
+  return Object.values(QueryLanguage).includes(language as QueryLanguage);
+}
+
 /**
  * Finds the language that a query targets.
  * If it can't be autodetected, prompt the user to specify the language manually.
@@ -733,7 +737,7 @@ export async function isLikelyDbLanguageFolder(dbPath: string) {
 export async function findLanguage(
   cliServer: CodeQLCliServer,
   queryUri: Uri | undefined,
-): Promise<string | undefined> {
+): Promise<QueryLanguage | undefined> {
   const uri = queryUri || Window.activeTextEditor?.document.uri;
   if (uri !== undefined) {
     try {
@@ -743,7 +747,14 @@ export async function findLanguage(
       );
       const language = Object.keys(queryInfo.byLanguage)[0];
       void extLogger.log(`Detected query language: ${language}`);
-      return language;
+
+      if (isQueryLanguage(language)) {
+        return language;
+      }
+
+      void extLogger.log(
+        "Query language is unsupported. Select language manually.",
+      );
     } catch (e) {
       void extLogger.log(
         "Could not autodetect query language. Select language manually.",
@@ -758,7 +769,7 @@ export async function findLanguage(
 export async function askForLanguage(
   cliServer: CodeQLCliServer,
   throwOnEmpty = true,
-): Promise<string | undefined> {
+): Promise<QueryLanguage | undefined> {
   const language = await Window.showQuickPick(
     await cliServer.getSupportedLanguages(),
     {
@@ -775,7 +786,16 @@ export async function askForLanguage(
         "Language not found. Language must be specified manually.",
       );
     }
+    return undefined;
   }
+
+  if (!isQueryLanguage(language)) {
+    void showAndLogErrorMessage(
+      `Language '${language}' is not supported. Language must be specified manually.`,
+    );
+    return undefined;
+  }
+
   return language;
 }
 

extensions/ql-vscode/src/skeleton-query-wizard.ts

@@ -41,7 +41,7 @@ export const QUERY_LANGUAGE_TO_DATABASE_REPO: QueryLanguagesToDatabaseMap = {
 };
 
 export class SkeletonQueryWizard {
-  private language: string | undefined;
+  private language: QueryLanguage | undefined;
   private fileName = "example.ql";
   private qlPackStoragePath: string | undefined;
 
@@ -154,6 +154,9 @@ export class SkeletonQueryWizard {
     if (this.folderName === undefined) {
       throw new Error("Folder name is undefined");
     }
+    if (this.language === undefined) {
+      throw new Error("Language is undefined");
+    }
 
     this.progress({
       message: "Creating skeleton QL pack around query",
@@ -164,7 +167,7 @@ export class SkeletonQueryWizard {
     try {
       const qlPackGenerator = new QlPackGenerator(
         this.folderName,
-        this.language as QueryLanguage,
+        this.language,
         this.cliServer,
         this.qlPackStoragePath,
       );
@@ -181,6 +184,9 @@ export class SkeletonQueryWizard {
     if (this.folderName === undefined) {
       throw new Error("Folder name is undefined");
     }
+    if (this.language === undefined) {
+      throw new Error("Language is undefined");
+    }
 
     this.progress({
       message:
@@ -192,7 +198,7 @@ export class SkeletonQueryWizard {
     try {
       const qlPackGenerator = new QlPackGenerator(
         this.folderName,
-        this.language as QueryLanguage,
+        this.language,
         this.cliServer,
         this.qlPackStoragePath,
       );

extensions/ql-vscode/src/variant-analysis/run-remote-query.ts

@@ -39,6 +39,7 @@ import {
   QLPACK_FILENAMES,
   QLPACK_LOCK_FILENAMES,
 } from "../pure/ql";
+import { QueryLanguage } from "../common/query-language";
 
 export interface QlPack {
   name: string;
@@ -76,7 +77,7 @@ async function generateQueryPack(
   const targetQueryFileName = join(queryPackDir, packRelativePath);
   const workspaceFolders = getOnDiskWorkspaceFolders();
 
-  let language: string | undefined;
+  let language: QueryLanguage | undefined;
 
   // Check if the query is already in a query pack.
   // If so, copy the entire query pack to the temporary directory.