Address review comments

- Tweak return types + logging
- Update changelog

extensions/ql-vscode/CHANGELOG.md

@@ -3,6 +3,7 @@
 ## [UNRELEASED]
 
 - Add a command _CodeQL: Run Query on Multiple Databases_, which lets users select multiple databases to run a query on. [#898](https://github.com/github/vscode-codeql/pull/898)
+- Autodetect what language a query targets. This refines the _CodeQL: Run Query on Multiple Databases_ command to only show relevant databases. [#915](https://github.com/github/vscode-codeql/pull/915)
 
 ## 1.5.2 - 13 July 2021
 

extensions/ql-vscode/src/extension.ts

@@ -570,11 +570,15 @@ async function activateWithInstalledDistribution(
         token: CancellationToken,
         uri: Uri | undefined
       ) => {
+        let filteredDBs = dbm.databaseItems;
+        // If possible, only show databases with the right language (otherwise show all databases).
         const queryLanguage = await findLanguage(cliServer, uri);
-        const filteredDBs = dbm.databaseItems.filter(db => db.language === queryLanguage);
-        if (filteredDBs.length === 0) {
-          void helpers.showAndLogErrorMessage(`No databases found for language ${queryLanguage}`);
-          return;
+        if (queryLanguage) {
+          filteredDBs = dbm.databaseItems.filter(db => db.language === queryLanguage);
+          if (filteredDBs.length === 0) {
+            void helpers.showAndLogErrorMessage(`No databases found for language ${queryLanguage}. Please add a suitable database to your workspace.`);
+            return;
+          }
         }
         const quickPickItems = filteredDBs.map<DatabaseQuickPickItem>(dbItem => (
           {
@@ -588,7 +592,7 @@ async function activateWithInstalledDistribution(
          */
         const quickpick = await window.showQuickPick<DatabaseQuickPickItem>(
           quickPickItems,
-          { canPickMany: true }
+          { canPickMany: true, ignoreFocusOut: true }
         );
         if (quickpick !== undefined) {
           // Collect all skipped databases and display them at the end (instead of popping up individual errors)

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

@@ -23,12 +23,14 @@ const REPO = 'qc-controller';
 export async function findLanguage(
   cliServer: cli.CodeQLCliServer,
   queryUri: Uri | undefined
-): Promise<string> {
+): Promise<string | undefined> {
   const uri = queryUri || window.activeTextEditor?.document.uri;
   if (uri !== undefined) {
     try {
       const queryInfo = await cliServer.resolveQueryByLanguage(getOnDiskWorkspaceFolders(), uri);
-      return (Object.keys(queryInfo.byLanguage))[0];
+      const language = (Object.keys(queryInfo.byLanguage))[0];
+      void logger.log(`Detected query language: ${language}`);
+      return language;
     } catch (e) {
       void logger.log('Could not autodetect query language. Select language manually.');
     }
@@ -37,8 +39,8 @@ export async function findLanguage(
   const language = await window.showQuickPick(
     availableLanguages,
     { placeHolder: 'Select target language for your query', ignoreFocusOut: true }
-  ) || '';
-  if (language === '') {
+  );
+  if (!language) {
     // This only happens if the user cancels the quick pick.
     void showAndLogErrorMessage('Language not found. Language must be specified manually.');
   }
@@ -68,6 +70,10 @@ export async function runRemoteQuery(cliServer: cli.CodeQLCliServer, credentials
   const language = config.language || await findLanguage(cliServer, uri);
   const repositories = config.repositories;
 
+  if (!language) {
+    return;
+  }
+
   try {
     await octokit.request(
       'POST /repos/:owner/:repo/code-scanning/codeql/queries',