Properly validate hls executables wrt ghc version

Author: hasufell

src/extension.ts

@@ -22,7 +22,7 @@ import {
 import { CommandNames } from './commands/constants';
 import { ImportIdentifier } from './commands/importIdentifier';
 import { DocsBrowser } from './docsBrowser';
-import { IEnvVars, addPathToProcessPath, downloadHaskellLanguageServer, downloadGHCup, getProjectGHCVersion } from './hlsBinaries';
+import { IEnvVars, addPathToProcessPath, downloadHaskellLanguageServer, downloadGHCup, validateHLSToolchain } from './hlsBinaries';
 import { directoryExists, executableExists, expandHomeDir, ExtensionLogger, resolvePathPlaceHolders } from './utils';
 
 
@@ -190,7 +190,7 @@ async function activateServerForFolder(context: ExtensionContext, uri: Uri, fold
       // If not, then try to download haskell-language-server binaries if it's selected
       await downloadGHCup(context, logger);
       serverExecutable = await downloadHaskellLanguageServer(context, logger);
-      await getProjectGHCVersion(serverExecutable, currentWorkingDir, logger)
+      await validateHLSToolchain(serverExecutable, currentWorkingDir, logger)
       addInternalServerPath = path.dirname(serverExecutable);
       if (!serverExecutable) {
         return;

src/hlsBinaries.ts

@@ -238,6 +238,23 @@ export async function downloadHaskellLanguageServer(context: ExtensionContext, l
     }
 }
 
+// also serves as sanity check
+export async function validateHLSToolchain(
+    wrapper: string,
+    workingDir: string,
+    logger: Logger
+): Promise<void> {
+    const ghc = await getProjectGHCVersion(wrapper, workingDir, logger);
+    const wrapperDir = path.dirname(wrapper);
+    const hlsExe = path.join(wrapperDir, `haskell-language-server-${ghc}${exeExt}`)
+    const hlsVer = await callAsync(wrapper, ["--numeric-version"], workingDir, logger);
+    if (!executableExists(hlsExe)) {
+        const msg = `Couldn't find ${hlsExe}. Your project ghc version ${ghc} may not be supported! Consider building HLS from source, e.g.: ghcup compile hls --jobs 8 --ghc ${ghc} ${hlsVer}`;
+        window.showErrorMessage(msg);
+        throw new Error(msg);
+    }
+}
+
 // also serves as sanity check
 export async function getProjectGHCVersion(
     wrapper: string,