Introduce 'haskell.toolchain' setting

README.md

@@ -105,6 +105,57 @@ or set `haskell.serverExecutablePath` (overrides all other settings) to a valid
 
 If you need to set mirrors for ghcup download info, check the settings `haskell.metadataURL` and `haskell.releasesURL`.
 
+### Setting a specific toolchain
+
+When `manageHLS` is set to `GHCup`, you can define a specific toolchain (`hls`, `ghc`, `cabal` and `stack`),
+either globally or per project. E.g.:
+
+```json
+{
+    "haskell.toolchain": {
+        "hls": "1.6.1.1",
+        "cabal": "recommended",
+        "stack": null
+    }    
+}
+```
+
+This means:
+
+1. install the `ghc` version corresponding to the project (default, because it's omitted)
+2. install `hls` 1.6.1.1
+3. install the recommended `cabal` version from ghcup
+4. don't install any `stack` version
+
+Another config could be:
+
+```json
+{
+    "haskell.toolchain": {
+        "ghc": "9.2.2",
+        "hls": "latest"
+        "cabal": "recommended"
+    }    
+}
+```
+
+Meaning:
+
+1. install `ghc` 9.2.2 regardless of what the project requires
+2. always install latest `hls`, even if it doesn't support the given GHC version
+3. install recommended `cabal`
+4. install latest `stack` (default, because it's omitted)
+
+The defaults (when omitted) are as follows:
+
+1. install the project required `ghc` (corresponding to `with-compiler` setting in `cabal.project` for example)
+2. install the latest `hls` version that supports the project required ghc version
+3. install latest `cabal`
+3. install latest `stack`
+
+When a the value is `null`, the extension will refrain from installing it.
+
+
 ### Supported GHC versions
 
 These are the versions of GHC that there are binaries of `haskell-language-server-1.6.1` for. Building from source may support more versions!

package.json

@@ -163,6 +163,12 @@
           "default": {},
           "markdownDescription": "Define environment variables for the language server."
         },
+        "haskell.promptBeforeDownloads": {
+          "scope": "machine",
+          "type": "boolean",
+          "default": "true",
+          "markdownDescription": "Prompt before performing any downloads."
+        },
         "haskell.manageHLS": {
           "scope": "resource",
           "type": "string",
@@ -177,23 +183,11 @@
             "Discovers HLS and other executables in system PATH"
           ]
         },
-        "haskell.installStack": {
-          "scope": "resource",
-          "type": "boolean",
-          "default": true,
-          "description": "Whether to also install/manage stack when 'manageHLS' is set to 'GHCup'."
-        },
-        "haskell.installCabal": {
-          "scope": "resource",
-          "type": "boolean",
-          "default": true,
-          "description": "Whether to also install/manage cabal when 'manageHLS' is set to 'GHCup'."
-        },
-        "haskell.installGHC": {
+        "haskell.toolchain": {
           "scope": "resource",
-          "type": "boolean",
-          "default": true,
-          "description": "Whether to also install/manage GHC when 'manageHLS' is set to 'GHCup'."
+          "type": "object",
+          "default": {},
+          "description": "When manageHLS is set to GHCup, this can overwrite the automatic toolchain configuration with a more specific one. When a tool is omitted, the extension will manage the version (for 'ghc' we try to figure out the version the project requires). The format is '{\"tool\": \"version\", ...}'. 'version' accepts all identifiers that 'ghcup' accepts."
         },
         "haskell.upgradeGHCup": {
           "scope": "resource",

src/extension.ts

@@ -145,11 +145,15 @@ async function activateServerForFolder(context: ExtensionContext, uri: Uri, fold
     logger.log(`  ${key}: ${value}`);
   });
 
-  let serverExecutable;
+  let serverExecutable: string;
   let addInternalServerPath: string | undefined; // if we download HLS, add that bin dir to PATH
   try {
-    serverExecutable = await findHaskellLanguageServer(context, logger, currentWorkingDir, folder);
-    addInternalServerPath = path.dirname(serverExecutable);
+    [serverExecutable, addInternalServerPath] = await findHaskellLanguageServer(
+      context,
+      logger,
+      currentWorkingDir,
+      folder
+    );
     if (!serverExecutable) {
       return;
     }