Remove LegacyHackTypeChecker and supporting code (#181)

`hh_client` has provided an LSP server since HHVM 3.23.
There is thus no need to keep around `LegacyHackTypeChecker`
and supporting code. Let's remove it.

Author: mszabo-wikia

CLAUDE.md

@@ -20,11 +20,8 @@ To debug the extension in VS Code, use the "Run Extension" launch configuration
 
 The extension activates when a workspace contains a `.hhconfig` file. Entry point is `src/main.ts`.
 
-**Two type-checking modes:**
-- `LSPHackTypeChecker` — Primary mode using `hh_client` in LSP mode via `vscode-languageclient`. Requires HHVM API version >= 5.
-- `LegacyHackTypeChecker` — Fallback for older HHVM versions. Uses `hh_client` CLI directly through `src/proxy.ts` and registers VS Code providers manually (`src/providers.ts`).
-
 **Key modules:**
+- `src/LSPHackTypeChecker.ts` — Typechecker integration using `hh_client` in LSP mode via `vscode-languageclient`.
 - `src/Config.ts` — Reads all `hack.*` VS Code settings at extension startup (not dynamically reloaded except for `hack.remote.*` which prompts a window reload)
 - `src/proxy.ts` — Wraps `hh_client` CLI invocations (version check, type-at-pos, autocomplete, format, etc.), always passing `--json`
 - `src/remote.ts` — Translates commands/args for SSH or Docker remote execution based on `hack.remote.*` config

package.json

@@ -207,12 +207,7 @@
           "default": false,
           "description": "Enable calculation of Hack type coverage percentage for every file and display in status bar."
         },
-        "hack.useLanguageServer": {
-          "type": "boolean",
-          "default": true,
-          "description": "Start hh_client in Language Server mode. Only works for HHVM version 3.23 and above."
-        },
-        "hack.useHhast": {
+"hack.useHhast": {
           "type": "boolean",
           "default": true,
           "description": "Enable linting (needs HHAST library set up and configured in project)",

src/Config.ts

@@ -18,10 +18,6 @@ export const enableCoverageCheck = hackConfig.get<boolean>(
   "enableCoverageCheck",
   true,
 );
-export const useLanguageServer = hackConfig.get<boolean>(
-  "useLanguageServer",
-  true,
-);
 export const useHhast = hackConfig.get<boolean>("useHhast", true);
 export const hhastLintMode: "whole-project" | "open-files" = hackConfig.get(
   "hhastLintMode",

src/LegacyHackTypeChecker.ts

@@ -4,7 +4,6 @@
 
 import * as vscode from "vscode";
 import * as config from "./Config";
-import { LegacyHackTypeChecker } from "./LegacyHackTypeChecker";
 import { LSPHackTypeChecker } from "./LSPHackTypeChecker";
 import { LSPHHASTLint } from "./LSPHHASTLint";
 import * as hh_client from "./proxy";
@@ -36,14 +35,16 @@ export async function activate(context: vscode.ExtensionContext) {
     },
   );
 
+  if (!LSPHackTypeChecker.IS_SUPPORTED(version)) {
+    vscode.window.showErrorMessage(
+      "The installed version of hh_client is too old and does not support LSP. Please upgrade HHVM to at least version 3.23.",
+    );
+    return;
+  }
+
   const services: Promise<void>[] = [];
   services.push(LSPHHASTLint.START_IF_CONFIGURED_AND_ENABLED(context));
-
-  if (LSPHackTypeChecker.IS_SUPPORTED(version) && config.useLanguageServer) {
-    services.push(new LSPHackTypeChecker(context, version).run());
-  } else {
-    services.push(new LegacyHackTypeChecker(context).run());
-  }
+  services.push(new LSPHackTypeChecker(context, version).run());
 
   vscode.debug.registerDebugConfigurationProvider(
     "hhvm",