Restarting clangd break the exported API

[sr-tream]

1. Write an extension what used the clangd API added in Export client from activation as API for use in other extensions #575 (for example https://github.com/HighCommander4/vscode-clangd-api-example)
2. Trigger extension activation (in provided example hover information for C/C++ symbol)
3. Execute command clangd.restart
4. Now extension from example have language client with State.Stopped state.

Getting new instance of API do not fix this issue, because clangd do not update exported language client instance

[sr-tream]

Possible fix:

diff --git a/src/api.ts b/src/api.ts
index dc1968b..d6f17ca 100644
--- a/src/api.ts
+++ b/src/api.ts
@@ -3,7 +3,7 @@ import {BaseLanguageClient} from 'vscode-languageclient';
 import {ClangdApiV1, ClangdExtension} from '../api/vscode-clangd';
 
 export class ClangdExtensionImpl implements ClangdExtension {
-  constructor(private readonly client: BaseLanguageClient) {}
+  constructor(public client: BaseLanguageClient) { }
 
   public getApi(version: 1): ClangdApiV1;
   public getApi(version: number): unknown {
diff --git a/src/extension.ts b/src/extension.ts
index c062fde..250038b 100644
--- a/src/extension.ts
+++ b/src/extension.ts
@@ -3,7 +3,9 @@ import * as vscode from 'vscode';
 import {ClangdExtension} from '../api/vscode-clangd';
 
 import {ClangdExtensionImpl} from './api';
-import {ClangdContext} from './clangd-context';
+import { ClangdContext } from './clangd-context';
+
+let apiInstance: ClangdExtensionImpl | undefined;
 
 /**
  *  This method is called when the extension is activated. The extension is
@@ -34,6 +36,9 @@ export async function activate(context: vscode.ExtensionContext):
         }
         await clangdContext.dispose();
         await clangdContext.activate(context.globalStoragePath, outputChannel);
+        if (apiInstance) {
+          apiInstance.client = clangdContext.client;
+        }
       }));
 
   await clangdContext.activate(context.globalStoragePath, outputChannel);
@@ -72,5 +77,6 @@ export async function activate(context: vscode.ExtensionContext):
     }, 5000);
   }
 
-  return new ClangdExtensionImpl(clangdContext.client);
+  apiInstance = new ClangdExtensionImpl(clangdContext.client);
+  return apiInstance;
 }

With this patch, extension can get new instance via ClangdExtension.getApi(1), when state of old language client changed to State.Stopped

[HighCommander4]

Fixed by #649