"A request has failed. See the output for more information." dialog always shows output channel, even when being dismissed

[perrinjerome]

When a request fail, typically because of an error on the language server side, client shows a popup offering to go to output channel to see the error:

Problem is when user close the dialog, this open the output channel anyway.

---

I prepared a reproduction if necessary:

• use https://github.com/microsoft/vscode-extension-samples/tree/main/lsp-embedded-language-service
• apply a patch so that the server always error on completions, for example:

diff --git a/lsp-embedded-language-service/server/src/server.ts b/lsp-embedded-language-service/server/src/server.ts
index 4093561..d9805d4 100644
--- a/lsp-embedded-language-service/server/src/server.ts
+++ b/lsp-embedded-language-service/server/src/server.ts
@@ -85,18 +85,7 @@ async function validateTextDocument(textDocument: TextDocument) {
 }
 
 connection.onCompletion(async (textDocumentPosition, token) => {
-	const document = documents.get(textDocumentPosition.textDocument.uri);
-	if (!document) {
-		return null;
-	}
-
-	const mode = languageModes.getModeAtPosition(document, textDocumentPosition.position);
-	if (!mode || !mode.doComplete) {
-		return CompletionList.create();
-	}
-	const doComplete = mode.doComplete!;
-
-	return doComplete(document, textDocumentPosition.position);
+	throw new Error("💥");
 });
 
 // Make the text document manager listen on the connection

• build the extension and debug it
• change file type to html1 (this is what this extension sample uses)
• trigger a completion
• the "A request has failed. See the output for more information." dialog popup
• close the dialog

Expected behaviour:

The Output channel is not opened, focus remain on the current editor pane

Actual behaviour:

The Output channel is opened

Screen.Recording.2021-07-10.at.14.52.38.mov

---

I believe the problems is here :

vscode-languageserver-node/client/src/common/client.ts

Lines 3063 to 3067 in cf5d1e4

	private showNotificationMessage() {
	void Window.showInformationMessage('A request has failed. See the output for more information.', 'Go to output').then(() => {
	this.outputChannel.show(true);
	});
	}

as we can see in vscode API ( https://code.visualstudio.com/api/references/vscode-api#window.showInformationMessage ) this returns a thenable that resolves to the selected item or undefined when being dismissed.

I believe in case the returned value is undefined the output channel should not be revealed.