Returning empty array for onReferences() throws a TypeError

[sgranade]

In my language server implementation, if I return an empty Locations array, null, or undefined from a call to onReferences(), then a TypeError is raised.

let connection = createConnection(ProposedFeatures.all);
connection.onInitialize((params: InitializeParams) => {
	return {
		capabilities: {
			referencesProvider: true
		}
	};
});
connection.onReferences(
	(referencesParams: ReferenceParams): Location[] => {
		return [];
	}
)

This results in the following:

rejected promise not handled within 1 second: TypeError: Cannot read property 'items' of undefined
extensionHostProcess.js:820
stack trace: TypeError: Cannot read property 'items' of undefined
	at g (c:\Users\steph\AppData\Local\Programs\Microsoft VS Code\resources\app\extensions\ms-vscode.references-view\dist\extension.js:1:8246)

Is this an issue with the language server implementation or a VS Code issue?

Setup:

• vscode-languageserver 5.2.1
• vscode-languageserver-protocol 3.14.1
• VS Code 1.41.1
• OS: Windows 10.0.18362.

[rcjsuen]

@sgranade Doesn't sound like a bug with your language server to me.

What do you see in your VS Code's "References" view? Do you at least get a No results found. message similar to what you'd get if you tried to search for the references of some word in a comment for example?

[sgranade]

Yeah, I get a "No results found." message like I should.

[dbaeumer]

To me neither. I check the LSP code and a empty [] is converted into an empty []. Even undefined and null are allowed per API spec.

Moving to https://github.com/microsoft/vscode-references-view

[dbaeumer]

@jrieken I cannot move to the issue to https://github.com/microsoft/vscode-references-view.

Any idea what could cause the exception in the references view code. I did a quick check of the code but couldn't detect a code path that would cause this.

[jrieken]

🤷‍♂ idk - the viewlet should be able to handle the empty case, e.g that's what you get when search for references on a keyword or string. Are those steps above all it takes to reproduce? Can someone create a repo with just vscode.d.ts API being used?

[dbaeumer]

I tried this in my testbed and both returning [] and null from the language server works as expected. @sgranade any additional info. Best would be a test case to reproduce.

[sgranade]

I swear it (didn't) work earlier on the minimum version I posted. Let me go back to my full extension and trim back until I confirm.

[dbaeumer]

OK, let me know as soon as you have found out something.

[sgranade]

I've put together a test repo that reproduces the issue. You'll need to compile the extension, debug it, open a .txt file, place the cursor in the middle of a word, and press Alt+Shift+F12.

[dbaeumer]

I can reproduce this:

@jrieken OK to move to VS Code or is there a special repository for the references view?

[dbaeumer]

@sgranade thanks for the repro case!

[dbaeumer]

@jrieken I checked an the LSP clients returns an empty array as well in this case.

[vscodebot]

This issue has been closed automatically because it needs more information and has not had recent activity. See also our issue reporting guidelines.

Happy Coding!

[kjeremy]

@dbaeumer I think this was closed in error.

[dbaeumer]

@jrieken any advice on https://github.com/microsoft/vscode-languageserver-node/issues/558#issuecomment-587483723

[jrieken]

references viewlet issues are in the "main" repo

[dbaeumer]

@jrieken. Thanks. Moving.

[jrieken]

Thanks for the good repo.