Which @angular/* package(s) are relevant/related to the feature request?

language-service

Description

TL;DR: If ALS returns null to a textDocument/definition request in a TS file, then pass the request to TSLS. This does not currently happen, and because of this, Zed editor, which uses a language server for the entire file, cannot go the definition from a reference outside the "Angular-specific code".

We are developing an Angular extension for the Zed editor. Zed supports language servers and LSP. As I work, I compare the work of the extension on Zed and VS Code.

Currently, the Angular VS Code extension passes the textDocument/references commands from the entire .ts file to ALS, and ALS responds to them correctly, taking into account that symbol can also be used in the template. The handler of this method does not have the angularOnly condition, unlike the others:

The situation is different with the textDocument/definition command: the Angular extension passes the command to ALS only under certain conditions. It seems to be decided here. ALS also has the angularOnly condition, which prevents the command from being passed to TSLS.

The catch is that in Zed the selected language server works on the entire file, and all commands are passed to it unconditionally. Including the textDocument/definition command. If you request a definition in a TS file outside the "Angular-specific code", ALS cannot handle this command because angularOnly: true is set and passes null, although it could pass the command to TSLS and return the correct answer (nathansbradshaw/zed-angular#19 (comment)).

I understand that the angularOnly condition in the handlers did not just appear out of nowhere. But for what reason was this condition bypassed in the textDocument/references handler? Isn't this reason also suitable for getting rid of the angularOnly condition for the textDocument/definition command? I don't think this will harm ALS in any way. But if you make it possible to pass the command to TSLS, Zed will be able to receive the correct definition and the feature will work as expected.

Proposed solution

I can propose a simple and stupid solution there. Just update function getDefinitionAndBoundSpan so that it falls back to TSLS if ALS returns null.

  function getDefinitionAndBoundSpan(
    fileName: string,
    position: number,
  ): ts.DefinitionInfoAndBoundSpan | undefined {
    if (!isTypeScriptFile(fileName)) {
      return ngLS.getDefinitionAndBoundSpan(fileName, position);
    } else {
      return (
        ngLS.getDefinitionAndBoundSpan(fileName, position) ??
        tsLS.getDefinitionAndBoundSpan(fileName, position)
      );
    }
  }

At least it works. Although, from what I understand, tsLS probably shouldn't be used at all if angularOnly is true. However, I can go deeper and provide a more valid solution if I'm sure my request is valid.

Alternatives considered

To tell the truth, the feature in Zed is crooked, but it works: since the definition request always returns null, Zed thinks that any symbol is a definition and immediately requests and displays references, among which there is also a definition, but you have to search it in the list.

It is also possible to replace the angularOnly parameter in the downloaded package with false, but in this case, when you hover over the symbols, two hints are displayed simultaneously: from TSLS and ALS. In addition, making changes to the package is not the best practice.