Allow configuring CompletionItem dropdown suggestions list order, or partial disabling of language server altogether

[hamirmahal]

It would be nice if we could give preference to our language's CompletionItems in the suggestions dropdown list.

We made our language very similar to JavaScript, by design, so that it's more familiar to new developers.

So, it's nice when VSCode auto-detects our source files as JavaScript, because then we get nice things like syntax highlighting and variable renaming.

What isn't ideal, however, is that when developers type lines of code into a source file in our programming language, all the JavaScript suggestions appear first, and then our language's keywords appear in the suggestions dropdown list, near the bottom.

It would be awesome if we could give preference to our language's keywords, or just disable JavaScript's CompletionItems suggestions dropdown list altogether, i.e., pick-and-choose which parts of the JavaScript language server we want to enable, so that the CompletionItem suggestions dropdown list only shows our own keywords.

Or, it would also be very helpful if we could at least tell Visual Studio Code that we want JavaScript's CompletionItems to appear lower down in the suggestions dropdown list, i.e., let us be able to tell Visual Studio Code which precedence to give different language servers' CompletionItems in the suggestions dropdown list, if we can't disable a language's CompletionItems altogether, so that our language's keywords aren't appearing dead-last when developers write in our programming language.

We don't want to straight-up remove all of the functionality that JavaScript's language server provides, because like I said earlier, we get nice functionality like syntax highlighting and variable renaming by letting Visual Studio Code auto-detect our sources files as JavaScript. It would just be nice if we could pick-and-choose which parts of the JavaScript language server we want, or to at least give precedence to our language's keywords in the CompletionItem dropdown suggestions list.

I looked into implementing this in our programming language's language server, but Dirk recommended I open an issue here, since this is not under the control of the LSP library.

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[yume-chan]

i.e., pick-and-choose which parts of the JavaScript language server we want to enable

I think you need to create your own language server. You can forward some requests (like semantic highlighting) to Typescript (note that TypeScript server doesn't use LSP, the TypeScript extension bridges TypeScript server protocol to Code extension APIs directly, but you can still use some of its code), and do others (like suggestions) yourself. Some extensions (including HTML extension and Vuter) already do it, Code also recommends this pattern.

It's also possible by creating a TypeScript server plugin. Technically you can adjust every part of TypeScript server, but it's very poorly documented and heavily relies on internal parts of TypeScript which can change between versions.

[jrieken]

Extensions are all equal and cannot suppress each other. On the other hand there is also no logic to sort completions from one extension higher up than those of other extension. It is all based on the range and sortText of completion items - so that might be something that you can tweak. Also, as suggested by @yume-chan you should look into tsserver plugins.

[hamirmahal]

I did try setting item.sortText = 'A'; for our language's CompletionItems in connection.onCompletionResolve( (item: CompletionItem): CompletionItem => {, but I believe that only affected the order of CompletionItems within our own language server.

This didn't allow any of our language's CompletionItems to "jump ahead" of CompletionItems from Visual Studio Code's built-in JavaScript language server.

[jrieken]

The sortText property is applied globally. To inspect further, you can use the explain mode: trigger suggest, make sure suggest details show, and hit cmd+/. That will change the details window into explain mode, showing sort text, ranges, scores etc. Like so

[hamirmahal]

Whoa! I did not know we could do that. Thank you for showing me that.

So, our language's keywords show up with score: -100, by default, and keywords from Visual Studio Code's built-in JavaScript TypeScript language server have score: 2.

Screen.Recording.2021-12-16.at.10.44.49.AM.mov

If I do item.sortText = 'A';, score: -100 still, for our language's keywords, and keywords from the JavaScript TypeScript language server still have score: 2.

Screen.Recording.2021-12-16.at.11.01.28.AM.mov

For what it's worth, even if I change the language to 'plaintext' instead of 'javascript' for these CompletionItems, and look at the score in plaintext files, they still have score: -100.

Screen.Recording.2021-12-16.at.10.50.32.AM.mov

It would be amazing if we could manually edit these scores to give them a score of, for example, 3, to let our language's suggestions show up, first.

Or, if we could remove JavaScript keyword suggestions from JavaScript's TypeScript's language server altogether, that would be nice, since we could use the features of the JavaScript TypeScript language server that we want, like 'jump to definition', and smart 'variable renaming', while still having our language's keywords show up at the top of a CompletionItem suggestions dropdown list.

Also, for fun, I tried item.sortText = '0';, but the scores of our language's CompletionItems are still score: -100.

Screen.Recording.2021-12-16.at.11.06.56.AM.mov