Completions that are effectively code-generated overrides aren't inserted properly

[SCWells72]

Some LSP-provided completions are intended to behave as code generation, e.g., implementing/overriding a method from an interface/base class. When I accepted such a completion, it resulted in invalid code, e.g., HTMLElement.click() in JavaScript/TypeScript which results in:

click(): void {
    $0
\}()

Here's a demonstration of the issue:

It looks like it's just a current limited handling of templatized completion results.

[angelozerr]

Are you sure this completion comes from language server and not from IJ himself?

Could you check in lsp completion returns this click snippet.

[angelozerr]

If it comes from language server, could yiu copy paste the lsp response in the issue please.

[SCWells72]

Yes, it's coming from the TypeScript language server. Here's the response to textDocument/completion (retaining only the relevant completion):

{
  "isIncomplete": false,
  "items": [
    {
      "label": "click",
      "kind": 2,
      "sortText": "11",
      "filterText": "click(): void {\n    $0\n}",
      "insertText": "click(): void {\n    $0\n}",
      "insertTextFormat": 2,
      "data": {
        "cacheId": 87
      }
    }
  ]
}

and here's the request/response for completionItem/resolve for that completion:

Request

{
  "label": "click",
  "kind": 2,
  "sortText": "11",
  "filterText": "click(): void {\n    $0\n}",
  "insertText": "click(): void {\n    $0\n}",
  "insertTextFormat": 2,
  "data": {
    "cacheId": 87
  }
}

Response

{
  "label": "click",
  "kind": 2,
  "detail": "(method) HTMLElement.click(): void",
  "documentation": {
    "kind": "markdown",
    "value": "Called when the element is inserted in a document"
  },
  "sortText": "11",
  "filterText": "click(): void {\n    $0\n}",
  "insertText": "click(): void {\n    \\$0\n\\}()$0",
  "insertTextFormat": 2,
  "data": {
    "file": "/path/to/sourceFile.ts",
    "line": 41,
    "offset": 9,
    "entryNames": [
      "click"
    ]
  }
}

To be honest, the insertText from the detailed response looks suspicious to me since it would have parentheses after the method body close brace. I'm not sure what "insertTextFormat": 2 implies either, but presumably some type of guidance on how to process the "template" from the insert text.