[Baccata]

Problem

In the LSP, typing a . after an already-complete name never triggers an autocomplete request. For example, given a saved file:

foo =
  List

adding a . after List does not trigger a completion request. But with:

foo =
  Lis

adding a t to make List does.

Cause

Editors only auto-request completions when you type an identifier character — that's why extending Lis with t works. A . is not an identifier character, so per the LSP spec the client only requests completions after it if the server declares . as a completion trigger character. lspOptions never set optCompletionTriggerCharacters, so it defaulted to Nothing and no trigger characters were registered.

Fix

Register . as a completion trigger character:

optCompletionTriggerCharacters = Just ['.']

The downstream prefix handling already copes with a trailing dot (the completion handler strips it before querying), so once the request fires it resolves correctly.

Tests

Factored the pure prefix-splitting logic out of identifierSplitAtPosition into splitIdentifierAtChar :: Int -> Text -> (Text, Text) and added unit tests for the dotted-name cases — including the List. case this fixes — so the behaviour that makes the trigger useful is guarded against regression.

Also tested manually. Works as expected in vscode.

🤖 (partially) Generated with Claude Code

[Baccata]

extracting this to avoid having to build a virtual file just for testing completions