We, at Tarides, are very happy to announce some improvements made to Merlin’s `signature-help` feature!
As a reminder, `signature-help` is a feature in Merlin that displays the function signature and highlights the active parameter. In the editor, this is typically displayed in a tooltip, floating window, or minibuffer. For instance, the following image displays the `signature-help` for the function `exec_prog` in VSCode.
The implementation of the signature-help command had a few shortcomings, which have been fixed. These fixes are making the feature way more pleasant to use. Some of these improvements are already part of the last Merlin and ocaml-lsp releases, others will be included in the next release.
Results:
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Merlin only displays `signature-help` information on the function parameters and no longer displays it on the function name.
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`signature-help` displays the function’s information only for the active parameters, and no longer loops back to highlight the first parameter after the last one.
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`signature-help` is now triggered even if used inside a `let .. in` binding, in which the `in` is not yet written after the function call
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The optional parameters are now detected and highlighted when the active parameter starts writing one.