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bug#72184: 31.0.50; typescript-ts-mode does not bind RET to newline-and-


From: Dmitry Gutov
Subject: bug#72184: 31.0.50; typescript-ts-mode does not bind RET to newline-and-indent
Date: Thu, 1 Aug 2024 03:42:27 +0300
User-agent: Mozilla Thunderbird

Hi Jostein,

On 31/07/2024 11:55, Jostein Kjønigsen wrote:

PREFACE

I've now looked further into this issue, and what we're actually seeing here is not indentation code "not working", but indentation rules not taking into account incomplete parse-trees while code is being written.

Makes sense, thanks.

So as the original bug-submitter, I will have to just declare that the original bug-description is clearly inaccurate. Sorry about that!

Below is my attempt to better express what is actually failing and why.

*My hypothesis is that this could be an issue for other tree-sitter based major-modes as well, and maintainers of those modes are encouraged to check for similar issues.*

If more major-modes than typescript-ts-mode is affected, the optimum solution may best be decided together, rather than individually per mode.

AS FOR THE BUG - DETAILS

Consider the following pre-existing typescript/javascript function:

    function stuff() {
       // TODO implement
    }


Using the typescript tree-sitter grammer, it gets the following nodes in its tree-sitter AST:

      (function_declaration function name: (identifier)
       parameters: (formal_parameters ( ))
       body: (statement_block { (comment) }))

This matches the rules for indentation in typescript-ts-mode and indents correctly regardless.

But in a bare config with only electric-indent-mode enabled (and not electric-pair-mode), trying to enter a new function will produce a incomplete syntax tree, due to the missing final brace.

The code will look like this:

    function gnu2() {  // NOTE: no closing brace!


And the tree-sitter AST will then look like this until completed:

      (expression_statement
       (function function name: (identifier)
        parameters: (formal_parameters ( ))
        body: (statement_block { (comment) }))))


And typescript-ts-mode has no indentation rules for this AST. *Thus pressing enter wont cause indentation, despite electric-indent-mode being enabled.*

I suspect this sort of issue could possibly affect other treesitter based modes which has been developed mostly in existing configs with "all the bells and whistles" (like electric-pair-mode) enabled.

I'll hold off any fixes or suggestions for such until we have some reports from other maintainers, if that is ok?

We've seen this before - take a look at https://debbugs.gnu.org/62717, for example.

In short, some ad-hoc counter-measures can and sometimes are added (proposals welcome), but ultimately when we know we can't reliably distinguish problem situations, or can only detect a minor fraction of them, we're also okay giving up and recommending people use electric-pair-mode for better experience.





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