Rewrap incorrectly accounts for tabs

[andreyvit]

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• Completed

Describe the bug / provide steps to reproduce it

The new Rewrap command from #17909 produces a line that soft-wraps in the editor when using tabs:

The above is produced with preferred_line_length=80 soft_wrap=preferred_line_length (and I assume tab_size=4 by default for Go) and after invoking Rewrap.

Golang always uses tabs for indentation, so the issue is most relevant for Go code.

Environment

Zed: v0.155.2 (Zed)
OS: macOS 14.1.1
Memory: 24 GiB
Architecture: aarch64

If applicable, add mockups / screenshots to help explain present your vision of the feature

Looking at the code, Rewrap clearly deals in characters; current_line.len() + word.len() >= wrap_column condition doesn't account for tab characters.

An easy fix would be to count the tabs and subtract (tab_count * (tab-size - 1)) from the left-hand side of that comparison. Of course, expanding tabs correctly would be even better, in case those are mixed with spaces.

(Also I'm wondering that Rewrap has to implement its own wrapping. This seems perilous. Zed already has code to wrap text correctly somewhere, I wish we could reuse that.)

If applicable, attach your Zed.log file to this issue.

Zed.log