Extension inserts null bytes at end of meson.build file after saving

[clstatham]

Type: Bug

I have the following simple meson.build file for a test C project. With the meson VS Code extension enabled, anytime I modify this file and save it, a handful (around 9) of null bytes are inserted at the end, causing the language server to crash and meson itself to fail to lex the file. I'm pretty new to meson so if my build file is malformed in anyway (besides the null bytes I didn't ask for), that's on me :)

Edit: If it's worth mentioning, I do have format-on-save enabled globally in VS Code, and I used the extension bisect feature to narrow it down to the Meson extension.

Edit 2: I just confirmed that it's happening when I format the document manually from the command pallet as well. So probably something to do with the language server's formatting functionality?

project('crac', 'c', default_options: 'default_library=static')
incdir = include_directories('include')
deps = []
executable(
  'crac',
  'main.c',
  include_directories: incdir,
  dependencies: deps,
)

Extension version: 1.25.1
VS Code version: Code 1.91.1 (f1e16e1e6214d7c44d078b1f0607b2388f29d729, 2024-07-09T22:06:49.809Z)
OS version: Windows_NT x64 10.0.22631
Modes:

System Info

Item	Value
CPUs	AMD Ryzen 9 5900X 12-Core Processor (24 x 3700)
GPU Status	2d_canvas: enabled canvas_oop_rasterization: enabled_on direct_rendering_display_compositor: disabled_off_ok gpu_compositing: enabled multiple_raster_threads: enabled_on opengl: enabled_on rasterization: enabled raw_draw: disabled_off_ok skia_graphite: disabled_off video_decode: enabled video_encode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled webgpu: enabled
Load (avg)	undefined
Memory (System)	31.92GB (21.31GB free)
Process Argv	--crash-reporter-id 54a44d29-4e67-454a-891a-d029558f2d94
Screen Reader	no
VM	0%

A/B Experiments

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[JCWasmx86]

Sadly I wasn't able to reproduce this with any mesonlsp version I tested

[scott-wilson]

I'm seeing the same issue here on Windows 10 Pro. Here's the steps to reproduce:

1. Open the project in the dir https://github.com/scott-wilson/openchecks/tree/8de1028178863dc4ba0ea7c24ecb259efcbf28ca/bindings/cpp
2. Open the root meson.build and format (I'm doing format on save)

This should cause the error to happen.

[JCWasmx86]

You are both on Windows, maybe it's a windows issue. I will check it later

[tristan957]

Thanks @JCWasmx86 for investigating. I only work on Linux, so can't test.

[mdrobot7]

Saw the same issue, and have been for a month or so. Had to disable the meson extension because of it. Save without formatting also works, but that's a bit of a hassle. It happens every time I save any meson.build file, I end up with NUL chars inserted in my text.

• Windows 11 Home
• VSCode v. 1.90.1
• Meson extension v. 1.25.1

[JCWasmx86]

Even on Windows I was unable to reproduce this bug:

• The code is here: https://github.com/JCWasmx86/mesonlsp/blob/main/src/liblangserver/formatting.cpp if anybody wants to try to fix it
• If the NULs are really only at the end, I can first write a patch to remove trailing NULs
• But outside of the NULs, the code is valid, right?

[JCWasmx86]

This build could fix that: https://github.com/JCWasmx86/mesonlsp/actions/runs/10226037533 Could anybody of you please try it out, whether it really fixes the problem?

[clstatham]

Yes, outside of the trailing NULs at the end of the file, the formatted meson.build seems to be valid.

Also, the patched build has fixed the issue for me!

[clstatham]

Also, if it helps at all, the NULs only appeared when the file is actually formatted, as in, a modification is made first (inserting or removing a newline, for instance).

[JCWasmx86]

Also, the patched build has fixed the issue for me!

Great, then I will make a release tomorrow and make a PR here for a bump