Autoformatting with `modificationsIfAvailable` changes too many lines

[ArnoGW1]

Type: Bug

When auto-formatting on save with these settings:

    "[cpp]": {
        "editor.formatOnType": true,
        "editor.formatOnSave": true,
        "editor.formatOnSaveMode": "modificationsIfAvailable"
    },

my changes and the line after them are formatted. Because of that, every save formats one more line (the extra formatted line from the first save counts as a change for the second save, which formats one more extra line, etc.)

This leads to way too many changes when saving a file multiple times.

Some more details: I'm using clang-format configured for space-indentation while changing a tab-indented file.

Extension version: 1.19.8
VS Code version: Code 1.87.2 (863d2581ecda6849923a2118d93a088b0745d9d6, 2024-03-08T15:20:17.278Z)
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)	63.93GB (37.62GB free)
Process Argv	--crash-reporter-id 0ac330db-34c3-4766-8c92-8e2a96e97825
Screen Reader	no
VM	0%

A/B Experiments

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[sean-mcmanus]

Yeah, the fix is for us to implement provideDocumentRangesFormattingEdits . The previous issue was #12082 and microsoft/vscode#207655 .

[sean-mcmanus]

Oops, this is a little different from those previous issues, but it might still would probably be fixed by implementing provideDocumentRangesFormattingEdits .