Implement support format request: provideDocumentRangesFormattingEdits

[ArnoGW1]

Type: Bug

Formatting any simple 60-line C++ file is sometimes instant, sometimes so long that I give up and try again. I've seen it take 20 seconds or more.

This doesn't depend on contents; formatting randomly takes a long or short time when doing minor changes in the same small .cpp file.

Extension version: 1.19.6
VS Code version: Code 1.87.0 (Universal) (019f4d1419fbc8219a181fab7892ebccf7ee29a2, 2024-02-27T23:42:56.944Z)
OS version: Darwin arm64 23.2.0
Modes:
Remote OS version: Windows_NT x64 10.0.22631

System Info

Item	Value
CPUs	Apple M1 (8 x 24)
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 webgl: enabled webgl2: enabled webgpu: enabled
Load (avg)	2, 2, 3
Memory (System)	16.00GB (0.08GB free)
Process Argv	--crash-reporter-id 177e6a93-bd0d-4e86-b1ce-b463c9692a68
Screen Reader	no
VM	0%

Item	Value
Remote	pc1
OS	Windows_NT x64 10.0.22631
CPUs	AMD Ryzen 9 5900X 12-Core Processor (24 x 3700)
Memory (System)	63.93GB (36.37GB free)
VM	0%

A/B Experiments

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[sean-mcmanus]

This is caused by the formatting task getting stuck behind a long IntelliSense parsing operation. It's being tracked by #6156 already, although that issue mentions format on type and vcFormat, the same issue would repro with clang-format and not on type.

...unless you don't see the C/C++ task bar progress indicator showing "IntelliSense: Updating" (and/or cpptools-srv isn't using CPU).

[ArnoGW1]

...unless you don't see the C/C++ task bar progress indicator showing "IntelliSense: Updating" (and/or cpptools-srv isn't using CPU).

I don't see this indicator. The problem happens no matter which IntelliSense operations are underway. If I wait for the open file to be fully parsed and for VSCode to do nothing, then save, the save operation can still hang for a long time.

[sean-mcmanus]

@ArnoGW1 Can you set C_Cpp.loggingLevel to "Debug" and look in the C/C++ logging to see what it shows when your format and the bug repros?

e.g. normally, you should see something like

LSP: (received) cpptools/formatDocument: file:///
LSP: (invoked) cpptools/formatDocument: file:///
Formatting document: file:///
Formatting Engine: clangFormat
LSP: Sending response (id: 47)

but if there are other messages then those could be contributing to the issue.

[romanholidaypancakes]

I also encountered this problem. I have been worried about the performance issues of vs (api components and the like), because as far as I know, we only need to call the clang-format executable file to format the source code. If this is the case The technical solution should be optimized very soon!
Formatting using visual studio only takes a moment (also clang-format), and if there are syntax errors in the code, it will take a long time and fail.

[ArnoGW1]

@ArnoGW1 Can you set C_Cpp.loggingLevel to "Debug" and look in the C/C++ logging to see what it shows when your format and the bug repros?

Copying a bit more than what you asked; this was with formatOnSave and saving took around 4 seconds in a 116-line file:

LSP: (invoked) cpptools/getCodeActions: file:///d%3A/projects/my_project/include/header_1.h (id: 278)
LSP: (invoked) textDocument/didChange: file:///d%3A/projects/my_project/include/header_1.h
LSP: (invoked) cpptools/didChangeTextEditorSelection
LSP: (invoked) cpptools/getCodeActions: file:///d%3A/projects/my_project/include/header_1.h (id: 279)
LSP: Sending response (id: 279)
LSP: (invoked) cpptools/getFoldingRanges: file:///d%3A/projects/my_project/include/header_1.h (id: 280)
LSP: (invoked) cpptools/formatRange: file:///d%3A/projects/my_project/include/header_1.h (id: 283)
Formatting document: file:///d%3A/projects/my_project/include/header_1.h
Formatting Engine: clangFormat
LSP: Sending response (id: 280)
c:\Users\user\.vscode-server\extensions\ms-vscode.cpptools-1.19.6-win32-x64/bin/../LLVM/bin/clang-format.exe -style=file -fallback-style=LLVM --Wno-error=unknown -offset=4956 -length=84 -assume-filename=D:\projects\my_project\header_1.h
LSP: Sending response (id: 283)
LSP: (received) cpptools/formatRange: file:///d%3A/projects/my_project/include/header_1.h (id: 284)
LSP: (invoked) cpptools/formatRange: file:///d%3A/projects/my_project/include/header_1.h (id: 284)
Formatting document: file:///d%3A/projects/my_project/include/header_1.h
Formatting Engine: clangFormat
c:\Users\user\.vscode-server\extensions\ms-vscode.cpptools-1.19.6-win32-x64/bin/../LLVM/bin/clang-format.exe -style=file -fallback-style=LLVM --Wno-error=unknown -offset=5301 -length=148 -assume-filename=D:\projects\my_project\header_1.h
LSP: Sending response (id: 284)
LSP: (received) textDocument/willSaveWaitUntil: file:///d%3A/projects/my_project/include/header_1.h (id: 285)
LSP: (invoked) textDocument/willSaveWaitUntil: file:///d%3A/projects/my_project/include/header_1.h (id: 285)
LSP: Sending response (id: 285)
willSaveWaitUntil: 0ms

Note that my settings contain:

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

But I remember having that issue before adding formatOnSaveMode.

[ArnoGW1]

Note that it sometimes doesn't finish at all. It's been happening a lot lately, which is blocking. Here's the log:

Formatting document: file:///d%3A/projects/my_project/include/header_1.h
Formatting Engine: clangFormat
c:\Users\user\.vscode-server\extensions\ms-vscode.cpptools-1.19.6-win32-x64/bin/../LLVM/bin/clang-format.exe -style=file -fallback-style=LLVM --Wno-error=unknown -offset=5443 -length=96 -assume-filename=D:\projects\my_project\header_1.h
LSP: Sending response (id: 812)