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)

[ArnoGW1]

I just had a formatting failure when saving a small change, not sure it's related:

LSP: (received) cpptools/formatRange: file:///d%3A/projects/my_project/src/src_1.cpp (id: 1435)
LSP: (invoked) cpptools/formatRange: file:///d%3A/projects/my_project/src/src_1.cpp (id: 1435)
Formatting document: file:///d%3A/projects/my_project/src/src_1.cpp
Formatting Engine: clangFormat
Formatting failed:
c:\Users\user\.vscode-server\extensions\ms-vscode.cpptools-1.19.7-win32-x64/bin/../LLVM/bin/clang-format.exe -style=file -fallback-style=LLVM --Wno-error=unknown -offset=10906 -length=0 -assume-filename=D:\projects\my_project\src\src_1.cpp D:\PROJECTS\MY_PROJECT\SRC\SRC_1.CPP
error: offset 10906 is outside the file

LSP: Sending response (id: 1435)
LSP: (received) cpptools/fileChanged: file:///d%3A/projects/my_project/src/src_1.cpp
LSP: (invoked) cpptools/fileChanged: file:///d%3A/projects/my_project/src/src_1.cpp
LSP: (received) textDocument/didSave: file:///d%3A/projects/my_project/src/src_1.cpp
LSP: (invoked) textDocument/didSave: file:///d%3A/projects/my_project/src/src_1.cpp

[sean-mcmanus]

@ArnoGW1 Is the id of the LSP: Sending response (id: 812) when formatting gets permanently stuck the id of the formatting message? We have one known IntelliSense deadlock at #12051 which should be fixed with our pending 1.19.8 release. After the formatting gets stuck, are most other operations stuck?

So is the issue just with formatOnSave or do you see an issue when invoking format document too?? I'm seeing 4 formatRange requests being sent when formatOnSave is invoked.

Do you have any more repro details for the "error' offset is outside the file"?

[sean-mcmanus]

@ArnoGW1 When a file has many edits with "editor.formatOnSaveMode": "modificationsIfAvailable", I've gotten VS Code to send 100+ formatRange requests which can take a very long time -- do you want us to create a separate issue to track that or use this issue? I'm unclear whether the issue you're hitting is due to these multiple formatRange requests or if there's a separate issue you want us to track with this issue that can repro with just a single formatRange being processed.

[ArnoGW1]

@ArnoGW1 When a file has many edits with "editor.formatOnSaveMode": "modificationsIfAvailable", I've gotten VS Code to send 100+ formatRange requests which can take a very long time -- do you want us to create a separate issue to track that or use this issue? I'm unclear whether the issue you're hitting is due to these multiple formatRange requests or if there's a separate issue you want us to track with this issue that can repro with just a single formatRange being processed.

There were very few changes, less than 10 lines in a 160-line file. I will answer your other questions when I have time to investigate.