Pre-commit complains that "Stashed changes conflicted with hook auto-fixes" despite manually formatting files?

Question

I am using pre-commit (version 2.20.0) for my C++ project with this hook:

repos:
- repo: https://github.com/pre-commit/mirrors-clang-format
  rev: v14.0.6
  hooks:
  - id: clang-format

I just staged a few lines each from a few different .cpp/.h/cmakelists files. When I try to commit those changes, I get the following error from pre-commit:

[WARNING] Unstaged files detected.
[INFO] Stashing unstaged files to C:\Users\tyler.shellberg\.cache\pre-commit\patch1665600217-21836.
clang-format.............................................................Failed
- hook id: clang-format
- files were modified by this hook
[WARNING] Stashed changes conflicted with hook auto-fixes... Rolling back fixes...
[INFO] Restored changes from C:\Users\tyler.shellberg\.cache\pre-commit\patch1665600217-21836.

I am confused by this. Does pre-commit not allow me to partially commit files, or to have unstaged changes at all when committing?

All the files, both staged and un-staged, have been formatted by clang-format. I've manually double-checked this.

Edit for clarity:

If I run pre-commit run --files [filename] on each file (staged and unstaged) all report back either "Passed" or "Skipped" (for the non-cpp files). If all files pass, why is there a problem?

Answer 1

the first part of your output is:

[WARNING] Unstaged files detected.

this means you had a partially staged commit -- this is fine, pre-commit supports this well

then after that a hook made changes:

- files were modified by this hook

these changes must've conflicted with the unstaged parts because then there's a message such as:

[WARNING] Stashed changes conflicted with hook auto-fixes... Rolling back fixes...

meaning you'll need to either make sure the unstaged parts are formatted properly (pre-commit run --files whatever.cpp) or stage those as well so they also get formatted

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disclaimer: I created pre-commit