Investigating issues with pre-commit hook/lint-staged.

[viveleroi]

Continuing a discussion from #460 which was tangential to that issue.

I stumbled into an issue while working on a PR for 460 where a typescript error during the lint-staged process of committing caused files to be completely reverted - losing all of my local changes. I've never seen this happen, having used lint-staged, husky, tsc, prettier, and eslint in multiple projects. I certainly don't want future contributors to lose their changes if this happens to them.

However, it's been difficult to explain 100%. Existing issues with lint-staged like this one don't help.

I have a few suggestions because I strongly suspect line-ending problems are involved, but are worth doing for any open source project:

• Run prettier on the entire repo and commit the changes. When I try, it wants to update line-endings in every single file.
• Add a .gitattributes to force all text files to specific line-ending. I usually choose LF
• Add an .editorconfig to ensure supporting editors are configured correctly, and even a .vscode extensions file to recommend the editorconfig plugin
• Update prettier to use settings in .editorconfig

I do know that something causes a mismatch between the file in the git stash that lint-staged stashed, and the local copy during the pre-commit hook process. I can't explain the difference yet, sadly. There are only two processes which write files during the hook: eslint with --fix and prettier. From my tests, eslint --fix is fine, but prettier changes the file's line-endings.

We use prettier just fine in our repositories, but we also have the files/settings above which might be preventing this issue.

This conflict between the staged file and the local file causes git, therefore lint-staged to fail when trying to restore the changes at the end of it's process, and it prints a warning to console. In some cases, the local file changes remain and are correct, and in some cases the file is reverted entirely. I can't reproduce the reverted file.

1. Start with my incomplete base branch https://github.com/viveleroi/remeda/tree/isSymbol
2. Open isDefined.test.ts and add | symbol to all of the type unions in the tests, save the file
3. Run git commit -am "wip"
4. See lint-staged throw the following error

[STARTED] Preparing lint-staged...
[COMPLETED] Preparing lint-staged...
[STARTED] Running tasks for staged files...
[STARTED] lint-staged.config.js — 1 file
[STARTED] *.ts?(x) — 1 file
[STARTED] *.@(js|jsx|ts|tsx|cjs|mjs) — 1 file
[STARTED] !(*.@(js|jsx|ts|tsx|cjs|mjs)) — 0 files
[SKIPPED] !(*.@(js|jsx|ts|tsx|cjs|mjs)) — no files
[STARTED] tsc -p tsconfig.json --noEmit
[STARTED] eslint --fix
[COMPLETED] eslint --fix
[STARTED] prettier --write
[FAILED] tsc -p tsconfig.json --noEmit [FAILED]
[FAILED] tsc -p tsconfig.json --noEmit [FAILED]
[COMPLETED] Running tasks for staged files...
[STARTED] Applying modifications from tasks...
[SKIPPED] Skipped because of errors from tasks.
[STARTED] Reverting to original state because of errors...
[FAILED] error: Your local changes to the following files would be overwritten by merge:
        src/isDefined.test.ts
Please commit your changes or stash them before you merge.
Aborting
Index was not unstashed.
[STARTED] Cleaning up temporary files...
[SKIPPED]
  ✖ lint-staged failed due to a git error.

  ✖ lint-staged failed due to a git error.
  Any lost modifications can be restored from a git stash:

    > git stash list
    stash@{0}: automatic lint-staged backup
    > git stash apply --index stash@{0}


✖ tsc -p tsconfig.json --noEmit:
src/isNonNull.test.ts(20,9): error TS2345: Argument of type 'string | number | boolean | symbol | number[] | Error | Date | { a: string; } | Promise<number> | (() => void) | undefined' is not assignable to parameter of type 'string | number | boolean | number[] | Error | Date | Promise<number> | { a: string; } | (() => void) | undefined'.
  Type 'symbol' is not assignable to type 'string | number | boolean | number[] | Error | Date | Promise<number> | { a: string; } | (() => void) | undefined'.
src/isNonNull.test.ts(48,7): error TS2345: Argument of type '(string | number | boolean | symbol | number[] | Error | Date | { a: string; } | Promise<number> | (() => void) | undefined)[]' is not assignable to parameter of type '(string | number | boolean | number[] | Error | Date | Promise<number> | { a: string; } | (() => void) | undefined)[]'.
  Type 'string | number | boolean | symbol | number[] | Error | Date | { a: string; } | Promise<number> | (() => void) | undefined' is not assignable to type 'string | number | boolean | number[] | Error | Date | Promise<number> | { a: string; } | (() => void) | undefined'.
    Type 'symbol' is not assignable to type 'string | number | boolean | number[] | Error | Date | Promise<number> | { a: string; } | (() => void) | undefined'.
husky - pre-commit hook exited with code 1 (error)

When I commit my changes with --no-amend and run prettier, it says: src/isDefined.test.ts 117ms

Running git status shows me the file has changed, yet git diff shows no changes, yet warns:
warning: in the working copy of 'src/isDefined.test.ts', LF will be replaced by CRLF the next time Git touches it

Currently, my suspected cause is line endings.

In my original work, I tried to commit my isSymbol files and tsc errored with missing symbol unions in isDefined.test.ts and isNonNull.test.ts. I update the files to fix the errors, but every time I went to commit and saw another tsc error, one of the files was reverted entirely. I wound up fixing both files a few times each before I figure out something was up.