Running TSLint only on changed files with Git Diff

Question

I want to run tslint only on files that were modified in a pull request, instead of the entire project.

git diff --name-only develop -- *.ts successfully prints out the filenames that have changed between the feature branch and develop.

I'm trying to pipe that command into my lint command. Lint can take in a list of files to run against instead of running against everything by placing the filenames after:

git diff --name-only develop -- *.ts | npm run lint

This works on our Jenkins box, but on my local Windows machine no text gets appended to the end of the lint command.

C:\code>git diff --name-only develop-- *.ts | npm run lint

tslint -c .\tslint.json -p .\tsconfig.json

Is there a simple one line method that will only run lint on changed files in a branch?

Answer 1

I got a list of modified files by running

git diff --name-only --diff-filter=ACMR origin/dev-123...develop -- *.ts

Where origin/dev-123 is the source branch and develop is the destination.

I put the output of that command into an array, and ran the linter against the array of files.

Answer 2

You can use Git Bash to run the below:

npm run lint $(git diff --name-only --diff-filter=ACMR origin/dev-123...develop -- *.ts)

Answer 3

On Windows, the commands above may not work because of unix based bash features. So, I made a cmd batch script that works on CMD, IDEs like VsCode, and even on git-bash (that has unix bash features).

Here it goes for those who, like me, are forced to work on Windows (kidding):

1. Create a lint-git-changed.bat script and save it on project's root:

@echo off
setlocal enableDelayedExpansion

set fileCount=0
set fileList=
for /f "eol=: delims=" %%F in ('git diff --name-only HEAD --diff-filter=ACMRTUXB -- *.ts') do (
  set /a fileCount+=1
  if .!fileList!==. (
    set fileList=%%F
  ) else (
    set fileList=!fileList! %%F
  )
)

if %fileCount% GTR 0 (
  echo Linting %fileCount% files...
  npx tslint "%fileList%"
) else (
  echo Lint: Nenhum arquivo para verificar.
  exit 0
)

2. Add a script command on package.json

"scripts": {
    ...
    "lint:changed": "lint-git-changed.bat",
    ...
 }

3. Run npm run lint:changed and it's done. Alternative you can add it also on pre-commit hooks.