Allowing non-zero exit code in some of the commands to support pre-commit autofixing

Description

This issue is essentially a reverse of #26 🙂

We use eslint and prettier as linting tools and our typical package.json looks like this:

{
  "scripts": {
    "fix": "yarn fix:eslint && yarn fix:prettier",
    "fix:eslint": "eslint --fix \"**/*\"",
    "fix:prettier": "prettier --write \"**/*\"",
    "lint": "yarn lint:eslint && yarn lint:prettier",
    "lint:eslint": "eslint \"**/*\"",
    "lint:prettier": "prettier --check \"**/*\""
  },
  "husky": {
    "hooks": {
      "pre-commit": "lint-staged"
    }
  },
  "lint-staged": {
    "**/*": [
      "eslint --fix",
      "prettier --write",
      "git add"
    ]
  },
  "devDependencies": {
    "eslint": "^5.16.0",
    "eslint-config-prettier": "^4.3.0",
    "husky": "^2.3.0",
    "lint-staged": "^8.1.7",
    "prettier": "^1.17.1"
  }
}

• We want to involve lint-staged as a pre-commit hook.
• We want eslint and prettier to fix autofixable problems, but not block the commit if unfixable errors or warnings are found.
• The reason why we use **/* everywhere is because we specify matched extensions in .eslintignore / .prettierignore – helps keep things DRY.

This strategy does not fully work at the moment: every time eslint --fix finds a problem, it exits with a non-zero exit code and so the commit is blocked. This is a reasonable default behaviour, however, it is not quite what we are after.

As in many other workflows, we merge PRs to master only when yarn lint passes in the CI. This means that the last commit in a PR needs to be crystal clean, however any work-in-progress commits to a new branch can include imperfections. Typical examples of acceptable issues would be console.log not yet removed from the code (because of ongoing debugging) or present unused variables (because the implementation is incomplete). A precommit hook that autofixes formatting and, say, sorts imports, is useful, however a superstrict guard that blocks a commit is an obstacle to the process. We want to commit and push imperfect code to new branches as soon as possible to avoid loss of work, we just want to stay as close to perfect as automation allows us.

What we can do now is to implement a wrapper around eslint --fix (e.g. wrapped-eslint-fix) that would always exit with zero. It would be used like this:

  "lint-staged": {
    "**/*": [
      "wrapped-eslint-fix",
      "prettier --write",
      "git add"
    ]
  },

However, to make it easier to re-use the same trick in multiple projects, it would be nice to be able to do something like this:

  "lint-staged": {
    "**/*": [
      // option 1
      ["eslint --fix", { ignoreExitCode: true }],
      // option 2
      { command: "eslint --fix", ignoreExitCode: true },
      // option 3
      { command: "eslint --fix", options: { ignoreExitCode: true }},
      // remaining commands can keep the current syntax, but may also switch to the new one
      "prettier --write",
      "git add"
    ]
  },

New syntax is similar to what we see in eslint and webpack configs:

"eslintRule1": "error",
"eslintRule2": [ "error", { someOption: true } ],

"use": [
  "some-webpack-loader",
  { loader: "some-other-loader", options: { foo: "bar" } },
]

The potential new feature seems backwards-compatible and may support the development process in teams like ours. WDYT?

[kachkaev]

I totally understand your arguments and also value tools that are dead-simple on the surface. I’ve opened this issue to share our situation and to discover if anyone else faces a similar problem.

This will probably work for us:

 "lint-staged": {
   "**/*": [
-    "eslint --fix",
-    "prettier --write",
+    "suppress-exit-code eslint --fix",
+    "suppress-exit-code prettier --write",
     "git add"
   ]
},

Just published suppress-exit-code to npm.

@okonet feel free to close the issue if you want and thank you for taking part in this conversation. If anyone else seeks for suppressing exit codes, please give a shout below – this will help others know if extending lint-staged is worth it.

[tdkn]

I use this workaround:

// lint-staged.config.js

const silent = shell => `sh -c '${shell} || exit 0'`

module.exports = {
  "**/*": (files) => {
    return `prettier --write --ignore-unknown ${files.join(" ")}`;
  },
  "*.{js,jsx,ts,tsx}": (files) => {
    return silent(`eslint --fix ${files.join(" ")}`);
  },
  "*.{css,scss}": (files) => {
    return silent(`stylelint --fix ${files.join(" ")}`);
  },
};

The important points are:

• sh -c: avoids errors such as Invalid option '-e'
• || exit 0: Forces the exit code to 0