Silencing errors on failures for npm run-script

Question

When you run npm test and it fails, you get the test outputs + a single error message, like so:

npm ERR! Test failed.  See above for more details.
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Answer 1

You can silence the errors by redirecting the stderr to /dev/null. For example:

{
 "test": "karma start" (package.json)
}

running:

$ npm run test 2> /dev/null

will now send all npm errors to /dev/null but normal input will still be visible in the console.

Because the error is thrown by npm, after karma exiting with a non-zero status, doing the following is not enough:

 {
     "test": "karma start 2> /dev/null"
 }

but you can overcome it by creating another task that calls that task with stderr redirection:

 {
     "test": "karma start",
     "test:silent": "npm run test 2> /dev/null" 
 }

this will ensure that the npm error messages are hidden

Answer 2

I've just been trying to figure out the same. Not a perfect answer but it kind of worked to specify linting as a pretest script (docs) like so:

// package.json
{
  // ...
  "scripts": {
    // ... definition for test ...
    "pretest": "./node_modules/jsxhint/cli.js src/",
  }
}

Then, when you type in npm test the first time, you will only get a single-line error from NPM. Obviously, that means you won't be able to run your tests if you haven't linted.

The other option is to use some kind of third party task runner like Make, Grunt or Gulp.

I've only used Make, and I think it's the most painless to set up (at least on OSX and Linux, not sure about Windows).

Create a Makefile in your root that looks like so:

lint:
    ./node_modules/.bin/jslint ./*.js # or whatever your lint command is

test:
    ./node_modules/.bin/mocha test/*.js # or whatever your test command is

.PHONY: lint test

Then type make test and make lint to run those commands.

Answer 3

If you don't care about preserving the return code of the linter process, you can always configure your package.json like this:

{
  // ...
  "scripts": {
    // ...
    "lint": "eslint . || true",
  }
}

Answer 4

Use the npm run --silent option:

$ npm run --silent test

Even less typing if you define a shell alias:

$ alias run='npm run --silent'
$ run test