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Quirks

Having trouble? Here are some known (mostly npm related) quirks and suggestions on how to work around them that might help.

  • It’s recommended to have elm-tooling in "devDependencies" in package.json. That makes sense since you only need elm-tooling for development and building your application, not at runtime in production. But, this has the consequence that npm install --production/npm ci --production will fail. Why? Because the "postinstall" script will still execute, and try to run elm-tooling install – but elm-tooling isn’t even installed ("devDependencies" is ignored when using the --production flag). So what are your options?

    • Maybe you don’t even need --production. Some applications use npm only for a build step and does not have any production Node.js server or anything like that.
    • Try --ignore-scripts. This will skip the "postinstall" script – but also any scripts that your dependencies might run during installation! Sometimes, only "devDependencies" (such as node-sass) need to run scripts during installation – so try it! If --ignore-scripts works you have nothing to lose.
    • Make a little wrapper script that runs elm-tooling install only if elm-tooling is installed. For example, you could write the script in JavaScript and use the API version of the CLI.
    • If you only need --production installs in for example a Dockerfile, try adding RUN sed -i '/postinstall/d' package.json to remove the "postinstall" script from package.json before running npm install --production. This specific example only works with GNU sed and if your "postinstall" script isn’t last (due to trailing commas being invalid JSON).
    • Move elm-tooling to "dependencies". elm-tooling is small and has no dependencies so it won’t bloat your build very much. Set the NO_ELM_TOOLING_INSTALL environment variable to turn elm-tooling install into a no-op (see below).
  • Due to a bug in npm, the "name" field must exist in package.json if you have a "postinstall" script – otherwise npm crashes with a confusing message. Worse, in a Dockerfile "name" must match your current WORKDIR – otherwise npm refuses to run your "postinstall" script. See npm/npm-lifecycle#49 for more information.

  • If you’re using npm’s ignore-scripts setting, that also means your own postinstall script won’t run. Which means that you’ll have to remember to run npm run postinstall or npx elm-tooling install yourself. npm tends to keep stuff in node_modules/.bin/ even when running npm ci (which claims to remove node_modules/ before installation), so it should hopefully not be too much of a hassle.

  • You can set the NO_ELM_TOOLING_INSTALL environment variable to turn elm-tooling install into a no-op. This lets you run npm install without also running elm-tooling install, which can be useful in CI.

  • If you’re creating an npm package that uses elm-tooling to install Elm and other tools during development, beware that "postinstall": "elm-tooling install" will run not only when developers run npm install in your repo, but also when users install your package with npm install your-package! You can solve this by using "prepare": "elm-tooling install" instead. prepare also runs after npm install in development, but not after npm install your-package. However, it also runs before npm publish, which unneeded but doesn’t hurt that much since it’s so fast after everything has been downloaded once.

    Another way is to generate the package.json that actually ends up in the npm package during a build step – a package.json without "scripts", "devDependencies" and other config that is only wasted bytes for all users of your package.