用自己的实现替换npm包

Question

In my package.json I have a dependency "protractor": "2.1.0" . That package in turn depends on "jasminewd2": "0.0.5" .

That jasminewd2 package has some behavior which I want to modify. I downloaded its sources and made the changes I need. Yarn's documentation tells about a possibility to use a local source for packages:

yarn add file:/path/to/local/folder installs a package that is on your local file system. This is useful to test out other packages of yours that haven't been published to the registry.

When I execute that command

1. "jasminewd2": "file:\\\\CustomNodeModules\\\\jasminewd2" gets added to my package.json .

2. And this to my yarn.lock file:

    "file:\\\\CustomNodeModules\\\\jasminewd2", jasminewd2@0.0.5: name jasminewd2 version "0.0.5" resolved "https://registry.yarnpkg.com/jasminewd2 /-/jasminewd2-0.0.5.tgz#528609a124dfc688c1e3f434a638e047066cd63e" 

As a result, node_modules/jasminewd2 contains the original version from the npm repository. How can I make yarn install my version instead?

Answer 1

I believe your solution doesn't work because jasminewd2 is a transitive dependency (of protractor ) and not a direct one. So when you add it directly, the transitive one isn't affected.

You can work around that using two approaches:

1. In case your change is temporary (meant for development or troubleshooting), you should yarn link as described in the documentation .
2. Otherwise, you can fork both protractor and jasminewd2 packages and reference them in the respective package.json s. package.json s syntax for that is "protractor": "<githubUser>/<githubRepo>" .

From my experience, the second approach has a caveat in the form of npm's cache: your git repo's HEAD is only pulled when that dependency is first installed . After that, it is kept cached and keeps getting reinstalled every time - even when your repo's HEAD has changed.

That's why I usually reference a commit hash as part of the dependency like so: "dependency": "user/repo.git#aef38fb2adc73304ae1ea87b0d607ad7fadc4d0g" . I didn't try this trick with yarn , but assume it behaves the exact same way (by design via the lockfile).

Answer 2

Overriding a submodule using postinstall and git

The " npm way " requires a specific commit (or version/tag) to install a package from a git repository, more info on npm install . I usually create a custom branch and push on that, so I wanted the possibility to clone a custom branch for testing a specific feature or just leaving master alone.

To override a package I use the postinstall hook hook of npm.

I add a script to postinstall in package.json :

"scripts": {
  "postinstall": "./postinstall.sh",
  "start": "node index.js"
},

Then I use a bash script ( postinstall.sh ) for removing packages and cloning them from github:

#!/bin/sh

function override_pkg {
  USER=$1
  REPO=$2
  DEST=$3

  rm -rf node_modules/$DEST

  echo "Overriding $DEST..."

  if [ -d custom_modules/$DEST ]; then
    cd custom_modules/$DEST
    git pull
    cd ../../
  else
    case $REPO in
      *:*)
      REPOBR=(${REPO//:/ })
      git clone -b ${REPOBR[1]} https://github.com/$USER/${REPOBR[0]}.git custom_modules/$DEST
      ;;
      *)
      git clone https://github.com/$USER/$REPO.git custom_modules/$DEST
      ;;
    esac
  fi

  npm install custom_modules/$DEST
}

# func       user    repo   branch dest
override_pkg johndoe myrepo:branch mynpmpackage

The script clones a package in the custom_modules folder, then it uses npm to install the local package to node_modules . The branch name after : is optional.

In the case of OP should be something like this:

override_pkg johndoe jasminewd:jasminewd2 jasminewd2

Then yarn:

yarn

If I do some local changes on the local git repository in custom_modules\\mypackage I call yarn again for re-override the pacakge.

If I change machine and I got already a local version of my custom package, then calling yarn will pull from the repository and override the pacakge.

PS. npm install works too, but yarn is a bit faster.

Multiple environments for testing purposes

This is a different idea, but sometimes I used it for testing different configurations. Maybe people can find it useful or if anyone knows a tool or something for doing this, please tell me.

Locally I create two distinct folders for node_modules like this:

First the original modules:

yarn --modules-folder=original-modules

Flags:

• --modules-folder <path> rather than installing modules into the node_modules folder relative to the cwd, output them here.

Then for the custom ones, I can simply copy original-modules for a clone:

cp -r original-modules custom-modules

Or I can use yarn to add more custom modules:

yarn add <modulename> --no-lockfile --modules-folder=custom-modules

Flags:

• --no-lockfile don't read or generate a lockfile

When I'm happy with the custom-modules folder I can switch between environments like this using NODE_PATH :

For the normal env:

NODE_PATH=original-modules npm start

Custom envrionment:

NODE_PATH=custom-modules npm start

It is important that the node_modules folder does not exist or the override will not work, the local node_modules folder has higher priority than NODE_PATH .