Patching node modules: Liferay Angular Build for pre-production

TL;DR: How to patch a node module package after execute npm install

Oh! This module needs a patch!

Why the hell do you need to patch a node module package?

Sometimes you are working in a npm project and a module dependency not works properly. You can submit a issue to its CVS (normally GitHub) but you can’t wait until the authors resolve it or approve your PR.

What can we do then? Well, we can patch the package after its installation.

We use a real example: Liferay Angular portlet build process.

Life Angular portlet

To build a 100% Angular Liferay portlet, we use a Liferay’s support libraries (lnbs-*).

It’s works perfectly if we build for a production environment. But, what’s happen if I want to build for pre-production environment? And for QA? DevOps?

Damn it! You can’t (by this moment).

After review the Liferay Build Support code, we can confirm which the “ — prod” build flag is “hardcoded”.

What can we do now?

Well, the solution is simple. Just replace the hard coded flags with optional configuration passed by arguments.

Simple, not?

Well, we only have to give it shape and automate the patching.

Creating the patch

Before coding the changes, we create a backup of the file (or files) to change.

After coding the changes directly under node_modules’ package source and test to works properly.

No just execute the diffcommand to create the patch and saves it into patches folder (for example).

diff file-orig node_modules/package/src/file-mod > patches/package.patch

The patch file for our examples is the following:

Patching in post-install

Just only we need to apply the patch after the npm install is executed.

The easiest way is by defining the predefined postinstallnpm command.

In our package.json just add a command similar to the following:

"scripts": {
"postinstall": "patch -N node_modules/liferay-npm-build-support/lib/scripts/build/index.js patches/liferay-builder-conf.patch || true"

And that’s all.

Now when we run the “npm install” the patch will be applied automatically.

Please, if you liked it, give it a round of applause. And if you want to know more about DevOps, Kubernetes, Docker, etc … follow me :)

Thanks so much!!!

CTO @ & Beyond-Full-stack developer #go #python #kubernetes

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