How to tell gradle to install npm within the project on build?

Question

My angular 4 UI for a java web application depends only on the below few bundles. I ran the below commands from webapps root. App works fine. I want to know the best practices as I'm new to angular.

npm install rxjs
npm install @angular/[email protected] @angular/[email protected] @angular/[email protected] @angular/[email protected] @angular/[email protected] @angular/[email protected] @angular/[email protected] --save
npm install [email protected] --save
npm install [email protected] --save

I'm referring the installed bundles from systemjs.config.js like below:

paths: {
       'npm:' : 'node_modules/'
},
map: {
       '@angular/core' : 'npm:@angular/core/bundles/core.umd.js'
       .
       .
}

Queries:

1. The app should not be heavy, could not include the entire node_modules in war
2. If I keep node_modules in project root instead of webapps, how do I refer it from systemjs.config.js
3. I just want those bundles and not the huge file stack that gets downloaded while running npm install @angular/cli
4. If we can use global node_modules, how to refer to that from systemjs.config.js (I prefer keeping it within project not to disturb other applications in the server using different versions)
5. Finally, what should I include in build.gradle to download the required bundles while gradle builds

Solution 1

As @Oliver Charlesworth said, Gradle has his limitations, but you can create a custom gradle task.

Example:

task npmInstall(type: Exec) {
    workingDir 'src/main/webapp'
    commandLine 'npm', 'install'
}

Add the build dependency to your war build step

war {
    dependsOn npmBuild
}

Solution 2

As Tim Hovius says: you can create your own task.

If you don't want it to execute all the time, you can add the OnlyIf clause.

(From the official documentation: https://docs.gradle.org/current/dsl/org.gradle.api.Task.html#org.gradle.api.Task:onlyIf(groovy.lang.Closure)

myTask.onlyIf(new Spec<Task>() {
    boolean isSatisfiedBy(Task task) {
        return isProductionEnvironment();
    }
});

OR

You can write the task more intelligently using standard Groovy. For example:

task doSomething {
    doLast {
        def file = new File("dummy.txt")

        if (file.exists()) {
            project.exec {
                commandLine 'someCommand', 'parameter'
            }
        }
    }
}

OR

In your build.gradle for example

task doSomething {
   doLast {
        ...
   }
}

doSomething.enabled = (some condition goes here)    

Comments

[Oliver Charlesworth]

Gradle doesn't have native understanding of the JS ecosystem. You can try e.g. the gradle-node-plugin, but it's a bit limited, in my experience.

[Oliver Charlesworth]

The issue with this is it's going to run npm install every time. So ideally you want to find some way to denote when the task is up to date.

[Tim Hovius]

You are right, but the dependencies will be downloaded once, so only the first time the task consumes some time.