Building NodeJS using Gradle

Question

I'm very new to Gradle. I started reading about it yesterday. I found an example build.gradle that builds a node application. I'm a little bit confused in the contents of the file. I'm not sure which ones are reserved or predefined words. One of the strings is node. It wasn't used somewhere but I figured out it was needed by the node plugin.

    buildscript {
        repositories {
            mavenCentral()
            maven {
                url 'https://plugins.gradle.org/m2/'
            }
        }

        dependencies {
            classpath 'com.moowork.gradle:gradle-node-plugin:1.2.0'
        }
    }

    apply plugin: 'base'
    apply plugin: 'com.moowork.node' // gradle-node-plugin

    node {
        /* gradle-node-plugin configuration
        https://github.com/srs/gradle-node-plugin/blob/master/docs/node.md

        Task name pattern:
        ./gradlew npm_<command> Executes an NPM command.
        */

        // Version of node to use.
        version = '10.14.1'

        // Version of npm to use.
        npmVersion = '6.4.1'

        // If true, it will download node using above parameters.
        // If false, it will try to use globally installed node.
        download = true
    }

    npm_run_build {
        // make sure the build task is executed only when appropriate files change
        inputs.files fileTree('public')
        inputs.files fileTree('src')

        // 'node_modules' appeared not reliable for dependency change detection (the task was rerun without changes)
        // though 'package.json' and 'package-lock.json' should be enough anyway
        inputs.file 'package.json'
        inputs.file 'package-lock.json'

        outputs.dir 'build'
    }

    // pack output of the build into JAR file
    task packageNpmApp(type: Zip) {
        dependsOn npm_run_build
        baseName 'npm-app'
        extension 'jar'
        destinationDir file("${projectDir}/build_packageNpmApp")
        from('build') {
            // optional path under which output will be visible in Java classpath, e.g. static resources path
            into 'static'
        }
    }

    // declare a dedicated scope for publishing the packaged JAR
    configurations {
        npmResources
    }

    configurations.default.extendsFrom(configurations.npmResources)

    // expose the artifact created by the packaging task
    artifacts {
        npmResources(packageNpmApp.archivePath) {
            builtBy packageNpmApp
            type 'jar'
        }
    }

    assemble.dependsOn packageNpmApp

    String testsExecutedMarkerName = "${projectDir}/.tests.executed"

    task test(type: NpmTask) {
        dependsOn assemble

        // force Jest test runner to execute tests once and finish the process instead of starting watch mode
        environment CI: 'true'

        args = ['run', 'test']

        inputs.files fileTree('src')
        inputs.file 'package.json'
        inputs.file 'package-lock.json'

        // allows easy triggering re-tests
        doLast {
            new File(testsExecutedMarkerName).text = 'delete this file to force re-execution JavaScript tests'
        }
        outputs.file testsExecutedMarkerName
    }

    check.dependsOn test

    clean {
        delete packageNpmApp.archivePath
        delete testsExecutedMarkerName
    }

Also, how is the build.gradle parsed? I'm also wondering how it is able to magically download node and npm tools.

Answer 1

This is a very general synopsis:

• Gradle aims to hide away the logic from developers.
• Most *.gradle files contain configuration blocks (closures) to specify HOW logic should run.
• Plugins augment gradle with more configurable logic.
• Also, 'convention over configuration' is a practice emphasize in gradle and its plugins, providing sensible defaults to minimize developers' configuration efforts.
• The com.moowork.node plugin is configured through the node extension block.
• Extension blocks are gradle's way to allow plugins to add more 'reserved' words to the standard gradle model.
• The download = true configuration tells the plugin to download node (version = '10.14.1') and nmp (npmVersion = '6.4.1') in your project's root (unless you override its defaults as well).
• The download of these tools will occur when any of the plugin's task is invoked.

Hope this helps.