JHipster-RFC-5: Modular needles.

• Feature Name: Modular needles.
• Start Date: 2022-05-25
• Issue: jhipster/generator-jhipster#0000

Summary

This RFC proposes to implement modular needles.

Motivation

JHipster 8 modular approach needs a new needle approach for a better modularity.

Guide-level explanation

JHipster 7 has lots of technology specific needles implemented at generator-base like:

• addIcon
• addElementToMenu
• addExternalResourcesToRoot
• addElementToAdminMenu
• addEntityToMenu
• addEntityToModule
• addAdminToModule
• addAngularModule
• addEntityToEhcache
• addChangelogToLiquibase
• addMainSCSSStyle
• addWebpackConfig
• addMavenPluginRepository
• Many others

Those needles should be implemented using a modular approach at the technology-specific generator.

Reference-level explanation

Needles will be implemented as a stand-alone function having the generator as first parameter. For convenience, it will be exposed at the technology-specific generator as a class member method.

export function aNeedle(generator, needleData) {
  if (!needles) {
    needles = generator;
    generator = null;
  }

 return createBaseNeedle(
  return createBaseNeedle(
    {
      generator,
      filePath, // File path for logging purpose
      needlesPrefix: 'needle-prefix',
    },
    needles
  );
}

export default class Generator {
  aNeedle(...args) {
    aNeedle(this, ...args);
  }
}

Using needles api inside a child generator:

import Generator from './base-generator.mjs'

export default class ChildGenerator extends Generator {
  get [POST_WRITING_PRIORITY]() {
    writeNeedle() {
      this.aNeedle(data);
    }
  }
}

Using a non-related generator:

import { aNeedle } from './base-generator.mjs'

export default class UnrelatedGenerator {
  get [POST_WRITING_PRIORITY]() {
    writeNeedle() {
      aNeedle(this, data);
    }
  }
}

Realistic example applying multiple needles in the same file:

import { addProperty, addDependency, addDependencyToDevProfile } from 'generator-jhipster/generators/java-simple-application/generators/maven'

export default class UnrelatedGenerator {
  get [POST_WRITING_PRIORITY]() {
    writeNeedle() {
      this.editFile('pom.xml',
        addProperty(properties),
        addDependency(prodDependencies),
        addDependencyToDevProfile(devDependencies)
      )
    }
  }
}

Drawbacks

Needles api will not be exposed to every generator by default. It needs to be imported to be used.

Rationale and alternatives

This will allow creating a modular implementation.

Unresolved questions

Implementation

Modular needle will be implemented in JHipster 7 keeping api stability and exposing the needles at generator-base.