RFC: uniform steps

[tripodsan]

Overview

the current pipeline has a clear separation of before, once and after pipeline functions.
This allows to easily replace the once action, but requires the extension mechanism to inject other steps. this proposal tries to remove this distinction and make it easier to manipulate an existing pipeline.

Proposal

1. Uniform steps

Deprecate (or remove): before(), once(), after() in favour of a single use() method that constructs the pipeline. Since the old methods were used in sequence anyways, they can easily just be mapped to theuse() method.

/**
 * Adds a processing function to this pipeline.
 * @param {pipelineFunction} f function to add.
 * @returns {Pipeline} this
 */
use(f:pipelineFunction):Pipeline;

Example:

pipe
  .every(dump.record)
  .before(fetch).expose('fetch').when(hascontent)
  .before(parse).expose('parse')
  .before(html).expose('html')
  .once(cont)
  .after(type('text/html'))
  .after(addHeaders)
  .after(tohtml)
  .after(debug)
  .after(timer.report)
  .error(dump.report)
  .error(selectStatus)

just becomes:

pipe
  .every(dump.record)
  .use(fetch).expose('fetch').when(hascontent)
  .use(parse).expose('parse')
  .use(html).expose('html')
  .use(cont)
  .use(type('text/html'))
  .use(addHeaders)
  .use(tohtml)
  .use(debug)
  .use(timer.report)
  .error(dump.report)
  .error(selectStatus)

2. Support replacing steps

Sometimes it might be convenient to modify an existing default pipeline. This is already marginally possible using attach.before() and attach.after(). However, it should also be possible to replace existing steps.

/**
 * Replaces an existing handler of this pipeline. The function `fn` will be run in
 * the pipeline instead the function called `name`. If `fn` is {@code null}, the 
 * respective function is removed. 
 * If `name` does not exist, this method has no effect.
 * @param {string} name - name of the extension point (typically the function name).
 * @param {pipelineFunction} fn - a new pipeline step that will replace `name`.
 * @returns {Pipeline} this.
 */
replace(name:string, fn:pipelineFunction):Pipeline;

Example:

module.exports.defaultPipe = pipe
  .use(fetch).expose('fetch').when(hascontent)
  .use(parse).expose('parse')
  .use(html).expose('html')
  .use(defaultRenderer).expose('render')
  .use(tohtml)
  .use(debug)
  .error(selectStatus)

some where else...

const p = require('./defaultPipe');
p.replace('render', myCoolRenderer).run(...);

[trieloff]

Let's do this.

[rofe]

👍 This would simplify things quite a bit.

[adobe-bot]

🎉 This issue has been resolved in version 5.0.0 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀