Gatsby: [gatsby-source-wordpress] Extend Normalisers

[moshie]

Description

It would be great if we could implement our own normalizers for manipulating WordPress entities.

For example when we want to search and replace the hostname in URLs.

I was playing around with a simple PR where normalizers are passed via the options object then executed like so:

  for (let i = 0; i < normalizers.length; i++) {
    if (typeof normalizers[i] === 'function') {
      entities = normalizers[i](entities)
      continue
    }
  }

This is a very crude example ideally you would prepare the code to accept promises as well as functions.

The remark package has some similar extension functionality

Environment

Gatsby version: Latest
Node.js version: 8.2.1
Operating System: OSX El Capitan

File contents (if changed):

gatsby-config.js: not changed
package.json: not changed
gatsby-node.js: not changed
gatsby-browser.js: not changed
gatsby-ssr.js: not changed

[calcsam]

This sounds like a great idea! Feel free to implement this!

[KyleAMathews]

Yeah, plugins can have plugins (which could have plugins!!!!!!! — but don't do that :-)). So this sounds great.

Though for this particular example of replacing hostnames — that sounds like something the source plugin should handle directly?

[moshie]

Great! I'll take a closer look at implementing this properly and submitting a PR soon!

I think your right about the replacement of hostnames being handled in the plugin, I'll write up a normaliser to do this.

[moshie]

I had difficulty testing this package any tips?

Also hope the PR is ok Let me know if you require any amendments.

[KyleAMathews]

@moshie checkout https://www.gatsbyjs.org/docs/how-to-contribute/#contributing

[Fetten]

Thought of passing custom normalizers as well today via gatsby-config.js and played around with an implementation before I saw this issue :)

Any progress on this? Do you need help with anything, @moshie?

[moshie]

Apologies, I have been short on time this week I have been working on bits here and there.

I will have something PR'd soon I promise() 👍

[moshie]

So I was thinking about how this might work and came up with this idea of setting the normalisers to an object.

Some people may want to run a normaliser before the "built in" ones so I specified a priority argument to define when it gets called, I was thinking the default priority could just be anything after.

This way also allows you to define multiple normalisers in one plugin.

// Plugin
// 
exports.normalizer = function (normalizer) {

    function modifyEntitys(entities, args) {
        // Normalizer
        return entities;
    }

    // returns normalizer
    return normalizer.set(modifyEntitys, 20); // callback, priority
}

[Fetten]

Giving priorities is a great idea! How about giving the built-in normalizers a priority as well, so you could modify entities between two of them?
Just a quick thought, could make things more complicated and might be a bit overengineered as well.

[moshie]

Glad you think so! I think that's a good idea about giving the built in normalisers the same priority argument, Ill write it up and report back soon :)

[moshie]

I am sort of stuck / out of my depth with this one.
Can't think of a clean way of integrating custom normalisers with the already coded ones.
I would appreciate a hand in making this happen.

[KyleAMathews]

Could you get by with a new normalize option that got called with each entity after all the built-in ones are finished? That wouldn't complicate the code much and would let you fix urls and other normal tweaks.

[KyleAMathews]

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