An idea of new plugin html-preparser

frissdiegurke

I guess your basic problem is: you don't know that javascript getter/setter can be defined (see my link to Object.defineProperty()).

I'll do some schematic code here (not tested):

function prepareData(data) {
  let postData = data.postData;
  let cache = null;
  let hasChanged = false;

  Object.defineProperty(data, "postDataWithoutCode", {
    set: function (value) {
      cache = value;
      hasChanged = true;
    },
    get: function () {
      if (cache == null) { cache = calculateCache(postData); }
      return cache;
    }
  });
  Object.defineProperty(data, "postData", {
    set: function (value) {
      postData = value;
      cache = null;
      hasChanged = false;
    },
    get: function () {
      if (hasChanged) { postData = calculatePostData(cache); hasChanged = false; }
      return postData;
    }
  });

  return data;
}

qgp9

@frissdiegurke I need to read a document what you gave more carefully , but before, is that so different from an usual OOP object which has 3 data-members and and 4 get/set accessors?

frissdiegurke

This way it calculates/merges at most as often as it's get/set (thus in worst case no performance decrease).
In best case (and likely case due to priority within hooks that'd be needed by those plugins) all plugins that know about the pre-parser are called in series thus it's only one calculation and one merge in total.

Overall: For m series of plugins that only use postDataWithoutCode there are m total calculations and merges.

@qgp9 It's pretty much like a private attribute and two public ones with get/set accessors except it's not needed to call those accessors explicitly. And we overwrite the get/set accessors of the original postData to keep in mind.

qgp9

@frissdiegurke Sorry, I read the documents, I don't understand some points. I may be missing some key point/feature of javascript.

My question is simply that,

How does pre-parser deal with a plugin which doesn't call any function/method of pre-parser?

In long, If plugin E knows nothing of pre-parser, How pre-prarse decide to merge cache to postdata when D called setWithoutCode. Any other chance after D's set before E take data in usual way?

qgp9

And If pre-parser has to decide and manage data Before a next plugin in a filtering pipe because of above reason ( D->E ), then again How pre-parser know next plugin will call getAnything in that moment?

frissdiegurke

When E does anything to the postData, it means E calls at least once the getter of postData; Thus the cache gets merged to the postData first (postData = calculatePostData(cache);). So E gets all changes of previous plugins.

When E does modify the postData the cache gets cleared to be re-generated when D gets postDataWithoutCode.

It's not about knowing which plugins comes next, but about providing up-to-date information when it is required.

We don't have to merge the cache back before the original data is required.
We don't have to calculate the cache before it's required.

qgp9

@frissdiegurke

OK, now I understand. Those getter and setter doesn't mean literal 'getpostData' but they are invoked whenever postData is accessed and modified. right?

I was totally stupid while reading. I have to go home. too tired

I see, let me think more based on that. I understand your story now, but not sure yet that's really better way or not.

Thank you!

frissdiegurke

@qgp9 said:

@frissdiegurke

OK, now I understand. Those getter and setter doesn't mean literal 'getpostData' but they are invoked whenever postData is accessed and modified. right?

Yes

I was totally stupid while reading. I have to go home. too tired

I see, let me think more based on that. I understand your story now, but not sure yet that's really better way or not.

If you find any cons let me know.

Thank you!

You're welcome

qgp9

@frissdiegurke said:

If you find any cons let me know.

Pros

Your method is very flexible. One can cooperate with other plugins just by just control of priorities. This is really un-replaceable advantage.
Also I can imagine that we could do this without activated NodeBB plugin called pre-parser but just with helper module per each plugin. I'm not sure of update and version control with npm, but I believe there are certain solutions.

Cons

If we want to provide "image list" or "link list" above "contents without code block", a situation will become too complicate. Without accurate and elaborate priorities configurations, we will loose an advantage in resources. In this situation, separated filtering pipe will be better.
Your method actually will be touching - let's say - core object. I think this is what we have to be very careful. In the future when NodeBB core development team wants to use get/set of postData, it can be a big problem. Actually it may be possible we check if there are already get/seter and make new get/seter which include old function, but depend on type of original functions, it's not easy to guarantee a proper working. I think a better way could be a pre-registration of plugins which use pre-parser and pre-parser access whole filtering pipe information and decide what to do in each step. An disadvantage of this is that after uninformed plugin before next get call of cached value, pre-parser should check what is changed.

Now what I want to say here is that your method is really brilliant and has un-replaceable advantage but too deep and touching core ( maybe not practically yet but conceptually ). Therefore it needs to be consulted by a core development team.

In other point, your method is quite independent from my custom filter hooks and we can even take both advantages ( of course it will make another problem like Too much or Too complicate :), but just as an idea ).

qgp9

So now, I have questions to the NodeBB development team. @julian

About @frissdiegurke 's idea.
- What do you think? Is it secure or do you have any better ideas, policies , plans?
To manage dependencies between plugin,
- Can we enforce to install and activate plugins by dependencies?
- Or can we give warnings of wrong configurations, dependencies and so on by plugin on admin UI ( dash board? )?
Do we have secure way to add/remove/modify custom data by plugin in a filtering pipe?
- For example, on filtering hook, data.pluginData.<plugin name> can be always for plugins (means some sure for core will not use it for different reason!! ), whether they are removed or not after filtering. I know if I select good name( random or highly uniq), then it will be quite safe but it will be better if we have an official space.
If I want to make a npm module which is dedicated to NodeBB while it's not a plugin, then what is good name for. Maybe nodebb-helper-any-name. It may be for individual plugins.

I had one more, but I forgot what was it while writing....