Assets.absoluteFilePath() is undocumented and doesn't work in build plugins

[tmeasday]

CF: 134707b#commitcomment-16742686

In the above commit, Assets.absoluteFilePath was implemented in tools/static-assets/server/boot.js. However the documentation for the other Assets APIs is in tools/isobuild/bundler.js, where the Assets APIs are duplicated.

This was confusing. It turns out the reason for this is when you are using the asset API from a build plugin. The only way you can do this is:

1. You have a build plugin X, that depends on package Y.
2. X calls Y.foo()
3. Y.foo() calls Assets.Z() -- this version of Assets.Z() is the bundler.js version.

Note that if Y.foo() is called from application code (possibly via some other package), it will use the version in boot.js.

The issue is that in bundler.js, we have the contents of the asset but not the on-disk path. This makes implementing Assets.absoluteFilePath difficult there.

Options from here:

1. Leave Assets.absoluteFilePath() undocumented.
2. Document Assets.absoluteFilePath() in boot.js and explain the limitation there (it's probably unlikely anyone will ever even try to use in the above way.
3. Try and figure out a way to implement Assets.absoluteFilePath() in the bundler.js context (if this is even possible.

[aldeed]

I like option 2, at least until someone complains it doesn't work in the build plugin.

[tmeasday]

Ok, finally did this.