Add support for highlighting typedoc/jsdoc comments

[lddubeau]

Having proper highlighting of typedoc/jsdoc comments, besides providing visual help, would allow skipping things that don't need spell-checking when using flyspell-prog-mode.

For instance, in the following:

/**
 * @param {SomeType} blah something
 */

The only thing that needs spell checking is "something". The rest is either a typedoc/jsdoc tag (@param), a type reference (SomeType) or a parameter name (blah). Flyspell determines whether a piece of text should be spell-checked by seeing whether it has any of the faces in flyspell-prog-text-faces. Right now typescript-mode assigns font-lock-comment-face to the whole comment and thus everything is subject to spell checking.

As usual, js-mode has no support for this, whereas js2-mode distinguishes the various parts appropriately.

[josteink]

I support the idea, but I don't have time to implement this right now.

In my email to emacs-devel for issue #48, I've also mentioned the ability to escape not only strings but also comments...

So maybe we'll in time see some more fundamental building blocks to handle syntax like this.

In the meantime, I guess the simplest way to land this for now (in a cross-version compatible way) would be simple font-lock regexes.

What that won't solve though (iirc) is the syntax-properties of the highlighted text, so flyspell-prog-mode is probably still going to be noisy about these statements.

[lddubeau]

What that won't solve though (iirc) is the syntax-properties of the highlighted text, so flyspell-prog-mode is probably still going to be noisy about these statements.

Flyspell cares only about the faces used, not the syntax properties.

I've pushed an experiment to https://github.com/ananthakumaran/typescript.el/tree/experiment/typedoc-tags

It works but is still incomplete. The regular expressions were taken from js2-mode and the variable/face names were derived from those there.

Things that are missing to reduce the number of false misspelling errors reported by Flyspell, besides fleshing out the jsdoc/typedoc support:

1. The strings in import statements should not be spell checked. To support this though I'm thinking typescript-mode should acquire a custom predicate that Flyspell can use to know whether a word should be checked or not. I had forgotten this feature, but setting the property flyspell-mode-predicate on the mode's name overrides the default predicate that flyspell uses.

2. tslint flags should also be excluded from spell checking. I'm thinking it would be nice to also have them be fontified with a different face than font-lock-comment-face so that besides being excluded from spell checking, they stand out from random comments.

[josteink]

Link to the relevant emacs-devel thread for those interested:

https://lists.gnu.org/archive/html/emacs-devel/2017-08/msg00560.html

[lddubeau]

Fixed by 782e8dd and 7172a23