bug#41897: 28.0.50; JavaScript comment filling with mhtml-mode

[Dmitry Gutov]

On 25.06.2020 19:33, Alan Mackenzie wrote:

> > I imagine that would not be a significant problem for the rare cases
> > that fill-paragraph is called in a JS region. Considering most of the
> > contents in mhtml-mode buffers are not JS code, on average, that should
> > tilt the scales in favor of parsing lazily, rather than affecting every
> > character insertion.
>
> The current patch does parse lazily.  You want to remove the benefit of
> using this cache, no matter how small, for reasons I still can't grasp.

That's not true. Like you confirmed, c-fill-paragraph refers to that 
cache multiple times. We'll only make sure the cache is reset in the 
beginning.

> > > It sounds like you want to use a facility without initialising it.
> > > This feels a bit unreasonable.
>
> > That cache reset at the beginning of js-fill-paragraph could as well
> > re-initialize the cache.
>
> You're misusing the work "initialize" here.  If you initialise a variable
> every time you read it, you might as well not have that variable.

Like explained above, not *every* time.

> > It doesn't automatically work in mmm-mode. With my suggestion, it very
> > likely would.
>
> It would work fine with the current patch, together with calls to
> initialise the mechanism.  What precisely is the problem in mmm-mode?

That there is no good place to plug in your new functions.

And, in general, to have per-mode before-change-functions contents.