Re: [GSoC][PATCH v2] Add a diff driver for JavaScript languages.

[xing zhi jiang <a97410985new@gmail.com>]

On Wed, 16 Mar 2022 at 05:34, Glen Choo <chooglen@google.com> wrote:
>
> Junio C Hamano <gitster@pobox.com> writes:
>
> > Glen Choo <chooglen@google.com> writes:
> >
> >> Interesting, I'll take note. I'm still personally not keen on supporting
> >> CommonJS-only patterns when we are purportedly trying to show diffs for
> >> JavaScript, but if we think this fits the style, I'm happy to oblige.
> >
> > The question is, with these patterns that are aware of CommonJS
> > convention, would your bog-standard-and-boring vanilla JS code be
> > detected incorrectly?  Becoming aware of popular conventions without
> > hurting others would be a good thing.
> >
> > And the "popular conventions" does not have to be limited to
> > CommonJS/Node.
>
> From the perspective of "'exports' is a special name", yes, we could
> detect vanilla JS code 'incorrectly' because, in vanilla JS, the names
> 'exports' or 'module.exports' are not special. So perhaps, one could
> imagine a browser-side script that deals with "imports" and "exports" as
> part of their business:
>
>   const exports = {
>     quantity: 1,
>     type: 'boxes',
>   };
>   exports.getQuantity = () => {
>     foo();
>   };
>
> This diff driver would mistakenly detect `exports.getQuantity = () =>
> {`.
>
> Although, the more I think about it, the spirit of this patch seems to
> be "we want to show headers whenever we think we are in a function", so
> we don't actually need to treat 'exports' or 'module.exports' specially
> at all, e.g. this case should also pass our diff driver tests:
>
>   const foo = {};
>   foo.RIGHT = () => {
>
>     ChangeMe();
>   };
>
> and if we do this, we will correctly handle 'exports' and
> 'module.exports' anyway by virtue of them being plain old JS objects.
The spirit of this patch is to show headers when we are in the
function body(which has a large code block). Because this can help
users understand the context.
And prevent mismatch non-related function. ex:
    function WRONG() {
        // ...
    }
    const foo = {};
    foo.RIGHT = () => {

      ChangeMe();
    };
if we don't match "foo.RIGHT = () => {". It may match the "function
WRONG() {". This would be very misleading.
So the v3 patch. I do not treat `exports` as a special keyword. And
can match the code like "foo.RIGHT = () => {".
The regex would be
"((module\\.)?[$_[:alpha:]][$_[:alnum:]]*\\.[$_[:alpha:]][$_[:alnum:]]*[\t
]*=[\t ]*(\\(.*\\)|[$_[:alpha:]][$_[:alnum:]]*)[\t ]*=>.*)"