Angular.js: 1.6.x: underscore prefix is not ignored in attribute directive's name

[curlydevil]

I'm submitting a ...

• [x] bug report
• [ ] feature request
• [ ] other (Please do not submit support requests here (see above))

Current behavior:
Attribute directive registered as e.g. "t" and used on elements as "_t" is not working.

Expected / new behavior:
Attribute directive registered as e.g. "t" can be used as "_t" again.

Minimal reproduction of the problem with instructions:
comment/uncomment 1.6 vs 1.5 ng version to see the difference
https://plnkr.co/edit/earjy4mhjccYIexn7WYk?p=preview

AngularJS version: 1.x.y
1.5.x - works as described in 'expected' section, 1.6.x - does not work.

Browser:
not a browser-specific issue

Anything else:
My best guess, this bug was introduced in this commit:
https://github.com/angular/angular.js/commit/73050cdda04675bfa6705dc841ddbbb6919eb048#diff-a732922b631efed1b9f33a24082ae0dbR3600

[petebacondarwin]

I can confirm that this is a bug. It appears that the regex replace is converting the _t to T rather than t, which stops it from being matched as a directive.

[petebacondarwin]

Previously our camelCase utility didn't upper case the letter if the preceding "special" character was at the start of the name:

   replace(SPECIAL_CHARS_REGEXP, function(_, separator, letter, offset) {
      return offset ? letter.toUpperCase() : letter;
    }).

[petebacondarwin]

But I wonder if this change was "on purpose" as part of 73050cdda04675bfa6705dc841ddbbb6919eb048... @mgol could say.

[petebacondarwin]

One option to fix this could be to update the PREFIX_REGEXP to capture and remove these special character prefixes before they get to the fnCamelCaseReplace if this is functioning as required for camel casing in general.

[curlydevil]

Is there any chance for this to be fixed in the nearest future?

[petebacondarwin]

@mgol confirmed that it is a regression. We now need a PR to fix it. Fancy having a go at that @curlydevil ?

[curlydevil]

@petebacondarwin I'll try)

[curlydevil]

@petebacondarwin I've created a PR but created it into master... should I (in case it passes CR and gets merged) create another one for v1.6.x branch?

[petebacondarwin]

No against master is fine. We will cherry-pick as necessary.