Fix a number of bugs reported for JSX indentation (caused by poor JSX detection): - https://github.com/mooz/js2-mode/issues/140#issuecomment-166250016 - https://github.com/mooz/js2-mode/issues/490 - Bug#24896 / https://github.com/mooz/js2-mode/issues/389 (with respect to comments) - Bug#26001 / https://github.com/mooz/js2-mode/issues/389#issuecomment-271869380 - https://github.com/mooz/js2-mode/issues/411 / Bug#27000 / https://github.com/mooz/js2-mode/issues/451 Potentially manifest some new bugs (due to false positives with ‘<’ and ‘>’ and SGML detection). Slow down indentation a fair bit. * list/progmodes/js.el (js-jsx-syntax, js--jsx-start-tag-re) (js--looking-at-jsx-start-tag-p, js--looking-back-at-jsx-end-tag-p): New variables and functions. (js--jsx-find-before-tag, js--jsx-after-tag-re): Deleted. (js--looking-at-operator-p): Don’t mistake a JSXOpeningElement for the ‘<’ operator. (js--continued-expression-p): Don’t mistake a JSXClosingElement as a fragment of a continued expression including the ‘>’ operator. (js--as-sgml): Simplify. Probably needn’t bind forward-sexp-function to nil (sgml-mode already does) and probably shouldn’t bind parse-sexp-lookup-properties to nil either (see Bug#24896). (js--outermost-enclosing-jsx-tag-pos): Find enclosing JSX more accurately than js--jsx-find-before-tag. Use sgml-mode’s parsing logic, rather than unreliable heuristics like paren-wrapping. This implementation is much slower; the previous implementation was fast, but at the expense of accuracy. To make up for all the grief we’ve caused users, we will prefer accuracy over speed from now on. That said, this can still probably be optimized a lot. (js--jsx-indented-element-p): Rename to js--jsx-indentation, since it doesn’t just return a boolean. (js--jsx-indentation): Refactor js--jsx-indented-element-p to simplify the implementation as the improved accuracy of other code allows (and to repent for some awful stylistic choices I made earlier). (js--expression-in-sgml-indent-line): Rename to js--indent-line-in-jsx-expression, since it’s a private function and we can give it a name that reads more like English. (js--indent-line-in-jsx-expression): Restructure point adjustment logic more like js-indent-line. (js--indent-n+1th-jsx-line): New function to complement js--indent-line-in-jsx-expression. (js-jsx-indent-line): Refactor. Don’t bind js--continued-expression-p to ignore any more; instead, rely on the improved accuracy of js--continued-expression-p. (js-jsx-mode): Set js-jsx-syntax to t. For now, this will be the flag we use to determine whether ‘JSX is enabled.’ (Maybe later, we will refactor the code to use this variable instead of requiring js-jsx-mode to be enabled, thus rendering the mode obsolete.)