Version 2.0 of package Xr has just been released in GNU ELPA. You can now find it in M-x list-packages RET.
Xr describes itself as: ==================================== Convert string regexp to rx notation ==================================== More at https://elpa.gnu.org/packages/xr.html ## Summary: xr -- Emacs regexp parser and analyser ====================================== XR converts Emacs regular expressions to the structured rx form, thus being an inverse of rx. It can also find mistakes and questionable constructs inside regexp strings. It can be useful for: - Migrating existing code to rx form - Understanding what a regexp string really means - Finding errors in regexp strings It can also parse and find mistakes in skip-sets, the regexp-like arguments to skip-chars-forward and skip-chars-backward. The xr package can be used interactively or by other code as a library. * Example (xr-pp "\\`\\(?:[^^]\\|\\^\\(?: \\*\\|\\[\\)\\)") outputs (seq bos (or (not (any "^")) (seq "^" (or " *" "[")))) ## Recent NEWS: xr version history ================== Version 2.0 - Compatibility break: `xr-lint` and `xr-skip-set-lint` now return a two-level list of diagnostics, each of which now include an endpoint and severity field. The diagnostics are grouped so that messages that apply to the same problem are in the same middle-level list. - Most warnings are now accompanied by info-level messages that point out related parts of the input string. - `xr-lint` and `xr-skip-set-lint` no longer signal errors for invalid syntax; they are now returned as error-level messages. Other functions such as `xr` now signal `xr-parse-error` when the input string contains something that Emacs would not accept. - Emacs version 27 or later now required - Further performance improvements Version 1.25 - Effective repetition of repetition check now always enabled - Some performance improvements Version 1.24 - \w and \W are now translated to (syntax word) and (not (syntax word)), instead of [[:word:]] and [^[:word:]] which are not exact equivalents. - Repetition operators are now literals after \`. For example, \`* is now (seq bos "*"), not (* bos), because this is how Emacs works. - New lint check: find [A-z] (range between upper and lower case) - New `checks' argument to xr-lint, used to enable these new checks: - Detect [+-X] and [X-+] (range to/from '+') - Detect [\\t] etc (escape sequences in character alternative) - Detect \(:?...\), as a possible typo for \(?:...\) - Detect a\|b that could be [ab] which is more efficient - Detect effective repetition of repetition such as \(A+B*\)* Version 1.23 - Represent explicitly the gap in ranges from ASCII to raw bytes: "[A-\xbb]" becomes (any "A-\x7f\x80-\xbb") because that is how Emacs regexps work. This also suppresses some false positives in `xr-lint' and `xr-skip-set-lint'. Version 1.22 - More compact distribution Version 1.21 - Suppress false complaint about (? (+ X)) Version 1.20 - Fix duplication removal in character alternatives, like [aaa] - All diagnostics are now described in the README file - Improved anchor conflict checks Version 1.19 - Added filename-specific checks; new PURPOSE argument to `xr-lint' - Warn about wrapped subsumption, like \(A*C[AB]*\)+ - Improved scope and accuracy of all subsumption checks - Warn about anchors in conflict with other expressions, like \(A$\)B Version 1.18 - Fix test broken in Emacs 26 Version 1.17 - Performance improvements Version 1.16 - Translate [^\n] into nonl - Better character class subset/superset analysis - More accurate repetition subsumption check - Use text quoting for messages Version 1.15 - Warn about subsuming repetitions in sequence, like [AB]+A* Version 1.14 - Warn about repetition of grouped repetition Version 1.13 - More robust pretty-printing, especially for characters - Generate (category CHAR) for unknown categories Version 1.12 - Warn about branch subsumption, like [AB]\|A Version 1.11 - Warn about repetition of empty-matching expressions - Detect `-' not first or last in char alternatives or skip-sets - Stronger ad-hoc [...] check in skip-sets Version 1.10 - Warn about [[:class:]] in skip-sets - Warn about two-character ranges like [*-+] in regexps Version 1.9 - Don't complain about [z-a] and [^z-a] specifically - Improved skip set checks Version 1.8 - Improved skip set checks Version 1.7 - Parse skip-sets, adding `xr-skip-set', `xr-skip-set-pp' and `xr-skip-set-lint' - Ad-hoc check for misplaced `]' in regexps Version 1.6 - Detect duplicated branches like A\|A Version 1.5 - Add dialect option to `xr' and `xr-pp' - Negative empty sets, [^z-a], now become `anything' Version 1.4 - Detect overlap in character alternatives Version 1.3 - Improved xr-lint warnings Version 1.2 - `xr-lint' added
