[elpa] externals/xr 2c0af48 2/3: Detect repetition-of-repetition with intervening group

[Mattias Engdegård]

branch: externals/xr
commit 2c0af48a230a02e4db5439fc9b02c77757f37d03
Author: Mattias Engdegård <address@hidden>
Commit: Mattias Engdegård <address@hidden>

    Detect repetition-of-repetition with intervening group
    
    For example, \(.*\)* -- groups are often used even though capture is
    not needed. Exception: \(X+\)? does not elicit a warning.
---
 xr-test.el |  6 ++++++
 xr.el      | 27 +++++++++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/xr-test.el b/xr-test.el
index 526740d..f995bfa 100644
--- a/xr-test.el
+++ b/xr-test.el
@@ -363,6 +363,12 @@
                  '((2  . "Repetition of repetition")
                    (14 . "Repetition of repetition")
                    (25 . "Repetition of repetition"))))
+  (should (equal (xr-lint "\\(a*\\)*\\(b+\\)*\\(c*\\)?\\(d+\\)?")
+                 '((6 .  "Repetition of repetition")
+                   (13 . "Repetition of repetition")
+                   (20 . "Repetition of repetition"))))
+  (should (equal (xr-lint "\\(e*\\)\\{3\\}")
+                 '((6 . "Repetition of repetition"))))
   (should (equal (xr-lint "[]-Qa-fz-t]")
                  '((1 . "Reversed range `]-Q' matches nothing")
                    (7 . "Reversed range `z-t' matches nothing"))))
diff --git a/xr.el b/xr.el
index 1c74527..abe4d75 100644
--- a/xr.el
+++ b/xr.el
@@ -490,11 +490,27 @@ UPPER may be nil, meaning infinity."
                   (operand (car sequence)))
               (when warnings
                 (cond
+                 ;; (* (* X)), for any repetitions *
                  ((and (consp operand)
                        (memq (car operand)
                              '(opt zero-or-more one-or-more +? *? ??)))
                   (xr--report warnings (match-beginning 0)
                               "Repetition of repetition"))
+                 ;; (* (group (* X))), for any repetitions *
+                 ((and (consp operand)
+                       (eq (car operand) 'group)
+                       (null (cddr operand))
+                       (let ((inner (cadr operand)))
+                         (and (consp inner)
+                              (memq (car inner)
+                                    '(opt zero-or-more one-or-more +? *? ??))
+                              ;; Except (? (group (+ X))), since that may
+                              ;; be legitimate.
+                              (not (and (equal operator "?")
+                                        (memq (car inner)
+                                              '(one-or-more +?)))))))
+                  (xr--report warnings (match-beginning 0)
+                              "Repetition of repetition"))
                  ((memq operand xr--zero-width-assertions)
                   (xr--report warnings (match-beginning 0)
                               "Repetition of zero-width assertion"))
@@ -522,11 +538,22 @@ UPPER may be nil, meaning infinity."
         (let ((operand (car sequence)))
           (when warnings
             (cond
+             ;; (** N M (* X)), for any repetition *
              ((and (consp operand)
                    (memq (car operand)
                          '(opt zero-or-more one-or-more +? *? ??)))
               (xr--report warnings (match-beginning 0)
                           "Repetition of repetition"))
+             ;; (** N M (group (* X))), for any repetition *
+             ((and (consp operand)
+                   (eq (car operand) 'group)
+                   (null (cddr operand))
+                   (let ((inner (cadr operand)))
+                     (and (consp inner)
+                          (memq (car inner)
+                                '(opt zero-or-more one-or-more +? *? ??)))))
+              (xr--report warnings (match-beginning 0)
+                          "Repetition of repetition"))
              ((memq operand xr--zero-width-assertions)
               (xr--report warnings (match-beginning 0)
                           "Repetition of zero-width assertion"))