feature/noverlay a2fde77b5c: Fix handling of overlays that begin at END in 'overlays_in'

[Stefan Monnier]

branch: feature/noverlay
commit a2fde77b5cc15ec5a1c29ca72c97c806204818a9
Author: Matt Armstrong <matt@rfc20.org>
Commit: Matt Armstrong <matt@rfc20.org>

    Fix handling of overlays that begin at END in 'overlays_in'
    
    When passed EMPTY, 'overlays_in' should return empty overlays at END.
    It was doing so, but it was also returning any other overlay that
    happened to begin at END.
    
    bug#58672
    
    * src/buffer.c (overlays_in): Don't return overlays at END unless they
    are empty overlays.
    (disable_line_numbers_overlay_at_eob): Pass 'false' instead of 'NULL'
    for the bool 'empty' arg.
    * test/src/buffer-tests.el (sorted-overlays-in): New helper function.
    (test-overlays-in-empty-range): New test exhaustively covering these
    edge conditions.
    (test-overlays-in-empty-range-bug58672): Simple test for one case.
---
 src/buffer.c             | 11 +++++++----
 test/src/buffer-tests.el | 45 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+), 4 deletions(-)

diff --git a/src/buffer.c b/src/buffer.c
index 3286cd338f..fe6b515493 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -2940,7 +2940,8 @@ the normal hook `change-major-mode-hook'.  */)
    [BEG, END).
 
    If EMPTY is true, include empty overlays in that range and also at
-   END, provided END denotes the position at the end of the buffer.
+   END, provided END denotes the position at the end of the accessible
+   part of the buffer.
 
    Return the number found, and store them in a vector in *VEC_PTR.
    Store in *LEN_PTR the size allocated for the vector.
@@ -2968,7 +2969,7 @@ overlays_in (ptrdiff_t beg, ptrdiff_t end, bool extend,
   struct itree_node *node;
 
   ITREE_FOREACH (node, current_buffer->overlays, beg,
-                 /* Find empty OV at Z ? */
+                 /* Find empty OV at ZV ? */
                  (end >= ZV && empty) ? ZV + 1 : ZV, ASCENDING)
     {
       if (node->begin > end)
@@ -2985,6 +2986,8 @@ overlays_in (ptrdiff_t beg, ptrdiff_t end, bool extend,
               ITREE_FOREACH_ABORT ();
               break;
             }
+          if (empty && node->begin != node->end)
+            continue;
         }
 
       if (! empty && node->begin == node->end)
@@ -3111,11 +3114,11 @@ disable_line_numbers_overlay_at_eob (void)
 
   size = ARRAYELTS (vbuf);
   v = vbuf;
-  n = overlays_in (ZV, ZV, 0, &v, &size, NULL, NULL);
+  n = overlays_in (ZV, ZV, 0, &v, &size, false, NULL);
   if (n > size)
     {
       SAFE_NALLOCA (v, 1, n);
-      overlays_in (ZV, ZV, 0, &v, &n, NULL, NULL);
+      overlays_in (ZV, ZV, 0, &v, &n, false, NULL);
     }
 
   for (i = 0; i < n; ++i)
diff --git a/test/src/buffer-tests.el b/test/src/buffer-tests.el
index 3833f88c5c..6d5d9913a0 100644
--- a/test/src/buffer-tests.el
+++ b/test/src/buffer-tests.el
@@ -937,6 +937,51 @@ with parameters from the *Messages* buffer modification."
 (deftest-overlays-in-1 ae 9 11 (a) (a 10 10))
 (deftest-overlays-in-1 af 10 11 (a) (a 10 10))
 
+(defun sorted-overlays-in (beg end)
+  (sort
+   (mapcar (lambda (overlay)
+             (list (overlay-start overlay)
+                   (overlay-end overlay)))
+           (overlays-in beg end))
+   (lambda (first second)
+     (cl-loop for a in first
+              for b in second
+              thereis (< a b)
+              until (> a b)))))
+
+;; behavior for empty range
+(ert-deftest test-overlays-in-empty-range ()
+    (with-temp-buffer
+      (insert (make-string 4 ?x))
+      (cl-loop for start from (point-min) to (point-max)
+               do (cl-loop for end from start to (point-max)
+                           do (when (<= start end)
+                                (make-overlay start end))))
+
+      (cl-loop for pos from (point-min) to (point-max)
+               do (ert-info ((format "after (overlay-recenter %d)" pos))
+                    (overlay-recenter pos)
+                    (should (equal
+                             '((1 1))
+                             (sorted-overlays-in (point-min) (point-min))))
+                    (should (equal
+                             '((1 3) (1 4) (1 5) (2 2))
+                             (sorted-overlays-in 2 2)))
+                    (should (equal
+                             '((1 4) (1 5) (2 4) (2 5) (3 3))
+                             (sorted-overlays-in 3 3)))
+                    (should (equal
+                             '((1 5) (2 5) (3 5) (4 4))
+                             (sorted-overlays-in 4 4)))
+                    (should (equal
+                             '((5 5))
+                             (sorted-overlays-in (point-max) (point-max))))))))
+
+(ert-deftest test-overlays-in-empty-range-bug58672 ()
+  (with-temp-buffer
+    (insert (make-string 10 ?=))
+    (make-overlay 5 7 nil nil t)
+    (should (equal nil (overlays-in 5 5)))))
 
 ;; behavior at point-max
 (ert-deftest test-overlays-in-2 ()