[elpa] externals/m-buffer a3078a58ed 055/115: exact-subtract no longer crashes on last non-match

[ELPA Syncer]

branch: externals/m-buffer
commit a3078a58edb50661c05c334d7a8c47b1b1188b70
Author: Phillip Lord <phillip.lord@newcastle.ac.uk>
Commit: Phillip Lord <phillip.lord@newcastle.ac.uk>

    exact-subtract no longer crashes on last non-match
    
    Previously exact-subtract would crash if the last element in n
    did not also occur in m. We now check for exhaustion of n explicitly and
    so avoid doing a numerical check between marker and nil.
---
 m-buffer.el           |  7 +++++++
 test/m-buffer-test.el | 16 ++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/m-buffer.el b/m-buffer.el
index a505c40156..96d8525c7c 100644
--- a/m-buffer.el
+++ b/m-buffer.el
@@ -374,10 +374,17 @@ runs faster but has some restrictions."
 Both M and N must be fully ordered, and any element in N must be
 in M."
   (if n
+      ;; n-eaten contains the remaining elements of n that we haven't tested
+      ;; for yet. We throw them away as we go
       (let ((n-eaten n))
         (-remove
          (lambda (o)
            (cond
+            ;; n-eaten has been eaten. Check here or later "<" comparison 
crashes.
+            ((not n-eaten)
+             ;; return nil because we always want things in m now.
+             nil
+             )
             ;; we have a match so throw away the first element of n-eaten
             ;; which we won't need again.
             ((m-buffer-match-equal
diff --git a/test/m-buffer-test.el b/test/m-buffer-test.el
index 3253ce2505..2e750c59ad 100644
--- a/test/m-buffer-test.el
+++ b/test/m-buffer-test.el
@@ -356,6 +356,22 @@
      '((1 1))
      nil))))
 
+(ert-deftest exact-subtract-error-simplified ()
+  (should
+   (equal
+    '((2 2))
+    (m-buffer-match-exact-subtract
+     '((1 1) (2 2))
+     '((1 1))))))
 
+(ert-deftest exact-subtract-error ()
+  "This is a test case for a bug found from linked-buffer."
+  (should
+   (equal
+    '((19 31 19 19))
+    (m-buffer-match-exact-subtract
+     '((1 18 1 1)
+       (19 31 19 19))
+     '((1 18))))))
 
 ;;; m-buffer-test.el ends here