bug#27841: 25.2; Patch for completion-table-with-predicate

[Ryan Thompson <rct@thompsonclan.org>]

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Ok, here is the revised patch. I added a test and reformatted the commit
message in (hopefully) ChangeLog format. The test includes a few basic
tests of "completion-table-with-predicate" including one which is fixed by
this patch (noted in the test comments).

I've dropped the second patch entirely, because I realized it was
inappropriately optimizing for a rare case (i.e. PRED1 being nil).

Also, a few other related things: First, I noticed that while the test file
name is minibuffer-tests.el, the lisp header and provide statement both
contain "completion-tests.el" instead. Presumably this file was renamed at
some point without updating its contents.

Second, I notice that there is not much in this file, in particular nothing
testing interactive completion in the minibuffer. I recently wrote a
package for simulating interactive input to a command in order to implement
tests for my ido-comrpleting-read+ package, and it might be useful for
adding more tests here. You can view it here:
https://github.com/DarwinAwardWinner/with-simulated-input and view example
usage in the ido-cr+ test suite here:
https://github.com/DarwinAwardWinner/ido-completing-read-plus/blob/master/tests/test-ido-completing-read%2B.el


Let me know if there is interest in using such an approach to add automated
tests for some of the core interactive Emacs functions like
"completing-read".

On Fri, Aug 4, 2017 at 4:11 PM Dmitry Gutov <dgutov@yandex.ru> wrote:

> On 8/5/17 2:00 AM, Ryan Thompson wrote:
> > Would you also like me
> > to provide an example where the old code does the wrong thing?
>
> Adding a test case or two to test/lisp/minibuffer-tests.el would be
> ideal (in the same patch that fixes it).
>

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From b5313defb1132021bd86d5d385e8ea6d2d92a663 Mon Sep 17 00:00:00 2001
From: "Ryan C. Thompson" <rct@thompsonclan.org>
Date: Wed, 26 Jul 2017 11:09:42 -0700
Subject: [PATCH] Fix a bug in completion-table-with-predicate

	* ../lisp/minibuffer.el (completion-table-with-predicate): Don't
	act as if strict is non-nil when pred2 is nil (Bug#27841).
	* ../test/lisp/minibuffer-tests.el
	(completion-table-with-predicate-test): Add a test for Bug#27841.
---
 lisp/minibuffer.el            |  2 +-
 test/lisp/minibuffer-tests.el | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index e5b1029c01..bb8cf21ad2 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -392,7 +392,7 @@ obeys predicates."
                                   (and (funcall pred1 x) (funcall pred2 x)))))
         ;; If completion failed and we're not applying pred1 strictly, try
         ;; again without pred1.
-        (and (not strict) pred1 pred2
+        (and (not strict) pred1
              (complete-with-action action table string pred2))))))
 
 (defun completion-table-in-turn (&rest tables)
diff --git a/test/lisp/minibuffer-tests.el b/test/lisp/minibuffer-tests.el
index 7c5fcb4838..b209ae1c22 100644
--- a/test/lisp/minibuffer-tests.el
+++ b/test/lisp/minibuffer-tests.el
@@ -42,5 +42,39 @@
         (should (equal (buffer-string)
                        "test: "))))))
 
+(ert-deftest completion-table-with-predicate-test ()
+  (cl-letf* ((full-collection
+              '("apple"                  ; Has A
+                "beet"                   ; Has B
+                "banana"                 ; Has A & B
+                "cherry"                 ; Has neither
+                ))
+             ((symbol-function 'no-A)
+              (lambda (x) (not (string-match-p "a" x))))
+             ((symbol-function 'no-B)
+              (lambda (x) (not (string-match-p "b" x)))))
+    (should
+     (member "cherry"
+             (completion-table-with-predicate
+              full-collection 'no-A t "" 'no-B t)))
+    (should-not
+     (member "banana"
+             (completion-table-with-predicate
+              full-collection 'no-A t "" 'no-B t)))
+    ;; "apple" should still match when strict is nil
+    (should (eq t (try-completion
+                   "apple"
+                   (apply-partially
+                    'completion-table-with-predicate
+                    full-collection 'no-A nil)
+                   'no-B)))
+    ;; "apple" should still match when strict is nil and pred2 is nil
+    ;; (Bug#27841)
+    (should (eq t (try-completion
+                   "apple"
+                   (apply-partially
+                    'completion-table-with-predicate
+                    full-collection 'no-A nil))))))
+
 (provide 'completion-tests)
 ;;; completion-tests.el ends here
-- 
2.13.4