bug#31318: emacs-26 fns-tests-collate-sort failure on glibc 2.27

[Paul Eggert <eggert@cs.ucla.edu>]

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I upgraded to Fedora 28 beta over the weekend (Fedora 28 is scheduled 
for release next week) and ran into one test case failure on the 
emacs-26 branch: fns-tests-collate-sort fails (test/src/fns-tests.log is 
attached). Looking into the test, it appears that the test is making 
unportable assumptions about strcoll behavior in non-POSIX locales, an 
assumption that is not true of glibc 2.27 as shipped in Fedora 28. 
Proposed patch attached.


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Running 37 tests (2018-04-30 10:14:49-0700)
Test fns-tests-collate-sort backtrace:
  signal(ert-test-failed (((should (equal (sort '("11" "1 2" "1.2" "12
  ert-fail(((should (equal (sort '("11" "1 2" "1.2" "12") (lambda (a b
  (if (unwind-protect (setq value-355 (apply fn-353 args-354)) (setq f
  (let (form-description-357) (if (unwind-protect (setq value-355 (app
  (let ((value-355 'ert-form-evaluation-aborted-356)) (let (form-descr
  (let* ((fn-353 (function equal)) (args-354 (condition-case err (let 
  (lambda nil (let* ((fn-343 (function fns-tests--collate-enabled-p)) 
  ert--run-test-internal(#s(ert--test-execution-info :test #s(ert-test
  ert-run-test(#s(ert-test :name fns-tests-collate-sort :documentation
  ert-run-or-rerun-test(#s(ert--stats :selector (not (or (tag :expensi
  ert-run-tests((not (or (tag :expensive-test) (tag :unstable))) #f(co
  ert-run-tests-batch((not (or (tag :expensive-test) (tag :unstable)))
  ert-run-tests-batch-and-exit((not (or (tag :expensive-test) (tag :un
  eval((ert-run-tests-batch-and-exit '(not (or (tag :expensive-test) (
  command-line-1(("-L" ":." "-l" "ert" "-l" "src/fns-tests.el" "--eval
  command-line()
  normal-top-level()
Test fns-tests-collate-sort condition:
    (ert-test-failed
     ((should
       (equal
	(sort ... ...)
	'...))
      :form
      (equal
       ("1 1" "1.1" "11" "1 2" "1.2" "12")
       ("11" "1 1" "1.1" "12" "1 2" "1.2"))
      :value nil :explanation
      (list-elt 0
		(arrays-of-different-length 3 2 "1 1" "11" first-mismatch-at 1))))
   FAILED   1/37  fns-tests-collate-sort
   passed   2/37  fns-tests-collate-strings
   passed   3/37  fns-tests-compare-strings
   passed   4/37  fns-tests-func-arity
   passed   5/37  fns-tests-hash-buffer
   passed   6/37  fns-tests-mapcan
   passed   7/37  fns-tests-nreverse
   passed   8/37  fns-tests-nreverse-bool-vector
   passed   9/37  fns-tests-reverse
   passed  10/37  fns-tests-reverse-bool-vector
   passed  11/37  fns-tests-sort
   passed  12/37  fns-tests-string-version-lessp
   passed  13/37  lax-plist-get/odd-number-of-elements
   passed  14/37  lax-plist-put/odd-number-of-elements
   passed  15/37  plist-get/odd-number-of-elements
   passed  16/37  plist-member/improper-list
   passed  17/37  plist-put/odd-number-of-elements
   passed  18/37  test-assoc-testfn
   passed  19/37  test-cycle-assoc
   passed  20/37  test-cycle-assq
   passed  21/37  test-cycle-delete
   passed  22/37  test-cycle-delq
   passed  23/37  test-cycle-equal
   passed  24/37  test-cycle-lax-plist-get
   passed  25/37  test-cycle-lax-plist-put
   passed  26/37  test-cycle-length
   passed  27/37  test-cycle-member
   passed  28/37  test-cycle-memq
   passed  29/37  test-cycle-memql
   passed  30/37  test-cycle-nconc
   passed  31/37  test-cycle-plist-get
   passed  32/37  test-cycle-plist-member
   passed  33/37  test-cycle-plist-put
   passed  34/37  test-cycle-rassoc
   passed  35/37  test-cycle-rassq
   passed  36/37  test-cycle-reverse
   passed  37/37  test-cycle-safe-length

Ran 37 tests, 36 results as expected, 1 unexpected (2018-04-30 10:14:52-0700)

1 unexpected results:
   FAILED  fns-tests-collate-sort


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From deaadc19c8a59b69bc53b735f9f66e93304010e9 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Mon, 30 Apr 2018 10:35:04 -0700
Subject: [PATCH] Port collation tests to glibc 2.27
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* test/src/fns-tests.el (fns-tests-collate-strings)
(fns-tests-collate-sort): Don’t make unportable assumptions
about how en_US.UTF-8 collation works.  These assumptions
are not true on Fedora 28, which ships with glibc 2.27.
---
 test/src/fns-tests.el | 48 +++++++++++++++++++++----------------------
 1 file changed, 24 insertions(+), 24 deletions(-)

diff --git a/test/src/fns-tests.el b/test/src/fns-tests.el
index f8554636ba..491915f56a 100644
--- a/test/src/fns-tests.el
+++ b/test/src/fns-tests.el
@@ -119,10 +119,9 @@ fns-tests--collate-enabled-p
 
   ;; In POSIX or C locales, collation order is lexicographic.
   (should (string-collate-lessp "XYZZY" "xyzzy" "POSIX"))
-  ;; In a language specific locale, collation order is different.
-  (should (string-collate-lessp
-	   "xyzzy" "XYZZY"
-	   (if (eq system-type 'windows-nt) "enu_USA" "en_US.UTF-8")))
+  ;; In a language specific locale on MS-Windows, collation order is different.
+  (when (eq system-type 'windows-nt)
+    (should (string-collate-lessp "xyzzy" "XYZZY" "en_US.UTF-8")))
 
   ;; Ignore case.
   (should (string-collate-equalp "xyzzy" "XYZZY" nil t))
@@ -154,8 +153,6 @@ fns-tests--collate-enabled-p
 	    (9 . "aaa") (9 . "zzz") (9 . "ppp") (9 . "fff")])))
 
 (ert-deftest fns-tests-collate-sort ()
-  ;; See https://lists.gnu.org/r/emacs-devel/2015-10/msg02505.html.
-  :expected-result (if (eq system-type 'cygwin) :failed :passed)
   (skip-unless (fns-tests--collate-enabled-p))
 
   ;; Punctuation and whitespace characters are relevant for POSIX.
@@ -165,15 +162,16 @@ fns-tests--collate-enabled-p
 	  (lambda (a b) (string-collate-lessp a b "POSIX")))
     '("1 1" "1 2" "1.1" "1.2" "11" "12")))
   ;; Punctuation and whitespace characters are not taken into account
-  ;; for collation in other locales.
-  (should
-   (equal
-    (sort '("11" "12" "1 1" "1 2" "1.1" "1.2")
-	  (lambda (a b)
-	    (let ((w32-collate-ignore-punctuation t))
-	      (string-collate-lessp
-	       a b (if (eq system-type 'windows-nt) "enu_USA" "en_US.UTF-8")))))
-    '("11" "1 1" "1.1" "12" "1 2" "1.2")))
+  ;; for collation in other locales, on MS-Windows systems.
+  (when (eq system-type 'windows-nt)
+    (should
+     (equal
+      (sort '("11" "12" "1 1" "1 2" "1.1" "1.2")
+            (lambda (a b)
+              (let ((w32-collate-ignore-punctuation t))
+                (string-collate-lessp
+                 a b "enu_USA"))))
+      '("11" "1 1" "1.1" "12" "1 2" "1.2"))))
 
   ;; Diacritics are different letters for POSIX, they sort lexicographical.
   (should
@@ -181,15 +179,17 @@ fns-tests--collate-enabled-p
     (sort '("Ævar" "Agustín" "Adrian" "Eli")
 	  (lambda (a b) (string-collate-lessp a b "POSIX")))
     '("Adrian" "Agustín" "Eli" "Ævar")))
-  ;; Diacritics are sorted between similar letters for other locales.
-  (should
-   (equal
-    (sort '("Ævar" "Agustín" "Adrian" "Eli")
-	  (lambda (a b)
-	    (let ((w32-collate-ignore-punctuation t))
-	      (string-collate-lessp
-	       a b (if (eq system-type 'windows-nt) "enu_USA" "en_US.UTF-8")))))
-    '("Adrian" "Ævar" "Agustín" "Eli"))))
+  ;; Diacritics are sorted between similar letters for other locales,
+  ;; on MS-Windows systems.
+  (when (eq system-type 'windows-nt)
+    (should
+     (equal
+      (sort '("Ævar" "Agustín" "Adrian" "Eli")
+            (lambda (a b)
+              (let ((w32-collate-ignore-punctuation t))
+                (string-collate-lessp
+                 a b "enu_USA"))))
+      '("Adrian" "Ævar" "Agustín" "Eli")))))
 
 (ert-deftest fns-tests-string-version-lessp ()
   (should (string-version-lessp "foo2.png" "foo12.png"))
-- 
2.17.0