bug #24594 [Translation] Fix InvalidArgumentException when using untranslated plural forms from .po files (BjornTwachtmann)

This PR was squashed before being merged into the 3.3 branch (closes #24594).

Discussion
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[Translation] Fix InvalidArgumentException when using untranslated plural forms from .po files

| Q             | A
| ------------- | ---
| Branch?       | 3.2
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #24593
| License       | MIT

This PR fixes the bug in #24593. It's not the absolutely ideal way to address the issue, but I don't see how else to handle it without either dropping support for pips in translation strings, or rearchitecting the code that feeds translations to the MessageSelector as pipe separated in the first place.

Commits
-------

fea815b2f5 [Translation] Fix InvalidArgumentException when using untranslated plural forms from .po files

Author: fabpot

MessageSelector.php

@@ -49,10 +49,16 @@ class MessageSelector
      */
     public function choose($message, $number, $locale)
     {
-        preg_match_all('/(?:\|\||[^\|])++/', $message, $parts);
+        $parts = array();
+        if (preg_match('/^\|++$/', $message)) {
+            $parts = explode('|', $message);
+        } elseif (preg_match_all('/(?:\|\||[^\|])++/', $message, $matches)) {
+            $parts = $matches[0];
+        }
+
         $explicitRules = array();
         $standardRules = array();
-        foreach ($parts[0] as $part) {
+        foreach ($parts as $part) {
             $part = trim(str_replace('||', '|', $part));
 
             if (preg_match('/^(?P<interval>'.Interval::getIntervalRegexp().')\s*(?P<message>.*?)$/xs', $part, $matches)) {
@@ -76,7 +82,7 @@ public function choose($message, $number, $locale)
         if (!isset($standardRules[$position])) {
             // when there's exactly one rule given, and that rule is a standard
             // rule, use this rule
-            if (1 === count($parts[0]) && isset($standardRules[0])) {
+            if (1 === count($parts) && isset($standardRules[0])) {
                 return $standardRules[0];
             }
 

Tests/MessageSelectorTest.php

@@ -128,6 +128,10 @@ public function getChooseTests()
             array("This is a text with a\nnew-line in it. Selector = 1.", "{0}This is a text with a\nnew-line in it. Selector = 0.|{1}This is a text with a\nnew-line in it. Selector = 1.|[1,Inf]This is a text with a\nnew-line in it. Selector > 1.", 1),
             // esacape pipe
             array('This is a text with | in it. Selector = 0.', '{0}This is a text with || in it. Selector = 0.|{1}This is a text with || in it. Selector = 1.', 0),
+            // Empty plural set (2 plural forms) from a .PO file
+            array('', '|', 1),
+            // Empty plural set (3 plural forms) from a .PO file
+            array('', '||', 1),
         );
     }
 }