Prefer single-quoted strings (#31)

* Prefer single-quoted strings

* Update quotes

src/Libero/ruleset.xml

@@ -63,6 +63,9 @@
     </rule>
     <rule ref="Squiz.Classes.ClassFileName"/>
     <rule ref="Squiz.PHP.InnerFunctions"/>
+    <rule ref="Squiz.Strings.DoubleQuoteUsage">
+        <exclude name="Squiz.Strings.DoubleQuoteUsage.ContainsVar"/>
+    </rule>
     <rule ref="Squiz.WhiteSpace.CastSpacing"/>
     <rule ref="Squiz.WhiteSpace.ObjectOperatorSpacing">
         <properties>

tests/RulesetTests.php

@@ -88,7 +88,7 @@ public function cases() : iterable
             if (empty($parts['contents'])) {
                 throw new LogicException("Couldn't find contents in {$file->getRelativePathname()}");
             } elseif (empty(select_keys($parts, $keys))) {
-                throw new LogicException("Expected one of ".implode(', ', $keys)." in {$file->getRelativePathname()}");
+                throw new LogicException('Expected one of '.implode(', ', $keys)." in {$file->getRelativePathname()}");
             }
 
             try {

tests/cases/php/string-quotes

@@ -0,0 +1,23 @@
+---DESCRIPTION---
+Double quotes must not be used for strings unless required
+---CONTENTS---
+<?php
+
+declare(strict_types=1);
+
+$foo = "bar";
+$baz = "qux {$quux}";
+$quuz = "'";
+$corge = "\n";
+
+---FIXED---
+<?php
+
+declare(strict_types=1);
+
+$foo = 'bar';
+$baz = "qux {$quux}";
+$quuz = "'";
+$corge = "\n";
+
+---