Improve database collation detection (5.1.x)

core/Db/Schema/Mysql.php

@@ -671,26 +671,19 @@ public function supportsComplexColumnUpdates(): bool
     /**
      * Returns the default collation for a charset.
      *
+     * Will return an empty string for an unknown charset
+     * (can happen for alias charsets like "utf8").
+     *
      * @param string $charset
      *
      * @return string
      * @throws Exception
      */
     public function getDefaultCollationForCharset(string $charset): string
     {
-        $result = $this->getDb()->fetchRow(
-            'SHOW COLLATION WHERE `Default` = "Yes" AND `Charset` = ?',
-            [$charset]
-        );
+        $result = $this->getDb()->fetchRow('SHOW CHARACTER SET WHERE `Charset` = ?', [$charset]);
 
-        if (!isset($result['Collation'])) {
-            throw new Exception(sprintf(
-                'Failed to detect default collation for character set "%s"',
-                $charset
-            ));
-        }
-
-        return $result['Collation'];
+        return $result['Default collation'] ?? '';
     }
 
     public function getDefaultPort(): int
@@ -723,7 +716,13 @@ protected function getDatabaseCreateOptions(): string
         $charset = DbHelper::getDefaultCharset();
         $collation = $this->getDefaultCollationForCharset($charset);
 
-        return "DEFAULT CHARACTER SET $charset COLLATE $collation";
+        $options = "DEFAULT CHARACTER SET $charset";
+
+        if ('' !== $collation) {
+            $options .= " COLLATE $collation";
+        }
+
+        return $options;
     }
 
     protected function getTableEngine()

plugins/Diagnostics/Diagnostic/DatabaseAbilitiesCheck.php

@@ -105,15 +105,17 @@ protected function checkCollation(): DiagnosticResultItem
         $collationConnection = Db::get()->fetchOne('SELECT @@collation_connection');
         $collationCharset = DbHelper::getDefaultCollationForCharset($dbSettings->getUsedCharset());
 
-        return new DiagnosticResultItem(
-            DiagnosticResult::STATUS_WARNING,
-            sprintf(
-                'Connection collation<br/><br/>%s<br/><br/>%s<br/>%s<br/>',
-                $this->translator->translate('Diagnostics_DatabaseCollationNotConfigured'),
-                $this->translator->translate('Diagnostics_DatabaseCollationConnection', [$collationConnection]),
-                $this->translator->translate('Diagnostics_DatabaseCollationCharset', [$collationCharset])
-            )
+        $message = sprintf(
+            'Connection collation<br/><br/>%s<br/><br/>%s<br/>',
+            $this->translator->translate('Diagnostics_DatabaseCollationNotConfigured'),
+            $this->translator->translate('Diagnostics_DatabaseCollationConnection', [$collationConnection])
         );
+
+        if ('' !== $collationCharset) {
+            $message .= $this->translator->translate('Diagnostics_DatabaseCollationCharset', [$collationCharset]) . '<br/>';
+        }
+
+        return new DiagnosticResultItem(DiagnosticResult::STATUS_WARNING, $message);
     }
 
     protected function checkLoadDataInfile()

tests/PHPUnit/Integration/DbHelperTest.php

@@ -130,12 +130,9 @@ public function testGetDefaultCollationForCharset(): void
         self::assertStringStartsWith($expectedPrefix, $collation);
     }
 
-    public function testGetDefaultCollationForCharsetThrowsForInvalidCharset(): void
+    public function testGetDefaultCollationForCharsetWithoutDefault(): void
     {
-        self::expectException(\Exception::class);
-        self::expectExceptionMessage('Failed to detect default collation for character set "invalid"');
-
-        DbHelper::getDefaultCollationForCharset('invalid');
+        self::assertSame('', DbHelper::getDefaultCollationForCharset('invalid'));
     }
 
     private function assertDbExists($dbName)