Add support for string concatenation (using || operator) (#226)

Co-authored-by: Martin Georgiev <martin-georgiev@users.noreply.github.com>

docs/AVAILABLE-FUNCTIONS-AND-OPERATORS.md

@@ -22,6 +22,7 @@
 | !~ | NOT_REGEXP | `MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\NotRegexp` |
 | !~* | NOT_IREGEXP | `MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\NotIRegexp` |
 | @@ | TSMATCH | `MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\Tsmatch` |
+| \|\| | STRCONCAT | `MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\StrConcat` |
 
 # Available functions
 

docs/INTEGRATING-WITH-LARAVEL.md

@@ -158,6 +158,7 @@ return [
         'REGEXP_LIKE' => MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\RegexpLike::class,
         'FLAGGED_REGEXP_MATCH' => MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\FlaggedRegexpMatch::class,
         'REGEXP_MATCH' => MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\RegexpMatch::class,
+        'STRCONCAT' => MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\StrConcat::class, // the `||` operator
     ],
 
     ...

docs/INTEGRATING-WITH-SYMFONY.md

@@ -154,4 +154,5 @@ doctrine:
                         REGEXP_LIKE: MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\FlaggedRegexpLike
                         FLAGGED_REGEXP_MATCH: MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\FlaggedRegexpMatch
                         REGEXP_MATCH: MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\RegexpMatch
+                        STRCONCAT: MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\StrConcat
 ```

src/MartinGeorgiev/Doctrine/ORM/Query/AST/Functions/StrConcat.php

@@ -0,0 +1,23 @@
+<?php
+
+declare(strict_types=1);
+
+namespace MartinGeorgiev\Doctrine\ORM\Query\AST\Functions;
+
+/**
+ * Implementation of PostgreSQL's string concatenation operator (using `||`).
+ *
+ * @see https://www.postgresql.org/docs/15/functions-string.html
+ * @since 2.6.0
+ *
+ * @author Alexander Makarov <sam@rmcreative.ru>
+ */
+class StrConcat extends BaseFunction
+{
+    protected function customiseFunction(): void
+    {
+        $this->setFunctionPrototype('(%s || %s)');
+        $this->addNodeMapping('StringPrimary');
+        $this->addNodeMapping('StringPrimary');
+    }
+}

tests/MartinGeorgiev/Doctrine/ORM/Query/AST/Functions/StrConcatTest.php

@@ -0,0 +1,32 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\MartinGeorgiev\Doctrine\ORM\Query\AST\Functions;
+
+use Fixtures\MartinGeorgiev\Doctrine\Entity\ContainsTexts;
+use MartinGeorgiev\Doctrine\ORM\Query\AST\Functions\StrConcat;
+
+class StrConcatTest extends TestCase
+{
+    protected function getStringFunctions(): array
+    {
+        return [
+            'STRCONCAT' => StrConcat::class,
+        ];
+    }
+
+    protected function getExpectedSqlStatements(): array
+    {
+        return [
+            "SELECT (c0_.text1 || 'text2') AS sclr_0 FROM ContainsTexts c0_",
+        ];
+    }
+
+    protected function getDqlStatements(): array
+    {
+        return [
+            \sprintf("SELECT STRCONCAT(e.text1, 'text2') FROM %s e", ContainsTexts::class),
+        ];
+    }
+}