Add StringBefore function with test

src/core/etl/src/Flow/ETL/Function/ScalarFunctionChain.php

@@ -482,6 +482,11 @@ public function startsWith(ScalarFunction|string $needle) : self
         return new StartsWith($this, $needle);
     }
 
+    public function stringBefore(ScalarFunction|string $needle, ScalarFunction|bool $includeNeedle = false) : self
+    {
+        return new StringBefore($this, $needle, $includeNeedle);
+    }
+
     public function stringFold() : self
     {
         return new StringFold($this);

src/core/etl/src/Flow/ETL/Function/StringBefore.php

@@ -0,0 +1,39 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Flow\ETL\Function;
+
+use function Flow\ETL\DSL\{type_list, type_string};
+use function Symfony\Component\String\u;
+use Flow\ETL\Function\ScalarFunction\TypedScalarFunction;
+use Flow\ETL\PHP\Type\Type;
+use Flow\ETL\Row;
+
+final class StringBefore extends ScalarFunctionChain implements TypedScalarFunction
+{
+    public function __construct(
+        private readonly ScalarFunction|string $string,
+        private readonly ScalarFunction|string $needle,
+        private readonly ScalarFunction|bool $includeNeedle = false,
+    ) {
+    }
+
+    public function eval(Row $row) : mixed
+    {
+        $string = (new Parameter($this->string))->asString($row);
+        $needle = (new Parameter($this->needle))->as($row, type_string(), type_list(type_string()));
+        $includeNeedle = (new Parameter($this->includeNeedle))->asBoolean($row);
+
+        if ($string === null) {
+            return null;
+        }
+
+        return u($string)->before($needle, $includeNeedle)->toString();
+    }
+
+    public function returns() : Type
+    {
+        return type_string();
+    }
+}

src/core/etl/tests/Flow/ETL/Tests/Unit/Function/StringBeforeTest.php

@@ -0,0 +1,60 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Flow\ETL\Tests\Unit\Function;
+
+use function Flow\ETL\DSL\row;
+use function Flow\ETL\DSL\{ref, str_entry, type_string};
+use Flow\ETL\Function\StringTitle;
+use Flow\ETL\PHP\Type\Type;
+use Flow\ETL\Tests\FlowTestCase;
+
+final class StringBeforeTest extends FlowTestCase
+{
+    public function test_returns_method_returns_string_type() : void
+    {
+        $stringTitleFunction = new StringTitle('str');
+        $returnType = $stringTitleFunction->returns();
+
+        self::assertInstanceOf(Type::class, $returnType);
+
+        self::assertTrue($returnType->isEqual(type_string()));
+    }
+
+    public function test_string_before() : void
+    {
+        self::assertSame(
+            'hello ',
+            ref('str')->stringBefore(ref('needle'))->eval(
+                row(
+                    str_entry('str', 'hello world'),
+                    str_entry('needle', 'world')
+                )
+            )
+        );
+
+        self::assertSame(
+            'hell',
+            ref('str')->stringBefore(ref('needle'))->eval(
+                row(
+                    str_entry('str', 'hello world'),
+                    str_entry('needle', 'o')
+                )
+            )
+        );
+    }
+
+    public function test_string_before_including_needle() : void
+    {
+        self::assertSame(
+            'hello',
+            ref('str')->stringBefore(ref('needle'), includeNeedle: true)->eval(
+                row(
+                    str_entry('str', 'hello world'),
+                    str_entry('needle', 'o')
+                )
+            )
+        );
+    }
+}