[FEATURE] Allow null coalesce operator in evaluation (#522)

src/Core/Parser/SyntaxTree/Expression/NullcoalescingExpressionNode.php

@@ -0,0 +1,85 @@
+<?php
+namespace TYPO3Fluid\Fluid\Core\Parser\SyntaxTree\Expression;
+
+/*
+ * This file belongs to the package "TYPO3 Fluid".
+ * See LICENSE.txt that was shipped with this package.
+ */
+
+use TYPO3Fluid\Fluid\Core\Compiler\TemplateCompiler;
+use TYPO3Fluid\Fluid\Core\Parser\BooleanParser;
+use TYPO3Fluid\Fluid\Core\Parser\SyntaxTree\BooleanNode;
+use TYPO3Fluid\Fluid\Core\Rendering\RenderingContextInterface;
+use TYPO3Fluid\Fluid\Core\Variables\VariableExtractor;
+
+/**
+ * Null Coalescing Condition Node - allows the shorthand of a null check
+ * for a default value as `{nullableVar ?? valueIfNull}`
+ */
+class NullcoalescingExpressionNode extends AbstractExpressionNode
+{
+
+    /**
+     * Pattern which detects null coalescing conditions written in shorthand
+     * syntax, e.g. {nullableVar ?? valueIfNull}.
+     */
+    public static $detectionExpression = '/
+		(
+			{                                                               # Start of shorthand syntax
+				(?:                                                         # Math expression is composed of...
+					[\\!_a-zA-Z0-9.\(\)\!\|\&\\\'\'\"\=\<\>\%\s\{\}\:\,]+    # Check variable side
+					[\s]?\?\?[\s]?
+					[_a-zA-Z0-9.\s\'\"\\.]+                                  # Fallback value side
+				)
+			}                                                               # End of shorthand syntax
+		)/x';
+
+    /**
+     * Filter out variable names form expression
+     */
+    protected static $variableDetection = '/[^\'_a-zA-Z0-9\.\\\\]{0,1}([_a-zA-Z0-9\.\\\\]*)[^\']{0,1}/';
+
+    /**
+     * @param RenderingContextInterface $renderingContext
+     * @param string $expression
+     * @param array $matches
+     * @return mixed
+     */
+    public static function evaluateExpression(RenderingContextInterface $renderingContext, $expression, array $matches)
+    {
+        $parts = preg_split('/([\?\?])/s', $expression);
+        $parts = array_map([__CLASS__, 'trimPart'], $parts);
+
+        foreach($parts as $part) {
+            $value = static::getTemplateVariableOrValueItself($part, $renderingContext);
+            if(!is_null($value)) {
+                return $value;
+            }
+        }
+
+        return null;
+    }
+
+
+    /**
+     * @param mixed $candidate
+     * @param RenderingContextInterface $renderingContext
+     * @return mixed
+     */
+    protected static function getTemplateVariableOrValueItself($candidate, RenderingContextInterface $renderingContext)
+    {
+        $variables = $renderingContext->getVariableProvider()->getAll();
+        $extractor = new VariableExtractor();
+        $suspect = $extractor->getByPath($variables, $candidate);
+
+        if (is_numeric($candidate)) {
+            $suspect = $candidate;
+        } elseif (mb_strpos($candidate, '\'') === 0) {
+            $suspect = trim($candidate, '\'');
+        } elseif (mb_strpos($candidate, '"') === 0) {
+            $suspect = trim($candidate, '"');
+        }
+
+        return $suspect;
+    }
+}

src/Core/Rendering/RenderingContext.php

@@ -14,6 +14,7 @@
 use TYPO3Fluid\Fluid\Core\Parser\Interceptor\Escape;
 use TYPO3Fluid\Fluid\Core\Parser\SyntaxTree\Expression\CastingExpressionNode;
 use TYPO3Fluid\Fluid\Core\Parser\SyntaxTree\Expression\MathExpressionNode;
+use TYPO3Fluid\Fluid\Core\Parser\SyntaxTree\Expression\NullcoalescingExpressionNode;
 use TYPO3Fluid\Fluid\Core\Parser\SyntaxTree\Expression\TernaryExpressionNode;
 use TYPO3Fluid\Fluid\Core\Parser\TemplateParser;
 use TYPO3Fluid\Fluid\Core\Parser\TemplateProcessor\EscapingModifierTemplateProcessor;
@@ -106,6 +107,7 @@ class RenderingContext implements RenderingContextInterface
     protected $expressionNodeTypes = [
         CastingExpressionNode::class,
         MathExpressionNode::class,
+        NullcoalescingExpressionNode::class,
         TernaryExpressionNode::class,
     ];
 

tests/Unit/Core/Parser/SyntaxTree/Expression/NullcoalescingExpressionNodeTest.php

@@ -0,0 +1,59 @@
+<?php
+namespace TYPO3Fluid\Fluid\Tests\Unit\Core\Parser\SyntaxTree;
+
+/*
+ * This file belongs to the package "TYPO3 Fluid".
+ * See LICENSE.txt that was shipped with this package.
+ */
+
+use TYPO3Fluid\Fluid\Core\Parser\SyntaxTree\Expression\NullcoalescingExpressionNode;
+use TYPO3Fluid\Fluid\Core\Rendering\RenderingContext;
+use TYPO3Fluid\Fluid\Core\Variables\StandardVariableProvider;
+use TYPO3Fluid\Fluid\Tests\UnitTestCase;
+
+/**
+ * Class TernaryExpressionNodeTest
+ */
+class NullcoalescingExpressionNodeTest extends UnitTestCase
+{
+
+
+    /**
+     * @dataProvider getEvaluateExpressionTestValues
+     * @param string $expression
+     * @param array $variables
+     * @param mixed $expected
+     */
+    public function testEvaluateExpression($expression, array $variables, $expected)
+    {
+        $renderingContext = new RenderingContext();
+        $renderingContext->setVariableProvider(new StandardVariableProvider($variables));
+        $result = NullcoalescingExpressionNode::evaluateExpression($renderingContext, $expression, []);
+        $this->assertEquals($expected, $result);
+    }
+
+    /**
+     * @return array
+     */
+    public function getEvaluateExpressionTestValues()
+    {
+        return [
+            ['{a ?? 1}', ['a' => 'a'], 'a'],
+            ['{a ?? 1}', ['a' => null], 1],
+            ['{a ?? b}', ['a' => 'a', 'b' => 'b'], 'a'],
+            ['{a ?? b}', ['a' => null, 'b' => 'b'], 'b'],
+            ['{a ?? b ?? c}', ['a' => 1, 'b' => 2, 'c' => 3], 1],
+            ['{a ?? b ?? c}', ['a' => 1, 'b' => null, 'c' => 3], 1],
+            ['{a ?? b ?? c}', ['a' => null, 'b' => 2, 'c' => 3], 2],
+            ['{a ?? b ?? c}', ['a' => null, 'b' => null, 'c' => 3], 3],
+            ['{a ?? b ?? c}', ['a' => 'd', 'b' => 'e', 'c' => 'f'], 'd'],
+            ['{a ?? b ?? c}', ['a' => 'd', 'b' => null, 'c' => 'f'], 'd'],
+            ['{a ?? b ?? c}', ['a' => null, 'b' => 'e', 'c' => 'f'], 'e'],
+            ['{a ?? b ?? c}', ['a' => null, 'b' => null, 'c' => 'f'], 'f'],
+            ['{a ?? b ?? c}', ['a' => null, 'b' => null, 'c' => null], null],
+            ['{a ?? b ?? \'test\'}', ['a' => null, 'b' => null], 'test'],
+            ['{a ?? b ?? "test"}', ['a' => null, 'b' => null], 'test'],
+
+        ];
+    }
+}