feat: add support for null literals

Author: CodeWithKyrian

src/AST/NullLiteral.php

@@ -0,0 +1,15 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Codewithkyrian\Jinja\AST;
+
+class NullLiteral extends Literal
+{
+    public string $type = "NullLiteral";
+
+    public function __construct()
+    {
+        parent::__construct(null);
+    }
+}

src/Core/Environment.php

@@ -70,6 +70,7 @@ public function __construct(?Environment $parent = null)
             },
             'false' => fn(RuntimeValue $operand) => $operand->type === "BooleanValue" && !$operand->value,
             'true' => fn(RuntimeValue $operand) => $operand->type === "BooleanValue" && $operand->value,
+            'null' => fn(RuntimeValue $operand) => $operand->type === "NullValue",
             'string' => fn(RuntimeValue $operand) => $operand->type === "StringValue",
             'number' => fn(RuntimeValue $operand) => $operand->type === "NumericValue",
             'integer' => function (RuntimeValue $operand) {

src/Core/Interpreter.php

@@ -82,6 +82,9 @@ function evaluate(?Statement $statement, Environment $environment): RuntimeValue
             case "BooleanLiteral":
                 return new BooleanValue($statement->value);
 
+            case "NullLiteral":
+                return new NullValue();
+
             case "ArrayLiteral":
                 $values = array_map(function ($x) use ($environment) {
                     return $this->evaluate($x, $environment);

src/Core/Lexer.php

@@ -121,11 +121,8 @@ public static function tokenize(string $source, bool $lstripBlocks = false, bool
             // Consume (and ignore) all whitespace inside Jinja statements or expressions
             $consumeWhile(fn($char) => preg_match('/\s/', $char));
 
-            //            if ($cursorPosition >= $srcLength) break; // End of input check
-
             $char = $src[$cursorPosition];
 
-
             // Check for unary operators
             if ($char === "-" || $char === "+") {
                 $lastTokenType = end($tokens)->type;
@@ -136,6 +133,7 @@ public static function tokenize(string $source, bool $lstripBlocks = false, bool
                     case TokenType::Identifier:
                     case TokenType::NumericLiteral:
                     case TokenType::BooleanLiteral:
+                    case TokenType::NullLiteral:
                     case TokenType::StringLiteral:
                     case TokenType::CloseParen:
                     case TokenType::CloseSquareBracket:

src/Core/Parser.php

@@ -15,6 +15,7 @@
 use Codewithkyrian\Jinja\AST\KeywordArgumentExpression;
 use Codewithkyrian\Jinja\AST\Macro;
 use Codewithkyrian\Jinja\AST\MemberExpression;
+use Codewithkyrian\Jinja\AST\NullLiteral;
 use Codewithkyrian\Jinja\AST\NumericLiteral;
 use Codewithkyrian\Jinja\AST\ObjectLiteral;
 use Codewithkyrian\Jinja\AST\Program;
@@ -541,16 +542,20 @@ private function parseMultiplicativeExpression(): Statement
     private function parseTestExpression(): Statement
     {
         $operand = $this->parseFilterExpression();
+
         while ($this->is(TokenType::Is)) {
             $this->current++; // consume is
             $negate = $this->is(TokenType::Not);
+
             if ($negate) {
                 $this->current++; // consume not
             }
+
             $filter = $this->parsePrimaryExpression();
             if ($filter instanceof BooleanLiteral) {
-                // PHP version: treating boolean literals as identifiers might require manual handling
                 $filter = new Identifier((string)$filter->value);
+            } elseif ($filter instanceof NullLiteral) {
+                $filter = new Identifier("none");
             }
             if (!($filter instanceof Identifier)) {
                 throw new SyntaxError("Expected identifier for the test");
@@ -597,6 +602,10 @@ private function parsePrimaryExpression(): Statement
                 $this->current++;
                 return new BooleanLiteral(strtolower($token->value) === "true");
 
+            case TokenType::NullLiteral:
+                $this->current++;
+                return new NullLiteral();
+
             case TokenType::Identifier:
                 $this->current++;
                 return new Identifier($token->value);

src/Core/Token.php

@@ -28,8 +28,10 @@ class Token
         // Literals
         'true' => TokenType::BooleanLiteral,
         'false' => TokenType::BooleanLiteral,
+        'none' => TokenType::NullLiteral,
         'True' => TokenType::BooleanLiteral,
         'False' => TokenType::BooleanLiteral,
+        'None' => TokenType::NullLiteral,
     ];
 
     public const ORDERED_MAPPING_TABLE = [

src/Core/TokenType.php

@@ -14,6 +14,7 @@ enum TokenType: string
     case Text = "Text";
     case NumericLiteral = "NumericLiteral"; // e.g., 123
     case BooleanLiteral = "BooleanLiteral"; // true or false
+    case NullLiteral = "NullLiteral"; // null
     case StringLiteral = "StringLiteral"; // 'string'
     case Identifier = "Identifier"; // Variables, functions, etc.
     case Equals = "Equals"; // =