Fix literal array with empty item outside of left-side assign

Author: ondrejmirtes

conf/config.level0.neon

@@ -17,6 +17,7 @@ parametersSchema:
 
 rules:
 	- PHPStan\Rules\Arrays\DuplicateKeysInLiteralArraysRule
+	- PHPStan\Rules\Arrays\EmptyArrayItemRule
 	- PHPStan\Rules\Arrays\OffsetAccessWithoutDimForReadingRule
 	- PHPStan\Rules\Classes\ClassConstantRule
 	- PHPStan\Rules\Classes\DuplicateDeclarationRule

src/Analyser/NodeScopeResolver.php

@@ -1755,10 +1755,10 @@ function (MutatingScope $scope) use ($expr, $nodeCallback, $context): Expression
 			$itemNodes = [];
 			$hasYield = false;
 			foreach ($expr->items as $arrayItem) {
+				$itemNodes[] = new LiteralArrayItem($scope, $arrayItem);
 				if ($arrayItem === null) {
-					throw new \PHPStan\ShouldNotHappenException();
+					continue;
 				}
-				$itemNodes[] = new LiteralArrayItem($scope, $arrayItem);
 				$result = $this->processExprNode($arrayItem, $scope, $nodeCallback, $context->enterDeep());
 				$hasYield = $hasYield || $result->hasYield();
 				$scope = $result->getScope();

src/Node/LiteralArrayItem.php

@@ -10,9 +10,9 @@ class LiteralArrayItem
 
 	private Scope $scope;
 
-	private ArrayItem $arrayItem;
+	private ?ArrayItem $arrayItem;
 
-	public function __construct(Scope $scope, ArrayItem $arrayItem)
+	public function __construct(Scope $scope, ?ArrayItem $arrayItem)
 	{
 		$this->scope = $scope;
 		$this->arrayItem = $arrayItem;
@@ -23,7 +23,7 @@ public function getScope(): Scope
 		return $this->scope;
 	}
 
-	public function getArrayItem(): ArrayItem
+	public function getArrayItem(): ?ArrayItem
 	{
 		return $this->arrayItem;
 	}

src/Rules/Arrays/DuplicateKeysInLiteralArraysRule.php

@@ -35,6 +35,9 @@ public function processNode(\PhpParser\Node $node, Scope $scope): array
 		$valueLines = [];
 		foreach ($node->getItemNodes() as $itemNode) {
 			$item = $itemNode->getArrayItem();
+			if ($item === null) {
+				continue;
+			}
 			if ($item->key === null) {
 				continue;
 			}

src/Rules/Arrays/EmptyArrayItemRule.php

@@ -0,0 +1,40 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Arrays;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+use PHPStan\Node\LiteralArrayNode;
+use PHPStan\Rules\Rule;
+use PHPStan\Rules\RuleErrorBuilder;
+
+/**
+ * @implements \PHPStan\Rules\Rule<\PHPStan\Node\LiteralArrayNode>
+ */
+class EmptyArrayItemRule implements Rule
+{
+
+	public function getNodeType(): string
+	{
+		return LiteralArrayNode::class;
+	}
+
+	public function processNode(Node $node, Scope $scope): array
+	{
+		foreach ($node->getItemNodes() as $itemNode) {
+			$item = $itemNode->getArrayItem();
+			if ($item !== null) {
+				continue;
+			}
+
+			return [
+				RuleErrorBuilder::message('Literal array contains empty item.')
+					->nonIgnorable()
+					->build(),
+			];
+		}
+
+		return [];
+	}
+
+}

src/Rules/Arrays/UnpackIterableInArrayRule.php

@@ -37,6 +37,9 @@ public function processNode(Node $node, Scope $scope): array
 		$errors = [];
 		foreach ($node->getItemNodes() as $itemNode) {
 			$item = $itemNode->getArrayItem();
+			if ($item === null) {
+				continue;
+			}
 			if (!$item->unpack) {
 				continue;
 			}

tests/PHPStan/Rules/Arrays/EmptyArrayItemRuleTest.php

@@ -0,0 +1,29 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\Arrays;
+
+use PHPStan\Rules\Rule;
+use PHPStan\Testing\RuleTestCase;
+
+/**
+ * @extends RuleTestCase<EmptyArrayItemRule>
+ */
+class EmptyArrayItemRuleTest extends RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new EmptyArrayItemRule();
+	}
+
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/empty-array-item.php'], [
+			[
+				'Literal array contains empty item.',
+				5,
+			],
+		]);
+	}
+
+}

tests/PHPStan/Rules/Arrays/data/empty-array-item.php

@@ -0,0 +1,7 @@
+<?php
+
+namespace EmptyArrayItem;
+
+doFoo([, 'foo']);
+
+[, $a] = doFoo();