Ban short ternary operator

Author: Majkl578

README.md

@@ -19,6 +19,7 @@
 * Types in `switch` condition and `case` value must match. PHP compares them loosely by default and that can lead to unexpected results.
 * Check that statically declared methods are called statically.
 * Disallow `empty()` - it's a very loose comparison (see [manual](https://php.net/empty)), it's recommended to use more strict one.
+* Disallow short ternary operator (`?:`) - implies weak comparison, it's recommended to use null coalesce operator (`??`) or ternary operator with strict condition.
 * Disallow variable variables (`$$foo`, `$this->$method()` etc.)
 * Disallow overwriting variables with foreach key and value variables
 * Always true `instanceof`, type-checking `is_*` functions and strict comparisons `===`/`!==`. These checks can be turned off by setting `checkAlwaysTrueInstanceof`/`checkAlwaysTrueCheckTypeFunctionCall`/`checkAlwaysTrueStrictComparison` to false.

rules.neon

@@ -21,6 +21,7 @@ rules:
 	- PHPStan\Rules\Classes\RequireParentConstructCallRule
 	- PHPStan\Rules\DisallowedConstructs\DisallowedEmptyRule
 	- PHPStan\Rules\DisallowedConstructs\DisallowedImplicitArrayCreationRule
+	- PHPStan\Rules\DisallowedConstructs\DisallowedShortTernaryRule
 	- PHPStan\Rules\ForeachLoop\OverwriteVariablesWithForeachRule
 	- PHPStan\Rules\Methods\WrongCaseOfInheritedMethodRule
 	- PHPStan\Rules\Operators\OperandInArithmeticPostDecrementRule

src/Rules/DisallowedConstructs/DisallowedShortTernaryRule.php

@@ -0,0 +1,32 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\DisallowedConstructs;
+
+use PhpParser\Node;
+use PHPStan\Analyser\Scope;
+
+class DisallowedShortTernaryRule implements \PHPStan\Rules\Rule
+{
+
+	public function getNodeType(): string
+	{
+		return \PhpParser\Node\Expr\Ternary::class;
+	}
+
+	/**
+	 * @param \PhpParser\Node\Expr\Ternary $node
+	 * @param \PHPStan\Analyser\Scope $scope
+	 * @return string[]
+	 */
+	public function processNode(Node $node, Scope $scope): array
+	{
+		if ($node->if !== null) {
+			return [];
+		}
+
+		return [
+			'Short ternary operator is not allowed. Use null coalesce operator if applicable or consider using long ternary.',
+		];
+	}
+
+}

tests/Rules/DisallowedConstructs/DisallowedShortTernaryRuleTest.php

@@ -0,0 +1,29 @@
+<?php declare(strict_types = 1);
+
+namespace PHPStan\Rules\DisallowedConstructs;
+
+use PHPStan\Rules\Rule;
+
+class DisallowedShortTernaryRuleTest extends \PHPStan\Testing\RuleTestCase
+{
+
+	protected function getRule(): Rule
+	{
+		return new DisallowedShortTernaryRule();
+	}
+
+	public function testRule(): void
+	{
+		$this->analyse([__DIR__ . '/data/short-ternary.php'], [
+			[
+				'Short ternary operator is not allowed. Use null coalesce operator if applicable or consider using long ternary.',
+				3,
+			],
+			[
+				'Short ternary operator is not allowed. Use null coalesce operator if applicable or consider using long ternary.',
+				4,
+			],
+		]);
+	}
+
+}

tests/Rules/DisallowedConstructs/data/short-ternary.php

@@ -0,0 +1,5 @@
+<?php
+
+$foo = 123 ?: 456;
+$bar = 123 ? : 456;
+$baz = 123 ? 456 : 789;