Add LineBreakBeforeThrowExpressionFixer

.gitignore

@@ -1,5 +1,6 @@
 .build/
 .idea
 .php-cs-fixer.cache
+.phpunit.result.cache
 composer.lock
 vendor

config.php

@@ -87,6 +87,7 @@ function config(Finder $finder, array $ruleOverrides = []): Config
             'less_and_greater' => false,
         ],
 
+        Fixer\LineBreakBeforeThrowExpressionFixer::NAME => true,
         Fixer\PhpdocSimplifyArrayKeyFixer::NAME => true,
 
         PhpCsFixerCustomFixers\Fixer\ConstructorEmptyBracesFixer::name() => true,
@@ -97,6 +98,7 @@ function config(Finder $finder, array $ruleOverrides = []): Config
     return (new Config())
         ->registerCustomFixers(new PhpCsFixerCustomFixers\Fixers())
         ->registerCustomFixers([
+            new Fixer\LineBreakBeforeThrowExpressionFixer(),
             new Fixer\PhpdocSimplifyArrayKeyFixer(),
         ])
         ->setFinder($finder)

phpunit.xml

@@ -8,6 +8,10 @@
     <testsuites>
         <testsuite name="Tests">
             <directory>tests</directory>
+            <exclude>tests/Fixer/Php80</exclude>
+        </testsuite>
+        <testsuite name="Php80">
+            <directory phpVersion="8.0" phpVersionOperator="&gt;=">tests/Fixer/Php80</directory>
         </testsuite>
     </testsuites>
 </phpunit>

src/Fixer/LineBreakBeforeThrowExpressionFixer.php

@@ -0,0 +1,189 @@
+<?php declare(strict_types=1);
+
+namespace MLL\PhpCsFixerConfig\Fixer;
+
+use PhpCsFixer\AbstractFixer;
+use PhpCsFixer\Fixer\WhitespacesAwareFixerInterface;
+use PhpCsFixer\FixerDefinition\CodeSample;
+use PhpCsFixer\FixerDefinition\FixerDefinition;
+use PhpCsFixer\FixerDefinition\FixerDefinitionInterface;
+use PhpCsFixer\Preg;
+use PhpCsFixer\Tokenizer\Token;
+use PhpCsFixer\Tokenizer\Tokens;
+
+/**
+ * Forces line breaks before `?? throw` and `?: throw` patterns.
+ */
+final class LineBreakBeforeThrowExpressionFixer extends AbstractFixer implements WhitespacesAwareFixerInterface
+{
+    public const NAME = 'MLL/line_break_before_throw_expression';
+
+    public function getName(): string
+    {
+        return self::NAME;
+    }
+
+    public function getDefinition(): FixerDefinitionInterface
+    {
+        return new FixerDefinition(
+            'Coalesce or elvis throw expressions (`?? throw`, `?: throw`) must be on their own line.',
+            [
+                new CodeSample(
+                    <<<'PHP'
+                        <?php
+                        $result = $this->fetchNullable() ?? throw new \RuntimeException('message');
+
+                        PHP
+                ),
+            ]
+        );
+    }
+
+    public function isCandidate(Tokens $tokens): bool
+    {
+        return $tokens->isTokenKindFound(T_THROW);
+    }
+
+    public function getPriority(): int
+    {
+        // Run before operator_linebreak (priority 0)
+        return 1;
+    }
+
+    protected function applyFix(\SplFileInfo $file, Tokens $tokens): void
+    {
+        for ($index = $tokens->count() - 1; $index > 0; --$index) {
+            if (! $tokens[$index]->isGivenKind(T_THROW)) {
+                continue;
+            }
+
+            $operatorIndex = $this->findPrecedingThrowOperator($tokens, $index);
+            if ($operatorIndex === null) {
+                continue;
+            }
+
+            $this->ensureLineBreakBeforeOperator($tokens, $operatorIndex);
+        }
+    }
+
+    /**
+     * Find `??` or `?:` operator immediately before the throw token.
+     *
+     * @return int|null The index of the operator (T_COALESCE or `?` for elvis), or null
+     */
+    private function findPrecedingThrowOperator(Tokens $tokens, int $throwIndex): ?int
+    {
+        $prevIndex = $tokens->getPrevMeaningfulToken($throwIndex);
+        if ($prevIndex === null) {
+            return null;
+        }
+
+        // Check for ?? (T_COALESCE)
+        if ($tokens[$prevIndex]->isGivenKind(T_COALESCE)) {
+            return $prevIndex;
+        }
+
+        // Check for ?: (elvis operator - two separate tokens)
+        if ($tokens[$prevIndex]->equals(':')) {
+            $questionIndex = $tokens->getPrevMeaningfulToken($prevIndex);
+            if ($questionIndex !== null && $tokens[$questionIndex]->equals('?')) {
+                return $questionIndex;
+            }
+        }
+
+        return null;
+    }
+
+    private function ensureLineBreakBeforeOperator(Tokens $tokens, int $operatorIndex): void
+    {
+        $prevMeaningfulIndex = $tokens->getPrevMeaningfulToken($operatorIndex);
+        if ($prevMeaningfulIndex === null) {
+            return;
+        }
+
+        $hasNewlineBeforeOperator = $this->hasNewlineBetween($tokens, $prevMeaningfulIndex, $operatorIndex);
+
+        // If the preceding expression is a multi-line block, don't add another line break
+        if (! $hasNewlineBeforeOperator
+            && $tokens[$prevMeaningfulIndex]->equals(')')
+        ) {
+            $openIndex = $tokens->findBlockStart(Tokens::BLOCK_TYPE_PARENTHESIS_BRACE, $prevMeaningfulIndex);
+            if ($this->hasNewlineBetween($tokens, $openIndex, $prevMeaningfulIndex)) {
+                return;
+            }
+        }
+
+        if (! $hasNewlineBeforeOperator
+            && $tokens[$prevMeaningfulIndex]->equals('}')
+        ) {
+            $openIndex = $tokens->findBlockStart(Tokens::BLOCK_TYPE_CURLY_BRACE, $prevMeaningfulIndex);
+            if ($this->hasNewlineBetween($tokens, $openIndex, $prevMeaningfulIndex)) {
+                return;
+            }
+        }
+
+        $statementStart = $this->findStatementStart($tokens, $operatorIndex);
+        $expressionAlreadyMultiline = $this->hasNewlineBetween($tokens, $statementStart, $prevMeaningfulIndex);
+
+        if ($expressionAlreadyMultiline) {
+            // Use the existing indentation level from the multiline expression
+            $indentation = $this->getIndentAt($tokens, $operatorIndex);
+        } else {
+            // Add one indent level from the statement start
+            $indentation = $this->getIndentAt($tokens, $statementStart) . $this->whitespacesConfig->getIndent();
+        }
+
+        $newWhitespace = $this->whitespacesConfig->getLineEnding() . $indentation;
+
+        $whitespaceIndex = $operatorIndex - 1;
+        if ($tokens[$whitespaceIndex]->isWhitespace()) {
+            if ($tokens[$whitespaceIndex]->getContent() === $newWhitespace) {
+                return;
+            }
+
+            $tokens[$whitespaceIndex] = new Token([T_WHITESPACE, $newWhitespace]);
+        } else {
+            $tokens->insertAt($operatorIndex, new Token([T_WHITESPACE, $newWhitespace]));
+        }
+    }
+
+    private function hasNewlineBetween(Tokens $tokens, int $startIndex, int $endIndex): bool
+    {
+        for ($i = $startIndex + 1; $i < $endIndex; ++$i) {
+            $token = $tokens[$i];
+            if ($token->isWhitespace() && strpos($token->getContent(), "\n") !== false) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    // TODO: Replace with IndentationTrait once we require php-cs-fixer ^3.87.0
+    private function getIndentAt(Tokens $tokens, int $index): string
+    {
+        for ($i = $index - 1; $i >= 0; --$i) {
+            $token = $tokens[$i];
+            $content = $token->getContent();
+
+            if (Preg::match('/\R(\h*)$/', $content, $matches)) {
+                return $matches[1];
+            }
+        }
+
+        return '';
+    }
+
+    private function findStatementStart(Tokens $tokens, int $index): int
+    {
+        for ($i = $index - 1; $i >= 0; --$i) {
+            $token = $tokens[$i];
+
+            if ($token->equals(';') || $token->equals('{') || $token->equals('}') || $token->isGivenKind(T_OPEN_TAG)) {
+                return $tokens->getNextMeaningfulToken($i) ?? $index;
+            }
+        }
+
+        return 0;
+    }
+}