Printer: indent a new tag like the other tags

When the printer added a child to a PHPDoc, it used the largest
indentation after the asterisk in the PHPDoc. The next lines of a
multi-line description often have a larger indentation, so the new
tag got it too.

Now the printer uses the indentation of the line where the last
existing child starts.

Amp-Thread-ID: https://ampcode.com/threads/T-01a17930-0285-73c5-a957-4325c77aa1b2

Author: ondrejmirtes

src/Printer/Printer.php

@@ -76,6 +76,7 @@
 use function implode;
 use function in_array;
 use function is_array;
+use function preg_match;
 use function preg_match_all;
 use function sprintf;
 use function str_replace;
@@ -589,6 +590,11 @@ private function printArrayFormatPreserving(array $nodes, array $originalNodes,
 		[$isMultiline, $beforeAsteriskIndent, $afterAsteriskIndent] = $this->isMultiline($tokenIndex, $originalNodes, $originalTokens);
 
 		if ($insertStr === "\n * ") {
+			$lastChildIndent = $this->detectLastChildIndent($originalNodes, $originalTokens);
+			if ($lastChildIndent !== null) {
+				[$beforeAsteriskIndent, $afterAsteriskIndent] = $lastChildIndent;
+			}
+
 			$insertStr = sprintf('%s%s*%s', $originalTokens->getDetectedNewline() ?? "\n", $beforeAsteriskIndent, $afterAsteriskIndent);
 		}
 
@@ -850,6 +856,39 @@ private function isMultiline(int $initialIndex, array $nodes, TokenIterator $ori
 		return [$isMultiline, $before, $after];
 	}
 
+	/**
+	 * Indentation before and after the asterisk on the line where the last child of a PHPDoc starts.
+	 * Other lines, e.g. the next lines of a multi-line description, can have a different indentation.
+	 *
+	 * @param Node[] $originalNodes
+	 * @return array{string, string}|null
+	 */
+	private function detectLastChildIndent(array $originalNodes, TokenIterator $originalTokens): ?array
+	{
+		$tokens = $originalTokens->getTokens();
+		for ($i = count($originalNodes) - 1; $i >= 0; $i--) {
+			$index = $originalNodes[$i]->getAttribute(Attribute::START_INDEX) - 1;
+			$lineStart = '';
+			while (isset($tokens[$index]) && $tokens[$index][Lexer::TYPE_OFFSET] === Lexer::TOKEN_HORIZONTAL_WS) {
+				$lineStart = $tokens[$index][Lexer::VALUE_OFFSET] . $lineStart;
+				$index--;
+			}
+
+			if (!isset($tokens[$index]) || $tokens[$index][Lexer::TYPE_OFFSET] !== Lexer::TOKEN_PHPDOC_EOL) {
+				continue;
+			}
+
+			$lineStart = $tokens[$index][Lexer::VALUE_OFFSET] . $lineStart;
+			if (preg_match('~\n(?<before>[\x09\x20]*)\*(?<after>[\x09\x20]*)$~', $lineStart, $match) !== 1) {
+				continue;
+			}
+
+			return [$match['before'], $match['after']];
+		}
+
+		return null;
+	}
+
 	private function printNodeFormatPreserving(Node $node, TokenIterator $originalTokens): string
 	{
 		/** @var Node|null $originalNode */

tests/PHPStan/Printer/PrinterTest.php

@@ -29,6 +29,7 @@
 use PHPStan\PhpDocParser\Ast\PhpDoc\PureUnlessParameterIsPassedTagValueNode;
 use PHPStan\PhpDocParser\Ast\PhpDoc\ReturnTagValueNode;
 use PHPStan\PhpDocParser\Ast\PhpDoc\TemplateTagValueNode;
+use PHPStan\PhpDocParser\Ast\PhpDoc\ThrowsTagValueNode;
 use PHPStan\PhpDocParser\Ast\PhpDoc\TypeAliasImportTagValueNode;
 use PHPStan\PhpDocParser\Ast\Type\ArrayShapeItemNode;
 use PHPStan\PhpDocParser\Ast\Type\ArrayShapeNode;
@@ -194,6 +195,51 @@ public function enterNode(Node $node)
 			$removeFirst,
 		];
 
+		$addThrows = new class extends AbstractNodeVisitor {
+
+			public function enterNode(Node $node)
+			{
+				if ($node instanceof PhpDocNode) {
+					$node->children[] = new PhpDocTagNode('@throws', new ThrowsTagValueNode(new IdentifierTypeNode('Exception'), ''));
+				}
+
+				return $node;
+			}
+
+		};
+
+		yield [
+			self::nowdoc('
+			/**
+			 * @param int $foo multi
+			 *          line description
+			 */'),
+			self::nowdoc('
+			/**
+			 * @param int $foo multi
+			 *          line description
+			 * @throws Exception
+			 */'),
+			$addThrows,
+		];
+
+		yield [
+			self::nowdoc('
+			/**
+			 *   @param int $foo multi
+			 *       line description
+			 *   @return void
+			 */'),
+			self::nowdoc('
+			/**
+			 *   @param int $foo multi
+			 *       line description
+			 *   @return void
+			 *   @throws Exception
+			 */'),
+			$addThrows,
+		];
+
 		$removeLast = new class extends AbstractNodeVisitor {
 
 			public function enterNode(Node $node)