Engine::setPhpBinary() allows to lint generated PHP templates

src/Latte/Compiler/PhpHelpers.php

@@ -224,4 +224,34 @@ private static function codePointToUtf8(int $num): string
 			default => throw new CompileException('Invalid UTF-8 codepoint escape sequence: Codepoint too large'),
 		};
 	}
+
+
+	public static function checkSyntax(string $phpBinary, string $code, string $name): void
+	{
+		$process = proc_open(
+			$phpBinary . ' -l -n',
+			[['pipe', 'r'], ['pipe', 'w'], ['pipe', 'w']],
+			$pipes,
+			null,
+			null,
+			['bypass_shell' => true],
+		);
+		if (!is_resource($process)) {
+			throw new CompileException('Unable to check that the generated PHP is syntactically correct.');
+		}
+
+		fwrite($pipes[0], $code);
+		fclose($pipes[0]);
+		$error = stream_get_contents($pipes[1]);
+		if (!proc_close($process)) {
+			return;
+		}
+		$error = strip_tags(explode("\n", $error)[1]);
+		$position = preg_match('~ on line (\d+)~', $error, $m)
+			? new Position((int) $m[1], 0)
+			: null;
+		$error = preg_replace('~(^Fatal error: | in Standard input code| on line \d+)~', '', $error);
+		throw (new CompileException('Syntax error in generated code: ' . trim($error), $position))
+			->setSource($code, $name);
+	}
 }

src/Latte/Compiler/Position.php

@@ -44,6 +44,6 @@ public function advance(string $str): self
 
 	public function toWords(): string
 	{
-		return "on line $this->line at column $this->column";
+		return "on line $this->line" . ($this->column ? " at column $this->column" : '');
 	}
 }

src/Latte/Engine.php

@@ -44,6 +44,7 @@ class Engine
 	private bool $strictTypes = false;
 	private ?Policy $policy = null;
 	private bool $sandboxed = false;
+	private ?string $phpBinary = null;
 
 
 	public function __construct()
@@ -126,6 +127,10 @@ public function compile(string $name): string
 			throw $e->setSource($source, $name);
 		}
 
+		if ($this->phpBinary) {
+			Compiler\PhpHelpers::checkSyntax($this->phpBinary, $code, "(compiled $name)");
+		}
+
 		return $code;
 	}
 
@@ -544,6 +549,16 @@ public function getLoader(): Loader
 	}
 
 
+	/**
+	 * Enables linting of generated PHP templates.
+	 */
+	public function setPhpBinary(?string $phpBinary): static
+	{
+		$this->phpBinary = $phpBinary;
+		return $this;
+	}
+
+
 	/**
 	 * @param  object|mixed[]  $params
 	 * @return mixed[]

src/Tools/Linter.php

@@ -53,6 +53,7 @@ public function scanDirectory(string $path): bool
 	private function createEngine(): Latte\Engine
 	{
 		$engine = new Latte\Engine;
+		$engine->setPhpBinary(PHP_BINARY);
 		$engine->addExtension(new Latte\Essential\TranslatorExtension(null));
 
 		if (class_exists(Nette\Bridges\ApplicationLatte\UIExtension::class)) {
@@ -91,7 +92,7 @@ public function lintLatte(string $file): bool
 		}
 
 		try {
-			$code = $this->engine->compile($s);
+			$this->engine->compile($s);
 
 		} catch (Latte\CompileException $e) {
 			if ($this->debug) {
@@ -106,40 +107,10 @@ public function lintLatte(string $file): bool
 			restore_error_handler();
 		}
 
-		if ($error = $this->lintPHP($code)) {
-			fwrite(STDERR, "[ERROR]      $file    $error\n");
-			return false;
-		}
-
 		return true;
 	}
 
 
-	private function lintPHP(string $code): ?string
-	{
-		$php = defined('PHP_BINARY') ? PHP_BINARY : 'php';
-		$stdin = tmpfile();
-		fwrite($stdin, $code);
-		fseek($stdin, 0);
-		$process = proc_open(
-			$php . ' -l -d display_errors=1',
-			[$stdin, ['pipe', 'w'], ['pipe', 'w']],
-			$pipes,
-			null,
-			null,
-			['bypass_shell' => true],
-		);
-		if (!is_resource($process)) {
-			return 'Unable to lint PHP code';
-		}
-		$error = stream_get_contents($pipes[1]);
-		if (proc_close($process)) {
-			return strip_tags(explode("\n", $error)[1]);
-		}
-		return null;
-	}
-
-
 	private function initialize(): void
 	{
 		if (function_exists('pcntl_signal')) {

tests/common/syntax.error.phpt

@@ -0,0 +1,18 @@
+<?php
+
+declare(strict_types=1);
+
+use Tester\Assert;
+
+require __DIR__ . '/../bootstrap.php';
+
+
+$latte = new Latte\Engine;
+$latte->setLoader(new Latte\Loaders\StringLoader);
+$latte->setPhpBinary(PHP_BINARY);
+
+Assert::exception(
+	fn() => $latte->compile('{= [&$x] = []}'),
+	Latte\CompileException::class,
+	'Syntax error in generated code: Cannot assign %a% (on line %d%)',
+);