F::load(): guard from output

src/Cms/App.php

@@ -1062,7 +1062,7 @@ protected function optionsFromConfig(): array
 
 		// load the main config options
 		$root    = $this->root('config');
-		$options = F::load($root . '/config.php', []);
+		$options = F::load($root . '/config.php', [], allowOutput: false);
 
 		// merge into one clean options array
 		return $this->options = array_replace_recursive(Config::$data, $options);
@@ -1080,7 +1080,7 @@ protected function optionsFromEnvironment(array $props = []): array
 		$root = $this->root('config');
 
 		// first load `config/env.php` to access its `url` option
-		$envOptions = F::load($root . '/env.php', []);
+		$envOptions = F::load($root . '/env.php', [], allowOutput: false);
 
 		// use the option from the main `config.php`,
 		// but allow the `env.php` to override it

src/Cms/AppPlugins.php

@@ -717,7 +717,7 @@ protected function extensionsFromFolders()
 			$class = str_replace(['.', '-', '_'], '', $name) . 'Page';
 
 			// load the model class
-			F::loadOnce($model);
+			F::loadOnce($model, allowOutput: false);
 
 			if (class_exists($class) === true) {
 				$models[$name] = $class;
@@ -908,7 +908,7 @@ protected function pluginsLoader(): array
 			$styles = $dir . '/index.css';
 
 			if (is_file($entry) === true) {
-				F::loadOnce($entry);
+				F::loadOnce($entry, allowOutput: false);
 			} elseif (is_file($script) === true || is_file($styles) === true) {
 				// if no PHP file is present but an index.js or index.css,
 				// register as anonymous plugin (without actual extensions)

src/Cms/Blueprint.php

@@ -731,7 +731,7 @@ protected function preset(array $props): array
 		$preset = static::$presets[$props['preset']];
 
 		if (is_string($preset) === true) {
-			$preset = require $preset;
+			$preset = F::load($preset, allowOutput: false);
 		}
 
 		return $preset($props);

src/Cms/Collections.php

@@ -123,7 +123,7 @@ public function load(string $name)
 		$file = $kirby->root('collections') . '/' . $name . '.php';
 
 		if (is_file($file) === true) {
-			$collection = F::load($file);
+			$collection = F::load($file, allowOutput: false);
 
 			if ($collection instanceof Closure) {
 				return $collection;

src/Cms/Languages.php

@@ -81,7 +81,7 @@ public static function load()
 		$files     = glob(App::instance()->root('languages') . '/*.php');
 
 		foreach ($files as $file) {
-			$props = F::load($file);
+			$props = F::load($file, allowOutput: false);
 
 			if (is_array($props) === true) {
 				// inject the language code from the filename

src/Cms/Loader.php

@@ -160,12 +160,12 @@ public function resolve($item)
 	{
 		if (is_string($item) === true) {
 			$item = match (F::extension($item)) {
-				'php'   => require $item,
+				'php'   => F::load($item, allowOutput: false),
 				default => Data::read($item)
 			};
 		}
 
-		if (is_callable($item)) {
+		if (is_callable($item) === true) {
 			$item = $item($this->kirby);
 		}
 

src/Cms/UserActions.php

@@ -308,7 +308,7 @@ protected function readCredentials(): array
 		$path = $this->root() . '/index.php';
 
 		if (is_file($path) === true) {
-			$credentials = F::load($path);
+			$credentials = F::load($path, allowOutput: false);
 
 			return is_array($credentials) === false ? [] : $credentials;
 		} else {

src/Cms/Users.php

@@ -148,7 +148,7 @@ public static function load(string $root, array $inject = [])
 			// get role information
 			$path = $root . '/' . $userDirectory . '/index.php';
 			if (is_file($path) === true) {
-				$credentials = F::load($path);
+				$credentials = F::load($path, allowOutput: false);
 			}
 
 			// create user model based on role

src/Data/PHP.php

@@ -61,7 +61,7 @@ public static function read(string $file): array
 			throw new Exception('The file "' . $file . '" does not exist');
 		}
 
-		return (array)F::load($file, []);
+		return (array)F::load($file, [], allowOutput: false);
 	}
 
 	/**

src/Filesystem/F.php

@@ -5,6 +5,7 @@
 use Exception;
 use IntlDateFormatter;
 use Kirby\Cms\Helpers;
+use Kirby\Http\Response;
 use Kirby\Toolkit\I18n;
 use Kirby\Toolkit\Str;
 use Throwable;
@@ -347,18 +348,34 @@ public static function link(string $source, string $link, string $method = 'link
 	 *
 	 * @param array $data Optional array of variables to extract in the variable scope
 	 */
-	public static function load(string $file, $fallback = null, array $data = [])
-	{
+	public static function load(
+		string $file,
+		mixed $fallback = null,
+		array $data = [],
+		bool $allowOutput = true
+	) {
 		if (is_file($file) === false) {
 			return $fallback;
 		}
 
 		// we use the loadIsolated() method here to prevent the included
 		// file from overwriting our $fallback in this variable scope; see
 		// https://www.php.net/manual/en/function.include.php#example-124
-		$result = static::loadIsolated($file, $data);
+		$callback = fn () => static::loadIsolated($file, $data);
+
+		// if the loaded file should not produce any output,
+		// call the loaidIsolated method from the Response class
+		// which checks for unintended ouput and throws an error if detected
+		if ($allowOutput === false) {
+			$result = Response::guardAgainstOutput($callback);
+		} else {
+			$result = $callback();
+		}
 
-		if ($fallback !== null && gettype($result) !== gettype($fallback)) {
+		if (
+			$fallback !== null &&
+			gettype($result) !== gettype($fallback)
+		) {
 			return $fallback;
 		}
 
@@ -369,24 +386,28 @@ public static function load(string $file, $fallback = null, array $data = [])
 	 * A super simple class autoloader
 	 * @since 3.7.0
 	 */
-	public static function loadClasses(array $classmap, string|null $base = null): void
-	{
+	public static function loadClasses(
+		array $classmap,
+		string|null $base = null
+	): void {
 		// convert all classnames to lowercase
 		$classmap = array_change_key_case($classmap);
 
-		spl_autoload_register(function ($class) use ($classmap, $base) {
-			$class = strtolower($class);
+		spl_autoload_register(
+			fn ($class) => Response::guardAgainstOutput(function () use ($class, $classmap, $base) {
+				$class = strtolower($class);
 
-			if (!isset($classmap[$class])) {
-				return false;
-			}
+				if (isset($classmap[$class]) === false) {
+					return false;
+				}
 
-			if ($base) {
-				include $base . '/' . $classmap[$class];
-			} else {
-				include $classmap[$class];
-			}
-		});
+				if ($base) {
+					include $base . '/' . $classmap[$class];
+				} else {
+					include $classmap[$class];
+				}
+			})
+		);
 	}
 
 	/**
@@ -408,13 +429,22 @@ protected static function loadIsolated(string $file, array $data = [])
 	 * Loads a file using `include_once()` and
 	 * returns whether loading was successful
 	 */
-	public static function loadOnce(string $file): bool
-	{
+	public static function loadOnce(
+		string $file,
+		bool $allowOutput = true
+	): bool {
 		if (is_file($file) === false) {
 			return false;
 		}
 
-		include_once $file;
+		$callback = fn () => include_once $file;
+
+		if ($allowOutput === false) {
+			Response::guardAgainstOutput($callback);
+		} else {
+			$callback();
+		}
+
 		return true;
 	}
 

src/Http/Environment.php

@@ -786,12 +786,20 @@ public function options(string $root): array
 
 		// load the config for the host
 		if (empty($host) === false) {
-			$configHost = F::load($root . '/config.' . $host . '.php', []);
+			$configHost = F::load(
+				file: $root . '/config.' . $host . '.php',
+				fallback: [],
+				allowOutput: false
+			);
 		}
 
 		// load the config for the server IP
 		if (empty($addr) === false) {
-			$configAddr = F::load($root . '/config.' . $addr . '.php', []);
+			$configAddr = F::load(
+				file: $root . '/config.' . $addr . '.php',
+				fallback: [],
+				allowOutput: false
+			);
 		}
 
 		return array_replace_recursive($configHost, $configAddr);

src/Http/Response.php

@@ -2,7 +2,9 @@
 
 namespace Kirby\Http;
 
+use Closure;
 use Exception;
+use Kirby\Exception\LogicException;
 use Kirby\Filesystem\F;
 use Throwable;
 
@@ -182,6 +184,23 @@ public static function go(string $url = '/', int $code = 302): void
 		die(static::redirect($url, $code));
 	}
 
+	/**
+	 * Ensures that the callback does not produce the first body output
+	 * (used to show when loading a file creates side effects)
+	 */
+	public static function guardAgainstOutput(Closure $callback, ...$args): mixed
+	{
+		$before = headers_sent();
+		$result = $callback(...$args);
+		$after  = headers_sent($file, $line);
+
+		if ($before === false && $after === true) {
+			throw new LogicException("Disallowed output from file $file:$line, possible accidental whitespace?");
+		}
+
+		return $result;
+	}
+
 	/**
 	 * Getter for single headers
 	 *

src/Toolkit/Component.php

@@ -232,7 +232,7 @@ public static function load(string $type): array
 				throw new Exception('Component definition ' . $definition . ' does not exist');
 			}
 
-			static::$types[$type] = $definition = F::load($definition);
+			static::$types[$type] = $definition = F::load($definition, allowOutput: false);
 		}
 
 		return $definition;
@@ -254,7 +254,11 @@ public static function setup(string $type): array
 
 		if (isset($definition['extends']) === true) {
 			// extend other definitions
-			$options = array_replace_recursive(static::defaults(), static::load($definition['extends']), $definition);
+			$options = array_replace_recursive(
+				static::defaults(),
+				static::load($definition['extends']),
+				$definition
+			);
 		} else {
 			// inject defaults
 			$options = array_replace_recursive(static::defaults(), $definition);
@@ -266,10 +270,14 @@ public static function setup(string $type): array
 				if (isset(static::$mixins[$mixin]) === true) {
 					if (is_string(static::$mixins[$mixin]) === true) {
 						// resolve a path to a mixin on demand
-						static::$mixins[$mixin] = include static::$mixins[$mixin];
+
+						static::$mixins[$mixin] = F::load(static::$mixins[$mixin], allowOutput: false);
 					}
 
-					$options = array_replace_recursive(static::$mixins[$mixin], $options);
+					$options = array_replace_recursive(
+						static::$mixins[$mixin],
+						$options
+					);
 				}
 			}
 		}

tests/Blueprint/NodeI18nTest.php

@@ -3,7 +3,7 @@
 namespace Kirby\Blueprint;
 
 /**
- * @covers \Kirby\Blueprint\NodeI18n
+ * @coversDefaultClass \Kirby\Blueprint\NodeI18n
  */
 class NodeI18nTest extends TestCase
 {