[BUGFIX] Do not let a detached <project> break the configuration

Two defects in the previous commit of this branch, both found by review and
both reproduced before fixing.

Detaching <project> can leave an empty root element behind, and
`XmlUtils::convertDomElementToArray()` returns null rather than an empty array
for one. `assert(is_array($rootConfig))` then fails for any `guides.xml` that
holds nothing but a project — which the `version-from-guides-xml` fixtures are.
It stays invisible under the default and the CI php.ini, both of which run with
`zend.assertions=-1`, where the following write to `$rootConfig['project']`
auto-vivifies null; with `zend.assertions=1` those two data sets fail.

`getElementsByTagName('project')` searches the whole subtree, and the schema
lets an `<extension>` carry arbitrary child elements. A nested `<project>` was
therefore read as the project configuration and removed from that extension,
while the real one at root level was dropped. Look at direct children only.

The new `version-from-guides-xml-nested-project` fixture covers the second
defect and fails against the previous state. The first one is only observable
with assertions enabled, and the existing fixtures already cover it there.

Assisted-by: claude-code:claude-opus-5
Agent-Session: https://claude.ai/code/session_015QXXkquh2eQNBiTYA39Wss
Signed-off-by: Sebastian Mendel <sebastian.mendel@netresearch.de>

Author: CybotTM

packages/guides-cli/src/Config/XmlFileLoader.php

@@ -46,8 +46,8 @@ public function load(mixed $resource, string|null $type = null): array
         // become 1). Reading them straight from the DOM and detaching <project>
         // beforehand keeps the version exactly as written.
         $projectConfig = null;
-        $project = $element->getElementsByTagName('project')->item(0);
-        if ($project instanceof DOMElement) {
+        $project = $this->firstChildElement($element, 'project');
+        if ($project !== null) {
             $projectConfig = [];
             foreach ($project->attributes as $attribute) {
                 if (!($attribute instanceof DOMAttr)) {
@@ -71,8 +71,12 @@ public function load(mixed $resource, string|null $type = null): array
             $project->parentNode?->removeChild($project);
         }
 
+        // Detaching <project> can leave an otherwise empty root element behind, and
+        // convertDomElementToArray() returns null rather than an empty array for that.
         $rootConfig = XmlUtils::convertDomElementToArray($element);
-        assert(is_array($rootConfig));
+        if (!is_array($rootConfig)) {
+            $rootConfig = [];
+        }
 
         if ($projectConfig !== null) {
             $rootConfig['project'] = $projectConfig;
@@ -95,6 +99,24 @@ public function load(mixed $resource, string|null $type = null): array
         return $configs;
     }
 
+    /**
+     * Returns the first direct child element of the given name.
+     *
+     * `getElementsByTagName()` would search the whole subtree, and the schema lets an <extension>
+     * carry arbitrary child elements, so a nested <project> could be read as the project configuration
+     * and removed from that extension.
+     */
+    private function firstChildElement(DOMElement $element, string $name): DOMElement|null
+    {
+        foreach ($element->childNodes as $child) {
+            if ($child instanceof DOMElement && $child->localName === $name) {
+                return $child;
+            }
+        }
+
+        return null;
+    }
+
     public function supports(mixed $resource, string|null $type = null): bool
     {
         return $type === 'xml' && is_string($resource);

tests/Integration/tests/meta/version-from-guides-xml-nested-project/expected/index.html

@@ -0,0 +1,8 @@
+<!-- content start -->
+    <div class="section" id="some-document">
+            <h1>Some Document</h1>
+            
+    <p>Project Render guides in version 0.10, release 3.0.0.</p>
+
+    </div>
+<!-- content end -->

tests/Integration/tests/meta/version-from-guides-xml-nested-project/input/guides.xml

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<guides
+    xmlns="https://www.phpdoc.org/guides"
+    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+    xsi:schemaLocation="https://www.phpdoc.org/guides vendor/phpdocumentor/guides-cli/resources/schema/guides.xsd"
+>
+    <!-- The schema lets an extension carry arbitrary child elements. A <project> among them
+         must not be read as the project configuration of the documentation. -->
+    <extension class="phpDocumentor\Guides\Bootstrap">
+        <project title="Nested" version="9.9" release="9.9.9"/>
+    </extension>
+    <project
+            title="Render guides"
+            version="0.10"
+            release="3.0.0"
+    />
+</guides>

tests/Integration/tests/meta/version-from-guides-xml-nested-project/input/index.rst

@@ -0,0 +1,4 @@
+Some Document
+=============
+
+Project |project| in version |version|, release |release|.