Collecting XML Theme Files in Magento 2

In order to get onto the issue, let’s have a look at the method loadFileLayoutUpdatesXml() of the class Magento\Framework\View\Model\Layout\Merge.

/**
	* Collect and merge layout updates from files
	*
	* @return \Magento\Framework\View\Layout\Element
	* @throws \Magento\Framework\Exception\LocalizedException
	*/
	protected function _loadFileLayoutUpdatesXml()
	{
       $layoutStr = '';
   	$theme = $this->_getPhysicalTheme($this->theme);
	...

/**

* Collect and merge layout updates from files

* @return \Magento\Framework\View\Layout\Element

* @throws \Magento\Framework\Exception\LocalizedException

protected function _loadFileLayoutUpdatesXml()

{

$layoutStr = '';

$theme = $this->_getPhysicalTheme($this->theme);

...

As for me, I use Magento 2.1.7, so in the picture, we can see the variable $theme that contains theme data. In my case, there are data concerning default theme “Magento Luma”.

$updateFiles = $this->fileSource->getFiles($theme, '*.xml');

1	$updateFiles = $this->fileSource->getFiles($theme, '*.xml');

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On the stage, we get all XML files with the help of the method getFiles placed in the class \lib\internal\Magento\Framework\View\Layout\File\Collector\Aggregated. Let’s have a closer look at the method to comprehend how it works.

/**
* Retrieve files
*
* Aggregate layout files from modules and a theme and its ancestors
*
* @param ThemeInterface $theme
* @param string $filePath
* @return \Magento\Framework\View\File[]
*/
public function getFiles(ThemeInterface $theme, $filePath)
{
    $list = $this->fileListFactory->create();
       $list->add($this->baseFiles->getFiles($theme, $filePath));
    foreach ($theme->getInheritedThemes() as $currentTheme) {
           $list->add($this->themeFiles->getFiles($currentTheme, $filePath));
           $list->replace($this->overrideBaseFiles->getFiles($currentTheme, $filePath));
           $list->replace($this->overrideThemeFiles->getFiles($currentTheme, $filePath));
    }
    return $list->getAll();
}

/**

* Retrieve files

* Aggregate layout files from modules and a theme and its ancestors

* @param ThemeInterface $theme

* @param string $filePath

* @return \Magento\Framework\View\File[]

public function getFiles(ThemeInterface $theme, $filePath)

{

$list = $this->fileListFactory->create();

$list->add($this->baseFiles->getFiles($theme, $filePath));

foreach ($theme->getInheritedThemes() as $currentTheme) {

$list->add($this->themeFiles->getFiles($currentTheme, $filePath));

$list->replace($this->overrideBaseFiles->getFiles($currentTheme, $filePath));

$list->replace($this->overrideThemeFiles->getFiles($currentTheme, $filePath));

}

return $list->getAll();

}

Here we create a list where pathways should be added to XML files. As before, it’s not clear where Magento finds XML files. Let’s define what is the method getFiles of the class /lib/internal/Magento/Framework/View/File/Collector/Decorator/ModuleDependency makes:

/**
* Retrieve view files, sorted by the priority of modules they belong to
*
* @param ThemeInterface $theme
* @param string $filePath
* @return \Magento\Framework\View\File[]
*/
public function getFiles(ThemeInterface $theme, $filePath)
{
    $result = $this->subject->getFiles($theme, $filePath);
       usort($result, [$this, 'compareFiles']);
    return $result;
}

/**

* Retrieve view files, sorted by the priority of modules they belong to

* @param ThemeInterface $theme

* @param string $filePath

* @return \Magento\Framework\View\File[]

public function getFiles(ThemeInterface $theme, $filePath)

{

$result = $this->subject->getFiles($theme, $filePath);

usort($result, [$this, 'compareFiles']);

return $result;

}

As you can see, the method is considered as significant and simple. So we should learn one more method getFiles of the class /lib/internal/Magento/Framework/View/File/Collector/Decorator/ModuleOutput:

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/**
* Retrieve files
*
* Filter out theme files that belong to inactive modules or ones explicitly configured to not produce any output
*
* @param ThemeInterface $theme
* @param string $filePath
* @return \Magento\Framework\View\File[]
*/
public function getFiles(ThemeInterface $theme, $filePath)
{
    $result = [];
    foreach ($this->subject->getFiles($theme, $filePath) as $file) {
        if ($this->moduleManager->isOutputEnabled($file->getModule())) {
            $result[] = $file;
        }
    }
    return $result;
}

/**

* Retrieve files

* Filter out theme files that belong to inactive modules or ones explicitly configured to not produce any output

* @param ThemeInterface $theme

* @param string $filePath

* @return \Magento\Framework\View\File[]

public function getFiles(ThemeInterface $theme, $filePath)

{

$result = [];

foreach ($this->subject->getFiles($theme, $filePath) as $file) {

if ($this->moduleManager->isOutputEnabled($file->getModule())) {

$result[] = $file;

}

return $result;

}

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As it is mentioned in the code, from the list of all modules we leave only active. Let’s continue reviewing the method getFiles of the class Magento/Framework/View/File/Collector/Base:

/**
* Retrieve files
*
* @param \Magento\Framework\View\Design\ThemeInterface $theme
* @param string $filePath
* @return \Magento\Framework\View\File[]
*/
public function getFiles(ThemeInterface $theme, $filePath)
{
    $result = [];
       $sharedFiles = $this->componentDirSearch->collectFilesWithContext(
        ComponentRegistrar::MODULE,
           "view/base/{$this->subDir}{$filePath}"
    );
    foreach ($sharedFiles as $file) {
           $result[] = $this->fileFactory->create($file->getFullPath(), $file->getComponentName(), null, true);
    }
    $area = $theme->getData('area');
       $themeFiles = $this->componentDirSearch->collectFilesWithContext(
           ComponentRegistrar::MODULE,
           "view/{$area}/{$this->subDir}{$filePath}"
    );
    foreach ($themeFiles as $file) {
           $result[] = $this->fileFactory->create($file->getFullPath(), $file->getComponentName());
    }
    return $result;
}

/**

* Retrieve files

* @param \Magento\Framework\View\Design\ThemeInterface $theme

* @param string $filePath

* @return \Magento\Framework\View\File[]

public function getFiles(ThemeInterface $theme, $filePath)

{

$result = [];

$sharedFiles = $this->componentDirSearch->collectFilesWithContext(

ComponentRegistrar::MODULE,

"view/base/{$this->subDir}{$filePath}"

);

foreach ($sharedFiles as $file) {

$result[] = $this->fileFactory->create($file->getFullPath(), $file->getComponentName(), null, true);

}

$area = $theme->getData('area');

$themeFiles = $this->componentDirSearch->collectFilesWithContext(

ComponentRegistrar::MODULE,

"view/{$area}/{$this->subDir}{$filePath}"

);

foreach ($themeFiles as $file) {

$result[] = $this->fileFactory->create($file->getFullPath(), $file->getComponentName());

}

return $result;

}

Here we can find something interesting. Let’s learn how XML files are collected:

...
$sharedFiles = $this->componentDirSearch->collectFilesWithContext(
           ComponentRegistrar::MODULE,
           "view/base/{$this->subDir}{$filePath}"
    );
…
$area = $theme->getData('area');
       $themeFiles = $this->componentDirSearch->collectFilesWithContext(
           ComponentRegistrar::MODULE,
           "view/{$area}/{$this->subDir}{$filePath}"
    );
...

...

$sharedFiles = $this->componentDirSearch->collectFilesWithContext(

ComponentRegistrar::MODULE,

"view/base/{$this->subDir}{$filePath}"

);

…

$area = $theme->getData('area');

$themeFiles = $this->componentDirSearch->collectFilesWithContext(

ComponentRegistrar::MODULE,

"view/{$area}/{$this->subDir}{$filePath}"

);

...

Where:

$area – frontend
$this->subDir – ui_componen/
$filePath – etc/definition.xml

First of all, we get the XML file of the pathway “view/base/ui_componen/etc/definition.xml”. Then it’s necessary to get the XML file of the pathway “view/frontend/ui_componen/etc/definition.xml”.

The method collectFilesWithContext of the class Magento\Framework\Component\DirSearch gets the list of files in the definite directory back. Even a needed file can be given back, as in our case. As a result, we have “view/base/ui_component/etc/definition.xml” file in $sharedFiles array. While $themeFiles array is empty, as the file has not been created on the way. Therefore, we get a file where all UI components have a base declaration.

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It’s high time to return to the method _loadFileLayoutUpdatesXml we started with. The following line is in it:

...
$updateFiles = array_merge($updateFiles, $this->pageLayoutFileSource->getFiles($theme, '*.xml'));
...

...

$updateFiles = array_merge($updateFiles, $this->pageLayoutFileSource->getFiles($theme, '*.xml'));

...

Since we know the whole pathway consisting of some getFiles methods, let’s jump of Magento/Framework/View/File/Collector/Base::getFiles

Now we get XML of not a definite XML file, but all XML files in the directory “view/base/layout/”.

Let’s have a look at the screenshots and define what is contained in $sharedFiles:

As a result, we get XML files of the directory “view/frontend/layout/”. Let’s look at the second screenshot and define what is contained in $themeFiles: