libraries.api.php

<?php

/**
 * @file
 * Documents API functions for Libraries module.
 */

/**
 * @defgroup libraries External libraries
 * @{
 * External libraries are not shipped as part of contributed modules for
 * licensing and maintenance reasons. The Libraries API module aims to solve the
 * problem of integrating with and loading external libraries as part of the
 * Drupal request-response process in a generic way.
 *
 * @section sec_definitions Library definitions
 * In order to be useful to other modules Libraries API needs a list of known
 * libraries and metadata about each of the libraries. Because multiple modules
 * themes may integrate with the same external library a key objective of
 * Libraries API is to keep this information separate from any one module or
 * theme.
 *
 * Definitions are accessed via a discovery that is responsible for checking
 * whether a given definition exists and fetching it, if it is. See
 * LibraryRegistryInterface and StreamDefinitionDiscovery for more information.
 *
 * @subsection sub_definitions_machine_name
 * A central part of a library's metadata is the library's machine name or ID.
 * For maximum interoperability it must consist of only lowercase ASCII letters,
 * numbers, and underscores. As the machine name is the single identifier of a
 * library and is independent of any given module or theme name it must be
 * unique among all libraries known to Libraries API.
 *
 * @subsection sub_definitions_history Historical background
 * In Drupal 7 library information could already be provided by
 * module-independent info files, but this was not widely used, because there
 * was no way to distribute these info files properly. The information was
 * predominantly provided by a hook that modules could implement, which caused
 * race conditions between modules providing information for the same library.
 * Thus, in Drupal 8 there is no longer a hook making it necessary to properly
 * solve the problem of centrally maintaining and distributing library info
 * files. This has yet to be done. See https://www.drupal.org/node/773508 for
 * more information.
 *
 * @section sec_types Library types
 * Libraries are classed objects that implement LibraryInterface. This generic
 * interface only dictates that a library is aware of its ID. Any further
 * functionality depends on the type of library, each type of library comes with
 * a dedicated interface. See LibraryInterface for more information.
 *
 * @subsection sub_types_version Version detection
 * A central aspect of Libraries API is version detection. Modules or themes may
 * only work with a specific version of an external library, so Libraries API
 * needs a way to detect the version of a library by inspecting the library
 * files.
 *
 * As the mechanism for doing this is generally not specific to any one
 * library, it is handled by version detector plugins. A 'line_pattern' plugin
 * that scans a file line by line whether for whether a pattern containing the
 * version is matched. It can be used if the version is always specified in a
 * particular place in a particular file, for example a changelog. See
 * VersionDetectorInterface and LinePatternDetector for more information.
 *
 * @subsection sub_types_dependency Dependency handling
 * Many libraries depend on other libraries to function. Thus, most library
 * classes should implement DependentLibraryInterface to allow libraries to
 * declare their dependencies as part of their metadata. In case of API changes
 * in the dependencies libraries need to be able to declare dependencies on
 * specific versions or version ranges of other libraries. This has yet to be
 * implemented.
 *
 * Furthermore, Libraries API must also maintain a list of libraries that are
 * required by the installed installation profile, modules, and themes
 * (extensions). With this information installation of extensions with library
 * dependencies can be prevented until the libraries are properly installed.
 * This is currently not implemented. In the future this will be used to
 * automatically retrieve library definitions of required libraries, and
 * possibly to automatically download the libraries themselves.
 *
 * To declare library dependencies extensions can place a 'library_dependencies'
 * key in their info file with a list of library machine names as the value.
 * For example:
 * @code
 *   name: My module
 *   type: module
 *   core: 8.x
 *   library_dependencies:
 *     - flexslider
 *     - jquery_mobile
 * @endcode
 *
 * @subsection sub_types_asset Asset libraries
 * With Drupal 8 relying on Composer for autoloading and dependency resolution
 * of PHP libraries, asset libraries are the primary use-case for Libraries API.
 * Because asset libraries cannot be loaded ad-hoc, but must be attached to a
 * renderable element, Libraries API registers external asset libraries that are
 * required by the installed extensions with the core asset library system. See
 * AssetLibraryInterface for more information.
 *
 * @subsection sub_types_php_file
 * For feature parity with the Drupal 7 version of this module, a PHP file
 * library type is provided, that can load a list of PHP files on demand.
 * Generally, it is encouraged to use Composer instead of this library type and
 * avoid Libraries API altogether for PHP libraries. See PhpFileLibraryInterface
 * for more information.
 *
 * This library type might be removed in a future version of Libraries API.
 *
 * @see \Drupal\libraries\ExternalLibrary\Definition\DefinitionDiscoveryInterface
 * @see \Drupal\libraries\ExternalLibrary\Definition\StreamDefinitionDiscovery
 * @see \Drupal\libraries\ExternalLibrary\LibraryInterface
 * @see \Drupal\libraries\ExternalLibrary\Version\VersionDetectorInterface
 * @see \Drupal\libraries\Plugin\libraries\VersionDetector\LinePatternDetector
 * @see \Drupal\libraries\ExternalLibrary\Version\VersionedLibraryInterface
 * @see \Drupal\libraries\ExternalLibrary\Dependency\DependentLibraryInterface
 * @see \Drupal\libraries\ExternalLibrary\Asset\AssetLibraryInterface
 * @see \Drupal\libraries\ExternalLibrary\PhpFile\PhpFileLibraryInterface
 *
 * @}
 */

/**
 * Alter library type information.
 *
 * @param array $library_types
 *   An array of library types keyed by ID. Each library type is an array with
 *   the following keys:
 *   - id: The ID of the library type.
 *   - class: The class to use for this library type.
 *   - provider: The provider of this library type.
 */
function hook_libraries_library_type_info_alter(array &$library_types) {
  // Use a different class for the asset library type. Note that this class is
  // distinct from the class actually for asset libraries themselves.
  $library_types['asset']['class'] = 'Drupal\mymodule\ExternalLibrary\BetterAssetLibraryType';
}

/**
 * Alter library locator information.
 *
 * @param array $locators
 *   An array of library locators keyed by ID. Each locator is an array with the
 *   following keys:
 *   - id: The ID of the library locator.
 *   - class: The class to use for this library locator.
 *   - provider: The provider of this library locator.
 */
function hook_libraries_locator_info_alter(array &$locators) {
  // Use a different class for the stream locator.
  $locators['stream']['class'] = 'Drupal\mymodule\ExternalLibrary\BetterStreamLocator';
}

/**
 * Alter library version detector information.
 *
 * @param array $version_detectors
 *   An array of library version detectors keyed by ID. Each detector is an
 *   array with the following keys:
 *   - id: The ID of the library version detector.
 *   - class: The class to use for this library version detector.
 *   - provider: The provider of this library version detector.
 */
function hook_libraries_version_detector_info_alter(array &$version_detectors) {
  // Use a different class for the line pattern locator.
  $version_detectors['line_pattern']['class'] = 'Drupal\mymodule\ExternalLibrary\BetterLinePatternDetector';
}

/**
 * Return information about external libraries.
 *
 * @return
 *   An associative array whose keys are internal names of libraries and whose
 *   values are describing each library. Each key is the directory name below
 *   the 'libraries' directory, in which the library may be found. Each value is
 *   an associative array containing:
 *   - name: The official, human-readable name of the library.
 *   - vendor url: The URL of the homepage of the library.
 *   - download url: The URL of a web page on which the library can be obtained.
 *   - path: (optional) A relative path from the directory of the library to the
 *     actual library. Only required if the extracted download package contains
 *     the actual library files in a sub-directory.
 *   - library path: (optional) The absolute path to the library directory. This
 *     should not be declared normally, as it is automatically detected, to
 *     allow for multiple possible library locations. A valid use-case is an
 *     external library, in which case the full URL to the library should be
 *     specified here.
 *   - version: (optional) The version of the library. This should not be
 *     declared normally, as it is automatically detected (see 'version
 *     callback' below) to allow for version changes of libraries without code
 *     changes of implementing modules and to support different versions of a
 *     library simultaneously (though only one version can be installed per
 *     site). A valid use-case is an external library whose version cannot be
 *     determined programmatically.
 *   - version callback: (optional) The name of a function that detects and
 *     returns the full version string of the library. The first argument is
 *     always $library, an array containing all library information as described
 *     here. There are two ways to declare the version callback's additional
 *     arguments, either as a single $options parameter or as multiple
 *     parameters, which correspond to the two ways to specify the argument
 *     values (see 'version arguments'). Defaults to libraries_get_version().
 *   - version arguments: A list of arguments to pass to the version callback.
 *     Version arguments can be declared either as an associative array whose
 *     keys are the argument names or as an indexed array without specifying
 *     keys. If declared as an associative array, the arguments get passed to
 *     the version callback as a single $options parameter whose keys are the
 *     argument names (i.e. $options is identical to the specified array). If
 *     declared as an indexed array, the array values get passed to the version
 *     callback as separate arguments in the order they were declared. The
 *     default version callback libraries_get_version() expects a single,
 *     associative array with named keys:
 *     - file: The filename to parse for the version, relative to the library
 *       path. For example: 'docs/changelog.txt'.
 *     - pattern: A string containing a regular expression (PCRE) to match the
 *       library version. For example: '@version\s+([0-9a-zA-Z\.-]+)@'. Note
 *       that the returned version is not the match of the entire pattern (i.e.
 *       '@version 1.2.3' in the above example) but the match of the first
 *       sub-pattern (i.e. '1.2.3' in the above example).
 *     - lines: (optional) The maximum number of lines to search the pattern in.
 *       Defaults to 20.
 *     - cols: (optional) The maximum number of characters per line to take into
 *       account. Defaults to 200. In case of minified or compressed files, this
 *       prevents reading the entire file into memory.
 *   - files: An associative array of library files to load. Supported keys are:
 *     - js: A list of JavaScript files to load, using the same syntax as Drupal
 *       core's hook_library().
 *     - css: A list of CSS files to load, using the same syntax as Drupal
 *       core's hook_library().
 *     - php: A list of PHP files to load.
 *   - dependencies: An array of libraries this library depends on. Similar to
 *     declaring module dependencies, the dependency declaration may contain
 *     information on the supported version. Examples of supported declarations:
 *     @code
 *     $libraries['dependencies'] = array(
 *       // Load the 'example' library, regardless of the version available:
 *       'example',
 *       // Only load the 'example' library, if version 1.2 is available:
 *       'example (1.2)',
 *       // Only load a version later than 1.3-beta2 of the 'example' library:
 *       'example (>1.3-beta2)'
 *       // Only load a version equal to or later than 1.3-beta3:
 *       'example (>=1.3-beta3)',
 *       // Only load a version earlier than 1.5:
 *       'example (<1.5)',
 *       // Only load a version equal to or earlier than 1.4:
 *       'example (<=1.4)',
 *       // Combinations of the above are allowed as well:
 *       'example (>=1.3-beta2, <1.5)',
 *     );
 *     @endcode
 *   - variants: (optional) An associative array of available library variants.
 *     For example, the top-level 'files' property may refer to a default
 *     variant that is compressed. If the library also ships with a minified and
 *     uncompressed/source variant, those can be defined here. Each key should
 *     describe the variant type, e.g. 'minified' or 'source'. Each value is an
 *     associative array of top-level properties that are entirely overridden by
 *     the variant, most often just 'files'. Additionally, each variant can
 *     contain following properties:
 *     - variant callback: (optional) The name of a function that detects the
 *       variant and returns TRUE or FALSE, depending on whether the variant is
 *       available or not. The first argument is always $library, an array
 *       containing all library information as described here. The second
 *       argument is always a string containing the variant name. There are two
 *       ways to declare the variant callback's additional arguments, either as a
 *       single $options parameter or as multiple parameters, which correspond
 *       to the two ways to specify the argument values (see 'variant
 *       arguments'). If omitted, the variant is expected to always be
 *       available.
 *     - variant arguments: A list of arguments to pass to the variant callback.
 *       Variant arguments can be declared either as an associative array whose
 *       keys are the argument names or as an indexed array without specifying
 *       keys. If declared as an associative array, the arguments get passed to
 *       the variant callback as a single $options parameter whose keys are the
 *       argument names (i.e. $options is identical to the specified array). If
 *       declared as an indexed array, the array values get passed to the
 *       variant callback as separate arguments in the order they were declared.
 *     Variants can be version-specific (see 'versions').
 *   - versions: (optional) An associative array of supported library versions.
 *     Naturally, libraries evolve over time and so do their APIs. In case a
 *     library changes between versions, different 'files' may need to be
 *     loaded, different 'variants' may become available, or Drupal modules need
 *     to load different integration files adapted to the new version. Each key
 *     is a version *string* (PHP does not support floats as keys). Each value
 *     is an associative array of top-level properties that are entirely
 *     overridden by the version.
 *   - integration files: (optional) An associative array whose keys are module
 *     names and whose values are sets of files to load for the module, using
 *     the same notion as the top-level 'files' property. Each specified file
 *     should contain the path to the file relative to the module it belongs to.
 *   - callbacks: An associative array whose keys are callback groups and whose
 *     values are arrays of callbacks to apply to the library in that group.
 *     Each callback receives the following arguments:
 *     - $library: An array of library information belonging to the top-level
 *       library, a specific version, a specific variant or a specific variant
 *       of a specific version. Because library information such as the 'files'
 *       property (see above) can be declared in all these different locations
 *       of the library array, but a callback may have to act on all these
 *       different parts of the library, it is called recursively for each
 *       library with a certain part of the libraries array passed as $library
 *       each time.
 *     - $version: If the $library array belongs to a certain version (see
 *       above), a string containing the version. This argument may be empty, so
 *       NULL should be specified as the default value.
 *     - $variant: If the $library array belongs to a certain variant (see
 *       above), a string containing the variant name. This argument may be
 *       empty, so NULL should be specified as the default value.
 *     Valid callback groups are:
 *     - info: Callbacks registered in this group are applied after the library
 *       information has been retrieved via hook_libraries_info() or info files.
 *     - pre-detect: Callbacks registered in this group are applied after the
 *       library path has been determined and before the version callback is
 *       invoked. At this point the following additional information is available:
 *       - $library['library path']: The path on the file system to the library.
 *     - post-detect: Callbacks registered in this group are applied after the
 *       library has been successfully detected. At this point the library
 *       contains the version-specific information, if specified, and following
 *       additional information is available:
 *       - $library['installed']: A boolean indicating whether the library is
 *         installed or not.
 *       - $library['version']: If it could be detected, a string containing the
 *         version of the library.
 *       - $library['variants'][$variant]['installed']: For each specified
 *         variant, a boolean indicating whether the variant is installed or
 *         not.
 *       Note that in this group the 'versions' property is no longer available.
 *     - pre-load: Callbacks registered in this group are applied directly
 *       before this library is loaded. At this point the library contains
 *       variant-specific information, if specified. Note that in this group the
 *       'variants' property is no longer available.
 *     - post-load: Callbacks registered in this group are applied directly
 *       after this library is loaded. At this point, the library contains a
 *       'loaded' key, which contains the number of files that were loaded.
 *   Additional top-level properties can be registered as needed.
 *
 * @see hook_library()
 *
 * @deprecated Will be removed before a stable Drupal 8 release.
 */
function hook_libraries_info() {
  // The following is a full explanation of all properties. See below for more
  // concrete example implementations.

  // This array key lets Libraries API search for 'sites/all/libraries/example'
  // directory, which should contain the entire, original extracted library.
  $libraries['example'] = [
    // Only used in administrative UI of Libraries API.
    'name' => 'Example library',
    'vendor url' => 'http://example.com',
    'download url' => 'http://example.com/download',
    // Optional: If, after extraction, the actual library files are contained in
    // 'sites/all/libraries/example/lib', specify the relative path here.
    'path' => 'lib',
    // Optional: Define a custom version detection callback, if required.
    'version callback' => 'mymodule_get_version',
    // Specify arguments for the version callback. By default,
    // libraries_get_version() takes a named argument array:
    'version arguments' => [
      'file' => 'docs/CHANGELOG.txt',
      'pattern' => '@version\s+([0-9a-zA-Z\.-]+)@',
      'lines' => 5,
      'cols' => 20,
    ],
    // Default list of files of the library to load. Important: Only specify
    // third-party files belonging to the library here, not integration files of
    // your module.
    'files' => [
      // 'js' and 'css' follow the syntax of hook_library(), but file paths are
      // relative to the library path.
      'js' => [
        'exlib.js',
        'gadgets/foo.js',
      ],
      'css' => [
        'lib_style.css',
        'skin/example.css',
      ],
      // For PHP libraries, specify include files here, still relative to the
      // library path.
      'php' => [
        'exlib.php',
        'exlib.inc',
      ],
    ],
    // Optional: Specify alternative variants of the library, if available.
    'variants' => [
      // All properties defined for 'minified' override top-level properties.
      'minified' => [
        'files' => [
          'js' => [
            'exlib.min.js',
            'gadgets/foo.min.js',
          ],
          'css' => [
            'lib_style.css',
            'skin/example.css',
          ],
        ],
        'variant callback' => 'mymodule_check_variant',
        'variant arguments' => [
          'variant' => 'minified',
        ],
      ],
    ],
    // Optional, but usually required: Override top-level properties for later
    // versions of the library. The properties of the minimum version that is
    // matched override the top-level properties. Note:
    // - When registering 'versions', it usually does not make sense to register
    //   'files', 'variants', and 'integration files' on the top-level, as most
    //   of those likely need to be different per version and there are no
    //   defaults.
    // - The array keys have to be strings, as PHP does not support floats for
    //   array keys.
    'versions' => [
      '2' => [
        'files' => [
          'js' => ['exlib.js'],
          'css' => ['exlib_style.css'],
        ],
      ],
      '3.0' => [
        'files' => [
          'js' => ['exlib.js'],
          'css' => ['lib_style.css'],
        ],
      ],
      '3.2' => [
        'files' => [
          'js' => [
            'exlib.js',
            'gadgets/foo.js',
          ],
          'css' => [
            'lib_style.css',
            'skin/example.css',
          ],
        ],
      ],
    ],
    // Optional: Register files to auto-load for your module. All files must be
    // keyed by module, and follow the syntax of the 'files' property.
    'integration files' => [
      'mymodule' => [
        'js' => ['ex_lib.inc'],
      ],
    ],
    // Optionally register callbacks to apply to the library during different
    // stages of its lifetime ('callback groups').
    'callbacks' => [
      // Used to alter the info associated with the library.
      'info' => [
        'mymodule_example_libraries_info_callback',
      ],
      // Called before detecting the given library.
      'pre-detect' => [
        'mymodule_example_libraries_predetect_callback',
      ],
      // Called after detecting the library.
      'post-detect' => [
        'mymodule_example_libraries_postdetect_callback',
      ],
      // Called before the library is loaded.
      'pre-load' => [
        'mymodule_example_libraries_preload_callback',
      ],
      // Called after the library is loaded.
      'post-load' => [
        'mymodule_example_libraries_postload_callback',
      ],
    ],
  ];

  // A very simple library. No changing APIs (hence, no versions), no variants.
  // Expected to be extracted into 'sites/all/libraries/simple'.
  $libraries['simple'] = [
    'name' => 'Simple library',
    'vendor url' => 'http://example.com/simple',
    'download url' => 'http://example.com/simple',
    'version arguments' => [
      'file' => 'readme.txt',
      // Best practice: Document the actual version strings for later reference.
      // 1.x: Version 1.0
      'pattern' => '/Version (\d+)/',
      'lines' => 5,
    ],
    'files' => [
      'js' => ['simple.js'],
    ],
  ];

  // A library that (naturally) evolves over time with API changes.
  $libraries['tinymce'] = [
    'name' => 'TinyMCE',
    'vendor url' => 'http://tinymce.moxiecode.com',
    'download url' => 'http://tinymce.moxiecode.com/download.php',
    'path' => 'jscripts/tiny_mce',
    // The regular expression catches two parts (the major and the minor
    // version), which libraries_get_version() doesn't allow.
    'version callback' => 'tinymce_get_version',
    'version arguments' => [
      // It can be easier to parse the first characters of a minified file
      // instead of doing a multi-line pattern matching in a source file. See
      // 'lines' and 'cols' below.
      'file' => 'jscripts/tiny_mce/tiny_mce.js',
      // Best practice: Document the actual version strings for later reference.
      // 2.x: this.majorVersion="2";this.minorVersion="1.3"
      // 3.x: majorVersion:'3',minorVersion:'2.0.1'
      'pattern' => '@majorVersion[=:]["\'](\d).+?minorVersion[=:]["\']([\d\.]+)@',
      'lines' => 1,
      'cols' => 100,
    ],
    'versions' => [
      '2.1' => [
        'files' => [
          'js' => ['tiny_mce.js'],
        ],
        'variants' => [
          'source' => [
            'files' => [
              'js' => ['tiny_mce_src.js'],
            ],
          ],
        ],
        'integration files' => [
          'wysiwyg' => [
            'js' => ['editors/js/tinymce-2.js'],
            'css' => ['editors/js/tinymce-2.css'],
          ],
        ],
      ],
      // Definition used if 3.1 or above is detected.
      '3.1' => [
        // Does not support JS aggregation.
        'files' => [
          'js' => [
            'tiny_mce.js' => ['preprocess' => FALSE],
          ],
        ],
        'variants' => [
          // New variant leveraging jQuery. Not stable yet; therefore not the
          // default variant.
          'jquery' => [
            'files' => [
              'js' => [
                'tiny_mce_jquery.js' => ['preprocess' => FALSE],
              ],
            ],
          ],
          'source' => [
            'files' => [
              'js' => [
                'tiny_mce_src.js' => ['preprocess' => FALSE],
              ],
            ],
          ],
        ],
        'integration files' => [
          'wysiwyg' => [
            'js' => ['editors/js/tinymce-3.js'],
            'css' => ['editors/js/tinymce-3.css'],
          ],
        ],
      ],
    ],
  ];
  return $libraries;
}

/**
 * Alter the library information before detection and caching takes place.
 *
 * The library definitions are passed by reference. A common use-case is adding
 * a module's integration files to the library array, so that the files are
 * loaded whenever the library is. As noted above, it is important to declare
 * integration files inside of an array, whose key is the module name.
 *
 * @see hook_libraries_info()
 *
 * @deprecated Will be removed before a stable Drupal 8 release.
 */
function hook_libraries_info_alter(&$libraries) {
  $files = [
    'php' => ['example_module.php_spellchecker.inc'],
  ];
  $libraries['php_spellchecker']['integration files']['example_module'] = $files;
}

/**
 * Specify paths to look for library info files.
 *
 * Libraries API looks in the following directories for library info files by
 * default:
 * - libraries
 * - profiles/$profile/libraries
 * - sites/all/libraries
 * - sites/$site/libraries
 * This hook allows you to specify additional locations to look for library info
 * files. This should only be used for modules that declare many libraries.
 * Modules that only implement a few libraries should implement
 * hook_libraries_info().
 *
 * @return
 *   An array of paths.
 *
 * @deprecated Will be removed before a stable Drupal 8 release.
 */
function hook_libraries_info_file_paths() {
  // Taken from the Libraries test module, which needs to specify the path to
  // the test library.
  return [drupal_get_path('module', 'libraries_test') . '/example'];
}