Issue #3196177 by Matroskeen, anmolgoyal74, quietone: Add documentation for variable source plugins

core/modules/migrate_drupal/src/Plugin/migrate/source/Variable.php

@@ -13,10 +13,14 @@
  * Depending on the configuration, this returns zero or a single row and as such
  * is not a good example for any normal source class returning multiple rows.
  *
- * The configuration may contain two lists of variable names, variables and
- * variables_no_row_if_missing. If any of the variables listed in
- * variables_no_row_if_missing is missing in the source, then the source will
- * return zero rows.
+ * Available configuration keys (one of which must be defined):
+ * - variables: (optional) The list of variables to retrieve from the source
+ *   database. Specified variables are retrieved in a single row.
+ * - variables_no_row_if_missing: (optional) The list of variables to retrieve
+ *   from the source database. If any of the variables listed here are missing
+ *   in the source, then the source will return zero rows.
+ *
+ * Examples:
  *
  * With this configuration, the source will return one row even when the
  * "filter_fallback_format" variable isn't available:
@@ -66,6 +70,10 @@
  *     - book_allowed_types
  * @endcode
  *
+ * For additional configuration keys, refer to the parent classes:
+ * @see \Drupal\migrate\Plugin\migrate\source\SqlBase
+ * @see \Drupal\migrate\Plugin\migrate\source\SourcePluginBase
+ *
  * @MigrateSource(
  *   id = "variable",
  *   source_module = "system",

core/modules/migrate_drupal/src/Plugin/migrate/source/VariableMultiRow.php

@@ -10,6 +10,27 @@
  * Unlike the variable source plugin, this one returns one row per
  * variable.
  *
+ * Available configuration keys:
+ * - variables: (required) The list of variables to retrieve from the source
+ *   database. Each variable is retrieved in a separate row.
+ *
+ * Example:
+ *
+ * @code
+ * plugin: variable_multirow
+ * variables:
+ *   - date_format_long
+ *   - date_format_medium
+ *   - date_format_short
+ * @endcode
+ *
+ * In this example the specified variables are retrieved from the source
+ * database one row per variable.
+ *
+ * For additional configuration keys, refer to the parent classes:
+ * @see \Drupal\migrate\Plugin\migrate\source\SqlBase
+ * @see \Drupal\migrate\Plugin\migrate\source\SourcePluginBase
+ *
  * @MigrateSource(
  *   id = "variable_multirow",
  *   source_module = "system",

core/modules/migrate_drupal/src/Plugin/migrate/source/d6/VariableTranslation.php

@@ -11,6 +11,24 @@
 /**
  * Drupal i18n_variable source from database.
  *
+ * Available configuration keys:
+ * - variables: (required) The list of variable translations to retrieve from
+ *   the source database. All translations are retrieved in a single row.
+ *
+ * Examples:
+ *
+ * @code
+ * plugin: d6_variable_translation
+ * variables:
+ *   - site_offline_message
+ * @endcode
+ * In this example the translations for site_offline_message variable are
+ * retrieved from the source database.
+ *
+ * For additional configuration keys, refer to the parent classes:
+ * @see \Drupal\migrate\Plugin\migrate\source\SqlBase
+ * @see \Drupal\migrate\Plugin\migrate\source\SourcePluginBase
+ *
  * @MigrateSource(
  *   id = "d6_variable_translation",
  *   source_module = "i18n",

core/modules/migrate_drupal/src/Plugin/migrate/source/d7/VariableTranslation.php

@@ -10,6 +10,25 @@
 /**
  * Gets Drupal variable_store source from database.
  *
+ * Available configuration keys:
+ * - variables: (required) The list of variable translations to retrieve from
+ *   the source database. All translations are retrieved in a single row.
+ *
+ * Example:
+ *
+ * @code
+ * plugin: d7_variable_translation
+ * variables:
+ *   - site_name
+ *   - site_slogan
+ * @endcode
+ * In this example the translations for site_name and site_slogan variables are
+ * retrieved from the source database.
+ *
+ * For additional configuration keys, refer to the parent classes:
+ * @see \Drupal\migrate\Plugin\migrate\source\SqlBase
+ * @see \Drupal\migrate\Plugin\migrate\source\SourcePluginBase
+ *
  * @MigrateSource(
  *   id = "d7_variable_translation",
  *   source_module = "i18n_variable",