Allows for a single base installation profile to exist in Drupal 7.

1356276-D7-inheritable-profiles

diff --git a/includes/common.inc b/includes/common.inc
index 262e1c5..5523ada 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -232,6 +232,29 @@ function drupal_get_profile() {
   return $profile;
 }
 
+/**
+ * Gets the name of the currently active installation profile's base profile.
+ *
+ * When this function is called during the Drupal's initial installation process,
+ * the name of the base profile that's about to be installed is stored in the global
+ * installation state. At all other times, the standard Drupal systems variable table
+ * contains the name of the current profile's base profile, and we can call
+ * variable_get() to determine what it is.
+ *
+ * @return $base_profile
+ *   The name of the installation profile's base installation profile.
+ */
+function drupal_get_base_profile() {
+  global $install_state;
+  if (isset($install_state['parameters']['base_profile'])) {
+    $base_profile = $install_state['parameters']['base_profile'];
+  }
+  else {
+    $base_profile = variable_get('install_base_profile', NULL);
+  }
+
+  return $base_profile;
+}
 
 /**
  * Sets the breadcrumb trail for the current page.
@@ -5349,6 +5372,7 @@ function drupal_system_listing($mask, $directory, $key = 'name', $min_depth = 1)
   // there in favor of sites/all or sites/<domain> directories.
   $profiles = array();
   $profile = drupal_get_profile();
+
   // For SimpleTest to be able to test modules packaged together with a
   // distribution we need to include the profile of the parent site (in which
   // test runs are triggered).
@@ -5361,6 +5385,14 @@ function drupal_system_listing($mask, $directory, $key = 'name', $min_depth = 1)
   // In case both profile directories contain the same extension, the actual
   // profile always has precedence.
   $profiles[] = $profile;
+
+  // In the event that the profile is inheriting a base profile, ensure that
+  // the base profile is added to the searchable directories.
+  $base_profile = drupal_get_base_profile();
+  if (!empty($base_profile)) {
+    $profiles[] = $base_profile;
+  }
+
   foreach ($profiles as $profile) {
     if (file_exists("profiles/$profile/$directory")) {
       $searchdir[] = "profiles/$profile/$directory";
diff --git a/includes/install.core.inc b/includes/install.core.inc
index 7a694e9..dcdf1cf 100644
--- a/includes/install.core.inc
+++ b/includes/install.core.inc
@@ -162,6 +162,10 @@ function install_state_defaults() {
     // An array of information about the chosen installation profile. This will
     // be filled in based on the profile's .info file.
     'profile_info' => array(),
+    // An array of information about the chosen installation profile's base.
+    // This will be filled in based on the profile's `base` property value
+    // if the base profile exists and its .info file.
+    'base_profile_info' => array(),
     // An array of available installation profiles.
     'profiles' => array(),
     // An array of server variables that will be substituted into the global
@@ -565,6 +569,21 @@ function install_tasks($install_state) {
     ),
   );
 
+  // Now add any tasks defined by the base installation profile, if one exists.
+  if (!empty($install_state['parameters']['base_profile'])) {
+    $base_profile_install_file = DRUPAL_ROOT . '/profiles/' . $install_state['parameters']['base_profile'] . '/' . $install_state['parameters']['profile'] . '.install';
+    if (file_exists($base_profile_install_file)) {
+      include_once $base_profile_install_file;
+    }
+    $function = $install_state['parameters']['base_profile'] . '_install_tasks';
+    if (function_exists($function)) {
+      $result = $function($install_state);
+      if (is_array($result)) {
+        $tasks += $result;
+      }
+    }
+  }
+
   // Now add any tasks defined by the installation profile.
   if (!empty($install_state['parameters']['profile'])) {
     // Load the profile install file, because it is not always loaded when
@@ -595,6 +614,18 @@ function install_tasks($install_state) {
     ),
   );
 
+  // All the base installation profile to modify the full list of tasks.
+  if (!empty($install_state['parameters']['base_profile'])) {
+    $base_profile_file = DRUPAL_ROOT . '/profiles/' . $install_state['parameters']['base_profile'] . '/' . $install_state['parameters']['base_profile'] . '.profile';
+    if (file_exists($base_profile_file)) {
+      include_once $base_profile_file;
+      $function = $install_state['parameters']['base_profile'] . '_install_tasks_alter';
+      if (function_exists($function)) {
+        $function($tasks, $install_state);
+      }
+    }
+  }
+
   // Allow the installation profile to modify the full list of tasks.
   if (!empty($install_state['parameters']['profile'])) {
     $profile_file = DRUPAL_ROOT . '/profiles/' . $install_state['parameters']['profile'] . '/' . $install_state['parameters']['profile'] . '.profile';
@@ -770,9 +801,21 @@ function install_system_module(&$install_state) {
   // upcoming bootstrap step.
   module_enable(array('user'), FALSE);
 
+  $base_profile = drupal_get_base_profile();
+  if (isset($base_profile)) {
+    $modules = $install_state['base_profile_info']['dependencies'];
+  }
+  else {
+    $modules = array();
+  }
+
   // Save the list of other modules to install for the upcoming tasks.
   // variable_set() can be used now that system.module is installed.
-  $modules = $install_state['profile_info']['dependencies'];
+  $modules = array_merge($modules, $install_state['profile_info']['dependencies']);
+
+  if (isset($base_profile)) {
+    $modules[] = $base_profile;
+  }
 
   // The installation profile is also a module, which needs to be installed
   // after all the dependencies have been installed.
@@ -1321,6 +1364,14 @@ function install_no_profile_error() {
 }
 
 /**
+ * Indicates that there are no base profile available.
+ */
+function install_no_base_profile_error() {
+  drupal_set_title(st('Base profile not available'));
+  return st('Cannot load base profile.');
+}
+
+/**
  * Indicates that Drupal has already been installed.
  */
 function install_already_done_error() {
@@ -1343,6 +1394,17 @@ function install_load_profile(&$install_state) {
   if (file_exists($profile_file)) {
     include_once $profile_file;
     $install_state['profile_info'] = install_profile_info($install_state['parameters']['profile'], $install_state['parameters']['locale']);
+    if (isset($install_state['profile_info']['base'])) {
+      $base_profile_file = DRUPAL_ROOT . '/profiles/' . $install_state['profile_info']['base'] . '/' . $install_state['profile_info']['base'] . '.profile';
+      if (file_exists($base_profile_file)) {
+        include_once $base_profile_file;
+        $install_state['parameters']['base_profile'] = $install_state['profile_info']['base'];
+        $install_state['base_profile_info'] = install_profile_info($install_state['parameters']['base_profile']);
+      }
+      else {
+        throw new Exception(st('Sorry, the base profile specified cannot be loaded.'));
+      }
+    }
   }
   else {
     throw new Exception(st('Sorry, the profile you have chosen cannot be loaded.'));
@@ -1381,6 +1443,11 @@ function install_profile_modules(&$install_state) {
   // every dependency, including non-required ones. So clear its required
   // flag for now to allow it to install late.
   $files[$install_state['parameters']['profile']]->info['required'] = FALSE;
+
+  if (isset($install_state['parameters']['base_profile'])) {
+    $files[$install_state['parameters']['base_profile']]->info['required'] = FALSE;
+  }
+
   // Add modules that other modules depend on.
   foreach ($modules as $module) {
     if ($files[$module]->requires) {
@@ -1539,6 +1606,9 @@ function install_finished(&$install_state) {
   // registered by the installation profile are registered correctly.
   drupal_flush_all_caches();
 
+  // If a base profile exists, remember which was used.
+  variable_set('install_base_profile', drupal_get_base_profile());
+
   // Remember the profile which was used.
   variable_set('install_profile', drupal_get_profile());
 
@@ -1591,6 +1661,11 @@ function install_check_requirements($install_state) {
   // Check the profile requirements.
   $requirements = drupal_check_profile($profile);
 
+  // If a base profile exists, check the base profile's requirements.
+  if (isset($install_state['parameters']['base_profile'])) {
+    $requirements += drupal_check_profile($install_state['parameters']['base_profile']);
+  }
+
   // If Drupal is not set up already, we need to create a settings file.
   if (!$install_state['settings_verified']) {
     $writable = FALSE;
diff --git a/includes/install.inc b/includes/install.inc
index 3631c36..99af96d 100644
--- a/includes/install.inc
+++ b/includes/install.inc
@@ -680,7 +680,18 @@ function drupal_verify_profile($install_state) {
   if (!isset($profile) || !file_exists($profile_file)) {
     throw new Exception(install_no_profile_error());
   }
-  $info = $install_state['profile_info'];
+  $dependencies = $install_state['profile_info']['dependencies'];
+
+  if (isset($install_state['parameters']['base_profile'])) {
+    $base_profile = $install_state['parameters']['base_profile'];
+    $base_profile_file = DRUPAL_ROOT . "/profiles/$base_profile/$base_profile.profile";
+    if (!file_exists($base_profile_file)) {
+      throw new Exception(install_no_base_profile_error());
+    }
+
+    $dependencies = array_merge($dependencies, $install_state['base_profile_info']['dependencies'], array($base_profile));
+    $dependencies = array_unique($dependencies);
+  }
 
   // Get a list of modules that exist in Drupal's assorted subdirectories.
   $present_modules = array();
@@ -688,12 +699,18 @@ function drupal_verify_profile($install_state) {
     $present_modules[] = $present_module->name;
   }
 
+  // If a base profile exists, like other installation profiles it is also a
+  // module, which needs to be installed after other dependencies have.
+  if (isset($base_profile)) {
+    $present_modules[] = $base_profile;
+  }
+
   // The installation profile is also a module, which needs to be installed
   // after all the other dependencies have been installed.
   $present_modules[] = drupal_get_profile();
 
   // Verify that all of the profile's required modules are present.
-  $missing_modules = array_diff($info['dependencies'], $present_modules);
+  $missing_modules = array_diff($dependencies, $present_modules);
 
   $requirements = array();
 
diff --git a/modules/system/system.module b/modules/system/system.module
index 2bbcd7f..d29783a 100644
--- a/modules/system/system.module
+++ b/modules/system/system.module
@@ -2369,6 +2369,18 @@ function _system_rebuild_module_data() {
   $modules[$profile]->uri = 'profiles/' . $profile . '/' . $profile . '.profile';
   $modules[$profile]->filename = $profile . '.profile';
 
+  $base_profile = drupal_get_base_profile();
+  if (!empty($base_profile)) {
+    $modules[$base_profile] = new stdClass();
+    $modules[$base_profile]->name = $base_profile;
+    $modules[$base_profile]->uri = 'profiles/' . $base_profile . '/' . $base_profile . '.profile';
+    $modules[$base_profile]->filename = $base_profile . '.profile';
+
+    // Base installation profile hooks are always executed immediately prior
+    // to those of the $profile.
+    $modules[$base_profile]->weight = 999;
+  }
+
   // Installation profile hooks are always executed last.
   $modules[$profile]->weight = 1000;
 
@@ -2422,6 +2434,16 @@ function _system_rebuild_module_data() {
     drupal_alter('system_info', $modules[$key]->info, $modules[$key], $type);
   }
 
+  if (isset($base_profile) && isset($modules[$base_profile])) {
+    // The base installation profile is required. if it's a valid module.
+    $modules[$base_profile]->info['required'] = TRUE;
+    // Add a default distribution name if the base profile did not provide one. This
+    // matches the default value used in the install_profile_info().
+    if (!isset($modules[$base_profile]->info['distribution_name'])) {
+      $modules[$base_profile]->info['distribution_name'] = 'Drupal';
+    }
+  }
+
   if (isset($modules[$profile])) {
     // The installation profile is required, if it's a valid module.
     $modules[$profile]->info['required'] = TRUE;