MDL-45113 auth: add is_configured method and convert auth_db to use it

auth/db/auth.php

@@ -58,6 +58,11 @@ class auth_plugin_db extends auth_plugin_base {
     function user_login($username, $password) {
         global $CFG, $DB;
 
+        if ($this->is_configured() === false) {
+            debugging(get_string('auth_notconfigured', 'auth', $this->authtype));
+            return false;
+        }
+
         $extusername = core_text::convert($username, 'utf-8', $this->config->extencoding);
         $extpassword = core_text::convert($password, 'utf-8', $this->config->extencoding);
 
@@ -144,8 +149,13 @@ class auth_plugin_db extends auth_plugin_base {
      * Connect to external database.
      *
      * @return ADOConnection
+     * @throws moodle_exception
      */
     function db_init() {
+        if ($this->is_configured() === false) {
+            throw new moodle_exception('auth_dbcantconnect', 'auth_db');
+        }
+
         // Connect to the external database (forcing new connection).
         $authdb = ADONewConnection($this->config->type);
         if (!empty($this->config->debugauthdb)) {
@@ -661,6 +671,18 @@ class auth_plugin_db extends auth_plugin_base {
         return ($this->config->passtype === 'internal');
     }
 
+    /**
+     * Returns false if this plugin is enabled but not configured.
+     *
+     * @return bool
+     */
+    public function is_configured() {
+        if (!empty($this->config->type)) {
+            return true;
+        }
+        return false;
+    }
+
     /**
      * Indicates if moodle should automatically update internal user
      * records with data from external sources using the information

lang/en/auth.php

@@ -40,6 +40,7 @@ $string['auth_changingemailaddress'] = 'You have requested a change of email add
 $string['authinstructions'] = 'Leave this blank for the default login instructions to be displayed on the login page. If you want to provide custom login instructions, enter them here.';
 $string['auth_invalidnewemailkey'] = 'Error: if you are trying to confirm a change of email address, you may have made a mistake in copying the URL we sent you by email. Please copy the address and try again.';
 $string['auth_multiplehosts'] = 'Multiple hosts OR addresses can be specified (eg host1.com;host2.com;host3.com) or (eg xxx.xxx.xxx.xxx;xxx.xxx.xxx.xxx)';
+$string['auth_notconfigured'] = 'The authentication method {$a} is not configured.';
 $string['auth_outofnewemailupdateattempts'] = 'You have run out of allowed attempts to update your email address. Your update request has been cancelled.';
 $string['auth_passwordisexpired'] = 'Your password is expired. Do you want change your password now?';
 $string['auth_passwordwillexpire'] = 'Your password will expire in {$a} days. Do you want change your password now?';

lib/authlib.php

@@ -212,6 +212,15 @@ class auth_plugin_base {
         return true;
     }
 
+    /**
+     * Returns false if this plugin is enabled but not configured.
+     *
+     * @return bool
+     */
+    public function is_configured() {
+        return false;
+    }
+
     /**
      * Indicates if password hashes should be stored in local moodle database.
      * @return bool true means md5 password hash stored in user table, false means flag 'not_cached' stored there instead