Workaround for Facebook data store API behavior regression, fixes saving

of empty notice prefix text in facebook settings.

Filed bug upstream at http://bugs.developers.facebook.com/show_bug.cgi?id=7110

Per documentation, saving a pref value of "" or "0" will delete the pref key:
http://wiki.developers.facebook.com/index.php/Data.setUserPreference

which used to do what we want... Now Facebook throws back an error
"Parameter value is required" when we do this. Workaround appends a
space to empty string or "0" at save time, then trims the string when
we load it.

The input string was already trimmed at pref save time, so this won't
alter any user-visible behavior.

Thanks to ^demon in #mediawiki for pointing out the behavior regression
after testing the identi.ca Facebook app!

2 files changed, 11 insertions, 4 deletions

diff --git a/actions/facebooksettings.php b/actions/facebooksettings.php
index 84bdde910..b2b1d6807 100644
--- a/actions/facebooksettings.php
+++ b/actions/facebooksettings.php
@@ -58,8 +58,15 @@ class FacebooksettingsAction extends FacebookAction
         $this->flink->set_flags($noticesync, $replysync, false, false);
         $result = $this->flink->update($original);
 
+        if ($prefix == '' || $prefix == '0') {
+        	// Facebook bug: saving empty strings to prefs now fails
+        	// http://bugs.developers.facebook.com/show_bug.cgi?id=7110
+        	$trimmed = $prefix . ' ';
+        } else {
+	        $trimmed = substr($prefix, 0, 128);
+	    }
         $this->facebook->api_client->data_setUserPreference(FACEBOOK_NOTICE_PREFIX,
-            substr($prefix, 0, 128));
+            $trimmed);
 
         if ($result === false) {
             $this->showForm(_('There was a problem saving your sync preferences!'));
@@ -101,7 +108,7 @@ class FacebooksettingsAction extends FacebookAction
 
             $this->elementStart('li');
 
-            $prefix = $this->facebook->api_client->data_getUserPreference(FACEBOOK_NOTICE_PREFIX);
+            $prefix = trim($this->facebook->api_client->data_getUserPreference(FACEBOOK_NOTICE_PREFIX));
 
             $this->input('prefix', _('Prefix'),
                          ($prefix) ? $prefix : null,
diff --git a/lib/facebookutil.php b/lib/facebookutil.php
index f5121609d..c991c5439 100644
--- a/lib/facebookutil.php
+++ b/lib/facebookutil.php
@@ -99,8 +99,8 @@ function facebookBroadcastNotice($notice)
             // XXX: Does this call count against our per user FB request limit?
             // If so we should consider storing verb elsewhere or not storing
 
-            $prefix = $facebook->api_client->data_getUserPreference(FACEBOOK_NOTICE_PREFIX,
-                                                                    $fbuid);
+            $prefix = trim($facebook->api_client->data_getUserPreference(FACEBOOK_NOTICE_PREFIX,
+                                                                         $fbuid));
 
             $status = "$prefix $notice->content";