Open Radar

 
Summary:
After git merging a .storyboard file, an invalid reference in the inferredMetricsTieBreakers section will make the app fail to compile.

Steps to Reproduce:
To emulate a merge:

1. Open a valid .storyboard file’s XML
2. In the inferredMetricsTieBreakers section, add an incorrect reference, for example:

        <segue reference=“abc-de-fgh”/>

3. Try to compile the app
4. Try running the storyboard through ibtool (`ibtool Main.storyboard`)

Expected Results:

I expect an error like: 

“Invalid segue reference “abc-de-fgh” in inferredMetricsTieBreakers section. If you deleted a segue during a source control merge, try deleting the segue reference.”

Actual Results:

Instead, I get this ibtool output with an NSArray exception:

2015-06-05 13:15:54.628 ibtoold[73000:8343663] Exception raised while unarchiving document objects - *** -[__NSArrayM insertObject:atIndex:]: object cannot be nil
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>com.apple.ibtool.errors</key>
	<array>
		<dict>
			<key>description</key>
			<string>The document "Main.storyboard" could not be opened. The operation couldn’t be completed. (com.apple.InterfaceBuilder error -1.)</string>
			<key>recovery-suggestion</key>
			<string>Check the console log for additional information.</string>
		</dict>
	</array>
</dict>
</plist>

Regression:
Unknown

Notes:

It appears the parser assumes interpreting the segue reference will return a non-nil value. Instead, the parser should check for nil, and then return a helpful error message if the segue identified isn’t found.