NSURL appends '..' path component on returned url from URLByDeletingLastPathComponent which seems to contradict the documentation

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Created 4h

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The documentation for URLByDeletingLastPathComponent states the following:

If the receiver’s URL represents the root path, this property contains a copy of the original URL. Otherwise, if the original URL has only one path component, this property contains the empty string.

So maybe this is new in Foundation with the Golden Gate or maybe I just noticed this but the documentation above doesn't seem to be true. This will create an infinite loop:

NSURL *fileURL = [NSURL fileURLWithPath:@"/Users/MyUsername/Desktop/AFolder" isDirectory:YES];
		NSLog(@"%@",fileURL);
		
		NSURL *ancestorURL = fileURL.URLByDeletingLastPathComponent;
		while (ancestorURL != nil) 
		{
			NSURL *nextAncestor = ancestorURL.URLByDeletingLastPathComponent;
			NSLog(@"Next: %@",nextAncestor);
			
			if ([nextAncestor isEqual:ancestorURL]) 
			{
				NSLog(@"Hit the root - got a copy of the same url");
				break;
			}
			else if ([nextAncestor.absoluteString isEqualToString:@""] 
				    || [nextAncestor.path isEqualToString:@""])
			{
				NSLog(@"Empty string means we had only 1 path component.");
				break;
			}
			else if (nextAncestor == nil)
			{
				NSLog(@"Got nil");
				break;
			}
			ancestorURL = nextAncestor;
		}

The infinite loop can be avoided by adding the following condition:

else if (nextAncestor.pathComponents.count == 1)
{
// One path component.
	NSURL *sneakPeak = nextAncestor.URLByDeletingLastPathComponent;
				NSLog(@"%lu",sneakPeak.pathComponents.count); // Logs 2.
	 break;
}

When you get to one path component URLByDeletingLastPathComponent appends a .. path component rather than deleting a path component or returning a copy of the receiver or a url with an empty string..

If this sounds like a bug let me know. When I call URLByDeletingLastPathComponent on a url with only one path component I'd like to get nil. I think that would be a cleaner design.

Answer 1

Etresoft OP

2h

The documentation says it returns an empty string, not nil.

Just so you know, manually traversing URLs is always tricky. Sometimes you'll get a reference URL, which can't be traversed. And sometimes you'll get a ".nofollow" URL, which is undocumented.

Answer 2

Macho Man Randy Savage OP

1h

Indeed. I checked for a url with an empty string but when I call URLByDeletingLastPathComponent on a file path url with only 1 component it does not return a url like that - it appends a path component with **.. **

And if you keep calling URLByDeletingLastPathComponent on the resulting URL (like I did in the dumb little sample above) it will continue to do so so you'll get file:///../../../../../ to infinity which is...weird.

This looks like a bug to me but at the very least the documentation should be updated to document IMO.