NilObjectException from SpecialFolder.Temporary on El Capitan?

Hamish_Symington · October 20, 2015, 5:08pm

Hi -
I have someone reporting a NilObjectException on El Capitan. I’ve narrowed it down to one of these two lines:

theCompressedFile = SpecialFolder.Temporary.Child( theUUID+".zip" ) theCompressedFileName = theCompressedFile.NameWithoutExtensionMBS

Because of some other stuff in our project I think it’s the former.

Would there be any reason why SpecialFolder.Temporary was returning Nil instead of its usual folderitem? Has anyone else seen this?

Kimball_Larsen · October 20, 2015, 5:10pm

I have not seen that, but to be sure you’d have to check for theCompressedFile <> nil before referencing anything in it.

I do make use of SpecialFolder.Temporary quite heavily though - and have not had any errors reported from my users.

Michel_Bujardet · October 20, 2015, 7:11pm

[quote=222254:@Hamish Symington]I have someone reporting a NilObjectException on El Capitan. I’ve narrowed it down to one of these two lines:

theCompressedFile = SpecialFolder.Temporary.Child( theUUID+".zip" ) theCompressedFileName = theCompressedFile.NameWithoutExtensionMBS
Because of some other stuff in our project I think it’s the former.[/quote]

I doubt the first line can trigger the NOE. Unless theCompressedFile is a computed property that tries to process it.

Looks more likely the second line triggers the error, when NameWithoutEXtensionMBS tries to get the name and finds Nil. You may want to step through to confirm.

Kimball_Larsen · October 20, 2015, 7:54pm

I agree with @Michel Bujardet - the first line should not be able to throw a NOE. But it could possibly return a nil, which when you try to call NameWithoutExtensionMBS will throw the NOE.

Hamish_Symington · October 21, 2015, 8:13am

I was wondering if SpecialFolder.Temporary was nil for some reason?
Anyway, I’ve seen one other quit this morning which looks like it was on a .Exists for a file which I know doesn’t exist (e.g. SpecialFolder.Desktop.Child(“fish.blah”) ) so I’m wondering if there’s something slightly different about how that’s handled on El Cap which is throwing errors.

Hamish_Symington · October 21, 2015, 8:14am

(Oh, and theCompressedFile is simply a folder item within the method.)

Hamish_Symington · October 21, 2015, 9:07am

OK, I’ve been doing a lot of testing on this this morning. First up, a recap of what I believe to be true.

SpecialFolder.Temporary should always exist. It should never be Nil.
SpecialFolder.Temporary.Child( ) should always return a folderItem, never Nil. That folderItem may not exist, but it won’t be Nil.

Now, looking at the code above:

theCompressedFile = SpecialFolder.Temporary.Child( theUUID+".zip" ) theCompressedFileName = theCompressedFile.NameWithoutExtensionMBS
the only way I can see that a NoE would be returned is if theCompressedFile is Nil. But I thought that it couldn’t ever be Nil. @Kimball Larsen , you say that it might return Nil; in what circumstances?

Somewhat banging my head against the desk on this one…

ChristopheDV · October 21, 2015, 9:07am

I think you may be right about this.
Previously the below code - deliberately without testing against being NIL - can throw a NIL object error.
This was not the case with 2015r2

Try
Dim f as folderitem = specialfolder.desktop.child(“test.txt”)
If f.exists then
Msgbox “hooray”
End if
Catch
Msgbox “not found”
End try

Hamish_Symington · October 21, 2015, 9:11am

@Christoph De Vocht : I am working with 2015 r1. The problems are being reported on El Capitan only, as far as I can see.

I have just run your code 50,000 times and it’s not given me an NoE - but then I’m not getting any from mine either. So, I’m wondering if there’s something which very, very intermittently makes specialfolder. return Nil. If so, that’s going to be a massive pain, because we assume that everything from specialFolder will return a valid folder.

ChristopheDV · October 21, 2015, 9:16am

Ok its OSX10.11 related.
I somethings can trigger this, sometimes not.
But I have users complaining it happens always.
Of course I fixed this by testing it against being NIL

Hamish_Symington · October 21, 2015, 9:18am

@Christoph De Vocht : How can you trigger it yourself? Should I run your loop more often? Is there anything which you can do to reliably trigger it?

My only thought for a workaround would be this: wherever I call SpecialFolder.Temporary (or SpecialFolder.whatever) I can replace it with a method called GetSpecialFolder(type as string) which I write myself. That gets the special folder and, if its Nil, loops until its not nil, then returns it. This has the great advantage that I can simply find and replace to implement the fix, rather than having to rework code to include Nil tests wherever I use specialfolder. However, if you say that there are some people who always complain that it happens, then SpecialFolder. will be nil for them always, in which case it’s hopeless.

Michel_Bujardet · October 21, 2015, 9:43am

[quote=222498:@Hamish Symington]@Christoph De Vocht : How can you trigger it yourself? Should I run your loop more often? Is there anything which you can do to reliably trigger it?

My only thought for a workaround would be this: wherever I call SpecialFolder.Temporary (or SpecialFolder.whatever) I can replace it with a method called GetSpecialFolder(type as string) which I write myself. That gets the special folder and, if its Nil, loops until its not nil, then returns it. This has the great advantage that I can simply find and replace to implement the fix, rather than having to rework code to include Nil tests wherever I use specialfolder. However, if you say that there are some people who always complain that it happens, then SpecialFolder. will be nil for them always, in which case it’s hopeless.[/quote]

Sounds like a winner.

Just a hunch, but worth verifying though : could it happen that theUUID be empty ? Then you could end up feeding NameWithoutExtensionMBS a FolderItem with no name. It is easy to verify if that kind of thing triggers a NOE.

Hamish_Symington · October 21, 2015, 9:48am

@Michel Bujardet : if theUUID is empty, then it’ll be fed “.zip”, which works ok. theUUID is never Nil.

Michel_Bujardet · October 21, 2015, 10:10am

Not necessarily. After trying x number of times, if still nil, you can fall back to something like :

SpecialFolder.ApplicationData.child("myTemp").child(str(totalseconds))

Of course, that will require a bit of overhead to create myTemp, and some additional cleanup upon closing the app.

Hamish_Symington · October 21, 2015, 10:12am

…except when SpecialFolder.ApplicationData is also Nil, that won’t work! (I’m thinking that I will have to assume that SpecialFolder. could be Nil.)

Michel_Bujardet · October 21, 2015, 10:13am

I frankly do not see what to do if there is no way to open a folderItem anywhere, besides warning the user and quit.

Hamish_Symington · October 21, 2015, 10:14am

I think I agree with you!

ChristopheDV · October 21, 2015, 6:28pm

Hmmm… got another user that gets a NilObjectException. It seems to crash with this code:

msgbox specialFolder.movies.NativePath

He says it does not crash with OSX.10.10 but it does gives a NilObjectException in OSX 10.11

Odd…

Kimball_Larsen · October 21, 2015, 9:58pm

Sorry @Hamish Symington - you are right. Your first line should NEVER return NIL. It could possibly return a folderItem that does not exist, which could in turn thrown a NOE on the second line. Sorry for my confusing language.

Michel_Bujardet · October 21, 2015, 10:40pm

[quote=222727:@Christoph De Vocht]Hmmm… got another user that gets a NilObjectException. It seems to crash with this code:

msgbox specialFolder.movies.NativePath

He says it does not crash with OSX.10.10 but it does gives a NilObjectException in OSX 10.11[/quote]

There seems to have be some random issues with opening files during beta.
https://github.com/atom/atom/issues/7811

Could your user have an older release ?