"3D Framework v0.3 +demo (basic)" fails to load

[towerofnix]

Expected Behavior

The project 3D Framework v0.3 +demo (basic) by DadOfMrLog (@TheLogFather) loads.

Actual Behavior

The project fails to load, with the following warning:

vm warn Couldn't find SB2 block: 0

Afterwards a critical error happens, probably related:

TypeError: innerBlocks[j] is null

Steps to Reproduce

Open this project, whose ID is 11471613. (scratch-vm link)

Operating System and Browser

Debian (testing), Firefox 60.0b8.

[TheLogFather]

Huh, interesting... hadn't noticed that "Render 2D Quad" script has an "undefined" block in it.

I'd expect you'll see the same with InterXeptor 3D, since that still has one, too.

If you look at the json for these, search for this string: ["0"]

If you want to see some history about where these undefined blocks originally came from, check out these forum posts:
https://scratch.mit.edu/discuss/topic/11569/
https://scratch.mit.edu/discuss/topic/11056/

I guess scratch-vm doesn't manage to deal with this kind of corrupted script...

[towerofnix]

Thanks for taking a look! I thought I'd seen a bug report for handling the "undefined" block (even if that just means ignoring it) but I can't find it anywhere.

[TheLogFather]

Actually, ignore what I say below about #414... dunno how my mind managed to merge the case of undefined custom blocks with a recollection of reading that issue.

There are a number of other references to fixing undefined blocks that you might be remembering (e.g. scratchfoundation/scratch-blocks#756), but they clearly didn't quite catch this case.

---

You're probably referring to #414, which is just about custom blocks with no define script(/stack).

The sense of the word "undefined" there means that, even though the json contains all the info about the block itself (i.e. to render that block within its stack), there is no custom block definition that corresponds to it, so it can't execute that block – and there was a bug fix for that case.

Scratch 2 shows such a block in red with the word "undefined", but does keep slots for any parameters it has. (TBH, I'd prefer if it hadn't dropped all the text that tells what that block was trying to call, since just replacing it all with "undefined" is not very helpful when trying to figure out what is actually missing...)

But the sense of "undefined" in this case is that the json contains nothing that defines what the block itself is meant to be. It's a block that really is completely undefined (and implies something got corrupted when writing the json).

[towerofnix]

This project now opens: https://llk.github.io/scratch-gui/develop/#11471613 - It also runs (and at a framerate that's better than I expected but slower than in 2.0)... although the pyramid doesn't render.

Note that there's a console error "vm warn Couldn't find SB2 block: 0". I guess the VM altogether ignores blocks that don't exist now?