Found bug in @use_ref

[schlichtanders]

Hi there,

I am experimenting a lot with PlutoHooks. They are still very very complex. Hence I guess it is super helpful if these primitives work 100% as intended, so that one can build an intuition on those primitives instead of thinking about how they work precisely.

The current @use_ref code is

if @use_did_deps_change([])
	$ref_ref[] = Ref{Any}($(esc(initial_value)))
end
$ref_ref[]

however if initial_value fails

• the Ref stays undefined, which is probably expected, but in addition
• if another cell is changed which now retriggers execution of this cell, the following uncomprehensible exception is thrown

UndefRefError: access to undefined reference

    [email protected]:37[inlined]
    [email protected]:56[inlined]
    macro expansion@[Local: 211](https://...#)[inlined]
    macro expansion@[Other: 26](https://...#)[inlined]
    top-level scope@[Local: 1](https://...#)[inlined]

One direction of thought how this may be fixed:

• Maybe get rid of @use_did_deps_change entirely and rewrite @use_deps so that it can check whether the initialization failed and create a new cell_id the second time. Then use @use_deps instead of @use_did_deps_change.

[Pangoraw]

Thanks for the issue!

Maybe we could go with something like this, which would retry initial_value until it succeeds:

value = $ref_ref[]
if !isassigned(value) || @use_did_deps_change([])
    $ref_ref[] = Ref{Any}($(esc(initial_value)))
end
value

What do you think?

[schlichtanders]

sounds really good, super simple actually