Can't resize empty table

[kazcw]

A newly-created Table.input can't be resized.

When attempting to resize a component containing Table.input (by its widget, not the visualization), an error message is logged: "Tried to set metadata on arg placeholder. This is not implemented yet!" It works if the component code is Table.input [], but this is not the default when creating a table component with the CB.

The cause is a technical limitation: We attach the table widget to the argument of Table.input, which may be code or a placeholder (if no argument is provided in source code, and the default value [] is used). When the value is a placeholder, we have no source code to associate the size metadata with. I think we should fix this by attaching the table widget to the whole Table.input expression.

[farmaazon]

I imagined just implementing metadata for placeholders (it could be keyed by App AST ID + arg name). But this is quite complicated, so above proposition may be better for now.

[kazcw]

I imagined just implementing metadata for placeholders (it could be keyed by App AST ID + arg name). But this is quite complicated, so above proposition may be better for now.

I'm not sure we should do that (even though I think I wrote the original TODO message, and I have done some design for how it would work). I could be convinced by one good use case, but I think that anything we could do that way, we could also do by keeping that information higher up the tree, on a node that is represented by code, and that the information is relevant to; and I think that that not only avoids needing to attach metadata to values not present in the code, but is a better approach in general. Is it not simpler to treat the table input function call as a table value, that is aware of its argument value (or its absence); than to treat the argument value as a table, when found in the context of a parent table input function? It seems like a matter of explicit relational logic vs implicit relationships and context-dependence.

[farmaazon]

Cases I have in mind:

• "widget picker": when we want to switch widget representation on placeholder, it's about this placeholder only, not entire node
• resizing text input in expr parameter - as above

Technically, perhaps we could make the state just non-persistent: I doubt anyone resizes/switches widget only to leave it that way, usually it is about putting some data, and then we do have AST to attach metadata to.