[BUG] ctx.triggered_id is not recognized as a dict

[ProfessorOwl]

Describe your context
Please provide us your environment, so we can easily reproduce the issue.

dash                      4.4.1
dash_ag_grid              35.3.0
dash-extensions           2.0.6
dash-iconify              0.1.2
dash_mantine_components   2.8.0

Describe the bug

I am defining multiple dynamic components and set their id like this:

id={"type": "entry", "index": id},

where the value of "index" gets changed depending on the component.
Now, when I want to use the id in a pattern-matching callback, I need to get the value of "index"to search a sqlite database. When I use

ctx.triggered_id.get("index"))

however, VS Code produces an error and says: ""get" is no known attribute of "None"". The call however correctly returns the value of "index"

The same problem happens with ctx.triggered_id["index"], although the error then says: "None" object is not subscriptable.

FYI: I translated the error messages from German to English. They could be slightly inaccurate, though their meaning should be correct

Expected behavior

I would expect it to see a dict as a possible type of triggered_id, so that there is no error shown.

[ProfessorOwl]

The same problem also seems to exist with ctx.outputs_grouping.
I am defining the outputs like this:

       output={
            "drawer": Output("drawer", "opened"),
            "entries": {
                "name": Output("entry_name", "value"),
                "amount": Output("entry_amount", "value"),
                "paid": Output("entry_paid", "checked"),
                "category": Output("entry_category", "value"),
                "date": Output("entry_date", "value"),
                "interval": Output("entry_interval", "value"),
                "description": Output("entry_description", "value"),
            },
        },

This gives the following error when calling ctx.outputs_grouping["entries"]

no overloads for "__getitem__" match the provided arguments

The function .get() is also not recognized as a valid function.

Both ["entries"] and .get() work, nonetheless

[AnnMarieW]

@ProfessorOwl

Could you please include a minimal example to replicate the issue? Here is one that show that ctx.triggered_id can be None when the callback first runs:

from dash import Dash, html, Input, Output, ALL, ctx

app = Dash()

app.layout = html.Div([
    html.Button("Entry 1", id={"type": "entry", "index": 1}),
    html.Button("Entry 1", id={"type": "entry", "index": 1}),
    html.Div(id="out")
])


@app.callback(
    Output("out", "children"),
    Input({"type": "entry", "index": ALL}, "n_clicks"),
    #prevent_initial_call=True,
)
def update_entries(n_clicks):
    return f"n: {n_clicks},    ctx: {ctx.triggered_id}"


if __name__ == "__main__":
    app.run(debug=True)

[ProfessorOwl]

HI @AnnMarieW, sorry, I should have done that from the beginning.
If I modify your example and put the .get function and ["index"] subscript behind ctx.triggered_id, then Pylance displays an error (reportOptionalMemberAccess for .get() and reportOptionalSubscript for ["index"]. I now see that if I test beforehand that ctx.triggered_idis not None, then the errors disappear. But since prevent_initial_call=True is set, only inputs with a dict as an id can trigger the callback, so the error is obsolete. But I can understand now that it can be argumented that – for type safety – there should be an additional check in place, independent from prevent_initial_call.

from dash import Dash, html, Input, Output, ALL, ctx
from dash.exceptions import PreventUpdate


app = Dash()

app.layout = html.Div(
    [
        html.Button("Entry 1", id={"type": "entry", "index": 1}),
        html.Button("Entry 1", id={"type": "entry", "index": 2}),
        html.Div(id="out"),
    ]
)


@app.callback(
    Output("out", "children"),
    Input({"type": "entry", "index": ALL}, "n_clicks"),
    prevent_initial_call=True,
)
def update_entries(n_clicks):
    # if ctx.triggered_id is None:
    #     raise PreventUpdate
    return f"n: {n_clicks},    ctx.get: {ctx.triggered_id.get("index")},    ctx.subscript: {ctx.triggered_id["index"]}"

if __name__ == "__main__":
    app.run(debug=True)

The error regarding ctx.outputs_grouping can also be circumvented by checking if isinstance(ctx.outputs_grouping, list), but since the outputs are statically written out as a dict, it would be nice if that could be somehow given over to Pylance. The issue Pylance reports is reportAttributeAccessIssue

Here is a MWE:

from dash import Dash, html, Input, Output, ALL, ctx
from dash.exceptions import PreventUpdate

app = Dash()

app.layout = html.Div(
    [
        html.Button("Entry 1", id={"type": "entry", "index": 1}),
        html.Button("Entry 1", id={"type": "entry", "index": 2}),
        html.Div(id="out"),
    ]
)


@app.callback(
    output={"div1": Output("out", "children")},
    inputs=Input({"type": "entry", "index": ALL}, "n_clicks"),
    prevent_initial_call=True,
)
def update_entries(n_clicks):
    # if isinstance(ctx.outputs_grouping, list):
    #     raise PreventUpdate
    return {key: f"n: {n_clicks}" for key in ctx.outputs_grouping.keys()}


if __name__ == "__main__":
    app.run(debug=True)

I understand now that the type problems can be mitigated by extensive type checking. If this is too extensive to implement, then I fully understand, though it is cumbersome to have all these lines of typechecking in place, where the types are pretty much hardcoded.

[camdecoster]

I'm inclined to leave the types as is, but I'll leave this open for now to see if anyone else would like to see a change.