[BUG] Cannot read properties of undefined (reading 'map')

[Llannelongue]

Hi, I've just updated to the last version of dash, and now get a cryptic error Cannot read properties of undefined (reading 'map') (on chrome) or y is undefined (on firefox) (full traceback below). The update is the only change. Any suggestions? :)

It's probably related to the go.Choropleth part of the code as it doesn't display properly. I haven't been able to create a minimal example but full code here.

Thanks!

I updated from:

dash==1.4.1
dash-core-components==1.3.1
dash-html-components==1.0.1
dash-renderer==1.1.2
dash-table==4.4.1

to:

dash==2.4.1
dash-bootstrap-components==1.1.0
dash-core-components==2.0.0
dash-html-components==2.0.0
dash-renderer==1.1.2
dash-table==5.0.0

EDIT: I've narrowed it down to 2 specific releases of dash:

• 1.8.0 is when the choropleth map stopped displaying (showing an empty div instead) but with no error message
• 2.4.0 is when the error message mentioned here appeared

Full traceback on Chrome:

TypeError: Cannot read properties of undefined (reading 'map')

    at http://127.0.0.1:8050/_dash-component-suites/dash/dcc/async-dropdown.js:2:4888

    at commitHookEffectListMount (http://127.0.0.1:8050/_dash-component-suites/dash/deps/react-dom@16.v2_4_1m1653310444.14.0.js:19866:28)

    at commitPassiveHookEffects (http://127.0.0.1:8050/_dash-component-suites/dash/deps/react-dom@16.v2_4_1m1653310444.14.0.js:19904:13)

    at HTMLUnknownElement.callCallback (http://127.0.0.1:8050/_dash-component-suites/dash/deps/react-dom@16.v2_4_1m1653310444.14.0.js:182:16)

    at Object.invokeGuardedCallbackDev (http://127.0.0.1:8050/_dash-component-suites/dash/deps/react-dom@16.v2_4_1m1653310444.14.0.js:231:18)

    at invokeGuardedCallback (http://127.0.0.1:8050/_dash-component-suites/dash/deps/react-dom@16.v2_4_1m1653310444.14.0.js:286:33)

    at flushPassiveEffectsImpl (http://127.0.0.1:8050/_dash-component-suites/dash/deps/react-dom@16.v2_4_1m1653310444.14.0.js:22988:11)

    at unstable_runWithPriority (http://127.0.0.1:8050/_dash-component-suites/dash/deps/react@16.v2_4_1m1653310444.14.0.js:2685:14)

    at runWithPriority$1 (http://127.0.0.1:8050/_dash-component-suites/dash/deps/react-dom@16.v2_4_1m1653310444.14.0.js:11174:12)

    at flushPassiveEffects (http://127.0.0.1:8050/_dash-component-suites/dash/deps/react-dom@16.v2_4_1m1653310444.14.0.js:22955:14)

[zirondi]

I had a similar issue where I was trying to change a value in a callback that was not properly initialized, see link.

I could not identify it in your code, but I think somewhere you're updating the Y value of some component and it isn't loaded properly yet.

This error message is rather cryptic.

[T4rk1n]

The dropdown was refactored in last release and is now missing a nil check when a value is provided but there is no options.