UI Freeze When Clicking “Samples” Tab in Treemap Chart – Empty 200 Response

[hassaansaleem28]

Bug description

Hi! While I was working on issue #36807, I discovered another problem. When experimenting with Treemap charts in the Explore view, clicking the “Samples” tab triggers a request to /datasource/samples. The backend responds with HTTP 200 but an empty body. The frontend loader spins for a while, and then the UI freezes.

STEPS TO REPRODUCE IT:

1- Run Superset in Docker (latest dev build - Docker Compose).
2- Go to the charts tab and create a Treemap chart using any dataset.
3- Click the “Samples” tab (bottom right).
4- Observe loader spins, UI freezes, and no data shown.

Expected Behavior:
The Samples tab should display rows or show a “No data available” message or something like that.

Actual Behavior:
The UI freezes after receiving a 200 response with no content.

Screenshots/recordings

HERE IS THE SCREEN RECORDING OF THAT EXACT ISSUE :

ScreenRecording.-.Made.with.Clipchamp.mp4

Superset version

master / latest-dev

Python version

3.11

Node version

18 or greater

Browser

Chrome

Additional context

Any Dataset will give the same response. I have checked it multiple times.

Backend log snippet :
POST /datasource/samples?force=false&datasource_type=table&datasource_id=1 HTTP/1.1" 200 -

Checklist

• I have searched the Superset docs and Slack and didn't find a solution to my problem.
• I have searched the GitHub issue tracker and didn't find a similar bug report.
• I have checked Superset's logs for errors, and if I found a relevant Python stacktrace, I included it here as text in the "additional context" section.

[hassaansaleem28]

I’d like to work on fixing this issue. Starting by investigating the frontend handling of empty responses in the Samples tab. If anyone has context or pointers, I’d appreciate it.

[dosubot]

Great place to start! The frontend Samples tab is handled by the SamplesPane component, which fetches data using getDatasourceSamples. Right now, the fetch logic expects a valid JSON response with a result key—if the backend returns a 200 with an empty body, the JSON parser throws, and the error is caught and surfaced as a generic error message in the UI. However, there’s no explicit check for empty or malformed responses before accessing fields, so the error message may not be very descriptive and could cause confusing UI states or freezes if not handled properly.

To improve this, consider adding a defensive check in getDatasourceSamples (in chartAction.js) to detect and handle empty or malformed responses before accessing response.json.result. You could throw a more descriptive error (like "No data returned from server") if the response is empty or missing expected fields. Also, ensure SamplesPane surfaces this error clearly to the user, rather than just spinning or freezing. The main files to look at are:

• superset-frontend/src/explore/components/DataTablesPane/components/SamplesPane.tsx
• superset-frontend/src/components/Chart/chartAction.js (getDatasourceSamples)
• superset-frontend/packages/superset-ui-core/src/connection/callApi/parseResponse.ts

Testing by simulating a 200 with an empty body will help verify your fix. Let me know if you want more details on any of these code paths!

References:
SamplesPane.tsx logic
getDatasourceSamples in chartAction.js
parseResponse.ts JSON parsing

To reply, just mention @dosu.

---

^{How did I do? Good | Irrelevant | Incorrect | Verbose | Hallucination | Report 🐛 | Other}