fix(bug): added missing json=payload for the mattermost destination

[MkhalFadel]

What type of PR is this?

• Bug Fix
• [ ]

Description

How is this tested?

• Unit tests (pytest, jest)
• E2E Tests (Cypress)
• Manually
• N/A

Related Tickets & Documents

Mobile & Desktop Screenshots/Recordings (if there are UI changes)

---

The PR fixes missing .encode("utf-8") in the mattermost.py file for the Mattermost class in line 47

[greptile-apps]

Greptile Summary

This PR fixes the Mattermost webhook destination by replacing data=json_dumps(payload) with json=payload in the requests.post call, which ensures the payload is properly serialized and the Content-Type: application/json header is automatically set — both were missing before, likely causing Mattermost to reject webhook payloads.

• Core fix: Switching to json=payload makes requests handle serialization and sets the correct content type header, resolving the broken webhook delivery.
• Cleanup needed: The json_dumps import from redash.utils is now unused and should be removed.

Confidence Score: 5/5

• Safe to merge — the one-line change correctly fixes webhook delivery by using the json= kwarg, and the only remaining item is an unused import cleanup.
• The change is small and targeted, switching from a raw data= call (missing Content-Type: application/json) to json=payload, which is the idiomatic requests approach for JSON payloads. The logic is straightforwardly correct and the rest of the notify method is untouched.
• No files require special attention.

Important Files Changed

Filename	Overview
redash/destinations/mattermost.py	Replaces data=json_dumps(payload) with json=payload so requests automatically serializes the payload and sets the Content-Type: application/json header, fixing webhook delivery to Mattermost. The now-unused json_dumps import should be cleaned up.

Sequence Diagram

sequenceDiagram
    participant Redash
    participant Mattermost

    Note over Redash,Mattermost: Before fix
    Redash->>Mattermost: "POST /webhook (data=json_string, no Content-Type header)"
    Mattermost-->>Redash: 400 / ignored (missing Content-Type)

    Note over Redash,Mattermost: After fix
    Redash->>Mattermost: "POST /webhook (json=payload, Content-Type: application/json)"
    Mattermost-->>Redash: 200 OK

Loading

_{Reviews (3): Last reviewed commit: "Merge branch 'master' into fix-mattermos..." | Re-trigger Greptile}

[cubic-dev-ai]

All reported issues were addressed across 1 file

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>