44655 backend [ My tasks ] Handle null values in /v3/tasks API

[andrey-usov]

Problem

When a user opens their task list and no filters are actively selected, some clients send empty filter values as the literal string null. The server treated those values as real filter criteria, which could return an empty task list even when the user had assigned tasks.

Fix / Solution

GET /v3/tasks now rejects the literal query-string value null for filter parameters with a 400 validation error. Validation lives in TaskListFilterSerializer (including shared RejectNullStringValidator for string fields).

Related staging work: #256 (merged into dev). This PR brings the same change cleanly onto master.

Release notes

Fixed an issue where the task list could return no results when clients sent the literal string null for filter parameters. The API now returns a clear 400 validation error instead.

Changes

API

• GET /v3/tasks — query parameters template_id, template_task_api_name, and assigned_to with the literal value null now return 400:
  • template_id / assigned_to: "A valid integer is required."
  • template_task_api_name: "This field may not be null."

Web-client

No changes in this PR. Related frontend fix covered separately (clients should omit unset filters instead of sending null).

Test cases

API

Authorization	Test case	Expected result
Token auth (account owner)	GET /v3/tasks?template_id=null	400, "A valid integer is required.", details.name = template_id
Token auth (account owner)	GET /v3/tasks?template_task_api_name=null	400, "This field may not be null.", details.name = template_task_api_name
Token auth (admin)	GET /v3/tasks?assigned_to=null	400, "A valid integer is required.", details.name = assigned_to
Token auth (account owner)	GET /v3/tasks?template_id=null&template_task_api_name=null	400, "A valid integer is required.", details.name = template_id

Web-client

No changes.

Made with Cursor

Note

Reject literal string 'null' in /v3/tasks filter parameters

• Adds RejectNullStringValidator in validators.py, a BaseValidator subclass that fails validation when a field value is exactly the string 'null', returning code null and message 'This field may not be null.'
• Applies the validator to the template_task_api_name field in TaskListFilterSerializer so ?template_task_api_name=null returns a 400 error.
• Integer fields (assigned_to, template_id) already reject 'null' via their existing integer validation; new tests cover all three fields plus combined cases.

^{Macroscope summarized 04c677c.}

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