fix(scope): Drop None user attribute values in set_user

[ericapisani]

set_user previously stored None values verbatim in the user dict, which would send null attributes to Sentry. Now any key with a None value is filtered out before the dict is stored on the scope, so only meaningful user attributes are captured in events.

Fixes PY-2567
Fixes #6689

[linear-code]

PY-2567

[github-actions]

Codecov Results 📊

✅ 89952 passed | ⏭️ 6288 skipped | Total: 96240 | Pass Rate: 93.47% | Execution Time: 315m 26s

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✅ Patch coverage is 100.00%. Project has 2436 uncovered lines.
✅ Project coverage is 89.77%. Comparing base (base) to head (head).

Coverage diff

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+ Coverage    89.77%    89.77%        —%
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  Files          192       192         —
  Lines        23809     23809         —
  Branches      8218      8218         —
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+ Hits         21374     21373        -1
- Misses        2435      2436        +1
- Partials      1347      1349        +2

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[sentrivana]

Since this is only a problem for attributes-based telemetry, I'd make the fix at the source in _apply_user_attributes_to_telemetry: basically, we're just missing a None check on this line: https://github.com/getsentry/sentry-python/blob/master/sentry_sdk/scope.py#L1756

My concern with changing it directly in the _user object on the scope is that this might be changing the existing behavior for (non-attributes-based) events, which is probably not what we want.

[ericapisani]

Sounds good - I thought that removing None value was something to be applied to all forms of telemetry, not just spans.

Have made the necessary changes in 37ba0fd

[sentry]

Bug: The set_user method stores the user dictionary without filtering None values, causing regular events to include null attributes, which contradicts the PR's goal.
_{Severity: MEDIUM}

Suggested Fix

Filter None values from the user dictionary within the set_user method before storing it in self._user. This ensures all subsequent uses of self._user, including in _apply_user_to_event, will have the correctly filtered data. Alternatively, modify _apply_user_to_event to filter the dictionary before adding it to the event.

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent. Verify if this is a real issue. If it is, propose a fix; if not, explain why it's
not valid.

Location: sentry_sdk/scope.py#L893

Potential issue: The `set_user` method stores the user dictionary in `self._user`
without filtering out keys that have `None` values. Subsequently, the
`_apply_user_to_event` method copies this dictionary directly to the event payload. As a
result, if a user is set with a dictionary containing `None` values (e.g.,
`scope.set_user({"username": None})`), the resulting Sentry event will still contain
`null` for that attribute. This behavior is inconsistent, as the filtering logic was
only added for the telemetry/span path in `_apply_user_attributes_to_telemetry`, but not
for the regular event path.

_{Did we get this right? 👍 / 👎 to inform future reviews.}

[ericapisani]

This is the existing behaviour. Leaving as-is because the string-ifying of 'None' happens on attributes-based telemetry (i.e. streamed spans)

[sentrivana]

🙏🏻