fix: sanitize None values from event properties before queueing

[hariom123-dev]

TL;DR

Adds defensive sanitization to the message queueing flow to strip None values from event properties before they are batched and sent over the network.

🔍 Context & Motivation

When developers pass dynamic property dictionaries into posthog.capture() (e.g., pulling data from an external API or scraper), keys with None values can easily slip in.

Currently, these null values are queued, serialized into JSON, and sent to the PostHog API. This causes two minor issues:

1. Network & Storage Inefficiency: Sending { "optional_field": null } across the wire consumes unnecessary bandwidth and inflates the size of the event payload.
2. Dashboard Clutter: Null properties can clutter the PostHog dashboard UI, showing fields that contain no actionable analytics data.

🛠️ Changes Implemented

Added a lightweight dictionary comprehension in posthog/client.py during the internal message preparation phase. It checks if msg.get("properties") is a dictionary, and if so, it filters out any keys where the value is explicitly None right before the msg is cleaned and appended to the batch.

Note: Empty strings, 0, and False are preserved, as they are often valid analytics values.

✅ Verification

• Unit Test: Added test_capture_sanitizes_none_properties in posthog/test/test_client.py. It simulates a client.capture call with both valid and None properties, mocking the network request to assert the batched payload only retains the valid keys.
• Local Tests: Verified using local test suite without breaking existing queueing behavior.

📉 Impact

• Safe: 100% backward-compatible. Valid properties remain untouched.
• Fast: Standard O(n) Python dictionary comprehension adds negligible overhead to the queueing process.

[marandaneto]

none serializes to null values and its a valid JSON so it's working as intended
you can strip those values in the before send callback if you dont need them

edit: its ok to pass none but we'll strip those during serialization so not really worth passing them
i will follow up with a separate pr, sry and thanks!