fix(alerts): handle dictionary payload for crashlytics digestDate

[hardikkaurani]

Summary

This PR fixes Crashlytics alert payload deserialization when digestDate is formatted as a dictionary. It ensures stability digests can be parsed without throwing type errors.

Problem

Eventarc stability digest payloads for Crashlytics occasionally format digestDate as a dictionary instead of a string, causing the Python SDK's deserialization to fail.

Root Cause

The alerts module assumes digestDate will always be a primitive string, lacking defensive parsing for the dictionary representation.

Changes

• Adds defensive dictionary parsing logic for digestDate in the Crashlytics alert payload handling.

Tests

Regression coverage is included for the affected behavior.

Why This Is Not a Duplicate

This PR addresses a different issue from #299.

• Different modules: This PR patches alerts parsing, while feat: add support for VPC direct connect #299 patches global options and VPC Direct Connect.
• Different behavior: This PR handles incoming Eventarc payload deserialization, whereas feat: add support for VPC direct connect #299 handles outgoing manifest generation.
• Different user-facing problem: Crashlytics alert failures vs VPC egress misconfiguration.

Therefore, the two PRs address independent problems and this change does not supersede or duplicate #299.

Scope

This change is limited to the Crashlytics alert payload parsing logic and does not alter other Eventarc handlers.

Original Template Items

Fixes #260

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[gemini-code-assist]

Code Review

This pull request updates the timestamp_conversion utility function to support dictionary-based timestamp inputs (containing seconds and nanoseconds) in addition to ISO 8601 strings, and adds corresponding unit tests. The review feedback highlights potential TypeError issues if dictionary keys are explicitly set to None, as well as potential floating-point precision issues when calculating fractional seconds. A robust alternative using datetime.timedelta and explicit None checks is suggested to address these concerns.

[gemini-code-assist]

Using dict.get(key, default) only returns the default value if the key is completely absent from the dictionary. If the key is present but its value is explicitly None, it will return None, which would cause int(None) to raise a TypeError.

Additionally, adding seconds + (nanos / 1e9) can introduce floating-point precision/rounding issues when converting to a datetime object.

Following the standard pattern used in Google's official protobuf library for Python, we can safely handle potential None values and use datetime.timedelta with integer division (nanos // 1000) to avoid floating-point precision issues.

Suggested change

	if isinstance(time, dict):
	seconds = int(time.get("seconds", 0))
	nanos = int(time.get("nanos", time.get("nanoseconds", 0)))
	return _dt.datetime.fromtimestamp(seconds + (nanos / 1e9), tz=_dt.timezone.utc)
	if isinstance(time, dict):
	seconds = int(time.get("seconds") if time.get("seconds") is not None else 0)
	nanos_val = time.get("nanos")
	if nanos_val is None:
	nanos_val = time.get("nanoseconds")
	nanos = int(nanos_val) if nanos_val is not None else 0
	return _dt.datetime.fromtimestamp(seconds, tz=_dt.timezone.utc) + _dt.timedelta(microseconds=nanos // 1000)

[hardikkaurani]

@IzaakGough @inlined Just checking in! The fix for Crashlytics digestDate dictionary parsing (#260) is fully implemented and tested. It properly falls back to dictionary deserialization when Eventarc payloads send objects instead of strings, preventing the SDK from crashing. All CI checks and CLA are green. Could you please take a look when you get a chance? Thanks!