Fix TypeError: '>' not supported between instances of 'float' and 'NoneType' in http

[VeskeR]

See internal slack discussion for errors received by a client: https://ably-real-time.slack.com/archives/CURL4U2FP/p1735900004756929.

Fixes the race condition error in http.get_rest_hosts when options.fallback_realtime_host is set.
You can see the error being reproduced in CI in this run: https://github.com/ably/ably-python/actions/runs/12692221157/job/35377048528?pr=573

Summary by CodeRabbit

• Tests

  • Added two new test cases to verify the behavior of REST host retrieval under different fallback host configurations.
  • Ensures proper functionality of host retrieval with and without a fallback realtime host.

• Bug Fixes

  • Improved host expiration logic to clarify checks for valid expiration time before evaluating host expiration.

[coderabbitai]

Walkthrough

The pull request introduces modifications to the host expiration logic in the get_rest_hosts method of the Http class. The changes involve a more explicit condition for checking host expiration by first verifying if the expiration time exists. Corresponding unit tests have been added to validate the behavior of REST host retrieval under different fallback host configurations.

Changes

File	Change Summary
ably/http/http.py	Updated host expiration check to explicitly verify self.__host_expires is not None. Added a comment regarding "unstoring" the fallback host after timeout.
test/unit/http_test.py	Added two new test functions to validate get_rest_hosts method behavior with different fallback host scenarios.

Poem

🐰 Hosts expire, but logic stays clear
A rabbit's code, with conditions sincere
Fallback paths, now tested with care
Explicit checks, beyond compare
Hopping through networks, without a fear! 🌐

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Reviewing files that changed from the base of the PR and between 36a599e and 1c22c68.

📒 Files selected for processing (2)

• ably/http/http.py (1 hunks)
• test/unit/http_test.py (1 hunks)

🚧 Files skipped from review as they are similar to previous changes (2)

• ably/http/http.py
• test/unit/http_test.py

⏰ Context from checks skipped due to timeout of 90000ms (5)

• GitHub Check: check (3.12)
• GitHub Check: check (3.11)
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• GitHub Check: check (3.8)

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[coderabbitai]

Actionable comments posted: 2

🧹 Nitpick comments (2)

ably/http/http.py (1)

149-150: The fix looks good but could be more robust.

The explicit None check prevents the TypeError, but we could make the code more maintainable by:

1. Adding a comment explaining why the None check is necessary
2. Using a more descriptive variable name for clarity

Consider this improvement:

-        # unstore saved fallback host after fallbackRetryTimeout (RSC15f)
-        if self.__host_expires is not None and time.time() > self.__host_expires:
+        # Check if fallback host has expired (RSC15f)
+        # host_expires can be None if no fallback host was cached or it was already cleared
+        fallback_host_expiry = self.__host_expires
+        if fallback_host_expiry is not None and time.time() > fallback_host_expiry:

test/unit/http_test.py (1)

1-13: Add test utilities for better maintainability.

The tests could benefit from utility functions to reduce duplication and improve readability.

Consider adding these utilities:

import time
from typing import List

def get_default_ably_rest() -> AblyRest:
    return AblyRest(token="foo")

def verify_host_list(hosts: List[str], expected_hosts: List[str], fallback_first: bool = False) -> None:
    """Verify that the host list contains all expected hosts in the correct order."""
    assert isinstance(hosts, list), "Expected list of hosts"
    assert all(isinstance(host, str) for host in hosts), "All hosts should be strings"
    assert set(hosts) == set(expected_hosts), "All expected hosts should be present"
    if fallback_first:
        assert hosts[0] == expected_hosts[-1], "Fallback host should be first"

📜 Review details

Configuration used: CodeRabbit UI
Review profile: CHILL
Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between f98e3d1 and 36a599e.

📒 Files selected for processing (2)

• ably/http/http.py (1 hunks)
• test/unit/http_test.py (1 hunks)

⏰ Context from checks skipped due to timeout of 90000ms (5)

• GitHub Check: check (3.12)
• GitHub Check: check (3.11)
• GitHub Check: check (3.10)
• GitHub Check: check (3.9)
• GitHub Check: check (3.8)

[sacOO7]

You can check coderabbit ai suggestions regarding tests, otherwise LGTM

[sacOO7]

Also, not sure why CI is failing, can you check

[VeskeR]

Mergin as tests failures are not related to this PR