fix(hmac): validate empty-payload POSTs, and repair the integration suite

[MarTrepodi]

The Integration Tests workflow has been red on every branch since 2026-07-26, including on main. This fixes a real HMAC bug found along the way, hardens the suite, and quarantines the one failure that is not ours to fix.

The /data failure is upstream, not a parameter problem

Comlink returns HTTP 400 with:

Did not receive a response code back from the server, even after a retry. The "items" parameter value "8" may be invalid. Try one of the GameDataItems values from /enums.

The trailing hint reads like a deprecation notice, but it is boilerplate appended whenever Comlink's own upstream fetch fails. Four CI runs show the hint is not the cause:

image	/data call	result
4.4.1	request_segment=1	400
4.4.1	items=2097151 — Segment1, read from that server's own /enums	400
4.4.1	items=8 — EquipmentDefinitions	400
4.4.0	items=8	400

Three parameter forms, two image versions, all failing identically while the other 27 tests pass. items=8 is unambiguously valid and returns in 0.6s against a warm instance. Since 4.4.0 is what latest resolved to during the green period ending 2026-07-19 and it fails now too, the change is upstream of this repository — a cold service container can no longer complete a /data fetch from the game servers.

Both /data tests are therefore marked xfail, non-strict: they pass against a warm instance, so an XPASS is the signal that upstream has recovered and the marker can be removed.

HMAC: empty-payload POSTs never validated

_construct_request_headers tested payload truthiness, so an empty dict hashed "" while httpx transmitted {}:

payload={}  wire=b'{}'  digest_matches=False

Every HMAC-authenticated POST with an empty payload was rejected with HTTP 403 HMACValidationError — including get_game_metadata() with no client_specs, the common case. The fix is one condition: hash the payload whenever a body is sent, and reserve the empty string for bodiless requests. CI confirms it — the two HMAC failures are gone and the passing count went 25 → 27.

This was invisible because the two tests covering it called get_enums(), a GET endpoint Comlink does not authenticate. They now issue a signed POST.

Assertion audit

/data always returns the full set of collection keys regardless of what was requested; unrequested collections come back empty. So len(result) > 0 passed even if the filter matched nothing. The same looseness ran through the suite:

• 4 HMAC rejection tests passed against an unreachable server. SwgohComlinkException wraps transport errors as well as HTTP status errors, so pytest.raises(SwgohComlinkException) was satisfied by "connection refused" — if the comlink-hmac service failed to start, they reported green having tested nothing. Now matched against HTTP 4\d{2}; CI confirms the rejection status is 403.
• 2 HMAC "success" tests did not exercise HMAC — see above.
• 2 context-manager tests asserted nothing about the context manager. They now assert the underlying HTTP client is open inside the block and closed after.
• Empty-value assertions tightened for version strings, metadata, pvpProfile, and gameEvent — each previously passed on empty.
• New coverage for player_details_only, used in four tests but never verified. It keeps the arena tabs and nulls out squad.

Also

Both service images are pinned to 4.4.1 instead of latest, so an upstream release can no longer turn the suite red with no commit of ours. Bump the tag deliberately.

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