bug(testing): tests/a2a_compat_shim.py breaks pytest in /tmp worktrees

[bokelley]

Context

Role.ROLE_USER AttributeError fires on tests/conftest.py load when running pytest from a /tmp git worktree. The shim's defensive imports succeed in the canonical checkout but fail in some envs. Hit during PR #391, #406, #407 fix-pack agents.

Acceptance Criteria

• Investigate why a2a_compat_shim.py defensive imports fail in /tmp worktrees
• Either fix the shim OR move it out of conftest.py's import path so test collection doesn't depend on it
• pytest runs cleanly from /tmp worktrees

Files

• tests/a2a_compat_shim.py
• tests/conftest.py

Refs

• PR feat(validation): ADCP_VALIDATION_MODE env var + outputSchema on tools/list #391, feat(server): /.well-known/adcp-agents.json discovery endpoint (#381) #406, feat(buyer-agent-registry): caching + rate-limit + audit emission (#380) #407

[bokelley]

Triage

Classification: Bug
Bucket(s): client
Status: drafting-pr
Milestone: (omitted)

What the experts said:

• code-reviewer: no blockers — _proto_alias per-alias guard is the right shape; stacklevel=2 and _STATE_STRING_MAP comment addressed
• dx-expert: approved — autouse no-op (vs. pytest.skip) confirmed correct for ~3000 non-A2A tests; warning messages include install command; stacklevel=2 fix applied

My take: Root cause is module-scope pb.Role.user = pb.Role.ROLE_USER (and 9 TaskState aliases) raising AttributeError when a2a-sdk isn't at >=1.0.1,<1.0.2 in fresh worktrees, propagating through conftest.py's bare top-level import and aborting collection globally. Fix: replace direct attribute assignments with a _proto_alias() helper that guards each alias independently and warns with the install command; wrap the conftest import in except (ImportError, AttributeError) with _a2a_compat_shim = None fallback.

Draft PR: #433 — adds _proto_alias to a2a_compat_shim.py and resilient import to conftest.py; collection always succeeds, only A2A tests fail when env is wrong.

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Triaged by Claude Code. Session: https://claude.ai/code/session_01AnL37fUet4e3yXt9YBxd7a

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Generated by Claude Code