style(agent): fix ruff lint + format to unblock CI build (aws-samples#247 PR aws-samples#373)

CI 'build (agentcore)' failed on //agent:lint (6 ruff errors that landed
across the #1 build-command + upstream-merge commits, committed without
the agent lint gate passing):
 - E501 ×4: config.py _KNOWN_WRITEABLE_WORKFLOW_IDS, test_prompts.py
 restack-assert + workflow-id loop, test_verify_commands.py real-failure
 fixture → wrapped.
 - PLR2004: post_hooks.py magic 127 → new SHELL_COMMAND_NOT_FOUND const.
 - SIM108: repo.py if/else default_branch → 'or' expression.
Then applied ruff format (the CI self-mutation guard enforces format, not
just check) — normalized config.py/repo.py/test_repo.py/test_verify_commands.py.
ruff check + ruff format --check both clean; agent suite 1116 green.

Author: isadeks

agent/src/config.py

@@ -26,7 +26,13 @@
 # on the write-deny invariant). pr-review-v1 is intentionally excluded (it is
 # read-only); default/agent-v1 is excluded because its conservative posture
 # should fail closed too.
-_KNOWN_WRITEABLE_WORKFLOW_IDS = frozenset(("coding/new-task-v1", "coding/pr-iteration-v1", "coding/restack-v1"))
+_KNOWN_WRITEABLE_WORKFLOW_IDS = frozenset(
+    (
+        "coding/new-task-v1",
+        "coding/pr-iteration-v1",
+        "coding/restack-v1",
+    )
+)
 
 
 def resolve_github_token() -> str:

agent/src/post_hooks.py

@@ -19,6 +19,10 @@
 DEFAULT_BUILD_COMMAND = "mise run build"
 DEFAULT_LINT_COMMAND = "mise run lint"
 
+# POSIX shell exit code for "command not found" — an inert build signal (the
+# configured verify command isn't installed), not a genuine build failure.
+SHELL_COMMAND_NOT_FOUND = 127
+
 
 def is_verify_command_inert(returncode: int, stderr: str) -> bool:
     """True when a verify command did not actually RUN (vs ran-and-failed).
@@ -34,7 +38,7 @@ def is_verify_command_inert(returncode: int, stderr: str) -> bool:
     A repo that genuinely fails its build returns some other non-zero code with
     real compiler/test output, which this does NOT flag.
     """
-    if returncode == 127:
+    if returncode == SHELL_COMMAND_NOT_FOUND:
         return True
     s = (stderr or "").lower()
     return (

agent/src/repo.py

@@ -127,8 +127,7 @@ def setup_repo(config: TaskConfig) -> RepoSetup:
             # still runs rather than failing setup; the predecessor's code
             # is likely in the default branch by now anyway.
             notes.append(
-                f"base branch '{config.base_branch}' not fetchable; "
-                "branched off default instead"
+                f"base branch '{config.base_branch}' not fetchable; branched off default instead"
             )
             log("SETUP", f"Base branch not found; creating {branch} off HEAD")
             run_cmd(["git", "checkout", "-b", branch], label="create-branch", cwd=repo_dir)
@@ -227,10 +226,7 @@ def setup_repo(config: TaskConfig) -> RepoSetup:
     # - #247 A4 stacked children: base_branch is the predecessor's branch
     #   (linear) or main (diamond) — the child's PR targets it.
     # - Otherwise: detect the repo default (main/master).
-    if config.base_branch:
-        default_branch = config.base_branch
-    else:
-        default_branch = detect_default_branch(config.repo_url, repo_dir)
+    default_branch = config.base_branch or detect_default_branch(config.repo_url, repo_dir)
 
     # Install prepare-commit-msg hook for code attribution
     _install_commit_hook(repo_dir)

agent/tests/test_prompts.py

@@ -109,14 +109,23 @@ def test_restack_returns_prompt_with_remerge_workflow(self):
         prompt = get_system_prompt("coding/restack-v1")
         assert "RE-STACKING" in prompt
         assert "predecessor" in prompt
-        assert "do NOT add features" in prompt or "NOT new feature work" in prompt or "not new feature" in prompt.lower()
+        assert (
+            "do NOT add features" in prompt
+            or "NOT new feature work" in prompt
+            or "not new feature" in prompt.lower()
+        )
         assert "{branch_name}" in prompt  # pushes to the SAME existing branch
         assert "{pr_number}" in prompt
         assert "{repo_url}" in prompt
         assert "{workflow}" not in prompt
 
     def test_all_workflows_contain_shared_base_sections(self):
-        for workflow_id in ("coding/new-task-v1", "coding/pr-iteration-v1", "coding/pr-review-v1", "coding/restack-v1"):
+        for workflow_id in (
+            "coding/new-task-v1",
+            "coding/pr-iteration-v1",
+            "coding/pr-review-v1",
+            "coding/restack-v1",
+        ):
             prompt = get_system_prompt(workflow_id)
             assert "## Environment" in prompt, f"Missing Environment in {workflow_id}"
             has_rules = "## Rules" in prompt or "## Rules override" in prompt

agent/tests/test_repo.py

@@ -154,30 +154,36 @@ def test_uses_platform_branch_name_verbatim_for_new_task(self, monkeypatch):
         fake = _fake_run_cmd()
         _patch_common(monkeypatch, fake)
         monkeypatch.setattr(repo, "detect_default_branch", lambda url, d: "main")
-        setup = repo.setup_repo(_config(
-            is_pr_workflow=False,
-            branch_name="bgagent/01TESTTASKID/abca-166-add-seville-guide-html",
-            task_description="ABCA-166: Add seville-guide.html",
-        ))
+        setup = repo.setup_repo(
+            _config(
+                is_pr_workflow=False,
+                branch_name="bgagent/01TESTTASKID/abca-166-add-seville-guide-html",
+                task_description="ABCA-166: Add seville-guide.html",
+            )
+        )
         assert setup.branch == "bgagent/01TESTTASKID/abca-166-add-seville-guide-html"
 
     def test_uses_platform_branch_name_verbatim_for_pr_workflow(self, monkeypatch):
         fake = _fake_run_cmd()
         _patch_common(monkeypatch, fake)
-        setup = repo.setup_repo(_config(
-            is_pr_workflow=True,
-            branch_name="bgagent/01TESTTASKID/abca-167-stacked-child",
-            base_branch="bgagent/01PREDTASK/abca-166-predecessor",
-        ))
+        setup = repo.setup_repo(
+            _config(
+                is_pr_workflow=True,
+                branch_name="bgagent/01TESTTASKID/abca-167-stacked-child",
+                base_branch="bgagent/01PREDTASK/abca-166-predecessor",
+            )
+        )
         assert setup.branch == "bgagent/01TESTTASKID/abca-167-stacked-child"
 
     def test_falls_back_to_derived_slug_only_when_no_branch_name(self, monkeypatch):
         # No platform branch_name → the agent derives its own slug (legacy path).
         fake = _fake_run_cmd()
         _patch_common(monkeypatch, fake)
         monkeypatch.setattr(repo, "detect_default_branch", lambda url, d: "main")
-        setup = repo.setup_repo(_config(
-            is_pr_workflow=False,
-            task_description="ABCA-168: derive me",
-        ))
+        setup = repo.setup_repo(
+            _config(
+                is_pr_workflow=False,
+                task_description="ABCA-168: derive me",
+            )
+        )
         assert setup.branch.startswith("bgagent/")

agent/tests/test_verify_commands.py

@@ -30,7 +30,8 @@ def test_configured_command_splits_to_argv(self):
 
     def test_quoted_args_preserved(self):
         assert resolve_verify_argv('make "target with spaces"', DEFAULT_BUILD_COMMAND) == [
-            "make", "target with spaces",
+            "make",
+            "target with spaces",
         ]
 
 
@@ -84,7 +85,8 @@ def test_no_task_named_is_inert(self):
 
     def test_genuine_build_failure_is_NOT_inert(self):
         # Real compiler/test output, exited non-zero → meaningful gating signal.
-        assert is_verify_command_inert(2, "TypeError: cannot read property 'x'\n1 test failed") is False
+        real_failure = "TypeError: cannot read property 'x'\n1 test failed"
+        assert is_verify_command_inert(2, real_failure) is False
 
     def test_clean_exit_is_not_inert(self):
         assert is_verify_command_inert(0, "") is False