fix: /answer command sends swapped question/answer strings to the LLM (#2495)

* fix: /answer command sends swapped question/answer strings to the LLM

* test(pr_reviewer): make /answer swap regression test behavioral

Replace the inspect.getsource source-text assertion (brittle to formatting,
and its runtime half only re-tested _get_user_answers, not the __init__ unpack
where the bug was) with a behavioral test: drive the real PRReviewer.__init__
with external collaborators stubbed and assert the user's question and answer
land in self.vars under the correct keys. Verified it fails on the swapped
unpack and passes with the fix. Also adds the missing trailing newline.

---------

Co-authored-by: naorpeled <me@naor.dev>

Author: victorljii

pr_agent/tools/pr_reviewer.py

@@ -64,7 +64,7 @@ def __init__(self, pr_url: str, is_answer: bool = False, is_auto: bool = False,
         self.ai_handler.main_pr_language = self.main_language
         self.patches_diff = None
         self.prediction = None
-        answer_str, question_str = self._get_user_answers()
+        question_str, answer_str = self._get_user_answers()
         self.pr_description, self.pr_description_files = (
             self.git_provider.get_pr_description(split_changes_walkthrough=True))
         if (self.pr_description_files and get_settings().get("config.is_auto_command", False) and

tests/unittest/test_pr_reviewer_core.py

@@ -90,3 +90,40 @@ def test_get_user_answers_collects_question_and_answer_from_issue_comments():
 
     assert question == "Questions to better understand the PR:\n- Why?"
     assert answer == "/answer Because it fixes production."
+
+
+def test_init_maps_user_question_and_answer_to_correct_prompt_vars(monkeypatch):
+    """Behavioral regression for the swapped-unpacking bug (#2496).
+
+    The bug lived in ``PRReviewer.__init__``: ``_get_user_answers()`` returns
+    ``(question, answer)`` but the tuple was unpacked as ``answer, question``,
+    so the review prompt rendered the user's answer under ``{{ question_str }}``
+    and the question under ``{{ answer_str }}``. This drives the real ``__init__``
+    (external collaborators stubbed) and asserts each value lands in ``self.vars``
+    under the correct key — so it fails if the unpack is ever swapped again,
+    regardless of how the line is formatted.
+    """
+    from pr_agent.tools import pr_reviewer as pr_reviewer_module
+
+    provider = MagicMock()
+    provider.is_supported.return_value = True
+    provider.get_languages.return_value = {}
+    provider.get_files.return_value = []
+    provider.get_issue_comments.return_value = SimpleNamespace(reversed=[
+        SimpleNamespace(body="Questions to better understand the PR:\n- Why?"),
+        SimpleNamespace(body="/answer Because it fixes production."),
+    ])
+    provider.get_pr_description.return_value = ("desc", [])
+
+    monkeypatch.setattr(pr_reviewer_module, "get_git_provider_with_context", lambda pr_url: provider)
+    monkeypatch.setattr(pr_reviewer_module, "get_main_pr_language", lambda languages, files: "Python")
+    monkeypatch.setattr(pr_reviewer_module, "TokenHandler", MagicMock())
+
+    reviewer = PRReviewer(
+        "https://example/pr/1",
+        is_answer=True,
+        ai_handler=lambda: SimpleNamespace(main_pr_language=None),
+    )
+
+    assert reviewer.vars["question_str"] == "Questions to better understand the PR:\n- Why?"
+    assert reviewer.vars["answer_str"] == "/answer Because it fixes production."