Publish /chat via explicit components: gr.api discarded every token

test_api_contract.py

@@ -0,0 +1,101 @@
+"""Assert the Space publishes the API contract chatmcd/hf_client.py calls.
+
+This is the test that did not exist while two contract bugs shipped, each of
+which returned an empty answer with no error and cost a Space rebuild to find:
+
+  * six arguments sent to a five-parameter endpoint (history -> temperature)
+  * an endpoint published with `returns: []`, which ran the generator on a GPU
+    and threw every token away
+
+Both are visible in the published schema, so this reads the schema. It builds
+the real ui.build_demo with a stub generator in place of Qwen3-8B, launches it
+on a local port, and calls it exactly as the Flask app does.
+
+    .venv-gradio/bin/python3 -m pytest space/test_api_contract.py -q
+
+Needs a Python with gradio installed; the project venv is 3.14 and gradio's
+pydantic pin has no wheel for it, hence the separate .venv-gradio (3.12).
+"""
+
+from __future__ import annotations
+
+import sys
+from pathlib import Path
+
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parent))
+
+from ui import CHAT_API_PARAMS, build_demo  # noqa: E402
+
+STUB_TOKENS = ["Nottingham ", "Forest", ", and he has since 1979."]
+
+
+def stub_chat(message, history=None, temperature=0.7, top_p=0.9,
+              repetition_penalty=1.05, max_new_tokens=512):
+    """Stands in for the real generator: same shape, no model.
+
+    Echoes the arguments it received so a silently shifted parameter shows up as
+    a wrong value rather than as a plausible answer.
+    """
+    yield f"[h={0 if not history else len(history)} t={temperature} " \
+          f"p={top_p} r={repetition_penalty} n={int(max_new_tokens)}] "
+    out = ""
+    for tok in STUB_TOKENS:
+        out += tok
+        yield f"[h={0 if not history else len(history)} t={temperature} " \
+              f"p={top_p} r={repetition_penalty} n={int(max_new_tokens)}] {out}"
+
+
+@pytest.fixture(scope="module")
+def client():
+    from gradio_client import Client
+
+    demo = build_demo(stub_chat, base_model="stub", adapter="", retrieval_on=True)
+    demo.queue(max_size=4).launch(prevent_thread_lock=True, quiet=True,
+                                  share=False, ssr_mode=False)
+    try:
+        yield Client(demo.local_url, verbose=False)
+    finally:
+        demo.close()
+
+
+def endpoint(client, name):
+    info = client.view_api(return_format="dict", print_info=False)
+    named = info["named_endpoints"]
+    assert name in named, f"{name} is not published; have {sorted(named)}"
+    return named[name]
+
+
+def test_chat_takes_the_six_arguments_flask_sends(client):
+    """hf_client.py submits six positionals. The endpoint must accept six."""
+    params = [p["parameter_name"] for p in endpoint(client, "/chat")["parameters"]]
+    assert tuple(params) == CHAT_API_PARAMS
+
+
+def test_chat_declares_an_output(client):
+    """`returns: []` is the bug that ran the GPU and discarded the answer."""
+    assert endpoint(client, "/chat")["returns"], \
+        "/chat publishes no outputs: every call will return an empty tuple"
+
+
+def test_chat_streams_and_returns_the_answer(client):
+    """submit() must yield partials, and the last one must be the full answer."""
+    job = client.submit("Which football team does Marc support?", None,
+                        0.7, 0.9, 1.05, 256, api_name="/chat")
+    partials = [p if isinstance(p, str) else str(p) for p in job]
+    assert partials, "the endpoint yielded nothing"
+    assert "".join(STUB_TOKENS) in partials[-1]
+
+
+def test_arguments_are_not_shifted(client):
+    """The stub echoes what it got. Non-default values must arrive intact."""
+    answer = client.predict("hello", [{"role": "user", "content": "hi"}],
+                            0.11, 0.22, 1.33, 128, api_name="/chat")
+    text = answer if isinstance(answer, str) else str(answer)
+    assert "h=1 t=0.11 p=0.22 r=1.33 n=128" in text, text[:200]
+
+
+def test_chat_ui_is_still_published(client):
+    """The debug UI's own endpoint, which must not collide with /chat."""
+    assert endpoint(client, "/chat_ui")["parameters"]