refactor: do not run all runners in ipywidgets_runner fixture

Each time the ipywidgets_runner fixture was used, all fixtures
are used. This means the ipywidgets_runner_solara runner was
also used, causing the solara_test fixture to always run
and also close the app each time, which close all the contexts.

This is bad for performance of the tests, but it is possibly also
the cause for some flakeyness in our tests.

solara/test/pytest_plugin.py

@@ -130,8 +130,11 @@ def page_session(context_session: "playwright.sync_api.BrowserContext"):
 
 @pytest.fixture()
 def solara_app(solara_server):
+    used_app = None
+
     @contextlib.contextmanager
     def run(app: Union[solara.server.app.AppScript, str]):
+        nonlocal used_app
         if "__default__" in solara.server.app.apps:
             solara.server.app.apps["__default__"].close()
         if isinstance(app, str):
@@ -146,9 +149,9 @@ def run(app: Union[solara.server.app.AppScript, str]):
                 if app.name in reload.reloader.watched_modules:
                     reload.reloader.watched_modules.remove(app.name)
 
-            app.close()
-
-    return run
+    yield run
+    if used_app:
+        used_app.close()
 
 
 run_event = threading.Event()
@@ -165,37 +168,23 @@ def SyncWrapper():
     return w.VBox(children=[w.HTML(value="Test in solara"), w.VBox()])
 
 
-@pytest.fixture()
-def solara_test(solara_server, solara_app, page_session: "playwright.sync_api.Page"):
+checks = 0
+
+
+@contextlib.contextmanager
+def _solara_test(solara_server, solara_app, page_session: "playwright.sync_api.Page"):
+    global checks
+    checks += 1
     global run_calls
     with solara_app("solara.test.pytest_plugin:SyncWrapper"):
-        # a currently open page will try to connect to solara, creating a
-        # new context, so we navigate away first, then close all contexts
-        page_session.goto("about:blank")
-        for key in list(solara.server.app.contexts):
-            try:
-                solara.server.app.contexts[key].close()
-            except:  # noqa
-                pass
         assert len(solara.server.app.contexts) == 0
         page_session.goto(solara_server.base_url)
         try:
             run_event.wait()
-            # for some reason, we still get 2 context sometimes, it could be the reconnection
-            # code of the websocket of the previous page still running. We wait a bit
-            # till we end up with only one context
-            n = 0
-            # we wait till the all contexts are closed
-            while len(solara.server.app.contexts) != 1:
-                page_session.wait_for_timeout(100)
-                n += 1
-                if n > 50:
-                    raise RuntimeError("Timeout waiting for a single context, contexts found: %r", list(solara.server.app.contexts))
-
             assert run_calls == 1
             keys = list(solara.server.app.contexts)
             assert len(keys) == 1, "expected only one context, got %s" % keys
-            context = solara.server.app.contexts[keys[0]]
+            context = solara.server.app.contexts[keys[-1]]
             with context:
                 test_output_warmup = widgets.Output()
                 test_output = widgets.Output()
@@ -218,6 +207,12 @@ def solara_test(solara_server, solara_app, page_session: "playwright.sync_api.Pa
             run_event.clear()
 
 
+@pytest.fixture()
+def solara_test(solara_server, solara_app, page_session: "playwright.sync_api.Page"):
+    with _solara_test(solara_server, solara_app, page_session):
+        yield
+
+
 class ServerVoila(ServerBase):
     popen = None
 
@@ -455,7 +450,8 @@ def run(f: Callable):
     return run
 
 
-def create_runner_solara(solara_test, solara_server, page_session: "playwright.sync_api.Page"):
+@contextlib.contextmanager
+def create_runner_solara(solara_server, solara_app, page_session: "playwright.sync_api.Page"):
     count = 0
 
     def run(f: Callable):
@@ -474,51 +470,35 @@ def run(f: Callable):
             sys.path.remove(cwd)
         count += 1
 
-    return run
-
-
-@pytest.fixture(scope="session")
-def ipywidgets_runner_voila(voila_server, notebook_path, page_session: "playwright.sync_api.Page"):
-    if "voila" not in runners:
-        return None
-    return create_runner_voila(voila_server, notebook_path, page_session)
-
-
-@pytest.fixture(scope="session")
-def ipywidgets_runner_jupyter_lab(jupyter_server, notebook_path, page_session: "playwright.sync_api.Page"):
-    if "jupyter_lab" not in runners:
-        return None
-    return create_runner_jupyter_lab(jupyter_server, notebook_path, page_session)
-
-
-@pytest.fixture(scope="session")
-def ipywidgets_runner_jupyter_notebook(jupyter_server, notebook_path, page_session: "playwright.sync_api.Page"):
-    if "jupyter_notebook" not in runners:
-        return None
-    return create_runner_jupyter_notebook(jupyter_server, notebook_path, page_session)
-
-
-@pytest.fixture()
-def ipywidgets_runner_solara(solara_test, solara_server, page_session: "playwright.sync_api.Page"):
-    if "solara" not in runners:
-        return None
-    return create_runner_solara(solara_test, solara_server, page_session)
+    with _solara_test(solara_server, solara_app, page_session):
+        yield run
 
 
 runners = os.environ.get("SOLARA_TEST_RUNNERS", "solara,voila,jupyter_lab,jupyter_notebook").split(",")
 
 
 @pytest.fixture(params=runners)
 def ipywidgets_runner(
-    ipywidgets_runner_jupyter_notebook,
-    ipywidgets_runner_jupyter_lab,
-    ipywidgets_runner_voila,
-    ipywidgets_runner_solara,
+    solara_server,
+    solara_app,
+    voila_server,
+    jupyter_server,
+    notebook_path,
+    page_session: "playwright.sync_api.Page",
     request,
 ):
     runner = request.param
-    name = f"ipywidgets_runner_{runner}"
-    return locals()[name]
+    if runner == "solara":
+        with create_runner_solara(solara_server, solara_app, page_session) as runner:
+            yield runner
+    elif runner == "voila":
+        yield create_runner_voila(voila_server, notebook_path, page_session)
+    elif runner == "jupyter_lab":
+        yield create_runner_jupyter_lab(jupyter_server, notebook_path, page_session)
+    elif runner == "jupyter_notebook":
+        yield create_runner_jupyter_notebook(jupyter_server, notebook_path, page_session)
+    else:
+        raise RuntimeError(f"Unknown runner {runner}")
 
 
 @pytest.fixture(scope="session")