fix: hot reload was broken

We now also pickle the state before and after the reload

solara/server/app.py

@@ -31,6 +31,8 @@
 state_directory = Path(".") / "states"
 state_directory.mkdir(exist_ok=True)
 
+reload.reloader.start()
+
 
 class AppType(str, Enum):
     SCRIPT = "script"
@@ -91,6 +93,7 @@ def __init__(self, name, default_app_name="Page"):
             warn_is_widget()
 
     def _execute(self):
+        logger.info("Executing %s", self.name)
         app = None
         local_scope = {
             "display": display,
@@ -270,7 +273,13 @@ def reload(self):
                     with context:
                         # we save the state for when the app reruns, so we stay in the same state.
                         # (e.g. button clicks, chosen options etc)
-                        context.state = render_context.state_get()
+                        # for instance a dataframe, needs to be pickled, because after the pandas
+                        # module is reloaded, it's a different class type
+                        logger.info("pickling state: %s", render_context.state_get())
+                        try:
+                            context.state = pickle.dumps(render_context.state_get())
+                        except Exception as e:
+                            logger.warning("Could not pickle state, next render the state will be lost: %s", e)
                         # clear/cleanup the render_context, so during reload we start
                         # from scratch
                         context.app_object = None
@@ -417,6 +426,9 @@ def _run_app(
 
     # app.signal_hook_install()
     main_object = app_script.run()
+    app_state = pickle.loads(app_state) if app_state is not None else None
+    if app_state:
+        logger.info("Restoring state: %r", app_state)
 
     context = get_current_context()
     container = context.container
@@ -464,35 +476,25 @@ def load_app_widget(app_state, app_script: AppScript, pathname: str):
     try:
         render_context = context.app_object
         with context:
-            with reload.reloader.watch():
-                while True:
-                    # reloading might take in extra dependencies, so the reload happens first
-                    if reload.reloader.requires_reload:
-                        reload.reloader.reload()
-                    # reload before starting app, because we may load state using pickle
-                    # if we do that before reloading, the classes are not compatible:
-                    app_state = app_state_initial
-                    # e.g.: _pickle.PicklingError: Can't pickle <class 'testapp.Clicks'>: it's not the same object as testapp.Clicks
-                    try:
-                        widget, render_context = _run_app(
-                            app_state,
-                            app_script,
-                            pathname,
-                            render_context=render_context,
-                        )
-                        if render_context is None:
-                            assert context.container is not None
-                            context.container.children = [widget]
-                    except Exception:
-                        if settings.main.use_pdb:
-                            logger.exception("Exception, will be handled by debugger")
-                            pdb.post_mortem()
-                        raise
-
-                    if render_context:
-                        context.app_object = render_context
-                    if not reload.reloader.requires_reload:
-                        break
+            app_state = app_state_initial
+            try:
+                widget, render_context = _run_app(
+                    app_state,
+                    app_script,
+                    pathname,
+                    render_context=render_context,
+                )
+                if render_context is None:
+                    assert context.container is not None
+                    context.container.children = [widget]
+            except Exception:
+                if settings.main.use_pdb:
+                    logger.exception("Exception, will be handled by debugger")
+                    pdb.post_mortem()
+                raise
+
+            if render_context:
+                context.app_object = render_context
 
     except BaseException as e:
         error = ""

solara/server/reload.py

@@ -156,17 +156,20 @@ def reload(self):
         # before we did this:
         # # don't reload modules like solara.server and react
         # # that may cause issues (like 2 Element classes existing)
-        reload_modules = {k for k in set(sys.modules) - set(self.ignore_modules) if not (k.startswith("solara.server") or k.startswith("anyio"))}
+        # not sure why, but if we reload pandas, the integration/reload_test.py fails
+        reload_modules = {
+            k for k in set(sys.modules) - set(self.ignore_modules) if not (k.startswith("solara.server") or k.startswith("anyio") or k.startswith("pandas"))
+        }
         # which picks up import that are done in threads etc, but it will also reload starlette, httptools etc
         # which causes issues with exceptions and isinstance checks.
         # reload_modules = self.watched_modules
         logger.info("Reloading modules... %s", reload_modules)
         # not sure if this is needed
         importlib.invalidate_caches()
-        for mod in reload_modules:
+        for mod in sorted(reload_modules):
             # don't reload modules like solara.server and react
             # that may cause issues (like 2 Element classes existing)
-            logger.info("Reloading module %s", mod)
+            logger.debug("Reloading module %s", mod)
             sys.modules.pop(mod, None)
         # if all succesfull...
         self.requires_reload = False

solara/server/starlette.py

@@ -19,7 +19,6 @@
 from starlette.staticfiles import StaticFiles
 
 import solara
-from solara.server import reload
 from solara.server.threaded import ServerBase
 
 from . import app as appmod
@@ -267,7 +266,6 @@ def lookup_path(self, path: str) -> typing.Tuple[str, typing.Optional[os.stat_re
 def on_startup():
     # TODO: configure and set max number of threads
     # see https://github.com/encode/starlette/issues/1724
-    reload.reloader.start()
     telemetry.server_start()
 
 

tests/integration/reload_test.py

@@ -1,48 +1,102 @@
-# import contextlib
-# import logging
-# from pathlib import Path
+import contextlib
+import logging
+
+# import subprocess
+from pathlib import Path
 
 # import playwright.sync_api
 
-# from solara.server import reload
+# import solara.server.server
 
-# app_path = Path(__file__).parent / "testapp.py"
+# from . import conftest
 
-# logger = logging.getLogger("solara-test.integration.reload_test")
+app_path = Path(__file__).parent / "testapp.py"
 
+logger = logging.getLogger("solara-test.integration.reload_test")
 
-# @contextlib.contextmanager
-# def append(text):
-#     with app_path.open() as f:
-#         content = f.read()
-#     try:
-#         with app_path.open("w") as f:
-#             f.write(content)
-#             f.write(text)
-#         yield
-#     finally:
-#         with app_path.open("w") as f:
-#             f.write(content)
-
-
-# @contextlib.contextmanager
-# def replace(path, text):
-#     with path.open() as f:
-#         content = f.read()
-#     try:
-#         with path.open("w") as f:
-#             f.write(text)
-#         yield
-#     finally:
-#         with path.open("w") as f:
-#             f.write(content)
+
+HERE = Path(__file__).parent
+
+
+@contextlib.contextmanager
+def append(text):
+    with app_path.open() as f:
+        content = f.read()
+    try:
+        with app_path.open("w") as f:
+            f.write(content)
+            f.write(text)
+        yield
+    finally:
+        with app_path.open("w") as f:
+            f.write(content)
+
+
+@contextlib.contextmanager
+def replace(path, text):
+    with path.open() as f:
+        content = f.read()
+    try:
+        with path.open("w") as f:
+            f.write(text)
+        yield
+    finally:
+        with path.open("w") as f:
+            f.write(content)
+
+
+# button_code = """
+# @solara.component
+# def ButtonClick():
+#     clicks, set_clicks = solara.use_state(Clicks(0))
+#     return rw.Button(description=f"!!! {clicks.value} times", on_click=lambda: set_clicks(Clicks(clicks.value + 1)))
+
+
+# app = ButtonClick()
+# """
 
 
+# def test_reload_with_pickle(page_session: playwright.sync_api.Page):
+#     port = conftest.TEST_PORT + 1000
+#     conftest.TEST_PORT += 1
+#     args = ["solara", "run", f"--port={port}", "--no-open", "tests.integration.testapp:app", "--log-level=debug"]
+#     popen = subprocess.Popen(args, shell=False, stdout=subprocess.PIPE, stderr=subprocess.PIPE, stdin=subprocess.PIPE)
+#     host = "localhost"
+#     try:
+#         solara.server.server.wait_ready(f"http://{host}:{port}", timeout=10)
+#         page_session.goto(f"http://localhost:{port}")
+#         page_session.locator("text=Clicked 0 times").click(timeout=5000)
+#         page_session.locator("text=Clicked 1 times").click(timeout=5000)
+#         page_session.locator("text=Clicked 2 times").wait_for(timeout=5000)
+#         page_session.wait_for_timeout(1000)
+#         with append(button_code):
+#             page_session.locator("text=!!! 0 times").click(timeout=5000)
+#             page_session.locator("text=!!! 1 times").click(timeout=5000)
+#         popen.kill()
+#     except Exception as e:
+#         try:
+#             popen.kill()
+#         except:  # noqa
+#             pass
+#         outs, errs = popen.communicate(timeout=5)
+#         if errs:
+#             print("STDERR:")  # noqa
+#             print(errs.decode("utf-8"))  # noqa
+#         if outs:
+#             print("STDOUT:")  # noqa
+#             print(outs.decode("utf-8"))  # noqa
+#         if errs:
+#             raise ValueError("Expected no errors in solara server output") from e
+#         raise
+
+
+# the following tests are flakey on CI
+
 # def test_reload_syntax_error(page_session: playwright.sync_api.Page, solara_server, solara_app, extra_include_path):
 #     with extra_include_path(app_path.parent), solara_app("testapp:ButtonClick"):
 #         # use as module, otherwise pickle wil not work
 #         page_session.goto(solara_server.base_url)
-#         assert page_session.title() == "Hello from Solara ☀️"
+#         assert page_session.title() == "Solara ☀️"
 #         page_session.locator("text=Clicked 0 times").click()
 #         page_session.locator("text=Clicked 1 times").click()
 
@@ -55,12 +109,25 @@
 #         page_session.locator("text=Clicked 3 times").wait_for()
 
 
+# def test_reload_change(page_session: playwright.sync_api.Page, solara_server, solara_app, extra_include_path):
+#     with extra_include_path(app_path.parent), solara_app("testapp:app"):
+#         logger.info("test_reload_many:run app")
+#         page_session.goto(solara_server.base_url)
+#         # assert page_session.title() == "Solara ☀️"
+#         page_session.locator("text=Clicked 0 times").click()
+#         page_session.locator("text=Clicked 1 times").click()
+#         with append(button_code):
+#             reload.reloader.reload_event_next.wait()
+#             # page_session.locator("text=Clicked 2 times").click()
+#             # page_session.locator("text=SyntaxError").wait_for()
+#             page_session.locator("text=!!! 0 times").click()
+
+
 # def test_reload_many(page_session: playwright.sync_api.Page, solara_server, solara_app, extra_include_path):
 #     with extra_include_path(app_path.parent), solara_app("testapp:app"):
 #         logger.info("test_reload_many:run app")
 #         # use as module, otherwise pickle wil not work
 #         page_session.goto(solara_server.base_url)
-#         assert page_session.title() == "Hello from Solara ☀️"
 #         page_session.locator("text=Clicked 0 times").click()
 #         page_session.locator("text=Clicked 1 times").click()
 
@@ -80,7 +147,6 @@
 # def test_reload_vue(page_session: playwright.sync_api.Page, solara_server, solara_app, extra_include_path):
 #     with extra_include_path(app_path.parent), solara_app("testapp:VueTestApp"):
 #         page_session.goto(solara_server.base_url)
-#         assert page_session.title() == "Hello from Solara ☀️"
 #         page_session.locator("text=foobar").wait_for()
 
 #         vuecode = """

tests/integration/testapp.py

@@ -2,8 +2,9 @@
 import os
 
 import ipyvue
-import solara
 import traitlets
+
+import solara
 from solara.alias import rw