refactor(build): rename web build platform from Pyodide to Emscripten (#6492)

* refactor: rename web build platform identifier from `Pyodide` to `Emscripten`

Aligns the value with `platform.system()` inside Pyodide, so PEP 508 markers
on `flet`'s deps (`oauthlib`, `httpx`) work both via `flet build web` (through
serious_python's sitecustomize) and when `flet` is installed directly via
micropip in a Pyodide runtime. Requires the matching rename in serious_python.

* chore: bump `serious_python` to 1.0.0 in build template

Required for the `Pyodide` → `Emscripten` platform-argument rename to take
effect on `flet build` runs.

* Add CHANGELOG entry for `Pyodide` → `Emscripten` rename (#6492)

* python-worker: load msgpack explicitly so prints from flet-less scripts reach the host Console

msgpack was only ever imported if the user's deps pulled it in (typically
via flet). Apps with no flet dependency — or no pyproject.toml at all —
left the python_output bridge unregistered, and their prints fell through
to the browser dev console silently. Load msgpack from Pyodide's prebuilt
repodata when it isn't already importable; the bridge install is now
unconditional.

* Restore main(page) wrapper in use_dialog_* examples

Integration test packages/flet/integration_tests/examples/apps/test_use_dialog.py imports `main` from each example expecting a `main(page)` callable. The wrapper was inadvertently removed in #6489, breaking pytest collection.

Author: FeodorFitsner

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * Fix `TooltipTheme.decoration` so it applies to controls using `ft.Tooltip(...)` when the tooltip does not explicitly set `decoration` or `bgcolor` ([#6432](https://github.com/flet-dev/flet/issues/6432), [#6482](https://github.com/flet-dev/flet/pull/6482)) by @ndonkoHenri.
 * Fix `flet-geolocator.Geolocator` reliability on web and desktop: `get_last_known_position()` no longer crashes with `TypeError: argument after ** must be a mapping, not NoneType` and now returns `Optional[GeolocatorPosition]`; `get_current_position()` no longer hangs forever on web (Dart-side workaround for the upstream [`geolocator_web` 4.1.3](https://pub.dev/packages/geolocator_web) `inMicroseconds`/`inMilliseconds` timeout typo) and uses sensible web defaults (`time_limit: 30s`, `maximum_age: 5m`); the previously-dropped `configuration` argument now actually reaches `getCurrentPosition` on the Dart side; the position stream is gated behind a registered `on_position_change`/`on_error` handler (with cancel-on-update to prevent leaks); and platform exceptions (`LocationServiceDisabledException`, `PermissionDeniedException`, `PermissionDefinitionsNotFoundException`, `PermissionRequestInProgressException`, `PositionUpdateException`, `TimeoutException`) are now translated into actionable error messages and surfaced to Python as `RuntimeError` without the default `Exception:` prefix ([#6487](https://github.com/flet-dev/flet/pull/6487)) by @FeodorFitsner.
+* Fix PEP 508 markers on `flet`'s `oauthlib`/`httpx` deps not actually excluding those packages under Pyodide: the `flet build web` package platform has been renamed from `Pyodide` to `Emscripten` to match `platform.system()` inside the Pyodide runtime, and the markers now use `platform_system != 'Emscripten'`, so the exclusion works both via `flet build` and a direct `micropip.install("flet")` in a Pyodide REPL. Requires `serious_python` `>= 1.0.0`, which is now pinned in the `flet build` template ([#6492](https://github.com/flet-dev/flet/pull/6492)) by @FeodorFitsner.
 
 ## 0.85.0
 

client/web/python-worker.js

@@ -149,23 +149,27 @@ self.initPyodide = async function () {
             micropip = await ensure_micropip()
             await micropip.install(py_args["dependencies"], pre=micropip_include_pre)
 
-        # Install the python_output bridge using msgpack from the
-        # already-loaded user deps (typically pulled in via flet). If
-        # msgpack isn't around — apps that don't depend on flet — skip
-        # silently; stdout/stderr just stays in the dev console.
+        # Install the python_output bridge. msgpack normally rides in
+        # with the user's flet dependency, but apps without a flet dep
+        # (or without a pyproject.toml at all) would otherwise leave the
+        # bridge unregistered and their prints stranded in the dev
+        # console. Pyodide ships msgpack as a prebuilt package, so we
+        # load it explicitly when it isn't already importable.
         try:
             import msgpack as _msgpack
+        except ImportError:
+            import pyodide_js
+            await pyodide_js.loadPackage("msgpack")
+            import msgpack as _msgpack
 
-            def _send_python_output(text, is_stderr):
-                flet_js.receive_callback(
-                    _msgpack.packb(
-                        [7, {"text": text, "is_stderr": bool(is_stderr)}]
-                    )
+        def _send_python_output(text, is_stderr):
+            flet_js.receive_callback(
+                _msgpack.packb(
+                    [7, {"text": text, "is_stderr": bool(is_stderr)}]
                 )
+            )
 
-            flet_js.send_python_output = _send_python_output
-        except ImportError:
-            pass
+        flet_js.send_python_output = _send_python_output
 
         # Flip the worker into "user code" mode so stdout/stderr starts
         # flowing to the host page's Console pane instead of dev console.

sdk/python/examples/apps/declarative/use_dialog_basic/main.py

@@ -53,5 +53,9 @@ async def handle_delete():
     )
 
 
+def main(page: ft.Page):
+    page.render(App)
+
+
 if __name__ == "__main__":
-    ft.run(lambda page: page.render(App))
+    ft.run(main)

sdk/python/examples/apps/declarative/use_dialog_chained/main.py

@@ -78,5 +78,9 @@ def on_confirm_dismiss():
     )
 
 
+def main(page: ft.Page):
+    page.render(App)
+
+
 if __name__ == "__main__":
-    ft.run(lambda page: page.render(App))
+    ft.run(main)

sdk/python/examples/apps/declarative/use_dialog_multiple/main.py

@@ -145,5 +145,9 @@ def handler():
     )
 
 
+def main(page: ft.Page):
+    page.render(App)
+
+
 if __name__ == "__main__":
-    ft.run(lambda page: page.render(App))
+    ft.run(main)

sdk/python/packages/flet-cli/src/flet_cli/commands/build_base.py

@@ -95,7 +95,7 @@ def __init__(self, parser: argparse.ArgumentParser) -> None:
                 "can_be_run_on": ["Linux"],
             },
             "web": {
-                "package_platform": "Pyodide",
+                "package_platform": "Emscripten",
                 "config_platform": "web",
                 "flutter_build_command": "web",
                 "status_text": "web app",
@@ -1833,7 +1833,7 @@ def package_python_app(self):
             package_args.extend(["-r", f"flet=={flet.version.flet_version}"])
 
         # site-packages variable
-        if self.package_platform != "Pyodide":
+        if self.package_platform != "Emscripten":
             package_env["SERIOUS_PYTHON_SITE_PACKAGES"] = str(
                 self.build_dir / "site-packages"
             )
@@ -2043,12 +2043,12 @@ def _run_flutter_command(self):
         build_env = {}
 
         # site-packages variable
-        if self.package_platform != "Pyodide":
+        if self.package_platform != "Emscripten":
             build_env["SERIOUS_PYTHON_SITE_PACKAGES"] = str(
                 self.build_dir / "site-packages"
             )
 
-        if self.package_platform == "Pyodide" and not self.template_data["no_wasm"]:
+        if self.package_platform == "Emscripten" and not self.template_data["no_wasm"]:
             build_args.append("--wasm")
 
         android_signing_key_store = (

sdk/python/packages/flet/pyproject.toml

@@ -9,8 +9,8 @@ requires-python = ">=3.10"
 dependencies = [
     "flet-cli; extra == 'cli'",
     "flet-web; extra == 'web'",
-    "oauthlib >=3.2.2; platform_system != 'Pyodide'",
-    "httpx >=0.28.1; platform_system != 'Pyodide'",
+    "oauthlib >=3.2.2; platform_system != 'Emscripten'",
+    "httpx >=0.28.1; platform_system != 'Emscripten'",
     "repath >=0.9.0",
     "msgpack >=1.1.0",
     "typing-extensions; python_version < '3.11'"

sdk/python/templates/build/{{cookiecutter.out_dir}}/pubspec.yaml

@@ -17,7 +17,7 @@ dependencies:
 
   flet:
     path: ../../../../../packages/flet
-  serious_python: 0.9.12
+  serious_python: 1.0.0
 
   package_info_plus: ^9.0.0
   path_provider: ^2.1.4

sdk/python/templates/build/{{cookiecutter.out_dir}}/web/python-worker.js

@@ -149,23 +149,27 @@ self.initPyodide = async function () {
             micropip = await ensure_micropip()
             await micropip.install(py_args["dependencies"], pre=micropip_include_pre)
 
-        # Install the python_output bridge using msgpack from the
-        # already-loaded user deps (typically pulled in via flet). If
-        # msgpack isn't around — apps that don't depend on flet — skip
-        # silently; stdout/stderr just stays in the dev console.
+        # Install the python_output bridge. msgpack normally rides in
+        # with the user's flet dependency, but apps without a flet dep
+        # (or without a pyproject.toml at all) would otherwise leave the
+        # bridge unregistered and their prints stranded in the dev
+        # console. Pyodide ships msgpack as a prebuilt package, so we
+        # load it explicitly when it isn't already importable.
         try:
             import msgpack as _msgpack
+        except ImportError:
+            import pyodide_js
+            await pyodide_js.loadPackage("msgpack")
+            import msgpack as _msgpack
 
-            def _send_python_output(text, is_stderr):
-                flet_js.receive_callback(
-                    _msgpack.packb(
-                        [7, {"text": text, "is_stderr": bool(is_stderr)}]
-                    )
+        def _send_python_output(text, is_stderr):
+            flet_js.receive_callback(
+                _msgpack.packb(
+                    [7, {"text": text, "is_stderr": bool(is_stderr)}]
                 )
+            )
 
-            flet_js.send_python_output = _send_python_output
-        except ImportError:
-            pass
+        flet_js.send_python_output = _send_python_output
 
         # Flip the worker into "user code" mode so stdout/stderr starts
         # flowing to the host page's Console pane instead of dev console.