fix: support Layout when specifying routes (#554)

Before, if we specified

```python

routes = [
    solara.Route(path="/", component=Home, label="Home", layout=Layout),
    solara.Route(path="about", component=About, label="About"),
]
```


We would not render the the page and layout correcly.

solara/autorouting.py

@@ -347,17 +347,22 @@ def get_title(module: ModuleType, required=True):
     return title
 
 
-def fix_route(route: solara.Route, new_file: Path) -> solara.Route:
+def fix_route(route: solara.Route, new_file: Path, new_layout=None) -> solara.Route:
     file = route.file or new_file
+    layout = route.layout or new_layout
     children = fix_routes(route.children, new_file) if route.children else []
 
-    return dataclasses.replace(route, file=file, children=children)
+    return dataclasses.replace(route, file=file, children=children, layout=layout)
 
 
-def fix_routes(routes: List[solara.Route], new_file: Path):
+def fix_routes(routes: List[solara.Route], new_file: Path, new_layout=None):
     new_routes = []
     for route in routes:
-        new_routes.append(fix_route(route, new_file))
+        if route.path == "/":
+            route = fix_route(route, new_file, new_layout)
+        else:
+            route = fix_route(route, new_file)
+        new_routes.append(route)
     return new_routes
 
 
@@ -378,6 +383,7 @@ def generate_routes(module: ModuleType) -> List[solara.Route]:
 
     assert module.__file__ is not None
     routes = []
+    children: List[solara.Route]
     file = Path(module.__file__)
 
     if module.__file__.endswith("__init__.py"):
@@ -429,11 +435,15 @@ def generate_routes(module: ModuleType) -> List[solara.Route]:
                 warnings.warn(f"Some routes are not in route_order: {set(lookup) - set(route_order)}")
 
     else:
-        children = getattr(module, "routes", [])
-        children = fix_routes(children, file)
         layout = getattr(module, "Layout", None)
-        # children = []
-        # single module, single route
+        children = []
+        if hasattr(module, "routes"):
+            children = getattr(module, "routes", [])
+            root = get_root(children)
+            if layout is not None and root is not None and root.layout is None:
+                warnings.warn(f'You defined routes in {file}, in this case, layout should be set on the root route (with path="/"), not on the module level')
+                children = fix_routes(children, file, layout)
+                layout = None
         return [solara.Route(path="/", component=RenderPage, data=None, module=module, label=get_title(module), layout=layout, children=children, file=file)]
 
     return routes
@@ -493,7 +503,7 @@ def _generate_route_path(subpath: Path, layout=None, first=False, has_index=Fals
         route_path = "-".join([k.lower() for k in title_parts])
     # used as a 'sentinel' to find the deepest level of the route tree we need to render in 'RenderPage'
     component = RenderPage
-    children = []
+    children: List[solara.Route] = []
     module: Optional[ModuleType] = None
     data: Any = None
     module_layout = layout if first else None
@@ -506,8 +516,21 @@ def _generate_route_path(subpath: Path, layout=None, first=False, has_index=Fals
         reload.reloader.watcher.add_file(subpath)
         module = source_to_module(subpath, initial_namespace=initial_namespace)
         title = get_title(module)
-        children = getattr(module, "routes", children)
+        layout = getattr(module, "Layout", module_layout)
+        if hasattr(module, "routes"):
+            children = getattr(module, "routes", [])
+            root = get_root(children)
+            if layout is not None and root is not None and root.layout is None:
+                warnings.warn(f'You defined routes in {subpath}, in this case, layout should be set on the root route (with path="/"), not on the module level')
+                children = fix_routes(children, subpath, layout)
+                layout = None
         children = fix_routes(children, subpath)
-        module_layout = getattr(module, "Layout", module_layout)
-    route = solara.Route(route_path, component=component, module=module, label=title, children=children, data=data, layout=module_layout, file=subpath)
+    route = solara.Route(route_path, component=component, module=module, label=title, children=children, data=data, layout=layout, file=subpath)
     return route
+
+
+def get_root(routes: List[solara.Route]) -> Optional[solara.Route]:
+    for route in routes:
+        if route.path == "/":
+            return route
+    return None

solara/server/app.py

@@ -5,6 +5,7 @@
 import sys
 import threading
 import traceback
+import warnings
 from enum import Enum
 from pathlib import Path
 from typing import Any, Dict, List, Optional, cast
@@ -148,10 +149,17 @@ def add_path():
                 mod = importlib.import_module(self.name)
                 routes = solara.generate_routes(mod)
 
-        app = solara.autorouting.RenderPage(self.app_name)
-        if not hasattr(routes[0].module, self.app_name) and routes[0].children:
+        # when the root moduled defined routes, skip the enclosing route object
+        if len(routes) == 1 and routes[0].module and hasattr(routes[0].module, "routes"):
+            if routes[0].component:
+                warnings.warn(
+                    f"{self.name} has a component defined, but you are also defining routes."
+                    " To avoid confusing, consider renaming the {self.app_name} component."
+                )
             routes = routes[0].children
 
+        app = solara.autorouting.RenderPage(self.app_name)
+
         if settings.ssg.build_path is None:
             settings.ssg.build_path = self.directory.parent.resolve() / "build"
 

tests/unit/autorouting_test.py

@@ -11,8 +11,9 @@
 import solara.website.pages.examples
 import solara.widgets
 from solara.components.title import TitleWidget
+from solara.server.app import AppScript
 
-HERE = Path(__file__)
+HERE = Path(__file__).parent
 
 
 def test_count_arguments():
@@ -133,7 +134,7 @@ def test_routes_examples_docs():
 
 
 def test_routes_directory():
-    routes = solara.autorouting.generate_routes_directory(HERE.parent / "solara_test_apps" / "multipage")
+    routes = solara.autorouting.generate_routes_directory(HERE / "solara_test_apps" / "multipage")
     assert len(routes) == 8
     assert routes[0].path == "/"
     assert routes[0].label == "Home"
@@ -221,7 +222,7 @@ def test_routes_directory():
 
 def test_routes_regular_widgets():
     # routes = solara.autorouting.generate_routes_directory(HERE.parent / "solara_test_apps" / "multipage")
-    routes = solara.autorouting.generate_routes_directory(HERE.parent / "solara_test_apps" / "multipage-widgets")
+    routes = solara.autorouting.generate_routes_directory(HERE / "solara_test_apps" / "multipage-widgets")
 
     main_object = solara.autorouting.RenderPage()
     solara_context = solara.RoutingProvider(children=[main_object], routes=routes, pathname="/")
@@ -253,3 +254,47 @@ def test_routes_regular_widgets():
     assert rc.find(widgets.Button).widget.description == "Viewed 1 times"
     nav.location = "/volume"
     assert rc.find(v.Slider).widget.v_model == 5
+
+
+def test_single_file_routes_as_file(kernel_context, no_kernel_context):
+    name = str(HERE / "solara_test_apps" / "single_file_routes.py")
+    app = AppScript(name)
+    assert len(app.routes) == 2
+    assert app.routes[0].path == "/"
+    assert app.routes[0].layout is not None
+    assert app.routes[1].path == "page2"
+    assert app.routes[1].layout is None
+    try:
+        with kernel_context:
+            el = app.run()
+            root = solara.RoutingProvider(children=[el], routes=app.routes, pathname="/")
+            _box, rc = solara.render(root, handle_error=False)
+            rc.find(children=["Page 1"]).assert_single()
+            rc.find(children=["Custom layout"]).assert_single()
+            rc.render(solara.RoutingProvider(children=[el], routes=app.routes, pathname="/page2").key("2"))
+            rc.find(children=["Custom layout"]).assert_single()
+            rc.find(children=["Page 2"]).assert_single()
+    finally:
+        app.close()
+
+
+def test_single_file_routes_as_module(kernel_context, no_kernel_context, extra_include_path):
+    with extra_include_path(HERE / "solara_test_apps"):
+        app = AppScript("single_file_routes")
+        assert len(app.routes) == 2
+        assert app.routes[0].path == "/"
+        assert app.routes[0].layout is not None
+        assert app.routes[1].path == "page2"
+        assert app.routes[1].layout is None
+        try:
+            with kernel_context:
+                el = app.run()
+                root = solara.RoutingProvider(children=[el], routes=app.routes, pathname="/")
+                _box, rc = solara.render(root, handle_error=False)
+                rc.find(children=["Page 1"]).assert_single()
+                rc.find(children=["Custom layout"]).assert_single()
+                rc.render(solara.RoutingProvider(children=[el], routes=app.routes, pathname="/page2").key("2"))
+                rc.find(children=["Custom layout"]).assert_single()
+                rc.find(children=["Page 2"]).assert_single()
+        finally:
+            app.close()

tests/unit/solara_test_apps/single_file_routes.py

@@ -0,0 +1,25 @@
+import solara
+
+
+@solara.component
+def Page1():
+    solara.Text("Page 1")
+
+
+@solara.component
+def Page2():
+    solara.Text("Page 2")
+
+
+@solara.component
+def Layout(children):
+    with solara.AppLayout():
+        with solara.Column():
+            solara.Text("Custom layout")
+            solara.display(*children)
+
+
+routes = [
+    solara.Route("/", component=Page1, layout=Layout),
+    solara.Route("page2", component=Page2),
+]