add --default-file option to pyscript run

Author: jdw170000

src/pyscript/plugins/run.py

@@ -14,6 +14,7 @@
 
 def get_folder_based_http_request_handler(
     folder: Path,
+    default_file: Path = None,
 ) -> type[SimpleHTTPRequestHandler]:
     """
     Returns a FolderBasedHTTPRequestHandler with the specified directory.
@@ -36,6 +37,16 @@ def end_headers(self):
             self.send_header("Cross-Origin-Resource-Policy", "cross-origin")
             self.send_header("Cache-Control", "no-cache, must-revalidate")
             SimpleHTTPRequestHandler.end_headers(self)
+        
+        def do_GET(self):
+            # intercept accesses to nonexistent files; replace them with the default file
+            # this is to service SPA use cases (see Github Issue #132)
+            if default_file:
+                path = Path(self.translate_path(self.path))
+                if not path.exists():
+                    self.path = f'/{default_file}'
+            
+            return super().do_GET()
 
     return FolderBasedHTTPRequestHandler
 
@@ -58,7 +69,7 @@ def split_path_and_filename(path: Path) -> tuple[Path, str]:
         return abs_path, ""
 
 
-def start_server(path: Path, show: bool, port: int):
+def start_server(path: Path, show: bool, port: int, default_file: Path = None):
     """
     Creates a local server to run the app on the path and port specified.
 
@@ -76,7 +87,7 @@ def start_server(path: Path, show: bool, port: int):
     socketserver.TCPServer.allow_reuse_address = True
 
     app_folder, filename = split_path_and_filename(path)
-    CustomHTTPRequestHandler = get_folder_based_http_request_handler(app_folder)
+    CustomHTTPRequestHandler = get_folder_based_http_request_handler(app_folder, default_file=default_file)
 
     # Start the server within a context manager to make sure we clean up after
     with socketserver.TCPServer(("", port), CustomHTTPRequestHandler) as httpd:
@@ -110,6 +121,7 @@ def run(
     ),
     view: bool = typer.Option(True, help="Open the app in web browser."),
     port: int = typer.Option(8000, help="The port that the app will run on."),
+    default_file: Path = typer.Option(None, help="A default file to serve when a nonexistent file is accessed."),
 ):
     """
     Creates a local server to run the app on the path and port specified.
@@ -120,7 +132,7 @@ def run(
         raise cli.Abort(f"Error: Path {str(path)} does not exist.", style="red")
 
     try:
-        start_server(path, view, port)
+        start_server(path, view, port, default_file=default_file)
     except OSError as e:
         if e.errno == 48:
             console.print(