v1: Flet CLI: Add flet serve command to run HTTP server with WASM support (#5441)

* Flet CLI: Add `flet serve` command to run HTTP server with WASM support

* Make web_root as a positional argument

* Rename and update Flet CLI documentation

Replaces old CLI command docs (build, create, doctor, pack, publish, run) with new files prefixed by 'flet-' and updates their content for improved clarity and completeness. Updates all internal references and navigation to use the new filenames and command names. Also updates build.py to recommend 'flet serve' for serving web apps instead of Python's http.server.

* `flet serve` to support `-p` option

Author: FeodorFitsner

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

@@ -8,6 +8,7 @@
 import flet_cli.commands.pack
 import flet_cli.commands.publish
 import flet_cli.commands.run
+import flet_cli.commands.serve
 from flet.version import update_version
 
 
@@ -76,6 +77,7 @@ def main():
     flet_cli.commands.build.Command.register_to(sp, "build")
     flet_cli.commands.pack.Command.register_to(sp, "pack")
     flet_cli.commands.publish.Command.register_to(sp, "publish")
+    flet_cli.commands.serve.Command.register_to(sp, "serve")
     flet_cli.commands.doctor.Command.register_to(
         sp, "doctor"
     )  # Register the doctor command

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

@@ -665,8 +665,7 @@ def handle(self, options: argparse.Namespace) -> None:
                     f"Find it in [cyan]{self.rel_out_dir}[/cyan] directory. "
                     f"{self.emojis['directory']}"
                     + (
-                        f"\nRun [cyan]python -m http.server --directory "
-                        f"{self.rel_out_dir}[/cyan] command to start dev web server "
+                        "\nRun [cyan]flet serve[/cyan] command to start a web server "
                         "with your app. "
                         if self.options.target_platform == "web"
                         else ""

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

@@ -0,0 +1,72 @@
+import argparse
+import http.server
+import socketserver
+from pathlib import Path
+
+from flet_cli.commands.base import BaseCommand
+from rich.console import Console
+from rich.style import Style
+
+error_style = Style(color="red1", bold=True)
+console = Console(log_path=False)
+
+
+class CustomHandler(http.server.SimpleHTTPRequestHandler):
+    def __init__(self, *args, directory=None, **kwargs):
+        super().__init__(*args, directory=directory, **kwargs)
+
+    def end_headers(self):
+        self.send_header("Cross-Origin-Opener-Policy", "same-origin")
+        self.send_header("Cross-Origin-Embedder-Policy", "require-corp")
+        self.send_header("Access-Control-Allow-Origin", "*")
+        super().end_headers()
+
+
+class Command(BaseCommand):
+    """
+    Serve static files from a directory with optional WASM headers.
+    """
+
+    def add_arguments(self, parser: argparse.ArgumentParser) -> None:
+        parser.add_argument(
+            "web_root",
+            type=str,
+            nargs="?",
+            help="directory to serve (default: ./build/web)",
+            default="build/web",
+        )
+        parser.add_argument(
+            "-p",
+            "--port",
+            type=int,
+            default=8000,
+            help="Port to serve on (default: 8000)",
+        )
+
+    def handle(self, options: argparse.Namespace) -> None:
+        directory = Path(options.web_root).resolve()
+        if not directory.is_dir():
+            console.print(
+                f"Error: Directory '{directory}' does not exist or is not a folder.",
+                style=error_style,
+            )
+            exit(1)
+
+        def handler(*args, **kwargs):
+            return CustomHandler(
+                *args,
+                directory=str(directory),
+                **kwargs,
+            )
+
+        try:
+            with socketserver.TCPServer(("", options.port), handler) as httpd:
+                console.print(
+                    f"Serving [green]{directory}[/green] at [cyan]http://localhost:{options.port}[/cyan] (Press Ctrl+C to stop)\n"
+                )
+                httpd.serve_forever()
+        except KeyboardInterrupt:
+            console.print("\n[bold yellow]Server stopped by user.[/bold yellow]")
+        except OSError as e:
+            console.print(f"Error: {e}", style=error_style)
+            exit(1)