add a template for the package readme (#12499)

Co-authored-by: Erick Friis <erick@langchain.dev>

libs/cli/langchain_cli/namespaces/template.py

@@ -0,0 +1,117 @@
+"""
+Develop installable templates.
+"""
+
+import re
+import shutil
+import subprocess
+from pathlib import Path
+from typing import Optional
+
+import typer
+from langserve.packages import get_langserve_export
+from typing_extensions import Annotated
+
+from langchain_cli.utils.packages import get_package_root
+
+package_cli = typer.Typer(no_args_is_help=True, add_completion=False)
+
+
+@package_cli.command()
+def new(
+    name: Annotated[str, typer.Argument(help="The name of the folder to create")],
+    with_poetry: Annotated[
+        bool,
+        typer.Option("--with-poetry/--no-poetry", help="Don't run poetry install"),
+    ] = False,
+):
+    """
+    Creates a new template package.
+    """
+    computed_name = name if name != "." else Path.cwd().name
+    destination_dir = Path.cwd() / name if name != "." else Path.cwd()
+
+    # copy over template from ../package_template
+    project_template_dir = Path(__file__).parents[1] / "package_template"
+    shutil.copytree(project_template_dir, destination_dir, dirs_exist_ok=name == ".")
+
+    package_name_split = computed_name.split("/")
+    package_name = (
+        package_name_split[-2]
+        if len(package_name_split) > 1 and package_name_split[-1] == ""
+        else package_name_split[-1]
+    )
+    module_name = re.sub(
+        r"[^a-zA-Z0-9_]",
+        "_",
+        package_name,
+    )
+
+    # generate app route code
+    chain_name = f"{module_name}_chain"
+    app_route_code = (
+        f"from {module_name} import chain as {chain_name}\n\n"
+        f'add_routes(app, {chain_name}, path="/{package_name}")'
+    )
+
+    # replace template strings
+    pyproject = destination_dir / "pyproject.toml"
+    pyproject_contents = pyproject.read_text()
+    pyproject.write_text(
+        pyproject_contents.replace("__package_name__", module_name).replace(
+            "__module_name__", module_name
+        )
+    )
+
+    # move module folder
+    package_dir = destination_dir / module_name
+    shutil.move(destination_dir / "package_template", package_dir)
+
+    # replace readme
+    readme = destination_dir / "README.md"
+    readme_contents = readme.read_text()
+    readme.write_text(
+        readme_contents.replace("__package_name_last__", package_name).replace(
+            "__app_route_code__", app_route_code
+        )
+    )
+
+    # poetry install
+    if with_poetry:
+        subprocess.run(["poetry", "install"], cwd=destination_dir)
+
+
+@package_cli.command()
+def serve(
+    *,
+    port: Annotated[
+        Optional[int], typer.Option(help="The port to run the server on")
+    ] = None,
+    host: Annotated[
+        Optional[str], typer.Option(help="The host to run the server on")
+    ] = None,
+) -> None:
+    """
+    Starts a demo app for this template.
+    """
+    # load pyproject.toml
+    project_dir = get_package_root()
+    pyproject = project_dir / "pyproject.toml"
+
+    # get langserve export - throws KeyError if invalid
+    get_langserve_export(pyproject)
+
+    port_str = str(port) if port is not None else "8000"
+    host_str = host if host is not None else "127.0.0.1"
+
+    command = [
+        "uvicorn",
+        "--factory",
+        "langchain_cli.dev_scripts:create_demo_server",
+        "--reload",
+        "--port",
+        port_str,
+        "--host",
+        host_str,
+    ]
+    subprocess.run(command)