WIP: monorepo support in CLI (#6028)

This PR introduces the `--build-command` and `--install-command`
arguments to `langgraph build`.

`--install-command` is a custom install command. If passed, it will be
run from wherever the `langgraph build` call was made, i.e. NOT where
the langgraph.json file lives (except if these are the same place). This
will override the detected install command that we previously used.

`--build-command` is a custom build command. This will run from wherever
the langgraph.json file lives, and will be done after the install has
been run.

You don't need to provide both. Just providing one will make the install
(detected or supplied) run in the directory from where `langgraph build
was called` and then have the build command (if one exists) run in the
directory where langgraph.json exists.

I think we should probably allow configuring the directories from which
these commands get run, but I don't think this needs to be part of the
MVP.

---------

Co-authored-by: William FH <13333726+hinthornw@users.noreply.github.com>

libs/cli/langgraph_cli/cli.py

@@ -303,6 +303,8 @@ def _build(
     pull: bool,
     tag: str,
     passthrough: Sequence[str] = (),
+    install_command: Optional[str] = None,
+    build_command: Optional[str] = None,
 ):
     # pull latest images
     if pull:
@@ -322,22 +324,38 @@ def _build(
         "-t",
         tag,
     ]
+    # determine build context: use current directory for JS projects, config parent for Python
+    is_js_project = config_json.get("node_version") and not config_json.get(
+        "python_version"
+    )
+    # build/install commands only apply to JS projects for now
+    # without install/build command, JS projects will follow the old behavior
+    if is_js_project and (build_command or install_command):
+        build_context = str(pathlib.Path.cwd())
+    else:
+        build_context = str(config.parent)
+
     # apply config
     stdin, additional_contexts = langgraph_cli.config.config_to_docker(
-        config, config_json, base_image, api_version
+        config,
+        config_json,
+        base_image,
+        api_version,
+        install_command,
+        build_command,
+        build_context,
     )
     # add additional_contexts
     if additional_contexts:
         for k, v in additional_contexts.items():
             args.extend(["--build-context", f"{k}={v}"])
-    # run docker build
     runner.run(
         subp_exec(
             "docker",
             "build",
             *args,
             *passthrough,
-            str(config.parent),
+            build_context,
             input=stdin,
             verbose=True,
         )
@@ -366,6 +384,14 @@ def _build(
     "\n    --base-image langchain/langgraph-server:0.2  # Pin to a minor version (Python)",
 )
 @OPT_API_VERSION
+@click.option(
+    "--install-command",
+    help="Custom install command to run from the build context root. If not provided, auto-detects based on package manager files.",
+)
+@click.option(
+    "--build-command",
+    help="Custom build command to run from the langgraph.json directory. If not provided, uses default build process.",
+)
 @click.argument("docker_build_args", nargs=-1, type=click.UNPROCESSED)
 @cli.command(
     help="📦 Build LangGraph API server Docker image.",
@@ -381,6 +407,8 @@ def build(
     api_version: Optional[str],
     pull: bool,
     tag: str,
+    install_command: Optional[str],
+    build_command: Optional[str],
 ):
     with Runner() as runner, Progress(message="Pulling...") as set:
         if shutil.which("docker") is None:
@@ -397,6 +425,8 @@ def build(
             pull,
             tag,
             docker_build_args,
+            install_command,
+            build_command,
         )