webui: implement /api/machines/{name}/schema

pkgs/clan-cli/clan_cli/config/machine.py

@@ -0,0 +1,47 @@
+import json
+import subprocess
+import sys
+from pathlib import Path
+from typing import Optional
+
+from ..dirs import get_clan_flake_toplevel
+
+
+def schema_for_machine(machine_name: str, flake: Optional[Path] = None) -> dict:
+    if flake is None:
+        flake = get_clan_flake_toplevel()
+    # use nix eval to read from .#clanModules.<module_name>.options
+    proc = subprocess.run(
+        [
+            "nix",
+            "eval",
+            "--json",
+            "--impure",
+            "--show-trace",
+            "--extra-experimental-features",
+            "nix-command flakes",
+            "--expr",
+            f"""
+            let
+                flake = builtins.getFlake (toString {flake});
+                lib = flake.inputs.nixpkgs.lib;
+                module = builtins.trace (builtins.attrNames flake) flake.clanModules.machine-{machine_name};
+                evaled = lib.evalModules {{
+                    modules = [module];
+                }};
+                clanOptions = evaled.options.clan;
+                jsonschemaLib = import {Path(__file__).parent / "jsonschema"} {{ inherit lib; }};
+                jsonschema = jsonschemaLib.parseOptions clanOptions;
+            in
+                jsonschema
+            """,
+        ],
+        capture_output=True,
+        text=True,
+    )
+    if proc.returncode != 0:
+        print(proc.stderr, file=sys.stderr)
+        raise Exception(
+            f"Failed to read schema for machine {machine_name}:\n{proc.stderr}"
+        )
+    return json.loads(proc.stdout)