python3Packages.mlflow: build from PyPI wheel, fix server subprocess

pkgs/development/python-modules/mlflow/default.nix

@@ -1,10 +1,7 @@
 {
   lib,
   buildPythonPackage,
-  fetchFromGitHub,
-
-  # build-system
-  setuptools,
+  fetchPypi,
 
   # dependencies
   aiohttp,
@@ -31,26 +28,32 @@
 buildPythonPackage (finalAttrs: {
   pname = "mlflow";
   version = "3.12.0";
-  pyproject = true;
+  format = "wheel";
   __structuredAttrs = true;
 
-  src = fetchFromGitHub {
-    owner = "mlflow";
-    repo = "mlflow";
-    tag = "v${finalAttrs.version}";
-    hash = "sha256-OxhM+KCem0sb9cwtyzrUD/MGfoiiCfgU47qipYRDaFk=";
+  # We build from the PyPI wheel rather than fetchFromGitHub, because the mlflow-server
+  # JS UI is absent from GitHub but provided in the wheel.
+  src = fetchPypi {
+    pname = "mlflow";
+    inherit (finalAttrs) version;
+    format = "wheel";
+    dist = "py3";
+    python = "py3";
+    hash = "sha256-4cKO1MSFV8xSx2bxfxylgmdT3fJB1D8w+ZxF9+prPOA=";
   };
 
-  # ppyproject.release.toml is the one shipped in the Pypi package, so we use it too.
-  postPatch = ''
-    mv pyproject.release.toml pyproject.toml
+  # Nix-wrapped python populates sys.path via NIX_PYTHONPATH/site hooks,
+  # but PYTHONPATH stays unset in os.environ. mlflow spawns the server
+  # in a subprocess with a curated env, so without this patch the child
+  # interpreter cannot import uvicorn / mlflow itself.
+  postInstall = ''
+    patch -p1 -d "$out/lib/python"*/site-packages < ${./subprocess-pythonpath.patch}
   '';
 
-  build-system = [ setuptools ];
-
   pythonRelaxDeps = [
     "cryptography"
   ];
+
   dependencies = [
     aiohttp
     alembic
@@ -85,8 +88,12 @@ buildPythonPackage (finalAttrs: {
     description = "Open source platform for the machine learning lifecycle";
     mainProgram = "mlflow";
     homepage = "https://github.com/mlflow/mlflow";
-    changelog = "https://github.com/mlflow/mlflow/blob/${finalAttrs.src.tag}/CHANGELOG.md";
+    changelog = "https://github.com/mlflow/mlflow/blob/v${finalAttrs.version}/CHANGELOG.md";
     license = lib.licenses.asl20;
+    # Build from wheel which contains pure Python and pre-built JS bundle.
+    sourceProvenance = with lib.sourceTypes; [
+      binaryBytecode
+    ];
     maintainers = with lib.maintainers; [
       GaetanLepage
     ];

pkgs/development/python-modules/mlflow/subprocess-pythonpath.patch

@@ -0,0 +1,14 @@
+--- a/mlflow/server/__init__.py
++++ b/mlflow/server/__init__.py
+@@ -471,6 +471,11 @@
+             else tempfile.mkdtemp()
+         )
++    # In Nix-packaged environments sys.path is populated by wrappers but
++    # PYTHONPATH is never set in os.environ, so subprocesses (uvicorn,
++    # gunicorn) cannot find packages. Propagate it when not already set.
++    if "PYTHONPATH" not in os.environ:
++        env_map.setdefault("PYTHONPATH", os.pathsep.join(p for p in sys.path if p))
+
+     server_proc = _exec_cmd(
+         full_command,
+         extra_env=env_map,