From c729f367e6a9ad779dbe4ccc5aeaacdd5327947b Mon Sep 17 00:00:00 2001
From: Mike DePaulo <mikedep333@redhat.com>
Date: Tue, 29 Sep 2026 19:01:26 -0400
Subject: [PATCH] fix(dependencies): use the sdist requirements hook

Call get_requires_for_build_sdist when discovering sdist dependencies instead
of invoking the wheel requirements hook. Correct the matching docstring.

Cover distinct wheel and sdist requirements, the empty default for an absent
sdist hook, and a failing wheel hook using real backend subprocess calls.

Closes: #1351
Co-Authored-By: OpenAI Codex <noreply@openai.com>
Signed-off-by: Mike DePaulo <mikedep333@redhat.com>
---
 src/fromager/dependencies.py |  4 +--
 tests/test_dependencies.py   | 56 ++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/src/fromager/dependencies.py b/src/fromager/dependencies.py
index 18dcdbef..9a756b1d 100644
--- a/src/fromager/dependencies.py
+++ b/src/fromager/dependencies.py
@@ -236,7 +236,7 @@ def default_get_build_sdist_dependencies(
     """Get build sdist dependencies
 
     Defaults to result of hook call
-    :meth:`~pyproject_hooks.BuildBackendHookCaller.get_requires_for_build_wheel`
+    :meth:`~pyproject_hooks.BuildBackendHookCaller.get_requires_for_build_sdist`
     """
     logger.info(f"looking for build sdist dependencies in {build_dir}")
     pbi = ctx.package_build_info(req)
@@ -247,7 +247,7 @@ def default_get_build_sdist_dependencies(
         override_environ=extra_environ,
         build_env=build_env,
     )
-    return hook_caller.get_requires_for_build_wheel(
+    return hook_caller.get_requires_for_build_sdist(
         config_settings=pbi.config_settings,
     )
 
diff --git a/tests/test_dependencies.py b/tests/test_dependencies.py
index 34a68ee8..ed986003 100644
--- a/tests/test_dependencies.py
+++ b/tests/test_dependencies.py
@@ -3,12 +3,14 @@
 import os
 import pathlib
 import shutil
+import sys
 import textwrap
 import typing
 import zipfile
 from unittest.mock import Mock, patch
 
 import hatchling.build
+import pyproject_hooks
 import pytest
 from packaging.metadata import Metadata
 from packaging.requirements import Requirement
@@ -294,6 +296,60 @@ def test_get_build_sdist_dependencies(
     assert names == set()
 
 
+@pytest.mark.parametrize(
+    "backend_source,expected",
+    [
+        (
+            "def get_requires_for_build_wheel(config_settings=None):\n"
+            "    return ['wheel-only>=1']\n"
+            "def get_requires_for_build_sdist(config_settings=None):\n"
+            "    return ['sdist-only>=2']\n",
+            ["sdist-only>=2"],
+        ),
+        (
+            "def get_requires_for_build_wheel(config_settings=None):\n"
+            "    return ['wheel-only>=1']\n",
+            [],
+        ),
+        (
+            "def get_requires_for_build_wheel(config_settings=None):\n"
+            "    raise RuntimeError('wheel hook must not run')\n"
+            "def get_requires_for_build_sdist(config_settings=None):\n"
+            "    return ['sdist-only>=2']\n",
+            ["sdist-only>=2"],
+        ),
+    ],
+    ids=["distinct-requirements", "optional-sdist-hook", "wheel-hook-fails"],
+)
+def test_default_get_build_sdist_dependencies_uses_sdist_hook(
+    backend_source: str,
+    expected: list[str],
+    tmp_context: context.WorkContext,
+    tmp_path: pathlib.Path,
+) -> None:
+    """Discover sdist requirements independently of the wheel hook."""
+    tmp_path.joinpath("backend.py").write_text(backend_source)
+    hook_caller = pyproject_hooks.BuildBackendHookCaller(
+        source_dir=str(tmp_path),
+        build_backend="backend",
+        backend_path=["."],
+        python_executable=sys.executable,
+    )
+    with patch(
+        "fromager.dependencies.get_build_backend_hook_caller",
+        return_value=hook_caller,
+    ):
+        results = dependencies.default_get_build_sdist_dependencies(
+            ctx=tmp_context,
+            req=Requirement("example"),
+            sdist_root_dir=tmp_path,
+            build_dir=tmp_path,
+            extra_environ={},
+            build_env=Mock(spec=build_environment.BuildEnvironment),
+        )
+    assert list(results) == expected
+
+
 def test_get_build_sdist_dependencies_cached(
     tmp_context: context.WorkContext, tmp_path: pathlib.Path
 ) -> None: