Allow pre-release to satisfy build requirements

news/11123.bugfix.rst

@@ -0,0 +1,3 @@
+Allow using a pre-release version to satisfy a build requirement. This helps
+manually populated build environments to more accurately detect build-time
+requirement conflicts.

src/pip/_internal/build_env.py

@@ -185,7 +185,7 @@ def check_requirements(
                     installed_req_str = f"{req.name}=={dist.version}"
                 else:
                     installed_req_str = f"{req.name}==={dist.version}"
-                if dist.version not in req.specifier:
+                if not req.specifier.contains(dist.version, prereleases=True):
                     conflicting.add((installed_req_str, req_str))
                 # FIXME: Consider direct URL?
         return conflicting, missing

tests/functional/test_pep517.py

@@ -5,7 +5,13 @@
 
 from pip._internal.build_env import BuildEnvironment
 from pip._internal.req import InstallRequirement
-from tests.lib import PipTestEnvironment, TestData, make_test_finder, path_to_url
+from tests.lib import (
+    PipTestEnvironment,
+    TestData,
+    create_basic_wheel_for_package,
+    make_test_finder,
+    path_to_url,
+)
 from tests.lib.path import Path
 
 
@@ -210,6 +216,25 @@ def test_validate_conflicting_pep517_backend_requirements(
     assert result.returncode != 0 and msg in result.stderr, str(result)
 
 
+def test_pep517_backend_requirements_satisfied_by_prerelease(
+    script: PipTestEnvironment,
+    data: TestData,
+) -> None:
+    create_basic_wheel_for_package(script, "myreq", "1.0a1")
+    script.pip("install", "myreq==1.0a1", "--no-index", "-f", script.scratch_path)
+    script.pip("install", "test_backend", "--no-index", "-f", data.backends)
+
+    project_dir = make_project(
+        script.temp_path,
+        requires=["test_backend", "myreq"],
+        backend="test_backend",
+    )
+    project_dir.joinpath("backend_reqs.txt").write_text("myreq")
+
+    result = script.pip("install", "--no-index", "--no-build-isolation", project_dir)
+    assert "Installing backend dependencies:" not in result.stdout
+
+
 def test_pep517_backend_requirements_already_satisfied(
     script: PipTestEnvironment, tmpdir: Path, data: TestData
 ) -> None: