Consolidate importlib metadata import

src/build/_importlib.py

@@ -0,0 +1,10 @@
+import sys
+
+
+if sys.version_info >= (3, 8):
+    from importlib import metadata
+else:
+    import importlib_metadata as metadata
+
+
+__all__ = ['metadata']

src/build/_util.py

@@ -1,7 +1,6 @@
 from __future__ import annotations
 
 import re
-import sys
 
 from collections.abc import Iterator, Set
 
@@ -25,10 +24,7 @@ def check_dependency(
     """
     import packaging.requirements
 
-    if sys.version_info >= (3, 8):
-        import importlib.metadata as importlib_metadata
-    else:
-        import importlib_metadata
+    from ._importlib import metadata
 
     req = packaging.requirements.Requirement(req_string)
     normalised_req_string = str(req)
@@ -49,8 +45,8 @@ def check_dependency(
             return
 
     try:
-        dist = importlib_metadata.distribution(req.name)
-    except importlib_metadata.PackageNotFoundError:
+        dist = metadata.distribution(req.name)
+    except metadata.PackageNotFoundError:
         # dependency is not installed in the environment.
         yield (*ancestral_req_strings, normalised_req_string)
     else:

src/build/util.py

@@ -3,33 +3,27 @@
 from __future__ import annotations
 
 import pathlib
-import sys
 import tempfile
 
 import pyproject_hooks
 
 from . import PathType, ProjectBuilder, RunnerType
+from ._importlib import metadata
 from .env import DefaultIsolatedEnv
 
 
-if sys.version_info >= (3, 8):
-    import importlib.metadata as importlib_metadata
-else:
-    import importlib_metadata
-
-
-def _project_wheel_metadata(builder: ProjectBuilder) -> importlib_metadata.PackageMetadata:
+def _project_wheel_metadata(builder: ProjectBuilder) -> metadata.PackageMetadata:
     with tempfile.TemporaryDirectory() as tmpdir:
         path = pathlib.Path(builder.metadata_path(tmpdir))
-        return importlib_metadata.PathDistribution(path).metadata
+        return metadata.PathDistribution(path).metadata
 
 
 def project_wheel_metadata(
     source_dir: PathType,
     isolated: bool = True,
     *,
     runner: RunnerType = pyproject_hooks.quiet_subprocess_runner,
-) -> importlib_metadata.PackageMetadata:
+) -> metadata.PackageMetadata:
     """
     Return the wheel metadata for a project.
 

tests/test_projectbuilder.py

@@ -4,6 +4,7 @@
 import copy
 import logging
 import os
+import pathlib
 import sys
 import textwrap
 
@@ -12,13 +13,7 @@
 
 import build
 
-
-if sys.version_info >= (3, 8):  # pragma: no cover
-    from importlib import metadata as importlib_metadata
-else:  # pragma: no cover
-    import importlib_metadata
-
-import pathlib
+from build import _importlib
 
 
 build_open_owner = 'builtins'
@@ -30,7 +25,7 @@
 }
 
 
-class MockDistribution(importlib_metadata.Distribution):
+class MockDistribution(_importlib.metadata.Distribution):
     def locate_file(self, path):  # pragma: no cover
         return ''
 
@@ -48,7 +43,7 @@ def from_name(cls, name):
             return CircularMockDistribution()
         elif name == 'nested_circular_dep':
             return NestedCircularMockDistribution()
-        raise importlib_metadata.PackageNotFoundError
+        raise _importlib.metadata.PackageNotFoundError
 
 
 class ExtraMockDistribution(MockDistribution):
@@ -167,7 +162,7 @@ def read_text(self, filename):
     ],
 )
 def test_check_dependency(monkeypatch, requirement_string, expected):
-    monkeypatch.setattr(importlib_metadata, 'Distribution', MockDistribution)
+    monkeypatch.setattr(_importlib.metadata, 'Distribution', MockDistribution)
     assert next(build.check_dependency(requirement_string), None) == expected
 
 
@@ -502,7 +497,7 @@ def dummy_runner(cmd, cwd=None, extra_environ=None):
 def test_metadata_path_no_prepare(tmp_dir, package_test_no_prepare):
     builder = build.ProjectBuilder(package_test_no_prepare)
 
-    metadata = importlib_metadata.PathDistribution(
+    metadata = _importlib.metadata.PathDistribution(
         pathlib.Path(builder.metadata_path(tmp_dir)),
     ).metadata
 
@@ -513,7 +508,7 @@ def test_metadata_path_no_prepare(tmp_dir, package_test_no_prepare):
 def test_metadata_path_with_prepare(tmp_dir, package_test_setuptools):
     builder = build.ProjectBuilder(package_test_setuptools)
 
-    metadata = importlib_metadata.PathDistribution(
+    metadata = _importlib.metadata.PathDistribution(
         pathlib.Path(builder.metadata_path(tmp_dir)),
     ).metadata
 
@@ -524,7 +519,7 @@ def test_metadata_path_with_prepare(tmp_dir, package_test_setuptools):
 def test_metadata_path_legacy(tmp_dir, package_legacy):
     builder = build.ProjectBuilder(package_legacy)
 
-    metadata = importlib_metadata.PathDistribution(
+    metadata = _importlib.metadata.PathDistribution(
         pathlib.Path(builder.metadata_path(tmp_dir)),
     ).metadata
 

tests/test_self_packaging.py

@@ -21,6 +21,7 @@
     'src/build/__init__.py',
     'src/build/__main__.py',
     'src/build/_exceptions.py',
+    'src/build/_importlib.py',
     'src/build/_util.py',
     'src/build/env.py',
     'src/build/py.typed',
@@ -31,6 +32,7 @@
     'build/__init__.py',
     'build/__main__.py',
     'build/_exceptions.py',
+    'build/_importlib.py',
     'build/_util.py',
     'build/env.py',
     'build/py.typed',