Support --python-tag for PEP 517 builds

src/pip/_internal/wheel.py

@@ -74,6 +74,14 @@ def open_for_csv(name, mode):
     return open(name, mode + bin, **nl)
 
 
+def replace_python_tag(wheelname, new_tag):
+    """Replace the Python tag in a wheel file name with a new value.
+    """
+    parts = wheelname.split('-')
+    parts[-3] = new_tag
+    return '-'.join(parts)
+
+
 def fix_script(path):
     """Replace #!python with #!/path/to/python
     Return True if file was changed."""
@@ -713,10 +721,19 @@ class WheelBuilder(object):
                         spinner=spinner
                     )
                 with req.pep517_backend.subprocess_runner(runner):
-                    req.pep517_backend.build_wheel(
+                    wheelname = req.pep517_backend.build_wheel(
                         tempd,
                         metadata_directory=req.metadata_directory
                     )
+                if python_tag:
+                    # General PEP 517 backends don't necessarily support
+                    # a "--python-tag" option, so we rename the wheel
+                    # file directly.
+                    newname = replace_python_tag(wheelname, python_tag)
+                    os.rename(
+                        os.path.join(tempd, wheelname),
+                        os.path.join(tempd, newname)
+                    )
                 return True
             except Exception:
                 spinner.finish("error")

tests/unit/test_wheel.py

@@ -70,6 +70,21 @@ def test_wheel_version(tmpdir, data):
     assert not wheel.wheel_version(tmpdir + 'broken')
 
 
+def test_python_tag():
+    wheelnames = [
+        'simplewheel-1.0-py2.py3-none-any.whl',
+        'simplewheel-1.0-py27-none-any.whl',
+        'simplewheel-2.0-1-py2.py3-none-any.whl',
+    ]
+    newnames = [
+        'simplewheel-1.0-py37-none-any.whl',
+        'simplewheel-1.0-py37-none-any.whl',
+        'simplewheel-2.0-1-py37-none-any.whl',
+    ]
+    for name, new in zip(wheelnames, newnames):
+        assert wheel.replace_python_tag(name, 'py37') == new
+
+
 def test_check_compatibility():
     name = 'test'
     vc = wheel.VERSION_COMPATIBLE