Add TargetPython.format_given().

Author: cjerdonek

src/pip/_internal/models/target_python.py

@@ -5,7 +5,8 @@
 from pip._internal.utils.typing import MYPY_CHECK_RUNNING
 
 if MYPY_CHECK_RUNNING:
-    from typing import Optional, Tuple
+    from typing import List, Optional, Tuple
+    from pip._internal.pep425tags import Pep425Tag
 
 
 class TargetPython(object):
@@ -54,9 +55,32 @@ def __init__(
         self.py_version_info = py_version_info
 
         # This is used to cache the return value of get_tags().
-        self._valid_tags = None
+        self._valid_tags = None  # type: Optional[List[Pep425Tag]]
+
+    def format_given(self):
+        # type: () -> str
+        """
+        Format the given, non-None attributes for display.
+        """
+        display_version = None
+        if self._given_py_version_info is not None:
+            display_version = '.'.join(
+                str(part) for part in self._given_py_version_info
+            )
+
+        key_values = [
+            ('platform', self.platform),
+            ('version_info', display_version),
+            ('abi', self.abi),
+            ('implementation', self.implementation),
+        ]
+        return ' '.join(
+            '{}={!r}'.format(key, value) for key, value in key_values
+            if value is not None
+        )
 
     def get_tags(self):
+        # type: () -> List[Pep425Tag]
         """
         Return the supported tags to check wheel candidates against.
         """

tests/unit/test_target_python.py

@@ -47,6 +47,29 @@ def test_init__py_version_info_none(self):
         assert target_python.py_version_info == CURRENT_PY_VERSION_INFO
         assert target_python.py_version == current_major_minor
 
+    @pytest.mark.parametrize('kwargs, expected', [
+        ({}, ''),
+        (dict(py_version_info=(3, 6)), "version_info='3.6'"),
+        (
+            dict(platform='darwin', py_version_info=(3, 6)),
+            "platform='darwin' version_info='3.6'",
+        ),
+        (
+            dict(
+                platform='darwin', py_version_info=(3, 6), abi='cp36m',
+                implementation='cp'
+            ),
+            (
+                "platform='darwin' version_info='3.6' abi='cp36m' "
+                "implementation='cp'"
+            ),
+        ),
+    ])
+    def test_format_given(self, kwargs, expected):
+        target_python = TargetPython(**kwargs)
+        actual = target_python.format_given()
+        assert actual == expected
+
     @pytest.mark.parametrize('py_version_info, expected_versions', [
         ((), ['']),
         ((2, ), ['2']),