added env override for default index URL

README.rst

@@ -173,6 +173,15 @@ To create a virtual environment to be used by ``micropipenv``:
 
   python3 -m venv venv/ && . venv/bin/activate
 
+To set the default Python Package Index to something other than ``https://pypi.org/simple``, set the ``MICROPIPENV_DEFAULT_INDEX_URLS`` to one or more comma-separated URLs.
+
+  Note: if the package manager file contains a package index URL, it will be used over this value.
+
+.. code-block:: console
+
+  export MICROPIPENV_DEFAULT_INDEX_URLS=https://pypi.example.com/simple,https://pypi.org/simple
+  micropipenv install
+
 
 ``micropipenv install --deploy``
 ================================

micropipenv.py

@@ -96,7 +96,16 @@
     from typing import Union
     from pip._internal.req.req_file import ParsedRequirement
 
-_DEFAULT_INDEX_URLS = ("https://pypi.org/simple",)
+
+def get_index_urls():  # type: () -> Tuple[str, ...]
+    """Return parsed MICROPIPENV_DEFAULT_INDEX_URLS env variable or the default value."""
+    urls = os.getenv("MICROPIPENV_DEFAULT_INDEX_URLS")
+    if urls and urls.strip() != "":
+        return tuple([url.strip() for url in urls.split(",")])
+    return ("https://pypi.org/simple",)
+
+
+_DEFAULT_INDEX_URLS = get_index_urls()
 _MAX_DIR_TRAVERSAL = 42  # Avoid any symlinks that would loop.
 _PIP_BIN = os.getenv("MICROPIPENV_PIP_BIN", "pip")
 _SUPPORTED_PIP = SpecifierSet(_SUPPORTED_PIP_STR)

tests/test_micropipenv.py

@@ -104,6 +104,31 @@ def check_generated_pipfile_lock(pipfile_lock_path, pipfile_lock_path_expected):
     os.remove(pipfile_lock_path)
 
 
+@pytest.mark.parametrize(
+    "input,expected",
+    [
+        [
+            "https://pypi.org/simple, https://example.org/simple",
+            ("https://pypi.org/simple", "https://example.org/simple"),
+        ],
+        ["https://example.org/simple", ("https://example.org/simple",)],
+        ["", ("https://pypi.org/simple",)],
+        [" ", ("https://pypi.org/simple",)],
+        ["\t", ("https://pypi.org/simple",)],
+        [None, ("https://pypi.org/simple",)],
+    ],
+)
+def test_get_index_urls(input, expected):
+    """Test index url parsing"""
+    if input is not None:
+        os.environ["MICROPIPENV_DEFAULT_INDEX_URLS"] = input
+    else:
+        del os.environ["MICROPIPENV_DEFAULT_INDEX_URLS"]
+
+    result = micropipenv.get_index_urls()
+    assert result == expected
+
+
 @pytest.mark.online
 def test_install_pipenv(venv):
     """Test invoking installation using information in Pipfile.lock."""