add seed packages via pip invoke

.coveragerc

@@ -10,6 +10,7 @@ exclude_lines =
 omit =
     # site.py is ran before the coverage can be enabled, no way to measure coverage on this
     src/virtualenv/interpreters/create/impl/cpython/site.py
+    src/virtualenv/seed/embed/wheels/pip-*.whl/*
 
 [coverage:paths]
 source =

src/virtualenv/seed/embed/pip_invoke.py

@@ -1,6 +1,10 @@
 from __future__ import absolute_import, unicode_literals
 
-from .base_embed import BaseEmbed
+import os
+import subprocess
+
+from virtualenv.seed.embed.base_embed import BaseEmbed
+from virtualenv.seed.embed.wheels.acquire import get_bundled_wheel
 
 
 class PipInvoke(BaseEmbed):
@@ -10,3 +14,29 @@ def __init__(self, options):
     def run(self, creator):
         if not self.enabled:
             return
+
+        version = creator.interpreter.version_release_str
+
+        cmd = [str(creator.exe), "-m", "pip", "install", "--only-binary", ":all:"]
+        for folder in {get_bundled_wheel(p, version).parent for p in ("pip", "setuptools")}:
+            cmd.extend(["--find-links", str(folder)])
+        if not self.download:
+            cmd.append("--no-index")
+        for key, version in {"pip": self.pip_version, "setuptools": self.setuptools_version}.items():
+            cmd.append("{}{}".format(key, "=={}".format(version) if version is not None else ""))
+
+        env = os.environ.copy()
+        env.update(
+            {
+                str(k): str(v)  # python 2 requires these to be string only (non-unicode)
+                for k, v in {
+                    # put the bundled wheel onto the path, and use it to do the bootstrap operation
+                    "PYTHONPATH": get_bundled_wheel("pip", version),
+                    "PIP_USE_WHEEL": "1",
+                    "PIP_USER": "0",
+                    "PIP_NO_INPUT": "1",
+                }.items()
+            }
+        )
+
+        subprocess.call(cmd, env=env)

src/virtualenv/seed/embed/wheels/acquire.py

@@ -1,6 +1,7 @@
 """Bootstrap"""
 from __future__ import absolute_import, unicode_literals
 
+import subprocess
 from collections import defaultdict
 from shutil import copy2
 
@@ -39,9 +40,8 @@ def download_wheel(version_str, must_download, wheel_download):
         str(wheel_download),
     ]
     cmd.extend(must_download)
-    from pip._internal import main
-
-    main(cmd)
+    # pip has no interface in python - must be a new sub-process
+    subprocess.call(cmd)
 
 
 def check_if_must_download(packages, wheel_download):
@@ -87,8 +87,12 @@ def _get_wheels_for_package(inside_folder, package):
 
 def ensure_bundle_cached(packages, version_release, wheel_download):
     for package in packages:
-        bundle = (BUNDLE_SUPPORT.get(version_release, {}) or BUNDLE_SUPPORT[MAX]).get(package)
+        bundle = get_bundled_wheel(package, version_release)
         if bundle is not None:
-            bundled_wheel_file = wheel_download / bundle
+            bundled_wheel_file = wheel_download / bundle.name
             if not bundled_wheel_file.exists():
-                copy2(str(BUNDLE_FOLDER / bundle), str(bundled_wheel_file))
+                copy2(str(bundle), str(bundled_wheel_file))
+
+
+def get_bundled_wheel(package, version_release):
+    return BUNDLE_FOLDER / (BUNDLE_SUPPORT.get(version_release, {}) or BUNDLE_SUPPORT[MAX]).get(package)

tests/unit/interpreters/boostrap/test_boostrap_link_via_app_data.py

@@ -13,6 +13,8 @@ def test_base_bootstrap_link_via_app_data(tmp_path, coverage_env):
     bundle_ver = BUNDLE_SUPPORT[CURRENT.version_release_str]
     create_cmd = [
         str(tmp_path / "env"),
+        "--seeder",
+        "link-app-data",
         "--download",
         "--pip",
         bundle_ver["pip"].split("-")[1],

tests/unit/interpreters/boostrap/test_pip_invoke.py

@@ -0,0 +1,31 @@
+from __future__ import absolute_import, unicode_literals
+
+from virtualenv.interpreters.discovery.py_info import CURRENT
+from virtualenv.run import run_via_cli
+from virtualenv.seed.embed.wheels import BUNDLE_SUPPORT
+
+
+def test_base_bootstrap_via_pip_invoke(tmp_path, coverage_env):
+    bundle_ver = BUNDLE_SUPPORT[CURRENT.version_release_str]
+    create_cmd = [
+        "--seeder",
+        "pip",
+        str(tmp_path / "env"),
+        "--download",
+        "--pip",
+        bundle_ver["pip"].split("-")[1],
+        "--setuptools",
+        bundle_ver["setuptools"].split("-")[1],
+    ]
+    result = run_via_cli(create_cmd)
+    coverage_env()
+    assert result
+
+    # uninstalling pip/setuptools now should leave us with a clean env
+    site_package = result.creator.site_packages[0]
+    pip = site_package / "pip"
+    setuptools = site_package / "setuptools"
+
+    files_post_first_create = list(site_package.iterdir())
+    assert pip in files_post_first_create
+    assert setuptools in files_post_first_create