[PATCH 09/27] mkvenv: create pip binary in virtual environment

[John Snow <jsnow@redhat.com>]

From: Paolo Bonzini <pbonzini@redhat.com>

While pip can be invoked as "python -m pip", it is more standard to
have it as a binary in the virtual environment.  Instead of using
ensurepip, which is slow, use the console shim generation that was
just added for "mkvenv ensure".

Signed-off-by: John Snow <jsnow@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 python/scripts/mkvenv.py | 34 ++++++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/python/scripts/mkvenv.py b/python/scripts/mkvenv.py
index 9c99122603..7a9a14124d 100644
--- a/python/scripts/mkvenv.py
+++ b/python/scripts/mkvenv.py
@@ -11,6 +11,8 @@
 Commands:
   command     Description
     create    create a venv
+    post_init
+              post-venv initialization
     ensure    Ensure that the specified package is installed.
 
 --------------------------------------------------
@@ -25,6 +27,13 @@
 
 --------------------------------------------------
 
+usage: mkvenv post_init [-h]
+
+options:
+  -h, --help         show this help message and exit
+
+--------------------------------------------------
+
 usage: mkvenv ensure [-h] [--online] [--dir DIR] dep_spec...
 
 positional arguments:
@@ -189,6 +198,13 @@ def post_post_setup(self, context: SimpleNamespace) -> None:
             with open(pth_file, "w", encoding="UTF-8") as file:
                 file.write(parent_libpath + os.linesep)
 
+        args = [
+            context.env_exe,
+            __file__,
+            "post_init",
+        ]
+        subprocess.run(args, check=True)
+
     def get_value(self, field: str) -> str:
         """
         Get a string value from the context namespace after a call to build.
@@ -727,6 +743,17 @@ def ensure(
         raise Ouch(diagnose(dep_specs[0], online, wheels_dir, prog)) from exc
 
 
+def post_venv_setup() -> None:
+    """
+    This is intended to be run *inside the venv* after it is created.
+    """
+    logger.debug("post_venv_setup()")
+    # Generate a 'pip' script so the venv is usable in a normal
+    # way from the CLI. This only happens when we inherited pip from a
+    # parent/system-site and haven't run ensurepip in some way.
+    generate_console_scripts(["pip"])
+
+
 def _add_create_subcommand(subparsers: Any) -> None:
     subparser = subparsers.add_parser("create", help="create a venv")
     subparser.add_argument(
@@ -737,6 +764,10 @@ def _add_create_subcommand(subparsers: Any) -> None:
     )
 
 
+def _add_post_init_subcommand(subparsers: Any) -> None:
+    subparsers.add_parser("post_init", help="post-venv initialization")
+
+
 def _add_ensure_subcommand(subparsers: Any) -> None:
     subparser = subparsers.add_parser(
         "ensure", help="Ensure that the specified package is installed."
@@ -790,6 +821,7 @@ def main() -> int:
     )
 
     _add_create_subcommand(subparsers)
+    _add_post_init_subcommand(subparsers)
     _add_ensure_subcommand(subparsers)
 
     args = parser.parse_args()
@@ -800,6 +832,8 @@ def main() -> int:
                 system_site_packages=True,
                 clear=True,
             )
+        if args.command == "post_init":
+            post_venv_setup()
         if args.command == "ensure":
             ensure(
                 dep_specs=args.dep_specs,
-- 
2.40.0