feat(install): add support for pre-injected packages (#900)

CHANGELOG.md

@@ -12,6 +12,7 @@
 - Move `pipx` paths to ensure compatibility with the platform-specific user directories
 - [docs] Add more examples for `pipx run`
 - [docs] Add subsection to make README easier to read
+- Add `pipx install --preinstall` to support preinstalling build requirements
 
 ## 1.2.0
 

src/pipx/commands/install.py

@@ -20,6 +20,7 @@ def install(
     *,
     force: bool,
     include_dependencies: bool,
+    preinstall_packages: Optional[List[str]],
     suffix: str = "",
 ) -> ExitCode:
     """Returns pipx exit code."""
@@ -58,6 +59,11 @@ def install(
 
     try:
         venv.create_venv(venv_args, pip_args)
+        for dep in preinstall_packages or []:
+            dep_name = package_name_from_spec(
+                dep, python, pip_args=pip_args, verbose=verbose
+            )
+            venv.upgrade_package_no_metadata(dep_name, [])
         venv.install_package(
             package_name=package_name,
             package_or_url=package_spec,

src/pipx/commands/reinstall.py

@@ -70,6 +70,7 @@ def reinstall(
         verbose,
         force=True,
         include_dependencies=venv.pipx_metadata.main_package.include_dependencies,
+        preinstall_packages=[],
         suffix=venv.pipx_metadata.main_package.suffix,
     )
 

src/pipx/main.py

@@ -213,6 +213,7 @@ def run_pipx_command(args: argparse.Namespace) -> ExitCode:  # noqa: C901
             verbose,
             force=args.force,
             include_dependencies=args.include_deps,
+            preinstall_packages=args.preinstall,
             suffix=args.suffix,
         )
     elif args.command == "inject":
@@ -350,6 +351,14 @@ def _add_install(subparsers: argparse._SubParsersAction) -> None:
             f"Requires Python {MINIMUM_PYTHON_VERSION} or above."
         ),
     )
+    p.add_argument(
+        "--preinstall",
+        action="append",
+        help=(
+            "Optional packages to be installed into the Virtual Environment before "
+            "installing the main package."
+        ),
+    )
     add_pip_venv_args(p)
 
 

src/pipx/venv.py

@@ -201,7 +201,7 @@ def upgrade_packaging_libraries(self, pip_args: List[str]) -> None:
         else:
             # TODO: setuptools and wheel? Original code didn't bother
             # but shared libs code does.
-            self._upgrade_package_no_metadata("pip", pip_args)
+            self.upgrade_package_no_metadata("pip", pip_args)
 
     def uninstall_package(self, package: str, was_injected: bool = False):
         try:
@@ -421,7 +421,7 @@ def has_app(self, app: str, filename: str) -> bool:
             return True
         return (self.bin_path / filename).is_file()
 
-    def _upgrade_package_no_metadata(
+    def upgrade_package_no_metadata(
         self, package_name: str, pip_args: List[str]
     ) -> None:
         with animate(