Delete all packages during deploy if we're about to install

- We check to see if all installed packages are in the cache, so this
  should be safe unless the user messes with their cache or does a
manual install we don't know about
- Just in case, we always ask the user before doing a deploy
- Fixes #82

robotpy_installer/cli_deploy.py

@@ -110,6 +110,13 @@ def __init__(self, parser: argparse.ArgumentParser):
             help="Force installation of packages required by pyproject.toml",
         )
 
+        parser.add_argument(
+            "--no-uninstall",
+            action="store_true",
+            default=False,
+            help="Do not uninstall packages from the RoboRIO",
+        )
+
         parser.add_argument(
             "--large",
             action="store_true",
@@ -135,6 +142,7 @@ def __init__(self, parser: argparse.ArgumentParser):
         )
 
         self._packages_in_cache: typing.Optional[pypackages.Packages] = None
+        self._robot_packages: typing.Optional[pypackages.Packages] = None
 
     @handle_cli_error
     def run(
@@ -150,6 +158,7 @@ def run(
         ignore_image_version: bool,
         no_install: bool,
         no_verify: bool,
+        no_uninstall: bool,
         force_install: bool,
         large: bool,
         robot: typing.Optional[str],
@@ -245,6 +254,7 @@ def run(
                 ignore_image_version,
                 no_install,
                 force_install,
+                no_uninstall,
             )
 
             if not self._do_deploy(ssh, debug, nc, nc_ds, robot_filename, project_path):
@@ -331,6 +341,14 @@ def _get_cached_packages(self, installer: RobotpyInstaller) -> pypackages.Packag
             )
         return self._packages_in_cache
 
+    def _get_robot_packages(
+        self, ssh: sshcontroller.SshController
+    ) -> pypackages.Packages:
+        if self._robot_packages is None:
+            rio_packages = roborio_utils.get_rio_py_packages(ssh)
+            self._robot_packages = pypackages.make_packages(rio_packages)
+        return self._robot_packages
+
     def _ensure_requirements(
         self,
         project: typing.Optional[pyproject.RobotPyProjectToml],
@@ -340,6 +358,7 @@ def _ensure_requirements(
         ignore_image_version: bool,
         no_install: bool,
         force_install: bool,
+        no_uninstall: bool,
     ):
         python_exists = False
         requirements_installed = False
@@ -362,15 +381,15 @@ def _ensure_requirements(
             if no_install:
                 requirements_installed = True
             elif not force_install:
-                pkgdata = roborio_utils.get_rio_py_packages(ssh)
+                pkgdata = self._get_robot_packages(ssh)
 
                 logger.debug("Roborio has these packages installed:")
                 for pkg, version in pkgdata.items():
-                    logger.debug("- %s (%s)", pkg, version)
+                    logger.debug("- %s (%s)", pkg, version[0])
 
                 assert project is not None
                 requirements_installed, desc = project.are_requirements_met(
-                    pypackages.make_packages(pkgdata),
+                    pkgdata,
                     pypackages.roborio_env(),
                     pypackages.make_cache_extra_resolver(
                         self._get_cached_packages(installer)
@@ -389,6 +408,28 @@ def _ensure_requirements(
 
         if force_install:
             requirements_installed = False
+        elif python_exists and not requirements_installed:
+            # if this is a pre-existing robotpy install, warn the user
+            # before changing their rio
+            print(
+                "\n"
+                "Deployer has detected that the packages installed on your RoboRIO do not match\n"
+                "the requirements in pyproject.toml. The installer will now:\n"
+            )
+            if not no_uninstall:
+                prompt = "Continue with uninstall + install?"
+                print("* Uninstall ALL Python packages from the RoboRIO")
+            else:
+                prompt = "Continue with install?"
+
+            print(
+                "* Install required packages on the RoboRIO\n"
+                "\n"
+                "If you do not wish to do this, specify --no-install as a deploy argument, or answer 'n'.\n"
+            )
+
+            if not yesno(prompt):
+                requirements_installed = True
 
         if cpp_java_exists or not python_exists or not requirements_installed:
             if no_install and not python_exists:
@@ -424,14 +465,8 @@ def _ensure_requirements(
                         ) from e
 
                 if not requirements_installed:
-                    # pip is greedy
-                    installer.ensure_more_memory()
-
-                    logger.info("Installing project requirements on RoboRIO:")
                     assert project is not None
                     packages = project.get_install_list()
-                    for package in packages:
-                        logger.info("- %s", package)
 
                     # Check if everything is in the cache before doing the install
                     cached = self._get_cached_packages(installer)
@@ -450,6 +485,25 @@ def _ensure_requirements(
                         ]
                         raise Error("\n".join(errmsg))
 
+                    if not no_uninstall:
+                        logger.info(
+                            "Clearing existing packages on RoboRIO before install (specify --no-uninstall to not do this)"
+                        )
+                        # The user may have deleted something from the project
+                        # requirements so the only way to ensure the exact
+                        # environment is to first clear the environment.
+                        # - can't do a partial uninstall without completely
+                        #   resolving everything
+
+                        rio_packages = self._get_robot_packages(installer.ssh)
+                        installer.pip_uninstall(
+                            [p for p in rio_packages.keys() if p != "pip"]
+                        )
+
+                    logger.info("Installing project requirements on RoboRIO:")
+                    for package in packages:
+                        logger.info("- %s", package)
+
                     try:
                         installer.pip_install(False, False, False, False, [], packages)
                     except PipInstallError as e: