GP-6252: pyghidra_launcher.py fixes

pyghidra_launcher.py can now use an existing pyghidra
installation in an externally managed environment. Upgrading is disabled
in this scenario.

Fixed an issue with getting the package version from an arbitrary
environment

Ghidra/Features/PyGhidra/support/pyghidra_launcher.py

@@ -21,7 +21,6 @@ import subprocess
 import sysconfig
 from pathlib import Path
 from itertools import chain
-from importlib import metadata
 from typing import List, Dict, Tuple, Optional  
 
 def get_application_properties(install_dir: Path) -> Dict[str, str]:
@@ -140,14 +139,10 @@ def version_tuple(v: str) -> Tuple[str, ...]:
         filled.append(point.zfill(8))
     return tuple(filled)
 
-def get_package_version(package: str) -> Optional[str]:
+def get_package_version(python_cmd: List[str], package: str) -> Optional[str]:
-    """
+    source = f'import importlib.metadata as m; print(m.version("{package}"))'
-    Checks for an installed package version.
+    result = subprocess.run(python_cmd + ['-c', source], capture_output=True, text=True)
-    """
+    return result.stdout.strip() if result.returncode == 0 else None
-    try:
-        return metadata.version(package)
-    except metadata.PackageNotFoundError:
-        return None
 
 def get_saved_python_cmd(install_dir: Path, dev: bool) -> List[str]:
     user_settings_dir: Path = get_user_settings_dir(install_dir, dev)
@@ -200,6 +195,10 @@ def upgrade(python_cmd: List[str], pip_args: List[str], dist_dir: Path, current_
     included_version = included_pyghidra.name.split('-')[1]
     current_version = current_pyghidra_version
     if version_tuple(included_version) > version_tuple(current_version):
+        print(f'PyGhidra upgrade available: {current_version} -> {included_version}')
+        if is_externally_managed():
+            print(f'Automated upgrade is not supported in an externally managed environment')
+            return False
         choice: str = input(f'Do you wish to upgrade PyGhidra {current_version} to {included_version} (y/n)? ')
         if choice.lower() in ('y', 'yes'):
             pip_args.append('-U')
@@ -238,11 +237,11 @@ def main() -> None:
     if args.dev:
         # If in dev mode, launch PyGhidra from the source tree using the development virtual environment
         if not venv_dir.is_dir():
-            print('Virtual environment not found!')
+            print('Development virtual environment not found!')
             print('Run "gradle prepPyGhidra" and try again.')
             sys.exit(1)
         python_cmd = get_venv_exe(venv_dir)
-        print(f'Switching to Ghidra virtual environment: {venv_dir}')
+        print(f'Switching to Ghidra development virtual environment: {venv_dir}')
     else:
         # If in release mode, offer to install or upgrade PyGhidra before launching from user-controlled environment
         pip_args: List[str] = ['-m', 'pip', 'install', '--no-index', '-f', str(dist_dir), 'pyghidra']
@@ -251,7 +250,7 @@ def main() -> None:
         # 1) If we are already in a virtual environment, use that
         # 2) If the Ghidra user settings virtual environment exists, use that
         # 3) If we are "externally managed", automatically create/use the Ghidra user settings virtual environment
-        offer_venv: bool = False
+        offer_venv = False
         if in_venv():
             # If we are already in a virtual environment, assume that's where the user wants to be
             python_cmd = get_venv_exe(Path(sys.prefix))
@@ -261,16 +260,21 @@ def main() -> None:
             python_cmd = get_venv_exe(venv_dir)
             print(f'Switching to Ghidra virtual environment: {venv_dir}')
         elif is_externally_managed():
-            print('Externally managed environment detected!')
+            print('Externally managed environment detected')
-            create_ghidra_venv(python_cmd, venv_dir)
+            current_pyghidra_version = get_package_version(python_cmd, 'pyghidra')
-            python_cmd = get_venv_exe(venv_dir)
+            if current_pyghidra_version is None:
-            print(f'Switching to Ghidra virtual environment: {venv_dir}')
+                create_ghidra_venv(python_cmd, venv_dir)
+                python_cmd = get_venv_exe(venv_dir)
+                print(f'Switching to Ghidra virtual environment: {venv_dir}')
+            else:
+                print(f'Using externally managed PyGhidra {current_pyghidra_version}')
+
         else:
             offer_venv = True
 
         # If PyGhidra is not installed in the execution environment, offer to install it
         # If it's already installed, offer to upgrade (if applicable)
-        current_pyghidra_version = get_package_version('pyghidra')
+        current_pyghidra_version = get_package_version(python_cmd, 'pyghidra')
         if current_pyghidra_version is None:
             python_cmd = install(install_dir, python_cmd, pip_args, offer_venv)
             if not python_cmd: