Factor out wingreg usage to simplify.

Querying the registry in each caller made the test mocks quite messy.
Factor that out so we can clean up the implementation and the tests.
This also removes the "is standalone" and "is steam" APIs since those
don't seem useful and they complicated the implementation. The other
cleanup this makes easy is switching to the contextmanager OpenKey,
which fixes the bug I found when writing the test in the previous PR.

dcs/installation.py

@@ -6,95 +6,40 @@
        (could be done either through windows registry, or through filesystem analysis ?)
 """
 
-import sys
 import os
 import re
+import sys
+from pathlib import Path
+from typing import List, Optional
 
-is_windows_os = True
-try:
-    import winreg
-except ImportError:
-    is_windows_os = False
-    print("WARNING : Trying to run pydcs on non Windows machine")
-
+from dcs.winreg import read_current_user_value
 
-# Note: Steam App ID for DCS World is 223750
-STEAM_REGISTRY_KEY_NAME = "Software\\Valve\\Steam\\Apps\\223750"
+STEAM_REGISTRY_KEY_NAME = "Software\\Valve\\Steam"
 DCS_STABLE_REGISTRY_KEY_NAME = "Software\\Eagle Dynamics\\DCS World"
 DCS_BETA_REGISTRY_KEY_NAME = "Software\\Eagle Dynamics\\DCS World OpenBeta"
 
 
-def is_using_dcs_steam_edition():
-    """
-    Check if DCS World : Steam Edition version is installed on this computer
-    :return True if DCS Steam edition is installed,
-            -1 if DCS Steam Edition is registered in Steam apps but not installed,
-            False if never installed in Steam
-    """
-    if not is_windows_os:
-        return False
-    try:
-        dcs_steam_app_key = winreg.OpenKey(winreg.HKEY_CURRENT_USER, STEAM_REGISTRY_KEY_NAME)
-        installed = winreg.QueryValueEx(dcs_steam_app_key, "Installed")
-        winreg.CloseKey(dcs_steam_app_key)
-        if installed[0] == 1:
-            return True
-        else:
-            return False
-    except FileNotFoundError:
-        return False
-
-
-def is_using_dcs_standalone_edition():
-    """
-    Check if DCS World standalone edition is installed on this computer
-    :return True if Standalone is installed, False if it is not
-    """
-    if not is_windows_os:
-        return False
-    try:
-        dcs_path_key = winreg.OpenKey(winreg.HKEY_CURRENT_USER, DCS_STABLE_REGISTRY_KEY_NAME)
-        winreg.CloseKey(dcs_path_key)
-        return True
-    except FileNotFoundError:
-        try:
-            dcs_path_key = winreg.OpenKey(winreg.HKEY_CURRENT_USER, DCS_BETA_REGISTRY_KEY_NAME)
-            winreg.CloseKey(dcs_path_key)
-            return True
-        except FileNotFoundError:
-            return False
-
-
-def get_dcs_install_directory():
+def get_dcs_install_directory() -> str:
     """
     Get the DCS World install directory for this computer
     :return DCS World install directory
     """
-    if is_using_dcs_standalone_edition():
-        try:
-            dcs_path_key = winreg.OpenKey(winreg.HKEY_CURRENT_USER, "Software\\Eagle Dynamics\\DCS World")
-            path = winreg.QueryValueEx(dcs_path_key, "Path")
-            dcs_dir = path[0] + os.path.sep
-            winreg.CloseKey(dcs_path_key)
-            return dcs_dir
-        except FileNotFoundError:
-            try:
-                dcs_path_key = winreg.OpenKey(winreg.HKEY_CURRENT_USER, "Software\\Eagle Dynamics\\DCS World OpenBeta")
-                path = winreg.QueryValueEx(dcs_path_key, "Path")
-                dcs_dir = path[0] + os.path.sep
-                winreg.CloseKey(dcs_path_key)
-                return dcs_dir
-            except FileNotFoundError:
-                print("Couldn't detect DCS World installation folder", file=sys.stderr)
-                return ""
-        except OSError:
-            print("Couldn't detect DCS World installation folder", file=sys.stderr)
-            return ""
-    elif is_using_dcs_steam_edition():
-        return _find_steam_dcs_directory()
-    else:
-        print("Couldn't detect any installed DCS World version", file=sys.stderr)
-        return ""
+    standalone_stable_path = read_current_user_value(
+        DCS_STABLE_REGISTRY_KEY_NAME, "Path", Path
+    )
+    if standalone_stable_path is not None:
+        return f"{standalone_stable_path}{os.path.sep}"
+    standalone_beta_path = read_current_user_value(
+        DCS_BETA_REGISTRY_KEY_NAME, "Path", Path
+    )
+    if standalone_beta_path is not None:
+        return f"{standalone_beta_path}{os.path.sep}"
+    steam_path = _dcs_steam_path()
+    if steam_path is not None:
+        return f"{steam_path}{os.path.sep}"
+
+    print("Couldn't detect any installed DCS World version", file=sys.stderr)
+    return ""
 
 
 def get_dcs_saved_games_directory():
@@ -107,68 +52,50 @@ def get_dcs_saved_games_directory():
     if os.path.exists(dcs_variant):
         # read from the file, append first line to saved games, e.g.: DCS.openbeta
         with open(dcs_variant, "r") as file:
-            suffix = re.sub(r'[^\w\d-]', '', file.read())
+            suffix = re.sub(r"[^\w\d-]", "", file.read())
             saved_games = saved_games + "." + suffix
     return saved_games
 
 
-def _find_steam_directory():
-    """
-    Get the Steam install directory for this computer from registry
-    :return Steam installation path
-    """
-    try:
-        steam_key = winreg.OpenKey(winreg.HKEY_CURRENT_USER, "Software\\Valve\\Steam")
-        path = winreg.QueryValueEx(steam_key, "SteamPath")[0]
-        winreg.CloseKey(steam_key)
-        return path
-    except FileNotFoundError as fnfe:
-        print(fnfe, file=sys.stderr)
-        return ""
-
-
-def _get_steam_library_folders():
+def _steam_library_directories() -> List[Path]:
     """
     Get the installation directory for Steam games
     :return List of Steam library folders where games can be installed
     """
-    try:
-        steam_dir = _find_steam_directory()
-        """
-        For reference here is what the vdf file is supposed to look like :
-
-        "LibraryFolders"
-        {
-            "TimeNextStatsReport"        "1561832478"
-            "ContentStatsID"        "-158337411110787451"
-            "1"        "D:\\Games\\Steam"
-            "2"        "E:\\Steam"
-        }
-        """
-        vdf_file_location = steam_dir + os.path.sep + "steamapps" + os.path.sep + "libraryfolders.vdf"
-        with open(vdf_file_location) as adf_file:
-            paths = [line.split("\"")[3] for line in adf_file.readlines()[1:] if ':\\\\' in line]
-            return paths
-    except Exception as e:
-        print(e)
+    steam_dir = read_current_user_value(STEAM_REGISTRY_KEY_NAME, "SteamPath", Path)
+    if steam_dir is None:
         return []
+    """
+    For reference here is what the vdf file is supposed to look like :
+
+    "LibraryFolders"
+    {
+        "TimeNextStatsReport"        "1561832478"
+        "ContentStatsID"        "-158337411110787451"
+        "1"        "D:\\Games\\Steam"
+        "2"        "E:\\Steam"
+    }
+    """
+    contents = (steam_dir / "steamapps/libraryfolders.vdf").read_text()
+    return [
+        Path(line.split('"')[3])
+        for line in contents.splitlines()[1:]
+        if ":\\\\" in line
+    ]
 
 
-def _find_steam_dcs_directory():
+def _dcs_steam_path() -> Optional[Path]:
     """
     Find the DCS install directory for DCS World Steam Edition
     :return: Install directory as string, empty string if not found
     """
-    for library_folder in _get_steam_library_folders():
-        folder = library_folder + os.path.sep + "steamapps" + os.path.sep + "common" + os.path.sep + "DCSWorld"
-        if os.path.isdir(folder):
-            return folder + os.path.sep
-    return ""
+    for library_folder in _steam_library_directories():
+        folder = library_folder / "steamapps/common/DCSWorld"
+        if folder.is_dir():
+            return folder
+    return None
 
 
 if __name__ == "__main__":
-    print("Using Windows : " + str(is_windows_os))
-    print("Using STEAM Edition : " + str(is_using_dcs_steam_edition()))
-    print("Using Standalone Edition : " + str(is_using_dcs_standalone_edition()))
     print("DCS Installation directory : " + get_dcs_install_directory())
     print("DCS saved games directory : " + get_dcs_saved_games_directory())

dcs/winreg.py

@@ -0,0 +1,25 @@
+"""Wrapper around the stdlib winreg that fails gracefully on non-Windows."""
+import logging
+import sys
+from typing import Any, Callable, Optional, TypeVar
+
+T = TypeVar("T")
+
+
+def read_current_user_value(
+    key: str, value: str, ctor: Callable[[Any], T] = lambda x: x
+) -> Optional[T]:
+    if sys.platform == "win32":
+        import winreg
+
+        try:
+            with winreg.OpenKey(winreg.HKEY_CURRENT_USER, key) as hkey:
+                # QueryValueEx returns a tuple of (value, type ID).
+                return ctor(winreg.QueryValueEx(hkey, value)[0])
+        except FileNotFoundError:
+            return None
+    else:
+        logging.getLogger("pydcs").error(
+            "Cannot read registry keys on non-Windows OS, returning None"
+        )
+        return None