Ignore empty compatibilitytool.vdf

Ignore empty compatibilitytool.vdf file when looking for custom Proton
installations. It is unknown what causes these empty manifests to be
created in the first place. In any case, the Steam client ignores the
installations, so do the same here.

Fixes #241

CHANGELOG.md

@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
+## [Unreleased]
+### Fixed
+ - Fix Protontricks crash when custom Proton has an empty `compatibilitytool.vdf` manifest
+
 ## [1.11.0] - 2023-12-30
 ### Added
  - Show app icons for custom shortcuts in the app selector

src/protontricks/steam.py

@@ -1007,6 +1007,14 @@ def get_custom_compat_tool_installations_in_dir(compat_tool_dir):
             )
             continue
 
+        if not vdf_data:
+            logger.warning(
+                "Compatibility tool declaration at %s is empty. You may need "
+                "to reinstall the application.",
+                vdf_path
+            )
+            continue
+
         # Traverse to 'compatibilitytools/compat_tools' in a case-insensitive
         # way. This is done because we can't turn all keys recursively to
         # lowercase from the get-go; the app name is stored as a key.

tests/test_steam.py

@@ -741,16 +741,24 @@ def test_get_steam_apps_custom_proton_empty_toolmanifest(
             "Tool manifest for Custom Proton is empty"
         )
 
+    @pytest.mark.parametrize(
+        "content,error",
+        [
+            (b"corrupted", " is corrupted. "),
+            (b"", " is empty. ")  # Regression test for #241
+        ]
+    )
     def test_get_steam_apps_custom_proton_corrupted_compatibilitytool(
-            self, custom_proton_factory, steam_dir, steam_root, caplog):
+            self, custom_proton_factory, steam_dir, steam_root, caplog,
+            content, error):
         """
         Create a custom Proton installation with a corrupted
         compatibilitytool.vdf and ensure a warning is printed and the app
         is ignored
         """
         custom_proton = custom_proton_factory(name="Custom Proton")
-        (custom_proton.install_path / "compatibilitytool.vdf").write_text(
-            "corrupted"
+        (custom_proton.install_path / "compatibilitytool.vdf").write_bytes(
+            content
         )
 
         steam_apps = get_steam_apps(
@@ -774,9 +782,7 @@ def test_get_steam_apps_custom_proton_corrupted_compatibilitytool(
             if record.levelname == "WARNING"
         )
 
-        assert record.getMessage().startswith(
-            "Compatibility tool declaration at"
-        )
+        assert error in record.getMessage()
 
     def test_get_steam_apps_in_library_folder(
             self, default_proton, steam_library_factory, steam_app_factory,