fix: support wrapper flag (for proton, mainly)

[Gustash]

No description provided.

[Copilot]

Pull request overview

This PR adds support for custom wrapper commands (primarily for Proton compatibility) that can wrap game executables during launch. The wrapper flag provides an alternative to Wine for running Windows games on Linux/macOS.

• Adds --wrapper CLI flag to specify custom wrapper commands with arguments (e.g., proton run)
• Implements wrapper command parsing and execution logic that takes precedence over Wine
• Includes four test cases covering basic wrapper usage, argument passing, Wine override behavior, and subcommand support

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
launch/launch.go	Adds Wrapper field to Options struct and implements launchWithWrapper() function to execute games through custom wrapper commands
cmd_launch.go	Adds --wrapper CLI flag with updated help text explaining wrapper usage and its relationship to Wine
launch/launch_test.go	Adds comprehensive test coverage for wrapper functionality including basic usage, argument passing, Wine override, and subcommand scenarios

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[Copilot]

The Windows batch script has a potential issue. After shift, using %* still includes all original arguments. In Windows batch, %* is not updated by shift.

Consider using a different approach for Windows, such as:

@echo off
if "%1" == "run" (
  shift
  %2 %3 %4 %5 %6 %7 %8 %9
) else (
  exit /b 1
)

Or for a more robust solution, use a different testing approach that doesn't rely on this behavior, since this test may not accurately verify the wrapper functionality on Windows.

Suggested change

	wrapperScript = "@echo off\nif \"%1\" == \"run\" (shift & call %*) else exit /b 1"
	wrapperScript = "@echo off\nif \"%1\" == \"run\" (\n shift\n call %2 %3 %4 %5 %6 %7 %8 %9\n) else (\n exit /b 1\n)"

[Copilot]

Using strings.Fields() to parse the wrapper command may not handle quoted arguments correctly. For example, if a user needs to pass a path with spaces like "/path/to/my wrapper" run, strings.Fields() will split on all whitespace, breaking the path.

Consider using a shell-aware parser like shlex or documenting this limitation explicitly. Alternatively, you could use shellquote or similar library to properly parse shell-like command strings with quoted arguments.

[Copilot]

The launchWithWrapper function is missing a doc comment. As an exported or important internal function, it should include documentation explaining:

• What the function does (launches a game through a custom wrapper command)
• The expected format of the wrapper string (command with space-separated arguments)
• Any limitations (e.g., quoted paths with spaces are not supported)

Suggested change

	// launchWithWrapper launches the specified game executable using a custom wrapper command.
	// The wrapper string (opts.Wrapper) should be a space-separated command and arguments,
	// e.g., "proton run" or "customwrapper --flag". The wrapper and its arguments are split
	// using strings.Fields, so quoted paths with spaces are NOT supported.
	// The resulting command is: [wrapper] [wrapper args...] [executablePath] [game args...].

[Copilot]

[nitpick] Consider adding a comment explaining why WINEPREFIX is passed through to wrapper commands. While this makes sense for Proton (which is Wine-based), it may not be relevant for other wrappers. A brief comment would clarify the design decision.

Example: // Pass through Wine-related environment variables if set (useful for Wine-based wrappers like Proton)

Suggested change

	// Pass through Wine-related environment variables if set
	// Pass through Wine-related environment variables if set.
	// This is useful for Wine-based wrappers like Proton, but may not be relevant for other wrappers.

[Copilot]

The wrapper functionality lacks test coverage for error cases. Consider adding tests for:

1. Invalid/non-existent wrapper path
2. Empty wrapper string (to verify the error in line 191 of launch.go)
3. Wrapper command that fails to execute

These edge cases are important to validate proper error handling and messaging.