Clean up executable injection

python/binharness/types/injection.py

@@ -74,17 +74,26 @@ class ExecutableInjection(Injection):
     environment.
     """
 
-    executable: Path
+    _executable: Path | None
 
     def __init__(
         self: ExecutableInjection,
-        executable: Path,
         host_path: Path,
         env_path: Path | None = None,
+        executable: Path | None = None,
     ) -> None:
         """Create an ExecutableInjection."""
         super().__init__(host_path, env_path)
-        self.executable = executable
+        self._executable = executable
+
+    @property
+    def executable(self: ExecutableInjection) -> Path:
+        """Return the executable path."""
+        if self.host_path is not None:
+            if self._executable is None:
+                return self.host_path
+            return self.host_path / self._executable
+        raise InjectionNotInstalledError
 
     def run(
         self: ExecutableInjection,
@@ -96,7 +105,7 @@ def run(
         if self._environment is None or self.env_path is None:
             raise InjectionNotInstalledError
         return self._environment.run_command(
-            [self.env_path, *args],
+            [self.executable, *args],
             env=env,
             cwd=cwd,
         )