env activate: fallback to POSIX compatible builtin (#10696)

Author: mymedia2

src/poetry/console/commands/env/activate.py

@@ -51,8 +51,10 @@ def _get_activate_command(self, env: Env, shell: str) -> str:
             command, filename = ".", "activate.ps1"
         elif shell == "cmd":
             command, filename = ".", "activate.bat"
-        else:
+        elif shell in ["bash", "mksh", "zsh"]:
             command, filename = "source", "activate"
+        else:
+            command, filename = ".", "activate"
 
         if (activation_script := env.bin_dir / filename).exists():
             if WINDOWS:

tests/console/commands/env/test_activate.py

@@ -24,6 +24,7 @@ def tester(command_tester_factory: CommandTesterFactory) -> CommandTester:
 @pytest.mark.parametrize(
     "shell, command, ext",
     (
+        ("dash", ".", ""),
         ("bash", "source", ""),
         ("zsh", "source", ""),
         ("fish", "source", ".fish"),