Default run.shell to /bin/sh

`/bin/bash` is not availabe on some popular distributions, for example
NixOS. Defaulting to the more conservative `/bin/sh` improves
portability.

Author: tobim

invoke/config.py

@@ -440,16 +440,16 @@ def global_defaults() -> Dict[str, Any]:
 
         .. versionadded:: 1.0
         """
-        # On Windows, which won't have /bin/bash, check for a set COMSPEC env
+        # On Windows, which won't have /bin/sh, check for a set COMSPEC env
         # var (https://en.wikipedia.org/wiki/COMSPEC) or fallback to an
         # unqualified cmd.exe otherwise.
         if WINDOWS:
             shell = os.environ.get("COMSPEC", "cmd.exe")
-        # Else, assume Unix, most distros of which have /bin/bash available.
-        # TODO: consider an automatic fallback to /bin/sh for systems lacking
-        # /bin/bash; however users may configure run.shell quite easily, so...
+        # Else, assume a POSIX compatible Unix, where /bin/sh is mandated by
+        # the standard. Users on more exotic platforms are expected to configure
+        # run.shell manually.
         else:
-            shell = "/bin/bash"
+            shell = "/bin/sh"
 
         return {
             # TODO: we document 'debug' but it's not truly implemented outside

invoke/runners.py

@@ -335,7 +335,7 @@ def run(self, command: str, **kwargs: Any) -> Optional["Result"]:
             Default: ``False``.
 
         :param str shell:
-            Which shell binary to use. Default: ``/bin/bash`` (on Unix;
+            Which shell binary to use. Default: ``/bin/sh`` (on Unix;
             ``COMSPEC`` or ``cmd.exe`` on Windows.)
 
         :param timeout:

tests/config.py

@@ -107,7 +107,7 @@ def basic_settings(self):
                     "out_stream": None,
                     "pty": False,
                     "replace_env": False,
-                    "shell": "/bin/bash",
+                    "shell": "/bin/sh",
                     "warn": False,
                     "watchers": [],
                 },

tests/runners.py

@@ -81,7 +81,7 @@ def _expect_platform_shell(shell):
     if WINDOWS:
         assert shell.endswith("cmd.exe")
     else:
-        assert shell == "/bin/bash"
+        assert shell == "/bin/sh"
 
 
 def _make_tcattrs(cc_is_ints=True, echo=False):
@@ -218,10 +218,10 @@ def kwarg_beats_config(self):
             assert runner.run(_, pty=True).pty is True
 
     class shell:
-        def defaults_to_bash_or_cmdexe_when_pty_True(self):
+        def defaults_to_sh_or_cmdexe_when_pty_True(self):
             _expect_platform_shell(self._run(_, pty=True).shell)
 
-        def defaults_to_bash_or_cmdexe_when_pty_False(self):
+        def defaults_to_sh_or_cmdexe_when_pty_False(self):
             _expect_platform_shell(self._run(_, pty=False).shell)
 
         def may_be_overridden(self):
@@ -1651,14 +1651,14 @@ def overridden_fallback_affects_result_pty_value(self):
 
     class shell:
         @mock_pty(insert_os=True)
-        def defaults_to_bash_or_cmdexe_when_pty_True(self, mock_os):
+        def defaults_to_sh_or_cmdexe_when_pty_True(self, mock_os):
             # NOTE: yea, windows can't run pty is true, but this is really
             # testing config behavior, so...meh
             self._run(_, pty=True)
             _expect_platform_shell(mock_os.execve.call_args_list[0][0][0])
 
         @mock_subprocess(insert_Popen=True)
-        def defaults_to_bash_or_cmdexe_when_pty_False(self, mock_Popen):
+        def defaults_to_sh_or_cmdexe_when_pty_False(self, mock_Popen):
             self._run(_, pty=False)
             _expect_platform_shell(
                 mock_Popen.call_args_list[0][1]["executable"]