Detect the program name when python -m was executed

fire/core.py

@@ -109,7 +109,8 @@ def Fire(component=None, command=None, name=None, serialize=None):
         code 2. When used with the help or trace flags, Fire will raise a
         FireExit with code 0 if successful.
   """
-  name = name or os.path.basename(sys.argv[0])
+
+  name = _GetProgName(name)
 
   # Get args as a list.
   if isinstance(command, six.string_types):
@@ -281,6 +282,45 @@ def _PrintResult(component_trace, verbose=False, serialize=None):
     Display(output, out=sys.stdout)
 
 
+def _GetProgName(name, main=None):
+  """Determines the program name.
+
+  This function returns the program name that should be
+  displayed.
+
+  If ``python -m`` was used to execute a module, ``python -m name`` will be
+  returned, instead of ``__main__.py``.
+
+  Args:
+    name: Optional. The name of the command as entered at the command line.
+    main: Optional. This should only be passed during testing.
+  Returns:
+    The program name determined by this function.
+  """
+  if name:
+    return name
+
+  name_from_arg = os.path.basename(sys.argv[0])
+
+  if main:
+    py_module = main
+  else:
+    py_module = sys.modules['__main__'].__package__ # pylint: disable=no-member
+
+  if py_module is not None:
+    if name_from_arg == '__main__.py':
+      return '{executable} -m {module}'.format(
+        executable=sys.executable, module=py_module)
+    else:
+        # For example: python -m sample.cli
+      name = os.path.splitext(name_from_arg)[0]
+      py_module = '{module}.{name}'.format(module=py_module, name=name)
+      return '{executable} -m {module}'.format(
+          executable=sys.executable, module=py_module.lstrip('.'))
+  else:
+    return name_from_arg
+
+
 def _DisplayError(component_trace):
   """Prints the Fire trace and the error to stdout."""
   result = component_trace.GetResult()

fire/fire_test.py

@@ -24,6 +24,7 @@
 import fire
 from fire import test_components as tc
 from fire import testutils
+from fire.core import _GetProgName
 
 import mock
 import six
@@ -63,6 +64,17 @@ def testFireDefaultName(self):
                                     stderr=None):
         fire.Fire(tc.Empty)
 
+  def testFireProgName(self):
+    # ``sample/__main__.py` would be argv[0] when ``python -m sample`` was
+    # executed.
+    with mock.patch.object(sys, 'argv', ['sample/__main__.py']):
+      self.assertEqual(_GetProgName('', main='sample'),
+      '{executable} -m sample'.format(executable=sys.executable))
+
+    with mock.patch.object(sys, 'argv', ['sample/cli.py']):
+      self.assertEqual(_GetProgName('', main='sample'),
+      '{executable} -m sample.cli'.format(executable=sys.executable))
+
   def testFireNoArgs(self):
     self.assertEqual(fire.Fire(tc.MixedDefaults, command=['ten']), 10)