Exit with a status code if Fire encounters an error

Copybara generated commit for Python Fire.


PiperOrigin-RevId: 150818132
Change-Id: Ice3b2977fe0e89fa6472f0831e7475f3318943cf
Reviewed-on: https://team-review.git.corp.google.com/65029
Reviewed-by: David Bieber <dbieber@google.com>

Author: dbieber

fire/__init__.py

@@ -12,12 +12,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""Python Fire module for third_party."""
+"""The Python Fire module."""
 
 from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 
 from fire.core import Fire
+from fire.core import FireExit
 
-__all__ = ['Fire']
+__all__ = ['Fire', 'FireExit']

fire/core.py

@@ -92,9 +92,9 @@ def Fire(component=None, command=None, name=None):
     it's a class). When all arguments are consumed and there's no function left
     to call or class left to instantiate, the resulting current component is
     the final result.
-    If a Fire error is encountered, the Fire Trace is displayed to stdout and
-    None is returned.
     If the trace command line argument is supplied, the FireTrace is returned.
+  Raises:
+    FireExit: If a FireError is countered.
   """
   # Get args as a list.
   if command is None:
@@ -127,7 +127,7 @@ def Fire(component=None, command=None, name=None):
     result = component_trace.GetResult()
     print(
         helputils.HelpString(result, component_trace, component_trace.verbose))
-    return None
+    raise FireExit(1, component_trace)
   elif component_trace.show_trace and component_trace.show_help:
     print('Fire trace:\n{trace}\n'.format(trace=component_trace))
     result = component_trace.GetResult()
@@ -161,6 +161,20 @@ class FireError(Exception):
   """
 
 
+class FireExit(SystemExit):
+  """An exception raised by Fire to the client in the case of a FireError.
+
+  Contains the trace of the Fire program.
+
+  If not caught, then a FireExit will cause the program to exit with a non-zero
+  status code.
+  """
+
+  def __init__(self, status, data):
+    super(FireExit, self).__init__(status)
+    self.trace = data
+
+
 def _PrintResult(component_trace, verbose=False):
   """Prints the result of the Fire call to stdout in a human readable way."""
   # TODO: Design human readable deserializable serialization method
@@ -558,8 +572,8 @@ def _ParseFn(args):
 
     # Note: _ParseArgs modifies kwargs.
     parsed_args, kwargs, remaining_args, capacity = _ParseArgs(
-        fn_spec.args, fn_spec.defaults, num_required_args, kwargs, remaining_args,
-        metadata)
+        fn_spec.args, fn_spec.defaults, num_required_args, kwargs,
+        remaining_args, metadata)
 
     if fn_spec.varargs or fn_spec.varkw:
       # If we're allowed *varargs or **kwargs, there's always capacity.

fire/core_test.py

@@ -67,7 +67,8 @@ def testInteractiveModeVariablesWithName(self, mock_embed):
 
   def testImproperUseOfHelp(self):
     # This should produce a warning and return None.
-    self.assertIsNone(core.Fire(tc.TypedProperties, 'alpha --help'))
+    with self.assertRaises(core.FireExit):
+      core.Fire(tc.TypedProperties, 'alpha --help')
 
   def testErrorRaising(self):
     # Errors in user code should not be caught; they should surface as normal.

fire/fire_test.py

@@ -41,10 +41,13 @@ def testFireNoArgs(self):
     self.assertEqual(fire.Fire(tc.MixedDefaults, 'ten'), 10)
 
   def testFireExceptions(self):
-    # Exceptions of Fire are printed to stderr and None is returned.
-    self.assertIsNone(fire.Fire(tc.Empty, 'nomethod'))  # Member doesn't exist.
-    self.assertIsNone(fire.Fire(tc.NoDefaults, 'double'))  # Missing argument.
-    self.assertIsNone(fire.Fire(tc.TypedProperties, 'delta x'))  # Missing key.
+    # Exceptions of Fire are printed to stderr and a FireExit is raised.
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.Empty, 'nomethod')  # Member doesn't exist.
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.NoDefaults, 'double')  # Missing argument.
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.TypedProperties, 'delta x')  # Missing key.
 
     # Exceptions of the target components are still raised.
     with self.assertRaises(ZeroDivisionError):
@@ -89,11 +92,13 @@ def testFirePartialNamedArgs(self):
         fire.Fire(tc.MixedDefaults, 'identity --beta 1 --alpha 2'), (2, 1))
 
   def testFirePartialNamedArgsOneMissing(self):
-    # By default, errors are written to standard out and None is returned.
-    self.assertIsNone(  # Identity needs an arg.
-        fire.Fire(tc.MixedDefaults, 'identity'))
-    self.assertIsNone(  # Identity needs a value for alpha.
-        fire.Fire(tc.MixedDefaults, 'identity --beta 2'))
+    # Errors are written to standard out and a FireExit is raised.
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.MixedDefaults, 'identity')  # Identity needs an arg.
+
+    with self.assertRaises(fire.FireExit):
+      # Identity needs a value for alpha.
+      fire.Fire(tc.MixedDefaults, 'identity --beta 2')
 
     self.assertEqual(fire.Fire(tc.MixedDefaults, 'identity 1'), (1, '0'))
     self.assertEqual(
@@ -103,9 +108,11 @@ def testFireAnnotatedArgs(self):
     self.assertEqual(fire.Fire(tc.Annotations, 'double 5'), 10)
     self.assertEqual(fire.Fire(tc.Annotations, 'triple 5'), 15)
 
-  @unittest.skipIf(six.PY2, 'Keyword-only arguments not supported in Python 2')
+  @unittest.skipIf(six.PY2, 'Keyword-only arguments not in Python 2.')
   def testFireKeywordOnlyArgs(self):
-    self.assertIsNone(fire.Fire(tc.py3.KeywordOnly, 'double 5'))
+    with self.assertRaises(fire.FireExit):
+      # Keyword arguments must be passed with flag syntax.
+      fire.Fire(tc.py3.KeywordOnly, 'double 5')
 
     self.assertEqual(fire.Fire(tc.py3.KeywordOnly, 'double --count 5'), 10)
     self.assertEqual(fire.Fire(tc.py3.KeywordOnly, 'triple --count 5'), 15)
@@ -252,17 +259,19 @@ def fn1(thing, nothing):
     self.assertEqual(fire.Fire(fn1, '--thing --nothing'), (True, True))
     self.assertEqual(fire.Fire(fn1, '--thing --nonothing'), (True, False))
 
-    # In the next example nothing=False (since rightmost setting of a flag gets
-    # precedence), but it errors because thing has no value.
-    self.assertEqual(fire.Fire(fn1, '--nothing --nonothing'), None)
+    with self.assertRaises(fire.FireExit):
+      # In this case nothing=False (since rightmost setting of a flag gets
+      # precedence), but it errors because thing has no value.
+      fire.Fire(fn1, '--nothing --nonothing')
 
     # In these examples, --nothing sets thing=False:
     def fn2(thing, **kwargs):
       return thing, kwargs
     self.assertEqual(fire.Fire(fn2, '--thing'), (True, {}))
     self.assertEqual(fire.Fire(fn2, '--nothing'), (False, {}))
-    # In the next one, nothing=True, but it errors because thing has no value.
-    self.assertEqual(fire.Fire(fn2, '--nothing=True'), None)
+    with self.assertRaises(fire.FireExit):
+      # In this case, nothing=True, but it errors because thing has no value.
+      fire.Fire(fn2, '--nothing=True')
     self.assertEqual(fire.Fire(fn2, '--nothing --nothing=True'),
                      (False, {'nothing': True}))
 
@@ -323,7 +332,8 @@ def testBasicSeparator(self):
         ('-', '_'))
 
     # The separator triggers a function call, but there aren't enough arguments.
-    self.assertEqual(fire.Fire(tc.MixedDefaults, 'identity - _ +'), None)
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.MixedDefaults, 'identity - _ +')
 
   def testNonComparable(self):
     """Fire should work with classes that disallow comparisons."""
@@ -367,24 +377,34 @@ def testFloatForExpectedInt(self):
   def testClassInstantiation(self):
     self.assertIsInstance(fire.Fire(tc.InstanceVars, '--arg1=a1 --arg2=a2'),
                           tc.InstanceVars)
-    # Cannot instantiate a class with positional args by default.
-    self.assertIsNone(fire.Fire(tc.InstanceVars, 'a1 a2'))
+    with self.assertRaises(fire.FireExit):
+      # Cannot instantiate a class with positional args.
+      fire.Fire(tc.InstanceVars, 'a1 a2')
 
   def testTraceErrors(self):
     # Class needs additional value but runs out of args.
-    self.assertIsNone(fire.Fire(tc.InstanceVars, 'a1'))
-    self.assertIsNone(fire.Fire(tc.InstanceVars, '--arg1=a1'))
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.InstanceVars, 'a1')
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.InstanceVars, '--arg1=a1')
+
     # Routine needs additional value but runs out of args.
-    self.assertIsNone(fire.Fire(tc.InstanceVars, 'a1 a2 - run b1'))
-    self.assertIsNone(
-        fire.Fire(tc.InstanceVars, '--arg1=a1 --arg2=a2 - run b1'))
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.InstanceVars, 'a1 a2 - run b1')
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.InstanceVars, '--arg1=a1 --arg2=a2 - run b1')
+
     # Extra args cannot be consumed.
-    self.assertIsNone(fire.Fire(tc.InstanceVars, 'a1 a2 - run b1 b2 b3'))
-    self.assertIsNone(
-        fire.Fire(tc.InstanceVars, '--arg1=a1 --arg2=a2 - run b1 b2 b3'))
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.InstanceVars, 'a1 a2 - run b1 b2 b3')
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.InstanceVars, '--arg1=a1 --arg2=a2 - run b1 b2 b3')
+
     # Cannot find member to access.
-    self.assertIsNone(fire.Fire(tc.InstanceVars, 'a1 a2 - jog'))
-    self.assertIsNone(fire.Fire(tc.InstanceVars, '--arg1=a1 --arg2=a2 - jog'))
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.InstanceVars, 'a1 a2 - jog')
+    with self.assertRaises(fire.FireExit):
+      fire.Fire(tc.InstanceVars, '--arg1=a1 --arg2=a2 - jog')
 
 
 if __name__ == '__main__':