Add provides=() validation for PythonTarget

RB_ID=https://rbcommons.com/s/twitter/r/93/

(sapling split of 9c817e9a999b02a819a200d90ed66aad4018d336)

src/python/twitter/pants/targets/python_artifact.py

@@ -16,8 +16,6 @@
 
 from twitter.pants.base.build_manual import manual
 
-from .python_target import PythonTarget
-
 
 @manual.builddict(tags=["python"])
 class PythonArtifact(object):

src/python/twitter/pants/targets/python_target.py

@@ -24,6 +24,7 @@
 from .with_dependencies import TargetWithDependencies
 from .with_sources import TargetWithSources
 
+from twitter.pants.targets.python_artifact import PythonArtifact
 
 class PythonTarget(TargetWithDependencies, TargetWithSources):
   """Base class for all Python targets."""
@@ -41,7 +42,13 @@ def __init__(self,
 
     self.add_labels('python')
     self.resources = self._resolve_paths(resources) if resources else OrderedSet()
+
+    if provides and not isinstance(provides, PythonArtifact):
+      raise TargetDefinitionException(self,
+        "Target must provide a valid pants setup_py object. Received a '%s' object instead." %
+          provides.__class__.__name__)
     self.provides = provides
+
     self.compatibility = compatibility or ['']
     for req in self.compatibility:
       try:

tests/python/twitter/pants/targets/BUILD

@@ -24,6 +24,7 @@ python_test_suite(
     pants(':jar_library'),
     pants(':pants_target'),
     pants(':python_binary'),
+    pants(':python_target'),
     pants(':target'),
     pants(':util'),
   ]
@@ -111,6 +112,17 @@ python_tests(
   ]
 )
 
+python_tests(
+  name = 'python_target',
+  sources = ['test_python_target.py'],
+  dependencies = [
+    pants('tests/python/twitter/pants:base-test'),
+    pants('src/python/twitter/pants/base:parse_context'),
+    pants('src/python/twitter/pants/base:target'),
+    pants('src/python/twitter/pants/targets:python'),
+  ]
+)
+
 python_tests(
   name = 'util',
   sources = ['test_util.py'],

tests/python/twitter/pants/targets/test_python_target.py

@@ -0,0 +1,64 @@
+# ==================================================================================================
+# Copyright 2014 Twitter, Inc.
+# --------------------------------------------------------------------------------------------------
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this work except in compliance with the License.
+# You may obtain a copy of the License in the LICENSE file, or at:
+#
+#  http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# ==================================================================================================
+
+import os
+import unittest
+
+from textwrap import dedent
+
+from twitter.pants.base.parse_context import ParseContext
+from twitter.pants.base.target import TargetDefinitionException
+from twitter.pants.base_build_root_test import BaseBuildRootTest
+from twitter.pants.targets.artifact import Artifact
+from twitter.pants.targets.python_target import PythonTarget
+from twitter.pants.targets.python_artifact import PythonArtifact
+from twitter.pants.targets.repository import Repository
+from twitter.pants.targets.sources import SourceRoot
+
+
+class PythonTargetTest(BaseBuildRootTest):
+
+  @classmethod
+  def setUpClass(self):
+    super(PythonTargetTest, self).setUpClass()
+    SourceRoot.register(os.path.realpath(os.path.join(self.build_root, 'test_python_target')),
+                        PythonTarget)
+
+    self.create_target('test_thrift_replacement', dedent('''
+      python_thrift_library(name='one',
+        sources=['thrift/keyword.thrift'],
+        dependencies=None
+      )
+    '''))
+
+  def test_validation(self):
+    with ParseContext.temp('PythonTargetTest/test_validation'):
+
+      # Adding a JVM Artifact as a provides on a PythonTarget doesn't make a lot of sense. This test
+      # sets up that very scenario, and verifies that pants throws a TargetDefinitionException.
+      self.assertRaises(TargetDefinitionException, PythonTarget, name="one", sources=[],
+        provides=Artifact(org='com.twitter', name='one-jar',
+        repo=Repository(name='internal', url=None, push_db=None, exclusives=None)))
+
+      name = "test-with-PythonArtifact"
+      pa = PythonArtifact(name='foo', version='1.0', description='foo')
+
+      # This test verifies that adding a 'setup_py' provides to a PythonTarget is okay.
+      self.assertEquals(PythonTarget(name=name, provides=pa, sources=[]).name, name)
+      name = "test-with-none"
+
+      # This test verifies that having no provides is okay.
+      self.assertEquals(PythonTarget(name=name, provides=None, sources=[]).name, name)