Add flake8 and isort lint checks (#46)

.isort.cfg

@@ -0,0 +1,2 @@
+[settings]
+from_first=True

opentelemetry-api/src/opentelemetry/loader.py

@@ -61,7 +61,7 @@ def my_factory_for_t(api_type: typing.Type[T]) -> typing.Optional[T]:
 means that the Python interpreter was invoked with the ``-E`` or ``-I`` flag).
 """
 
-from typing import Type, TypeVar, Optional, Callable
+from typing import Callable, Optional, Type, TypeVar
 import importlib
 import os
 import sys
@@ -78,10 +78,11 @@ def my_factory_for_t(api_type: typing.Type[T]) -> typing.Optional[T]:
 # annotate setters, were it not for https://github.com/python/mypy/issues/7092
 # Once that bug is resolved, setters should use this instead of duplicating the
 # code.
-#ImplementationFactory = Callable[[Type[_T]], Optional[_T]]
+# ImplementationFactory = Callable[[Type[_T]], Optional[_T]]
 
 _DEFAULT_FACTORY: Optional[_UntrustedImplFactory[object]] = None
 
+
 def _try_load_impl_from_modname(
         implementation_modname: str, api_type: Type[_T]) -> Optional[_T]:
     try:
@@ -92,6 +93,7 @@ def _try_load_impl_from_modname(
 
     return _try_load_impl_from_mod(implementation_mod, api_type)
 
+
 def _try_load_impl_from_mod(
         implementation_mod: object, api_type: Type[_T]) -> Optional[_T]:
 
@@ -109,6 +111,7 @@ def _try_load_impl_from_mod(
 
     return _try_load_impl_from_callback(implementation_fn, api_type)
 
+
 def _try_load_impl_from_callback(
         implementation_fn: _UntrustedImplFactory[_T],
         api_type: Type[_T]
@@ -149,11 +152,10 @@ def _try_load_configured_impl(
         return _try_load_impl_from_callback(_DEFAULT_FACTORY, api_type)
     return None
 
+
 # Public to other opentelemetry-api modules
-def _load_impl(
-        api_type: Type[_T],
-        factory: Optional[Callable[[Type[_T]], Optional[_T]]]
-    ) -> _T:
+def _load_impl(api_type: Type[_T],
+               factory: Optional[Callable[[Type[_T]], Optional[_T]]]) -> _T:
     """Tries to load a configured implementation, if unsuccessful, returns a
     fast no-op implemenation that is always available.
     """
@@ -163,9 +165,10 @@ def _load_impl(
         return api_type()
     return result
 
+
 def set_preferred_default_implementation(
         implementation_factory: _UntrustedImplFactory[_T]) -> None:
     """Sets a factory function that may be called for any implementation
     object. See the :ref:`module docs <loader-factory>` for more details."""
-    global _DEFAULT_FACTORY #pylint:disable=global-statement
+    global _DEFAULT_FACTORY  # pylint:disable=global-statement
     _DEFAULT_FACTORY = implementation_factory

opentelemetry-api/src/opentelemetry/trace/__init__.py

@@ -64,6 +64,7 @@
 
 from contextlib import contextmanager
 import typing
+
 from opentelemetry import loader
 
 

opentelemetry-api/tests/test_loader.py

@@ -13,25 +13,28 @@
 # limitations under the License.
 
 from importlib import reload
+import os
 import sys
 import unittest
-import os
 
 from opentelemetry import loader
 from opentelemetry import trace
 
 DUMMY_TRACER = None
 
+
 class DummyTracer(trace.Tracer):
     pass
 
+
 def get_opentelemetry_implementation(type_):
-    global DUMMY_TRACER #pylint:disable=global-statement
+    global DUMMY_TRACER  # pylint:disable=global-statement
     assert type_ is trace.Tracer
     DUMMY_TRACER = DummyTracer()
     return DUMMY_TRACER
 
-#pylint:disable=redefined-outer-name,protected-access,unidiomatic-typecheck
+
+# pylint:disable=redefined-outer-name,protected-access,unidiomatic-typecheck
 
 class TestLoader(unittest.TestCase):
 
@@ -43,7 +46,6 @@ def setUp(self):
         # class after reloading `trace`.
         reload(sys.modules[__name__])
 
-
     def test_get_default(self):
         tracer = trace.tracer()
         self.assertIs(type(tracer), trace.Tracer)
@@ -60,8 +62,10 @@ def do_test_preferred_impl(self, setter):
         setter(get_opentelemetry_implementation)
         tracer = trace.tracer()
         self.assertIs(tracer, DUMMY_TRACER)
+
     def test_preferred_impl_with_tracer(self):
         self.do_test_preferred_impl(trace.set_preferred_tracer_implementation)
+
     def test_preferred_impl_with_default(self):
         self.do_test_preferred_impl(
             loader.set_preferred_default_implementation)
@@ -75,7 +79,7 @@ def test_try_set_again(self):
         self.assertIn('already loaded', str(einfo.exception))
 
     def do_test_get_envvar(self, envvar_suffix):
-        global DUMMY_TRACER #pylint:disable=global-statement
+        global DUMMY_TRACER  # pylint:disable=global-statement
 
         # Test is not runnable with this!
         self.assertFalse(sys.flags.ignore_environment)
@@ -89,7 +93,9 @@ def do_test_get_envvar(self, envvar_suffix):
             DUMMY_TRACER = None
             del os.environ[envname]
         self.assertIs(type(tracer), DummyTracer)
+
     def test_get_envvar_tracer(self):
         return self.do_test_get_envvar('TRACER')
+
     def test_get_envvar_default(self):
         return self.do_test_get_envvar('DEFAULT')

tox.ini

@@ -1,14 +1,13 @@
 [tox]
 skipsdist = True
-envlist = py37-{lint,mypy,test}, docs
+envlist = py{34,35,36,37}-test, lint, py37-mypy, docs
 
 [travis]
 python =
-  3.7: py37, docs
+  3.7: py37, lint, docs
 
 [testenv]
 deps =
-  lint: pylint~=2.3.1
   mypy: mypy~=0.711
 
 setenv =
@@ -18,23 +17,32 @@ setenv =
 changedir =
   test: opentelemetry-api/tests
 
-
 commands =
-; Prefer putting everything in one pylint command to profit from duplication
-; warnings.
-  py37-lint: pylint opentelemetry-api/src/opentelemetry/ opentelemetry-api/tests/ opentelemetry-api/setup.py
   py37-mypy: mypy opentelemetry-api/src/opentelemetry/
 ; For test code, we don't want to enforce the full mypy strictness
-  py37-mypy: mypy opentelemetry-api/src/opentelemetry/
   py37-mypy: mypy --config-file=mypy-relaxed.ini opentelemetry-api/tests/ opentelemetry-api/setup.py
   test: python -m unittest discover
 
+[testenv:lint]
+deps =
+  pylint~=2.3
+  flake8~=3.7
+  isort~=4.3
+
+commands =
+; Prefer putting everything in one pylint command to profit from duplication
+; warnings.
+  pylint opentelemetry-api/src/opentelemetry/ opentelemetry-api/tests/
+  flake8 opentelemetry-api/src/opentelemetry/ opentelemetry-api/tests/
+  isort --check-only --recursive opentelemetry-api/src
+
 [testenv:docs]
 deps =
-  sphinx~=2.1.2
-  sphinx-rtd-theme~=0.4.3
-  sphinx-autodoc-typehints~=1.6.0
+  sphinx~=2.1
+  sphinx-rtd-theme~=0.4
+  sphinx-autodoc-typehints~=1.6
+
+changedir = docs
 
 commands =
   sphinx-build -W --keep-going -b html -T . _build/html
-changedir = docs