Override interpreter constraints if global option is passed down

src/python/pants/backend/python/interpreter_cache.py

@@ -77,6 +77,7 @@ def select_interpreter_for_targets(self, targets):
     """Pick an interpreter compatible with all the specified targets."""
     tgts_by_compatibilities = defaultdict(list)
     filters = set()
+
     for target in targets:
       if isinstance(target, PythonTarget):
         c = self._python_setup.compatibility_or_constraints(target)
@@ -86,7 +87,7 @@ def select_interpreter_for_targets(self, targets):
     allowed_interpreters = set(self.setup(filters=filters))
 
     # Constrain allowed_interpreters based on each target's compatibility requirements.
-    for compatibility in tgts_by_compatibilities.keys():
+    for compatibility in tgts_by_compatibilities:
       compatible_with_target = set(self._matching(allowed_interpreters, compatibility))
       allowed_interpreters &= compatible_with_target
 

src/python/pants/backend/python/subsystems/python_setup.py

@@ -133,7 +133,12 @@ def scratch_dir(self):
     return os.path.join(self.get_options().pants_workdir, *self.options_scope.split('.'))
 
   def compatibility_or_constraints(self, target):
-    """Return either the compatibility of the given target, or the interpreter constraints."""
+    """
+    Return either the compatibility of the given target, or the interpreter constraints.
+    If interpreter constraints are supplied by the CLI flag, return those only.
+    """
+    if self.get_options().is_flagged('interpreter_constraints'):
+      return tuple(self.interpreter_constraints)
     return tuple(target.compatibility or self.interpreter_constraints)
 
   def setuptools_requirement(self):

testprojects/src/python/interpreter_selection/python_3_selection_testing/BUILD

@@ -67,3 +67,29 @@ python_tests(
   ],
   compatibility=['CPython>2.7.6,<3']
 )
+
+python_binary(
+  name='main_py23',
+  source='main_py23.py',
+  compatibility=['CPython>2.7,<4'],
+  dependencies=[
+    ':lib_py23'
+  ]
+)
+
+python_library(
+  name='lib_py23',
+  sources=['lib_py23.py'],
+  compatibility=['CPython>2.7,<4']
+)
+
+python_tests(
+  name='test_py23',
+  sources=[
+    'test_py23.py',
+  ],
+  dependencies=[
+    ':main_py23'
+  ],
+  compatibility=['CPython>2.7,<4']
+)

testprojects/src/python/interpreter_selection/python_3_selection_testing/lib_py23.py

@@ -0,0 +1,19 @@
+# coding=utf-8
+# Copyright 2017 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from __future__ import (absolute_import, division, generators, nested_scopes, print_function,
+                        unicode_literals, with_statement)
+
+
+def say_something():
+  print('I am a python 2/3 compatible library method.')
+  # Note that ascii exists as a built-in in Python 3 and
+  # does not exist in Python 2.
+  try:
+    ret = ascii
+  except NameError:
+    ret = 'Python2'
+  else:
+    ret = 'Python3'
+  return ret

testprojects/src/python/interpreter_selection/python_3_selection_testing/main_py23.py

@@ -0,0 +1,23 @@
+# coding=utf-8
+# Copyright 2017 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from __future__ import (absolute_import, division, generators, nested_scopes, print_function,
+                        unicode_literals, with_statement)
+
+import sys
+
+from interpreter_selection.python_3_selection_testing.lib_py23 import say_something
+
+
+# A simple example to test building/running/testing a python 2 binary target
+
+
+def main():
+  v = sys.version_info
+  print(sys.executable)
+  print('%d.%d.%d' % v[0:3])
+  return say_something()
+
+if __name__ == '__main__':
+  main()

testprojects/src/python/interpreter_selection/python_3_selection_testing/test_py23.py

@@ -0,0 +1,22 @@
+# coding=utf-8
+# Copyright 2017 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from __future__ import (absolute_import, division, generators, nested_scopes, print_function,
+                        unicode_literals, with_statement)
+
+import sys
+
+from interpreter_selection.python_3_selection_testing.main_py23 import main
+
+
+def test_main():
+  print(sys.executable)
+  v = sys.version_info
+  # Note that ascii exists as a built-in in Python 3 and
+  # does not exist in Python 2
+  ret = main()
+  if v[0] == '3':
+    assert ret == 'Python3'
+  else:
+    assert ret == 'Python2'

tests/python/pants_test/backend/python/tasks/test_pytest_run_integration.py

@@ -147,3 +147,49 @@ def test_pants_test_interpreter_selection_with_pexrc(self):
     else:
       print('Could not find both python {} and python {} on system. Skipping.'.format(py27, py3))
       self.skipTest('Missing neccesary Python interpreters on system.')
+
+  def test_pants_test_interpreter_selection_with_option_2(self):
+    """
+    Test that the pants test goal properly constrains the SelectInterpreter task to Python 2
+    using the '--python-setup-interpreter-constraints' option.
+    """
+    if self.has_python_version('2.7'):
+      with temporary_dir() as interpreters_cache:
+        pants_ini_config = {
+          'python-setup': {
+            'interpreter_constraints': ['CPython>=2.7,<4'],
+            'interpreter_cache_dir': interpreters_cache,
+          }
+        }
+      pants_run_2 = self.run_pants(
+        command=[
+          'test',
+          '{}:test_py2'.format(os.path.join(self.testproject,'python_3_selection_testing')),
+          '--python-setup-interpreter-constraints=["CPython<3"]',
+        ],
+        config=pants_ini_config
+      )
+      self.assert_success(pants_run_2)
+
+  def test_pants_test_interpreter_selection_with_option_3(self):
+    """
+    Test that the pants test goal properly constrains the SelectInterpreter task to Python 3
+    using the '--python-setup-interpreter-constraints' option.
+    """
+    if self.has_python_version('3'):
+      with temporary_dir() as interpreters_cache:
+        pants_ini_config = {
+          'python-setup': {
+            'interpreter_constraints': ['CPython>=2.7,<4'],
+            'interpreter_cache_dir': interpreters_cache,
+          }
+        }
+      pants_run_3 = self.run_pants(
+            command=[
+              'test',
+              '{}:test_py3'.format(os.path.join(self.testproject,'python_3_selection_testing')),
+              '--python-setup-interpreter-constraints=["CPython>=3"]',
+            ],
+            config=pants_ini_config
+          )
+      self.assert_success(pants_run_3)

tests/python/pants_test/backend/python/tasks/test_python_repl_integration.py

@@ -15,9 +15,30 @@ def test_run_repl(self):
     command = ['repl',
                'testprojects/src/python/interpreter_selection:echo_interpreter_version_lib',
                '--python-setup-interpreter-constraints=CPython>=2.7,<3',
-               '--python-setup-interpreter-constraints=CPython>=3.3',
                '--quiet']
     program = 'from interpreter_selection.echo_interpreter_version import say_hello; say_hello()'
     pants_run = self.run_pants(command=command, stdin_data=program)
     output_lines = pants_run.stdout_data.rstrip().split('\n')
     self.assertIn('echo_interpreter_version loaded successfully.', output_lines)
+
+  @ensure_daemon
+  def test_run_repl_with_2(self):
+    # Run a Python 2 repl on a Python 2/3 library target.
+    command = ['repl',
+               'testprojects/src/python/interpreter_selection:echo_interpreter_version_lib',
+               '--python-setup-interpreter-constraints=["CPython<3"]',
+               '--quiet']
+    program = 'from interpreter_selection.echo_interpreter_version import say_hello; say_hello()'
+    pants_run = self.run_pants(command=command, stdin_data=program)
+    self.assertRegexpMatches(pants_run.stdout_data, r'2\.\d\.\d')
+
+  @ensure_daemon
+  def test_run_repl_with_3(self):
+    # Run a Python 3 repl on a Python 2/3 library target. Avoid some known-to-choke-on interpreters.
+    command = ['repl',
+               'testprojects/src/python/interpreter_selection:echo_interpreter_version_lib',
+               '--python-setup-interpreter-constraints=["CPython>=3.3"]',
+               '--quiet']
+    program = 'from interpreter_selection.echo_interpreter_version import say_hello; say_hello()'
+    pants_run = self.run_pants(command=command, stdin_data=program)
+    self.assertRegexpMatches(pants_run.stdout_data, r'3\.\d\.\d')

tests/python/pants_test/backend/python/tasks/test_python_run_integration.py

@@ -44,11 +44,38 @@ def test_run_27_and_then_3(self):
       )
       self.assert_success(pants_run_3)
 
+  def test_run_3_by_option(self):
+    if self.skip_if_no_python('3'):
+      return
+
+    with temporary_dir() as interpreters_cache:
+      pants_ini_config = {'python-setup': {'interpreter_constraints': ["CPython>=2.7,<4"],
+        'interpreter_cache_dir': interpreters_cache}}
+      pants_run_3 = self.run_pants(
+        command=['run', '{}:echo_interpreter_version_3'.format(self.testproject),
+        '--python-setup-interpreter-constraints=["CPython>=3"]'],
+        config=pants_ini_config
+      )
+      self.assert_success(pants_run_3)
+
+  def test_run_2_by_option(self):
+    if self.skip_if_no_python('2'):
+      return
+
+    with temporary_dir() as interpreters_cache:
+      pants_ini_config = {'python-setup': {'interpreter_constraints': ["CPython>=2.7,<4"],
+        'interpreter_cache_dir': interpreters_cache}}
+      pants_run_2 = self.run_pants(
+        command=['run', '{}:echo_interpreter_version_2.7'.format(self.testproject),
+        '--python-setup-interpreter-constraints=["CPython<3"]'],
+        config=pants_ini_config
+      )
+      self.assert_success(pants_run_2)
+
   def test_die(self):
     command = ['run',
                '{}:die'.format(self.testproject),
-               '--python-setup-interpreter-constraints=CPython>=2.7,<3',
-               '--python-setup-interpreter-constraints=CPython>=3.3',
+               '--python-setup-interpreter-constraints=["CPython>=2.7,<3", ">=3.3"]',
                '--quiet']
     pants_run = self.run_pants(command=command)
     assert pants_run.returncode == 57
@@ -181,10 +208,13 @@ def _run_echo_version(self, version):
     binary_target = '{}:{}'.format(self.testproject, binary_name)
     # Build a pex.
     # Avoid some known-to-choke-on interpreters.
+    if version == '3':
+      constraint = '["CPython>=3.3"]'
+    else:
+      constraint = '["CPython>=2.7,<3"]'
     command = ['run',
                binary_target,
-               '--python-setup-interpreter-constraints=CPython>=2.7,<3',
-               '--python-setup-interpreter-constraints=CPython>=3.3',
+               '--python-setup-interpreter-constraints={}'.format(constraint),
                '--quiet']
     pants_run = self.run_pants(command=command)
     return pants_run.stdout_data.rstrip().split('\n')[-1]

tests/python/pants_test/python/test_interpreter_selection_integration.py

@@ -14,14 +14,11 @@
 class InterpreterSelectionIntegrationTest(PantsRunIntegrationTest):
   testproject = 'testprojects/src/python/interpreter_selection'
 
-  def test_conflict_via_compatibility(self):
+  def test_cli_option_wins_compatibility_conflict(self):
     # Tests that targets with compatibility conflicts collide.
     binary_target = '{}:deliberately_conficting_compatibility'.format(self.testproject)
     pants_run = self._build_pex(binary_target)
-    self.assert_failure(pants_run,
-                        'Unexpected successful build of {binary}.'.format(binary=binary_target))
-    self.assertIn('Unable to detect a suitable interpreter for compatibilities',
-                  pants_run.stdout_data)
+    self.assert_success(pants_run, 'Failed to build {binary}.'.format(binary=binary_target))
 
   def test_conflict_via_config(self):
     # Tests that targets with compatibility conflict with targets with default compatibility.
@@ -65,7 +62,7 @@ def _echo_version(self, version):
       }
       binary_name = 'echo_interpreter_version_{}'.format(version)
       binary_target = '{}:{}'.format(self.testproject, binary_name)
-      pants_run = self._build_pex(binary_target, config)
+      pants_run = self._build_pex(binary_target, config, version=version)
       self.assert_success(pants_run, 'Failed to build {binary}.'.format(binary=binary_target))
 
       # Run the built pex.
@@ -74,11 +71,14 @@ def _echo_version(self, version):
       (stdout_data, _) = proc.communicate()
       return stdout_data
 
-  def _build_pex(self, binary_target, config=None, args=None):
+  def _build_pex(self, binary_target, config=None, args=None, version='2.7'):
     # By default, Avoid some known-to-choke-on interpreters.
+    if version == '3':
+      constraint = '["CPython>=3.3"]'
+    else:
+      constraint = '["CPython>=2.7,<3"]'
     args = list(args) if args is not None else [
-          '--python-setup-interpreter-constraints=CPython>=2.7,<3',
-          '--python-setup-interpreter-constraints=CPython>=3.3',
+          '--python-setup-interpreter-constraints={}'.format(constraint)
         ]
     command = ['binary', binary_target] + args
     return self.run_pants(command=command, config=config)