Move PlatformConstraint to a param.

src/python/pants/backend/python/rules/pex.py

@@ -16,7 +16,7 @@
   DirectoryWithPrefixToAdd,
 )
 from pants.engine.isolated_process import ExecuteProcessResult, MultiPlatformExecuteProcessRequest
-from pants.engine.platform import Platform, PlatformConstraint
+from pants.engine.platform import PlatformConstraint
 from pants.engine.rules import optionable_rule, rule
 from pants.engine.selectors import Get
 
@@ -46,7 +46,7 @@ def create_pex(
     python_setup: PythonSetup,
     subprocess_encoding_environment: SubprocessEncodingEnvironment,
     pex_build_environment: PexBuildEnvironment,
-    platform: Platform
+    platform: PlatformConstraint
 ) -> Pex:
   """Returns a PEX with the given requirements, optional entry point, and optional
   interpreter constraints."""
@@ -68,8 +68,12 @@ def create_pex(
   all_inputs = (pex_bin.directory_digest, sources_digest_as_subdir,)
   merged_digest = yield Get(Digest, DirectoriesToMerge(directories=all_inputs))
 
+  # ignore none constraint if some rule pushes a constraint down as none.
+  if platform == PlatformConstraint.none:
+    platform = PlatformConstraint.local_platform
+
   # NB: PEX outputs are platform dependent so in order to get a PEX that we can use locally, without
-  # cross-building we specify that out PEX command be run on the current local platform. When we
+  # cross-building, we specify that our PEX command be run on the current local platform. When we
   # support cross-building through CLI flags we can configure requests that build a PEX for out
   # local platform that are able to execute on a different platform, but for now in order to
   # guarantee correct build we need to restrict this command to execute on the same platform type
@@ -79,7 +83,7 @@ def create_pex(
   # constraint`".
   execute_process_request = MultiPlatformExecuteProcessRequest(
     {
-      (PlatformConstraint(platform.value), PlatformConstraint(platform.value)):
+      (platform, platform):
         pex_bin.create_execute_request(
           python_setup=python_setup,
           subprocess_encoding_environment=subprocess_encoding_environment,

src/python/pants/engine/platform.py

@@ -1,7 +1,7 @@
 # Copyright 2019 Pants project contributors (see CONTRIBUTORS.md).
 # Licensed under the Apache License, Version 2.0 (see LICENSE).
 
-from pants.engine.rules import rule
+from pants.engine.rules import RootRule, rule
 from pants.util.memo import memoized_classproperty, memoized_property
 from pants.util.objects import enum
 from pants.util.osutil import all_normalized_os_names, get_normalized_os_name
@@ -36,4 +36,4 @@ def materialize_platform() -> Platform:
 
 
 def create_platform_rules():
-  return [materialize_platform]
+  return [materialize_platform, RootRule(PlatformConstraint)]

src/python/pants/init/engine_initializer.py

@@ -41,7 +41,7 @@
 from pants.engine.legacy.structs import rules as structs_rules
 from pants.engine.mapper import AddressMapper
 from pants.engine.parser import SymbolTable
-from pants.engine.platform import create_platform_rules
+from pants.engine.platform import PlatformConstraint, create_platform_rules
 from pants.engine.rules import RootRule, UnionMembership, rule
 from pants.engine.scheduler import Scheduler
 from pants.engine.selectors import Params
@@ -199,14 +199,17 @@ def run_console_rules(self, options_bootstrapper, goals, target_roots):
     :returns: An exit code.
     """
     subject = target_roots.specs
+    global_options = options_bootstrapper.bootstrap_options.for_global_scope()
     console = Console(
-      use_colors=options_bootstrapper.bootstrap_options.for_global_scope().colors
+      use_colors=global_options.colors
     )
+    target_platform_constraint = PlatformConstraint.local_platform
     workspace = Workspace(self.scheduler_session)
 
     for goal in goals:
       goal_product = self.goal_map[goal]
-      params = Params(subject, options_bootstrapper, console, workspace)
+      params = Params(subject, options_bootstrapper, console,
+                      workspace, target_platform_constraint)
       logger.debug(f'requesting {goal_product} to satisfy execution of `{goal}` goal')
       try:
         exit_code = self.scheduler_session.run_console_rule(goal_product, params)

src/python/pants/option/global_options.py

@@ -21,6 +21,7 @@
 from pants.option.scope import ScopeInfo
 from pants.subsystem.subsystem_client_mixin import SubsystemClientMixin
 from pants.util.objects import enum
+from pants.util.osutil import all_normalized_os_names, get_normalized_os_name
 
 
 class GlobMatchErrorBehavior(enum(['ignore', 'warn', 'error'])):

tests/python/pants_test/backend/python/rules/BUILD

@@ -8,6 +8,7 @@ python_tests(
     'src/python/pants/backend/python/rules',
     'src/python/pants/backend/python/subsystems',
     'src/python/pants/engine:fs',
+    'src/python/pants/engine:platform',
     'src/python/pants/engine:rules',
     'src/python/pants/engine:selectors',
     'src/python/pants/util:collections',

tests/python/pants_test/backend/python/rules/test_pex.py

@@ -19,6 +19,7 @@
 )
 from pants.engine.fs import Digest, DirectoryToMaterialize, FileContent, InputFilesContent
 from pants.engine.isolated_process import ExecuteProcessRequest, ExecuteProcessResult
+from pants.engine.platform import PlatformConstraint
 from pants.engine.rules import RootRule
 from pants.engine.selectors import Params
 from pants.util.collections import assert_single_element
@@ -64,7 +65,8 @@ def hashify_optional_collection(iterable):
         request,
         PythonSetup.global_instance(),
         SubprocessEnvironment.global_instance(),
-        PythonNativeCode.global_instance()
+        PythonNativeCode.global_instance(),
+        PlatformConstraint.local_platform,
       )])
     )
     with temporary_dir() as tmp_dir:

tests/python/pants_test/engine/BUILD

@@ -76,6 +76,7 @@ python_tests(
   name='isolated_process',
   sources=['test_isolated_process.py'],
   dependencies=[
+    '3rdparty/python:dataclasses',
     'src/python/pants/engine:fs',
     'src/python/pants/engine:isolated_process',
     'src/python/pants/engine:rules',