Ensure no duplicate scope registrations, and move legacy/v1 implement…

…ations of tasks to a subscope.

src/python/pants/backend/project_info/register.py

@@ -22,4 +22,4 @@ def register_goals():
 
   task(name='depmap', action=Depmap).install()
   task(name='dependencies', action=Dependencies).install()
-  task(name='filedeps', action=FileDeps).install('filedeps')
+  task(name='legacy', action=FileDeps).install('filedeps')

src/python/pants/backend/project_info/tasks/filedeps.py

@@ -10,21 +10,15 @@
 from pants.backend.jvm.targets.jvm_app import JvmApp
 from pants.backend.jvm.targets.scala_library import ScalaLibrary
 from pants.base.build_environment import get_buildroot
+from pants.rules.core import filedeps as filedeps_rules
 from pants.task.console_task import ConsoleTask
 
 
 class FileDeps(ConsoleTask):
-  """List all source and BUILD files a target transitively depends on.
-
-  Files are listed with absolute paths and any BUILD files implied in the transitive closure of
-  targets are also included.
-  """
 
   @classmethod
-  def register_options(cls, register):
-    super(FileDeps, cls).register_options(register)
-    register('--globs', type=bool,
-             help='Instead of outputting filenames, output globs (ignoring excludes)')
+  def subsystem_dependencies(cls):
+    return super(FileDeps, cls).subsystem_dependencies() + (filedeps_rules.Filedeps,)
 
   def _full_path(self, path):
     return os.path.join(get_buildroot(), path)

src/python/pants/core_tasks/register.py

@@ -84,7 +84,7 @@ def register_goals():
   task(name='compile-prep-command', action=RunCompilePrepCommand).install('compile', first=True)
 
   # Stub for other goals to schedule 'test'. See noop_exec_task.py for why this is useful.
-  task(name='test', action=NoopTest).install('test')
+  task(name='legacy', action=NoopTest).install('test')
 
   # Workspace information.
   task(name='roots', action=ListRoots).install()

src/python/pants/engine/goal.py

@@ -28,6 +28,14 @@ def options_scope(cls):
       raise AssertionError('{} must have a `Goal.name` defined.'.format(cls.__name__))
     return cls.name
 
+  @classmethod
+  def subsystem_dependencies_iter(cls):
+    # NB: `Goal` quacks like a `SubsystemClientMixin` in order to allow v1 `Tasks` to depend on
+    # v2 Goals for backwards compatibility purposes. But v2 Goals should _not_ have subsystem
+    # dependencies: instead, the @rules participating (transitively) in a Goal should directly
+    # declare Subsystem deps.
+    return iter([])
+
   def __init__(self, scope, scoped_options):
     # NB: This constructor is shaped to meet the contract of `Optionable(Factory).signature`.
     super(Goal, self).__init__()

src/python/pants/option/options.py

@@ -79,6 +79,9 @@ class Options(object):
   class FrozenOptionsError(Exception):
     """Options are frozen and can't be mutated."""
 
+  class DuplicateScopeError(Exception):
+    """More than one registration occurred for the same scope."""
+
   @classmethod
   def complete_scopes(cls, scope_infos):
     """Expand a set of scopes to include all enclosing scopes.
@@ -88,13 +91,17 @@ def complete_scopes(cls, scope_infos):
     Also adds any deprecated scopes.
     """
     ret = {GlobalOptionsRegistrar.get_scope_info()}
-    original_scopes = set()
+    original_scopes = dict()
     for si in scope_infos:
       ret.add(si)
-      original_scopes.add(si.scope)
+      if si.scope in original_scopes:
+        raise cls.DuplicateScopeError('Scope `{}` claimed by {}, was also claimed by {}.'.format(
+            si.scope, si, original_scopes[si.scope]
+          ))
+      original_scopes[si.scope] = si
       if si.deprecated_scope:
         ret.add(ScopeInfo(si.deprecated_scope, si.category, si.optionable_cls))
-        original_scopes.add(si.deprecated_scope)
+        original_scopes[si.deprecated_scope] = si
 
     # TODO: Once scope name validation is enforced (so there can be no dots in scope name
     # components) we can replace this line with `for si in scope_infos:`, because it will

src/python/pants/rules/core/filedeps.py

@@ -22,6 +22,12 @@ class Filedeps(Goal):
 
   name = 'filedeps'
 
+  @classmethod
+  def register_options(cls, register):
+    super(Filedeps, cls).register_options(register)
+    register('--globs', type=bool,
+             help='Instead of outputting filenames, output globs (ignoring excludes)')
+
 
 @console_rule(Filedeps, [Select(Console), Select(TransitiveHydratedTargets)])
 def file_deps(console, transitive_hydrated_targets):