Fix up for go

contrib/go/src/python/pants/contrib/go/targets/go_binary.py

@@ -12,6 +12,7 @@ class GoBinary(GoLocalSource):
   """A local Go main package."""
 
   default_sources_globs = '*'
+  default_sources_exclude_globs = ('BUILD', 'BUILD.*')
 
   @classmethod
   def alias(cls):

contrib/go/src/python/pants/contrib/go/targets/go_library.py

@@ -12,6 +12,7 @@ class GoLibrary(GoLocalSource):
   """A local Go package."""
 
   default_sources_globs = '*'
+  default_sources_exclude_globs = ('BUILD', 'BUILD.*')
 
   @classmethod
   def alias(cls):

src/python/pants/engine/legacy/structs.py

@@ -273,23 +273,6 @@ def default_sources_globs(self):
     return self.python_test_globs
 
 
-class GoTargetAdaptor(TargetAdaptor):
-
-  @property
-  def default_sources(self):
-    # Go has always used implicit_sources: override to ignore the option.
-    return True
-
-  @property
-  def default_sources_globs(self):
-    # N.B. Go targets glob on `*` due to the way resources and .c companion files are handled.
-    return ('*',)
-
-  @property
-  def default_sources_exclude_globs(self):
-    return ('BUILD', 'BUILD.*')
-
-
 class PantsPluginAdaptor(PythonTargetAdaptor):
   def get_sources(self):
     return ['register.py']

src/python/pants/init/engine_initializer.py

@@ -58,6 +58,19 @@ def __init__(self, build_file_aliases):
       for alias, target_type in build_file_aliases.target_types.items()
     }
 
+    for alias, factory in build_file_aliases.target_macro_factories.items():
+      # TargetMacro.Factory with more than one target type is deprecated.
+      # For default sources, this means that TargetMacro Factories with more than one target_type
+      # will not parse sources through the engine, and will fall back to the legacy python sources
+      # parsing.
+      # Conveniently, multi-target_type TargetMacro.Factory, and legacy python source parsing, are
+      # targeted to be removed in the same version of pants.
+      if len(factory.target_types) == 1:
+        self._table[alias] = self._make_target_adaptor(
+          TargetAdaptor,
+          tuple(factory.target_types)[0],
+        )
+
     # TODO: The alias replacement here is to avoid elevating "TargetAdaptors" into the public
     # API until after https://github.com/pantsbuild/pants/issues/3560 has been completed.
     # These should likely move onto Target subclasses as the engine gets deeper into beta