Hide BuildFileParser and switch tests that need access to BuildFile b…

…ack to BaseTest.

contrib/buildgen/tests/python/pants_test/contrib/buildgen/BUILD

@@ -7,6 +7,6 @@ python_tests(
   dependencies = [
     'contrib/buildgen/src/python/pants/contrib/buildgen:build_file_manipulator',
     'src/python/pants/build_graph',
-    'tests/python/pants_test:test_base',
+    'tests/python/pants_test:base_test',
   ],
 )

contrib/buildgen/tests/python/pants_test/contrib/buildgen/test_build_file_manipulator.py

@@ -8,13 +8,13 @@
 from textwrap import dedent
 
 from pants.build_graph.address import Address
-from pants_test.test_base import TestBase
+from pants_test.base_test import BaseTest
 
 from pants.contrib.buildgen.build_file_manipulator import (BuildFileManipulator,
                                                            BuildTargetParseError)
 
 
-class BuildFileManipulatorTest(TestBase):
+class BuildFileManipulatorTest(BaseTest):
 
   def setUp(self):
     super(BuildFileManipulatorTest, self).setUp()

tests/python/pants_test/test_base.py

@@ -115,10 +115,10 @@ def _invalidate_for(self, *relpaths):
     Many python operations implicitly create parent directories, so we assume that touching a
     file located below directories that do not currently exist will result in their creation.
     """
-    if self._graph_helper is None:
+    if self._scheduler is None:
       return
     files = {f for relpath in relpaths for f in recursive_dirname(relpath)}
-    self._graph_helper.scheduler.invalidate_files(files)
+    self._scheduler.invalidate_files(files)
 
   def create_link(self, relsrc, reldst):
     """Creates a symlink within the buildroot.
@@ -288,12 +288,10 @@ def setUp(self):
 
     self._build_configuration = BuildConfiguration()
     self._build_configuration.register_aliases(self.alias_groups)
-    self.build_file_parser = BuildFileParser(self._build_configuration, self.build_root)
+    self._build_file_parser = BuildFileParser(self._build_configuration, self.build_root)
     self.project_tree = FileSystemProjectTree(self.build_root)
 
-    self._graph_helper = None
-    self._build_graph = None
-    self._address_mapper = None
+    self._reset_engine()
 
   def buildroot_files(self, relpath=None):
     """Returns the set of all files under the test build root.
@@ -310,8 +308,21 @@ def scan():
           yield os.path.relpath(os.path.join(root, f), self.build_root)
     return set(scan())
 
+  def _reset_engine(self):
+    # TODO: The BuildGraph and AddressMapper end up held a bunch of places, making garbage
+    # collection difficult. The Scheduler manages threads and database handles, so we try
+    # harder to ensure that it is dropped.
+    for attr in ['_build_graph', '_address_mapper']:
+      field = getattr(self, attr, None)
+      if field is not None:
+        field._scheduler = None
+
+    self._scheduler = None
+    self._build_graph = None
+    self._address_mapper = None
+
   def _initialize_engine(self):
-    self._graph_helper = EngineInitializer.setup_legacy_graph(
+    graph_helper = EngineInitializer.setup_legacy_graph(
         self.pants_ignore_patterns,
         self.pants_workdir,
         build_file_imports_behavior='allow',
@@ -320,7 +331,8 @@ def _initialize_engine(self):
         build_ignore_patterns=self.build_ignore_patterns,
       )
 
-    self._build_graph, self._address_mapper = self._graph_helper.create_build_graph(
+    self._scheduler = graph_helper.scheduler
+    self._build_graph, self._address_mapper = graph_helper.create_build_graph(
         LiteralTargetRoots([]),
         self.build_root,
       )
@@ -404,7 +416,7 @@ def context(self, for_task_types=None, for_subsystems=None, options=None,
     context = create_context_from_options(fake_options,
                                           target_roots=target_roots,
                                           build_graph=self.build_graph,
-                                          build_file_parser=self.build_file_parser,
+                                          build_file_parser=self._build_file_parser,
                                           address_mapper=self.address_mapper,
                                           console_outstream=console_outstream,
                                           workspace=workspace)
@@ -416,6 +428,7 @@ def tearDown(self):
     """
     super(TestBase, self).tearDown()
     Subsystem.reset()
+    self._reset_engine()
 
   def target(self, spec):
     """Resolves the given target address to a Target object.