Only lint the direct sources of a linted target. (pantsbuild#7219)

### Problem

The thrift linter currently redundantly lints the transitive dependencies of each target, leading to repetitive errors, and larger tool invokes than necessary.

### Solution

Lint only the directly owned sources of a target, and expand unit tests.

contrib/scrooge/src/python/pants/contrib/scrooge/tasks/scrooge_gen.py

@@ -24,7 +24,7 @@
 
 from pants.contrib.scrooge.tasks.java_thrift_library_fingerprint_strategy import \
   JavaThriftLibraryFingerprintStrategy
-from pants.contrib.scrooge.tasks.thrift_util import calculate_compile_sources
+from pants.contrib.scrooge.tasks.thrift_util import calculate_include_paths
 
 
 class ScroogeGen(SimpleCodegenTask, NailgunTask):
@@ -148,7 +148,7 @@ def execute_codegen(self, target, target_workdir):
     self.gen(partial_cmd, target, target_workdir)
 
   def gen(self, partial_cmd, target, target_workdir):
-    import_paths, _ = calculate_compile_sources([target], self.is_gentarget)
+    import_paths = calculate_include_paths([target], self.is_gentarget)
 
     args = list(partial_cmd.compiler_args)
 

contrib/scrooge/src/python/pants/contrib/scrooge/tasks/thrift_linter.py

@@ -15,7 +15,7 @@
 from pants.option.ranked_value import RankedValue
 from pants.task.lint_task_mixin import LintTaskMixin
 
-from pants.contrib.scrooge.tasks.thrift_util import calculate_compile_sources
+from pants.contrib.scrooge.tasks.thrift_util import calculate_include_paths
 
 
 class ThriftLintError(Exception):
@@ -87,14 +87,14 @@ def _lint(self, target, classpath):
     if not self._is_strict(target):
       config_args.append('--ignore-errors')
 
-    include_paths , paths = calculate_compile_sources([target], self._is_thrift)
+    paths = list(target.sources_relative_to_buildroot())
+    include_paths = calculate_include_paths([target], self._is_thrift)
     if target.include_paths:
       include_paths |= set(target.include_paths)
     for p in include_paths:
       config_args.extend(['--include-path', p])
 
-    args = config_args + list(paths)
-
+    args = config_args + paths
 
     # If runjava returns non-zero, this marks the workunit as a
     # FAILURE, and there is no way to wrap this here.

contrib/scrooge/src/python/pants/contrib/scrooge/tasks/thrift_util.py

@@ -57,22 +57,19 @@ def find_root_thrifts(basedirs, sources, log=None):
   return root_sources
 
 
-def calculate_compile_sources(targets, is_thrift_target):
-  """Calculates the set of thrift source files that need to be compiled.
-  It does not exclude sources that are included in other sources.
-
-  A tuple of (include basedirs, thrift sources) is returned.
+def calculate_include_paths(targets, is_thrift_target):
+  """Calculates the set of import paths for the given targets.
 
   :targets: The targets to examine.
   :is_thrift_target: A predicate to pick out thrift targets for consideration in the analysis.
+
+  :returns: Include basedirs for the target.
   """
 
   basedirs = set()
-  sources = set()
-  def collect_sources(target):
+  def collect_paths(target):
     basedirs.add(target.target_base)
-    sources.update(target.sources_relative_to_buildroot())
 
   for target in targets:
-    target.walk(collect_sources, predicate=is_thrift_target)
-  return basedirs, sources
+    target.walk(collect_paths, predicate=is_thrift_target)
+  return basedirs

contrib/scrooge/tests/python/pants_test/contrib/scrooge/tasks/test_thrift_linter.py

@@ -31,25 +31,47 @@ def alias_groups(cls):
   def task_type(cls):
     return ThriftLinter
 
-  @patch('pants.contrib.scrooge.tasks.thrift_linter.calculate_compile_sources')
-  def test_lint(self, mock_calculate_compile_sources):
+  @patch('pants.contrib.scrooge.tasks.thrift_linter.calculate_include_paths')
+  def test_lint(self, mock_calculate_include_paths):
 
     def get_default_jvm_options():
       return self.task_type().get_jvm_options_default(self.context().options.for_global_scope())
 
-    thrift_target = self.create_library('a', 'java_thrift_library', 'a', ['A.thrift'])
+    thrift_target = self.create_library('src/thrift/tweet', 'java_thrift_library', 'a', ['A.thrift'])
     task = self.create_task(self.context(target_roots=thrift_target))
     self._prepare_mocks(task)
     expected_include_paths = ['src/thrift/users', 'src/thrift/tweet']
-    expected_paths = ['src/thrift/tweet/a.thrift', 'src/thrift/tweet/b.thrift']
-    mock_calculate_compile_sources.return_value = (expected_include_paths, expected_paths)
+    mock_calculate_include_paths.return_value = expected_include_paths
     task._lint(thrift_target, task.tool_classpath('scrooge-linter'))
 
     self._run_java_mock.assert_called_once_with(
       classpath='foo_classpath',
       main='com.twitter.scrooge.linter.Main',
       args=['--fatal-warnings', '--ignore-errors', '--include-path', 'src/thrift/users',
-            '--include-path', 'src/thrift/tweet', 'src/thrift/tweet/a.thrift',
-            'src/thrift/tweet/b.thrift'],
+            '--include-path', 'src/thrift/tweet', 'src/thrift/tweet/A.thrift'],
+      jvm_options=get_default_jvm_options(),
+      workunit_labels=[WorkUnitLabel.COMPILER, WorkUnitLabel.SUPPRESS_LABEL])
+
+  @patch('pants.contrib.scrooge.tasks.thrift_linter.calculate_include_paths')
+  def test_lint_direct_only(self, mock_calculate_include_paths):
+    # Validate that we do lint only the direct sources of a target, rather than including the
+    # sources of its transitive deps.
+
+    def get_default_jvm_options():
+      return self.task_type().get_jvm_options_default(self.context().options.for_global_scope())
+
+    self.create_library('src/thrift/tweet', 'java_thrift_library', 'a', ['A.thrift'])
+    target_b = self.create_library('src/thrift/tweet', 'java_thrift_library', 'b', ['B.thrift'], dependencies=[':a'])
+    task = self.create_task(self.context(target_roots=target_b))
+    self._prepare_mocks(task)
+    mock_calculate_include_paths.return_value = ['src/thrift/tweet']
+    task._lint(target_b, task.tool_classpath('scrooge-linter'))
+
+    # Confirm that we did not include the sources of the dependency.
+    self._run_java_mock.assert_called_once_with(
+      classpath='foo_classpath',
+      main='com.twitter.scrooge.linter.Main',
+      args=['--fatal-warnings', '--ignore-errors',
+            '--include-path', 'src/thrift/tweet', 'src/thrift/tweet/B.thrift'],
       jvm_options=get_default_jvm_options(),
       workunit_labels=[WorkUnitLabel.COMPILER, WorkUnitLabel.SUPPRESS_LABEL])