Peek Target using Buildozer

This adds the ability to peek a BUILD file for a named target, printing the target name if it is found.
Additionally, peek allows a line_number flag which will print the starting line of the named target if it is found in the BUILD file.

Also, this adds a suppress warnings feature to Buildozer.

Example:
$ ./pants peek
--line_number=true path/to/directory:target_name

To Verify:
$ ./pants test
contrib/buildrefactor/tests/python/pants_test/contrib/buildrefactor:peek_integration

This addresses:
pantsbuild#4861 Please enter the commit message for your changes. Lines starting

contrib/buildrefactor/src/python/pants/contrib/buildrefactor/BUILD

@@ -25,3 +25,9 @@ python_library(
   name='meta_rename',
   sources=['meta_rename.py']
 )
+
+
+python_library(
+  name='peek',
+  sources=['peek.py']
+)

contrib/buildrefactor/src/python/pants/contrib/buildrefactor/buildozer.py

@@ -72,17 +72,18 @@ def _execute_buildozer_script(self, command):
       Buildozer.execute_binary(command, address.spec, binary=self._executable)
 
   @classmethod
-  def execute_binary(cls, command, spec, binary=None, version='0.6.0.dce8b3c287652cbcaf43c8dd076b3f48c92ab44c'):
+  def execute_binary(cls, command, spec, binary=None, version='0.6.0.dce8b3c287652cbcaf43c8dd076b3f48c92ab44c', supress_warnings=False):
     binary = binary if binary else BinaryUtil.Factory.create().select_binary('scripts/buildozer', version, 'buildozer')
 
-    Buildozer._execute_buildozer_command([binary, command, spec])
+    Buildozer._execute_buildozer_command([binary, command, spec], supress_warnings)
 
   @classmethod
-  def _execute_buildozer_command(cls, buildozer_command):
+  def _execute_buildozer_command(cls, buildozer_command, supress_warnings):
     try:
       subprocess.check_call(buildozer_command, cwd=get_buildroot())
     except subprocess.CalledProcessError as err:
       if err.returncode == 3:
-        logger.warn('{} ... no changes were made'.format(buildozer_command))
+        if not supress_warnings:
+          logger.warn('{} ... no changes were made'.format(buildozer_command))
       else:
-        raise TaskError('{} ... exited non-zero ({}).'.format(buildozer_command, err.returncode))
+        raise TaskError('{} ... exited non-zero ({}).'.format(buildozer_command, err.returncode))

contrib/buildrefactor/src/python/pants/contrib/buildrefactor/peek.py

@@ -0,0 +1,46 @@
+# coding=utf-8
+# Copyright 2017 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+#./pants peek --path=src/scala/org/pantsbuild/zinc/analysis --target-name=zinc-analysis
+#./pants peek --path=src/scala/org/pantsbuild/zinc/extractor --target-name=zinc-extractor --line_number=True
+
+from __future__ import (absolute_import, division, generators, nested_scopes, print_function,
+                        unicode_literals, with_statement)
+
+from pants.task.task import Task
+from pants.contrib.buildrefactor.buildozer import Buildozer
+
+
+class Peek(Task):
+    """Peek a build file for a specified target
+
+    $ ./pants peek --line_number=true path/to/directory:target_name
+
+    line_number: optional flag to print the starting line of the target if found
+    """
+
+    @classmethod
+    def register_options(cls, register):
+        super(Peek, cls).register_options(register)
+
+        register('--line_number', help='Prints the starting line number of the named target.', type=bool, default=False)
+
+    def __init__(self, *args, **kwargs):
+        super(Peek, self).__init__(*args, **kwargs)
+
+        self.options = self.get_options()
+
+    def execute(self):
+        self.print_name()
+
+    def print_name(self):
+        for root in self.context.target_roots:
+            address_spec = root.address.spec
+            print('\n')
+            Buildozer.execute_binary('print name', address_spec, supress_warnings=True)
+            print('Named target found in BUILD file.')
+
+            if self.options.line_number:
+                print('\n\'{}\' starts on line number:'.format(root.name))
+                Buildozer.execute_binary('print startline', address_spec, supress_warnings=True)

contrib/buildrefactor/src/python/pants/contrib/buildrefactor/register.py

@@ -6,11 +6,12 @@
                         unicode_literals, with_statement)
 
 from pants.goal.task_registrar import TaskRegistrar as task
-
 from pants.contrib.buildrefactor.buildozer import Buildozer
 from pants.contrib.buildrefactor.meta_rename import MetaRename
+from pants.contrib.buildrefactor.peek import Peek
 
 
 def register_goals():
   task(name='buildozer', action=Buildozer).install('buildozer')
   task(name='meta-rename', action=MetaRename).install('meta-rename')
+  task(name='peek', action=Peek).install('peek')

contrib/buildrefactor/tests/python/pants_test/contrib/buildrefactor/BUILD

@@ -36,6 +36,13 @@ python_tests(
   ]
 )
 
+python_tests(
+  name='peek_integration',
+  sources=['test_peek_integration.py'],
+  dependencies=[
+    'tests/python/pants_test:int-test',
+  ]
+)
 
 python_tests(
   name='meta_rename_integration',
@@ -53,3 +60,5 @@ python_tests(
     'tests/python/pants_test:int-test',
   ]
 )
+
+

contrib/buildrefactor/tests/python/pants_test/contrib/buildrefactor/test_peek_integration.py

@@ -0,0 +1,27 @@
+# coding=utf-8
+# Copyright 2017 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from __future__ import (absolute_import, division, generators, nested_scopes, print_function,
+                        unicode_literals, with_statement)
+
+from pants_test.pants_run_integration_test import PantsRunIntegrationTest
+
+
+class PeekIntegrationTest(PantsRunIntegrationTest):
+  """Test Peek goal functionality"""
+
+  def test_print_name(self):
+    peek_print_run = self.run_pants(['peek',
+      'testprojects/tests/java/org/pantsbuild/testproject/buildrefactor/x:X'])
+
+    self.assertIn('[peek]\n\nX\nNamed target found in BUILD file.', peek_print_run.stdout_data)
+    self.assertIn('SUCCESS', peek_print_run.stdout_data)
+
+  def test_print_line_number(self):
+    peek_line_number_run = self.run_pants(['peek',
+      '--line_number=true',
+      'testprojects/tests/java/org/pantsbuild/testproject/buildrefactor/x:X'])
+
+    self.assertIn('\n\n\'X\' starts on line number:\n4', peek_line_number_run.stdout_data)
+    self.assertIn('SUCCESS', peek_line_number_run.stdout_data)