Add the -no-header argument to jaxb generator to give deterministic o…

…utput

Makes the jaxb output deterministic to make it compatible with caching.
Also removed some logic for global codegen strategy that is no longer needed.

The jaxb generator adds a timestamp to each java file it generates by default.

```
  // This file was generated by the JavaTM Architecture for XML Binding(JAXB) Reference Implementation, v2.2.4-2
  // See <a href="http://java.sun.com/xml/jaxb">http://java.sun.com/xml/jaxb</a>
  // Any modifications to this file will be lost upon recompilation of the source schema.
  // Generated on: 2015.07.09 at 03:50:50 PM PDT
```

Fortuantely, you can easiliy turn this off

```
$ xjc -h | grep header
  -no-header         :  suppress generation of a file header with timestamp
```

Testing Done:
CI is running at https://travis-ci.org/pantsbuild/pants/builds/93226958
Updated unit tests.

Bugs closed: 1768, 2627

Reviewed at https://rbcommons.com/s/twitter/r/3179/

src/python/pants/backend/codegen/tasks/BUILD

@@ -66,12 +66,8 @@ python_library(
     'src/python/pants/backend/codegen/targets:java',
     'src/python/pants/backend/jvm/targets:java',
     'src/python/pants/backend/jvm/tasks:nailgun_task',
-    'src/python/pants/base:build_environment',
     'src/python/pants/base:exceptions',
-    'src/python/pants/base:source_root',
-    'src/python/pants/build_graph',
     'src/python/pants/java/distribution:distribution',
-    'src/python/pants/util:dirutil',
   ],
 )
 

src/python/pants/backend/codegen/tasks/jaxb_gen.py

@@ -7,16 +7,13 @@
 
 import os
 import re
-# just running it on code in our repositories, not on externally acquired data.
-from xml.dom.minidom import parse
 
 from pants.backend.codegen.targets.jaxb_library import JaxbLibrary
 from pants.backend.codegen.tasks.simple_codegen_task import SimpleCodegenTask
 from pants.backend.jvm.targets.java_library import JavaLibrary
 from pants.backend.jvm.tasks.nailgun_task import NailgunTask
 from pants.base.exceptions import TaskError
 from pants.java.distribution.distribution import DistributionLocator
-from pants.util.dirutil import safe_mkdir
 
 
 class JaxbGen(SimpleCodegenTask, NailgunTask):
@@ -49,7 +46,6 @@ def execute_codegen(self, target, target_workdir):
       raise TaskError('Invalid target type "{class_type}" (expected JaxbLibrary)'
                       .format(class_type=type(target).__name__))
 
-    target_files = []
     for source in target.sources_relative_to_buildroot():
       path_to_xsd = source
       output_package = target.package
@@ -58,12 +54,13 @@ def execute_codegen(self, target, target_workdir):
         output_package = self._guess_package(source)
       output_package = self._correct_package(output_package)
 
-      args = ['-p', output_package, '-d', target_workdir, path_to_xsd]
+      # NB(zundel): The -no-header option keeps it from writing a timestamp, making the
+      # output non-deterministic.  See https://github.com/pantsbuild/pants/issues/1786
+      args = ['-p', output_package, '-d', target_workdir, '-no-header', path_to_xsd]
       result = self._compile_schema(args)
 
       if result != 0:
         raise TaskError('xjc ... exited non-zero ({code})'.format(code=result))
-      target_files.append(self._sources_to_be_generated(target.package, path_to_xsd))
 
   @classmethod
   def _guess_package(self, path):
@@ -91,31 +88,3 @@ def _correct_package(self, package):
     if re.search(r'\.{2,}', package) is not None:
       raise ValueError('Package name cannot have consecutive periods! ({})'.format(package))
     return package
-
-  @classmethod
-  def _sources_to_be_generated(self, package, path):
-    """Predicts what java sources will be generated by an individual schema file.
-
-    :param str package: the package for the generated java files.
-    :param str path: the path to the .xsd schema file.
-    :return: a list of relative filepaths.
-    """
-    doc = parse(path)
-    if package is None:
-      package = self._guess_package(path)
-    package = self._correct_package(package)
-
-    names = []
-    for root in doc.childNodes:
-      if re.match('.*?:schema$', root.nodeName, re.I) is not None:
-        for element in root.childNodes:
-          if element.nodeName != '#text' and element.attributes.has_key('name'):
-            name = element.attributes['name'].nodeValue
-            if len(name) == 0: continue
-            # enforce pascal-case class names
-            name = name[0:1].upper() + name[1:]
-            names.append(name)
-
-    names.append('ObjectFactory')
-    outdir = package.replace('.', '/')
-    return [os.path.join(outdir, '{}.java'.format(name)) for name in names]

tests/python/pants_test/backend/codegen/tasks/BUILD

@@ -42,8 +42,9 @@ python_tests(
   name = 'jaxb_gen',
   sources = ['test_jaxb_gen.py'],
   dependencies = [
-    'src/python/pants/backend/codegen/tasks:jaxb_gen',
+    'src/python/pants/backend/codegen:plugin',
     'src/python/pants/backend/codegen/targets:java',
+    'src/python/pants/backend/codegen/tasks:jaxb_gen',
     'src/python/pants/backend/core:plugin',
     'src/python/pants/util:contextutil',
     'tests/python/pants_test/tasks:task_test_base',

tests/python/pants_test/backend/codegen/tasks/test_jaxb_gen.py

@@ -5,10 +5,12 @@
 from __future__ import (absolute_import, division, generators, nested_scopes, print_function,
                         unicode_literals, with_statement)
 
+import os
+
 from pants.backend.codegen.register import build_file_aliases as register_codegen
+from pants.backend.codegen.targets.jaxb_library import JaxbLibrary
 from pants.backend.codegen.tasks.jaxb_gen import JaxbGen
 from pants.backend.core.register import build_file_aliases as register_core
-from pants.util.contextutil import temporary_file
 from pants_test.tasks.task_test_base import TaskTestBase
 
 
@@ -21,12 +23,6 @@ def task_type(cls):
   def alias_groups(self):
     return register_core().merge(register_codegen())
 
-  def assert_files(self, package, contents, *expected_files):
-    with temporary_file() as fp:
-      fp.write(contents)
-      fp.close()
-      self.assertEqual(set(expected_files), set(JaxbGen._sources_to_be_generated(package, fp.name)))
-
   def create_schema(self, *component_names):
     return ('<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">\n'
          + '\n'.join(self.create_complex_type(c) for c in component_names)
@@ -44,39 +40,6 @@ def create_complex_type(self, name):
             </xsd:complexType>'''.format(name=name)
     )
 
-  def test_plain(self):
-    self.assert_files(
-      'com.actual.package',
-      self.create_schema('ComplicatedVegetable', 'Orange', 'Apple', 'Aardvark'),
-      'com/actual/package/ObjectFactory.java',
-      'com/actual/package/ComplicatedVegetable.java',
-      'com/actual/package/Orange.java',
-      'com/actual/package/Aardvark.java',
-      'com/actual/package/Apple.java'
-    )
-
-  def test_slashes(self):
-    self.assert_files(
-      'com/actual/package',
-      self.create_schema('ComplicatedVegetable', 'Orange', 'Apple', 'Aardvark'),
-      'com/actual/package/ObjectFactory.java',
-      'com/actual/package/ComplicatedVegetable.java',
-      'com/actual/package/Orange.java',
-      'com/actual/package/Aardvark.java',
-      'com/actual/package/Apple.java'
-    )
-
-  def test_leadtail(self):
-    self.assert_files(
-      '/com/actual/package/',
-      self.create_schema('ComplicatedVegetable', 'Orange', 'Apple', 'Aardvark'),
-      'com/actual/package/ObjectFactory.java',
-      'com/actual/package/ComplicatedVegetable.java',
-      'com/actual/package/Orange.java',
-      'com/actual/package/Aardvark.java',
-      'com/actual/package/Apple.java'
-    )
-
   def test_correct_package(self):
     fix = JaxbGen._correct_package
     self.assertEqual(fix('com.foo.bar'), 'com.foo.bar', 'Expected no change.')
@@ -114,3 +77,24 @@ def guess(path):
     self.assertEqual(guess('pantsbuild/potato/Potato.java'),
                      'pantsbuild.potato',
                      'Failed with no prefix: {0}'.format(guess_history[-1]))
+
+  def test_simple(self):
+    self.set_options(use_nailgun=False)
+    self.create_file('foo/vegetable.xml', self.create_schema('Vegetable'))
+    jaxblib = self.make_target('foo:jaxblib', JaxbLibrary, sources=['vegetable.xml'])
+    context = self.context(target_roots=[jaxblib])
+    task = self.create_task(context)
+    task.execute()
+    files = []
+    for (dirpath, dirnames, filenames) in os.walk(task.workdir):
+      for filename in filenames:
+        if filename.endswith('.java'):
+          files.append(os.path.join(dirpath, filename))
+    self.assertEquals(sorted(['ObjectFactory.java', 'Vegetable.java']),
+                      sorted([os.path.basename(f) for f in files]))
+
+    # Make sure there is no header with a timestamp in the generated file
+    for f in files:
+      with open(f) as jaxb_file:
+        contents = jaxb_file.read()
+        self.assertNotIn('// Generated on:', contents)