A mixin for v2 goals that have non-line-oriented output. (#8565)

The LineOriented mixin is reimplemented as a subclass.

Also detangles print_stderr from this. Callers can access that
directly at console.print_stderr.

src/python/pants/engine/goal.py

@@ -109,42 +109,63 @@ class _GoalOptions(object):
   """A marker trait for the anonymous inner `Goal.Options` classes for `Goal`s."""
 
 
-class LineOriented:
-  """A mixin for Goal that adds Options to support the `line_oriented` context manager."""
+class Outputting:
+  """A mixin for Goal that adds options to support output-related context managers.
+
+  Allows output to go to a file or to stdout.
+
+  Useful for goals whose purpose is to emit output to the end user (as distinct from incidental logging to stderr).
+  """
 
   @classmethod
   def register_options(cls, register):
     super().register_options(register)
-    register('--sep', default='\\n', metavar='<separator>',
-             help='String to use to separate result lines.')
     register('--output-file', metavar='<path>',
-             help='Write line-oriented output to this file instead.')
+             help='Output to this file.  If unspecified, outputs to stdout.')
 
   @classmethod
   @contextmanager
-  def line_oriented(cls, line_oriented_options, console):
-    """Given Goal.Options and a Console, yields functions for writing to stdout and stderr, respectively.
+  def output(cls, options, console):
+    """Given Goal.Options and a Console, yields a function for writing data to stdout, or a file.
 
-    The passed options instance will generally be the `Goal.Options` of a `LineOriented` `Goal`.
+    The passed options instance will generally be the `Goal.Options` of an `Outputting` `Goal`.
     """
-    if type(line_oriented_options) != cls.Options:
-      raise AssertionError(
-          'Expected Options for `{}`, got: {}'.format(cls.__name__, line_oriented_options))
-
-    output_file = line_oriented_options.values.output_file
-    sep = line_oriented_options.values.sep.encode().decode('unicode_escape')
+    with cls.output_sink(options, console) as output_sink:
+      yield lambda msg: output_sink.write(msg)
 
-    if output_file:
-      stdout_file = open(output_file, 'w')
-      print_stdout = lambda msg: print(msg, file=stdout_file, end=sep)
+  @classmethod
+  @contextmanager
+  def output_sink(cls, options, console):
+    if type(options) != cls.Options:
+      raise AssertionError('Expected Options for `{}`, got: {}'.format(cls.__name__, options))
+    stdout_file = None
+    if options.values.output_file:
+      stdout_file = open(options.values.output_file, 'w')
+      output_sink = stdout_file
     else:
-      print_stdout = lambda msg: console.print_stdout(msg, end=sep)
-
-    print_stderr = lambda msg: console.print_stderr(msg)
-
+      output_sink = console.stdout
     try:
-      yield print_stdout, print_stderr
+      yield output_sink
     finally:
-      if output_file:
+      output_sink.flush()
+      if stdout_file:
         stdout_file.close()
-      console.flush()
+
+
+class LineOriented(Outputting):
+  @classmethod
+  def register_options(cls, register):
+    super().register_options(register)
+    register('--sep', default='\\n', metavar='<separator>',
+             help='String to use to separate lines in line-oriented output.')
+
+  @classmethod
+  @contextmanager
+  def line_oriented(cls, options, console):
+    """Given Goal.Options and a Console, yields a function for printing lines to stdout or a file.
+
+    The passed options instance will generally be the `Goal.Options` of an `Outputting` `Goal`.
+    """
+    sep = options.values.sep.encode().decode('unicode_escape')
+    with cls.output_sink(options, console) as output_sink:
+      yield lambda msg: print(msg, file=output_sink, end=sep)

src/python/pants/engine/goal_test.py

@@ -0,0 +1,14 @@
+# Copyright 2019 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from pants.engine.goal import Outputting
+from pants_test.engine.util import MockConsole
+
+
+def test_outputting_goal():
+  class DummyGoal(Outputting):
+    pass
+
+  console = MockConsole()
+  with DummyGoal.output(None, console) as output:
+    pass

src/python/pants/rules/core/binary.py

@@ -32,7 +32,7 @@ class CreatedBinary:
 
 @console_rule
 def create_binary(addresses: BuildFileAddresses, console: Console, workspace: Workspace, options: Binary.Options) -> Binary:
-  with Binary.line_oriented(options, console) as (print_stdout, print_stderr):
+  with Binary.line_oriented(options, console) as print_stdout:
     print_stdout("Generating binaries in `dist/`")
     binaries = yield [Get(CreatedBinary, Address, address.to_address()) for address in addresses]
     dirs_to_materialize = tuple(

src/python/pants/rules/core/filedeps.py

@@ -35,7 +35,7 @@ def file_deps(
     if hasattr(hydrated_target.adaptor, "sources"):
       uniq_set.update(hydrated_target.adaptor.sources.snapshot.files)
 
-  with Filedeps.line_oriented(filedeps_options, console) as (print_stdout, print_stderr):
+  with Filedeps.line_oriented(filedeps_options, console) as print_stdout:
     for f_path in uniq_set:
       print_stdout(f_path)
 

src/python/pants/rules/core/list_roots.py

@@ -46,7 +46,7 @@ def all_roots(source_root_config: SourceRootConfig) -> AllSourceRoots:
 
 @console_rule
 def list_roots(console: Console, options: Roots.Options, all_roots: AllSourceRoots) -> Roots:
-  with Roots.line_oriented(options, console) as (print_stdout, print_stderr):
+  with Roots.line_oriented(options, console) as print_stdout:
     for src_root in sorted(all_roots, key=lambda x: x.path):
       all_langs = ','.join(sorted(src_root.langs))
       print_stdout(f"{src_root.path}: {all_langs or '*'}")

src/python/pants/rules/core/list_targets.py

@@ -68,9 +68,9 @@ def print_documented(target):
     collection = yield Get(BuildFileAddresses, Specs, specs)
     print_fn = lambda address: address.spec
 
-  with List.line_oriented(list_options, console) as (print_stdout, print_stderr):
+  with List.line_oriented(list_options, console) as print_stdout:
     if not collection.dependencies:
-      print_stderr('WARNING: No targets were matched in goal `{}`.'.format('list'))
+      console.print_stderr('WARNING: No targets were matched in goal `{}`.'.format('list'))
 
     for item in collection:
       result = print_fn(item)