Add tests to lint-v2 and fmt-v2 (pantsbuild#8668)

### Problem

We weren't testing `lint`, which has an edge case when one of the targets results in a lint failure. `fmt` had an integration test which can be rewritten to a less costly unit test.

### Result

We test more edge cases.

It should be easier to write future tests for these files and to write `run_rule()`-based tests for other rules, as the more examples we have of how to test rules, the easier it will become.

src/python/pants/rules/core/BUILD

@@ -26,6 +26,7 @@ python_tests(
     'src/python/pants/backend/jvm/targets:all',
     'src/python/pants/backend/python/targets',
     'src/python/pants/build_graph',
+    'src/python/pants/engine:fs',
     'src/python/pants/engine/legacy:graph',
     'src/python/pants/engine/legacy:structs',
     'src/python/pants/testutil:test_base',
@@ -43,7 +44,6 @@ python_tests(
     'examples/src/java/org/pantsbuild/example:hello_directory',
     'examples/src/scala/org/pantsbuild/example:hello_directory',
     'examples/src/resources/org/pantsbuild/example:hello_directory',
-    'testprojects/tests/java/org/pantsbuild/testproject:dummies_directory',
   ],
   tags = {'integration'},
 )

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

@@ -36,12 +36,12 @@ class Fmt(Goal):
 @console_rule
 def fmt(console: Console, targets: HydratedTargets, union_membership: UnionMembership) -> Fmt:
   results = yield [
-          Get(FmtResult, TargetWithSources, target.adaptor)
-          for target in targets
-          # TODO: make TargetAdaptor return a 'sources' field with an empty snapshot instead of
-          # raising to remove the hasattr() checks here!
-          if union_membership.is_member(TargetWithSources, target.adaptor) and hasattr(target.adaptor, "sources")
-          ]
+    Get(FmtResult, TargetWithSources, target.adaptor)
+    for target in targets
+    # TODO: make TargetAdaptor return a 'sources' field with an empty snapshot instead of
+    # raising to remove the hasattr() checks here!
+    if union_membership.is_member(TargetWithSources, target.adaptor) and hasattr(target.adaptor, "sources")
+  ]
 
   for result in results:
     files_content = yield Get(FilesContent, Digest, result.digest)
@@ -64,5 +64,5 @@ def fmt(console: Console, targets: HydratedTargets, union_membership: UnionMembe
 
 def rules():
   return [
-      fmt,
-    ]
+    fmt,
+  ]

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

@@ -0,0 +1,53 @@
+# Copyright 2019 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from typing import Callable, List, Tuple, Type
+
+from pants.engine.fs import EMPTY_DIRECTORY_DIGEST, Digest, FilesContent
+from pants.engine.legacy.graph import HydratedTarget, HydratedTargets
+from pants.engine.legacy.structs import JvmAppAdaptor, PythonTargetAdaptor, TargetAdaptor
+from pants.engine.rules import UnionMembership
+from pants.rules.core.fmt import Fmt, FmtResult, TargetWithSources, fmt
+from pants.testutil.engine.util import MockConsole, MockGet, run_rule
+
+
+def make_target(
+  *, name: str = "target", adaptor_type: Type[TargetAdaptor] = PythonTargetAdaptor
+) -> HydratedTarget:
+  return HydratedTarget(
+    address=f"src/{name}",
+    adaptor=adaptor_type(sources=(), name=name),
+    dependencies=()
+  )
+
+
+def run_fmt_rule(
+  *,
+  targets: List[HydratedTarget],
+  mock_formatter: Callable[[PythonTargetAdaptor], FmtResult],
+) -> Tuple[Fmt, MockConsole]:
+  console = MockConsole(use_colors=False)
+  result: Fmt = run_rule(
+    fmt,
+    rule_args=[
+      console,
+      HydratedTargets(targets),
+      UnionMembership(union_rules={TargetWithSources: [PythonTargetAdaptor]})
+    ],
+    mock_gets=[
+      MockGet(product_type=FmtResult, subject_type=PythonTargetAdaptor, mock=mock_formatter),
+      MockGet(product_type=FilesContent, subject_type=Digest, mock=lambda _: FilesContent([]))
+    ],
+  )
+  return result, console
+
+
+def test_non_union_member_noops() -> None:
+  result, console = run_fmt_rule(
+    targets=[make_target(adaptor_type=JvmAppAdaptor)],
+    mock_formatter=lambda adaptor: FmtResult(
+      digest=EMPTY_DIRECTORY_DIGEST, stdout=f"Formatted target `{adaptor.name}`", stderr=""
+    ),
+  )
+  assert result.exit_code == 0
+  assert console.stdout.getvalue().strip() == ""

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

@@ -29,12 +29,12 @@ class Lint(Goal):
 @console_rule
 def lint(console: Console, targets: HydratedTargets, union_membership: UnionMembership) -> Lint:
   results = yield [
-          Get(LintResult, TargetWithSources, target.adaptor)
-          for target in targets
-          # TODO: make TargetAdaptor return a 'sources' field with an empty snapshot instead of
-          # raising to remove the hasattr() checks here!
-          if union_membership.is_member(TargetWithSources, target.adaptor) and hasattr(target.adaptor, "sources")
-          ]
+    Get(LintResult, TargetWithSources, target.adaptor)
+    for target in targets
+    # TODO: make TargetAdaptor return a 'sources' field with an empty snapshot instead of
+    # raising to remove the hasattr() checks here!
+    if union_membership.is_member(TargetWithSources, target.adaptor) and hasattr(target.adaptor, "sources")
+  ]
 
   exit_code = 0
   for result in results:
@@ -50,5 +50,5 @@ def lint(console: Console, targets: HydratedTargets, union_membership: UnionMemb
 
 def rules():
   return [
-      lint,
-    ]
+    lint,
+  ]

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

@@ -0,0 +1,63 @@
+# Copyright 2019 Pants project contributors (see CONTRIBUTORS.md).
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+from typing import Callable, List, Tuple, Type
+
+from pants.engine.legacy.graph import HydratedTarget, HydratedTargets
+from pants.engine.legacy.structs import JvmAppAdaptor, PythonTargetAdaptor, TargetAdaptor
+from pants.engine.rules import UnionMembership
+from pants.rules.core.lint import Lint, LintResult, TargetWithSources, lint
+from pants.testutil.engine.util import MockConsole, MockGet, run_rule
+
+
+def make_target(
+  *, name: str = "target", adaptor_type: Type[TargetAdaptor] = PythonTargetAdaptor
+) -> HydratedTarget:
+  return HydratedTarget(
+    address=f"src/{name}",
+    adaptor=adaptor_type(sources=(), name=name),
+    dependencies=()
+  )
+
+
+def run_lint_rule(
+  *,
+  targets: List[HydratedTarget],
+  mock_linter: Callable[[PythonTargetAdaptor], LintResult],
+) -> Tuple[Lint, MockConsole]:
+  console = MockConsole(use_colors=False)
+  result: Lint = run_rule(
+    lint,
+    rule_args=[
+      console,
+      HydratedTargets(targets),
+      UnionMembership(union_rules={TargetWithSources: [PythonTargetAdaptor]})
+    ],
+    mock_gets=[
+      MockGet(product_type=LintResult, subject_type=PythonTargetAdaptor, mock=mock_linter),
+    ],
+  )
+  return result, console
+
+
+def test_non_union_member_noops() -> None:
+  result, console = run_lint_rule(
+    targets=[make_target(adaptor_type=JvmAppAdaptor)],
+    mock_linter=lambda target: LintResult(exit_code=1, stdout="", stderr=""),
+  )
+  assert result.exit_code == 0
+  assert console.stdout.getvalue().strip() == ""
+
+
+def test_failure_for_a_single_target_propagates():
+  def mock_linter(adaptor: PythonTargetAdaptor) -> LintResult:
+    if adaptor.name == "bad":
+      return LintResult(exit_code=127, stdout="failure", stderr="failure")
+    return LintResult(exit_code=0, stdout=f"Linted the target `{adaptor.name}`", stderr="..")
+
+  result, console = run_lint_rule(
+    targets=[make_target(name="good"), make_target(name="bad")], mock_linter=mock_linter,
+  )
+  assert result.exit_code == 127
+  assert console.stdout.getvalue().splitlines() == ["Linted the target `good`", "failure"]
+  assert console.stderr.getvalue().splitlines() == ["..", "failure"]