Refactor find_valid_field_sets. (#10732)

- Now it's possible to get the FieldSets that subclass some
  given superclass for any arbitrary set of targets.
- The previous logic, that applies this to the target roots,
  now uses this new logic.
- Also removes FieldSetWithOrigin, which was unused,
  and would have complicated the refactoring.
- Also improves error messages in setup_py.py, that
  are unrelated to this change but didn't merit their
  own change.

[ci skip-rust]

[ci skip-build-wheels]

src/python/pants/backend/awslambda/common/awslambda_common_rules.py

@@ -10,7 +10,7 @@
 from pants.engine.fs import Digest, MergeDigests, Workspace
 from pants.engine.goal import Goal, GoalSubsystem, LineOriented
 from pants.engine.rules import Get, MultiGet, collect_rules, goal_rule
-from pants.engine.target import FieldSet, TargetsToValidFieldSets, TargetsToValidFieldSetsRequest
+from pants.engine.target import FieldSet, TargetRootsToFieldSets, TargetRootsToFieldSetsRequest
 from pants.engine.unions import union
 
 
@@ -49,11 +49,11 @@ async def create_awslambda(
     workspace: Workspace,
 ) -> AWSLambdaGoal:
     targets_to_valid_field_sets = await Get(
-        TargetsToValidFieldSets,
-        TargetsToValidFieldSetsRequest(
+        TargetRootsToFieldSets,
+        TargetRootsToFieldSetsRequest(
             AWSLambdaFieldSet,
             goal_description="the `awslambda` goal",
-            error_if_no_valid_targets=True,
+            error_if_no_applicable_targets=True,
         ),
     )
     awslambdas = await MultiGet(

src/python/pants/backend/python/goals/setup_py.py

@@ -87,20 +87,26 @@ class TargetNotExported(Exception):
     """Indicates a target that was expected to be exported is not."""
 
 
-class NoOwnerError(Exception):
-    """Indicates an exportable target has no owning exported target."""
+class InvalidEntryPoint(Exception):
+    """Indicates that a specified binary entry point was invalid."""
 
 
-class AmbiguousOwnerError(Exception):
-    """Indicates an exportable target has more than one owning exported target."""
+class OwnershipError(Exception):
+    """An error related to target ownership calculation."""
 
+    def __init__(self, msg: str):
+        super().__init__(
+            f"{msg} See https://www.pantsbuild.org/v2.0/docs/python-setup-py-goal for "
+            f"how python_library targets are mapped to distributions."
+        )
 
-class UnsupportedPythonVersion(Exception):
-    """Indicates that the Python version is unsupported for running setup.py commands."""
 
+class NoOwnerError(OwnershipError):
+    """Indicates an exportable target has no owning exported target."""
 
-class InvalidEntryPoint(Exception):
-    """Indicates that a specified binary entry point was invalid."""
+
+class AmbiguousOwnerError(OwnershipError):
+    """Indicates an exportable target has more than one owning exported target."""
 
 
 @dataclass(frozen=True)
@@ -739,14 +745,19 @@ async def get_exporting_owner(owned_dependency: OwnedDependency) -> ExportedTarg
                     sibling_owners.append(sibling)
                 sibling = next(exported_ancestor_iter, None)
             if sibling_owners:
+                all_owners = [exported_ancestor] + sibling_owners
                 raise AmbiguousOwnerError(
-                    f"Exporting owners for {target.address} are "
-                    f"ambiguous. Found {exported_ancestor.address} and "
-                    f"{len(sibling_owners)} others: "
-                    f'{", ".join(so.address.spec for so in sibling_owners)}'
+                    f"Found multiple sibling python_distribution targets that are the closest "
+                    f"ancestor dependees of {target.address} and are therefore candidates to "
+                    f"own it: {', '.join(o.address.spec for o in all_owners)}. Only a "
+                    f"single such owner is allowed, to avoid ambiguity."
                 )
             return ExportedTarget(owner)
-    raise NoOwnerError(f"No exported target owner found for {target.address}")
+    raise NoOwnerError(
+        f"No python_distribution target found to own {target.address}. Note that "
+        f"the owner must be in or above the owned target's directory, and must "
+        f"depend on it (directly or indirectly)."
+    )
 
 
 @rule(desc="Set up setuptools")

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

@@ -9,7 +9,7 @@
 from pants.engine.fs import Digest, MergeDigests, Snapshot, Workspace
 from pants.engine.goal import Goal, GoalSubsystem
 from pants.engine.rules import Get, MultiGet, collect_rules, goal_rule
-from pants.engine.target import FieldSet, TargetsToValidFieldSets, TargetsToValidFieldSetsRequest
+from pants.engine.target import FieldSet, TargetRootsToFieldSets, TargetRootsToFieldSetsRequest
 from pants.engine.unions import union
 
 logger = logging.getLogger(__name__)
@@ -41,9 +41,11 @@ class Binary(Goal):
 @goal_rule
 async def create_binary(workspace: Workspace, dist_dir: DistDir) -> Binary:
     targets_to_valid_field_sets = await Get(
-        TargetsToValidFieldSets,
-        TargetsToValidFieldSetsRequest(
-            BinaryFieldSet, goal_description="the `binary` goal", error_if_no_valid_targets=True
+        TargetRootsToFieldSets,
+        TargetRootsToFieldSetsRequest(
+            BinaryFieldSet,
+            goal_description="the `binary` goal",
+            error_if_no_applicable_targets=True,
         ),
     )
     binaries = await MultiGet(

src/python/pants/core/goals/run.py

@@ -12,7 +12,7 @@
 from pants.engine.goal import Goal, GoalSubsystem
 from pants.engine.process import InteractiveProcess, InteractiveRunner
 from pants.engine.rules import Get, collect_rules, goal_rule
-from pants.engine.target import FieldSet, TargetsToValidFieldSets, TargetsToValidFieldSetsRequest
+from pants.engine.target import FieldSet, TargetRootsToFieldSets, TargetRootsToFieldSetsRequest
 from pants.engine.unions import union
 from pants.option.custom_types import shell_str
 from pants.option.global_options import GlobalOptions
@@ -89,11 +89,11 @@ async def run(
     build_root: BuildRoot,
 ) -> Run:
     targets_to_valid_field_sets = await Get(
-        TargetsToValidFieldSets,
-        TargetsToValidFieldSetsRequest(
+        TargetRootsToFieldSets,
+        TargetRootsToFieldSetsRequest(
             RunFieldSet,
             goal_description="the `run` goal",
-            error_if_no_valid_targets=True,
+            error_if_no_applicable_targets=True,
             expect_single_field_set=True,
         ),
     )

src/python/pants/core/goals/run_test.py

@@ -14,8 +14,8 @@
 from pants.engine.process import InteractiveProcess, InteractiveRunner
 from pants.engine.target import (
     Target,
-    TargetsToValidFieldSets,
-    TargetsToValidFieldSetsRequest,
+    TargetRootsToFieldSets,
+    TargetRootsToFieldSetsRequest,
     TargetWithOrigin,
 )
 from pants.option.global_options import GlobalOptions
@@ -72,9 +72,9 @@ class TestBinaryTarget(Target):
         ],
         mock_gets=[
             MockGet(
-                product_type=TargetsToValidFieldSets,
-                subject_type=TargetsToValidFieldSetsRequest,
-                mock=lambda _: TargetsToValidFieldSets({target_with_origin: [field_set]}),
+                product_type=TargetRootsToFieldSets,
+                subject_type=TargetRootsToFieldSetsRequest,
+                mock=lambda _: TargetRootsToFieldSets({target_with_origin: [field_set]}),
             ),
             MockGet(
                 product_type=RunRequest,

src/python/pants/core/goals/style_request.py

@@ -7,10 +7,10 @@
 
 from pants.engine.collection import Collection
 from pants.engine.fs import Snapshot
-from pants.engine.target import FieldSetWithOrigin
+from pants.engine.target import FieldSet
 from pants.util.meta import frozen_after_init
 
-_FS = TypeVar("_FS", bound=FieldSetWithOrigin)
+_FS = TypeVar("_FS", bound=FieldSet)
 
 
 @frozen_after_init

src/python/pants/core/goals/test.py

@@ -26,8 +26,8 @@
 from pants.engine.target import (
     FieldSet,
     Sources,
-    TargetsToValidFieldSets,
-    TargetsToValidFieldSetsRequest,
+    TargetRootsToFieldSets,
+    TargetRootsToFieldSetsRequest,
 )
 from pants.engine.unions import UnionMembership, union
 from pants.util.frozendict import FrozenDict
@@ -376,9 +376,9 @@ async def run_tests(
 ) -> Test:
     if test_subsystem.debug:
         targets_to_valid_field_sets = await Get(
-            TargetsToValidFieldSets,
-            TargetsToValidFieldSetsRequest(
-                TestFieldSet, goal_description="`test --debug`", error_if_no_valid_targets=True
+            TargetRootsToFieldSets,
+            TargetRootsToFieldSetsRequest(
+                TestFieldSet, goal_description="`test --debug`", error_if_no_applicable_targets=True
             ),
         )
         debug_requests = await MultiGet(
@@ -395,11 +395,11 @@ async def run_tests(
         return Test(exit_code)
 
     targets_to_valid_field_sets = await Get(
-        TargetsToValidFieldSets,
-        TargetsToValidFieldSetsRequest(
+        TargetRootsToFieldSets,
+        TargetRootsToFieldSetsRequest(
             TestFieldSet,
             goal_description=f"the `{test_subsystem.name}` goal",
-            error_if_no_valid_targets=False,
+            error_if_no_applicable_targets=False,
         ),
     )
     field_sets_with_sources = await Get(

src/python/pants/core/goals/test_test.py

@@ -35,8 +35,8 @@
 from pants.engine.target import (
     Sources,
     Target,
-    TargetsToValidFieldSets,
-    TargetsToValidFieldSetsRequest,
+    TargetRootsToFieldSets,
+    TargetRootsToFieldSetsRequest,
     TargetWithOrigin,
 )
 from pants.engine.unions import UnionMembership
@@ -132,11 +132,11 @@ def run_test_rule(
     )
 
     def mock_find_valid_field_sets(
-        _: TargetsToValidFieldSetsRequest,
-    ) -> TargetsToValidFieldSets:
+        _: TargetRootsToFieldSetsRequest,
+    ) -> TargetRootsToFieldSets:
         if not valid_targets:
-            return TargetsToValidFieldSets({})
-        return TargetsToValidFieldSets(
+            return TargetRootsToFieldSets({})
+        return TargetRootsToFieldSets(
             {
                 tgt_with_origin: [field_set.create(tgt_with_origin.target)]
                 for tgt_with_origin in targets
@@ -171,8 +171,8 @@ def mock_coverage_report_generation(
         ],
         mock_gets=[
             MockGet(
-                product_type=TargetsToValidFieldSets,
-                subject_type=TargetsToValidFieldSetsRequest,
+                product_type=TargetRootsToFieldSets,
+                subject_type=TargetRootsToFieldSetsRequest,
                 mock=mock_find_valid_field_sets,
             ),
             MockGet(