Replace include_special_cased_deps flag with should_traverse_deps_predicate

src/python/pants/backend/project_info/dependencies.py

@@ -7,10 +7,10 @@
 from pants.engine.console import Console
 from pants.engine.goal import Goal, GoalSubsystem, LineOriented
 from pants.engine.rules import Get, MultiGet, collect_rules, goal_rule
+from pants.engine.target import AlwaysTraverseDeps
 from pants.engine.target import Dependencies as DependenciesField
 from pants.engine.target import (
     DependenciesRequest,
-    DepsTraversalPredicates,
     Targets,
     TransitiveTargets,
     TransitiveTargetsRequest,
@@ -46,7 +46,7 @@ async def dependencies(
         transitive_targets = await Get(
             TransitiveTargets,
             TransitiveTargetsRequest(
-                addresses, should_traverse_deps_predicate=DepsTraversalPredicates.always
+                addresses, should_traverse_deps_predicate=AlwaysTraverseDeps()
             ),
         )
         targets = Targets(transitive_targets.dependencies)
@@ -61,7 +61,7 @@ async def dependencies(
                 Targets,
                 DependenciesRequest(
                     tgt.get(DependenciesField),
-                    should_traverse_deps_predicate=DepsTraversalPredicates.always,
+                    should_traverse_deps_predicate=AlwaysTraverseDeps(),
                 ),
             )
             for tgt in target_roots

src/python/pants/backend/project_info/dependents.py

@@ -12,9 +12,9 @@
 from pants.engine.rules import Get, MultiGet, collect_rules, goal_rule, rule
 from pants.engine.target import (
     AllUnexpandedTargets,
+    AlwaysTraverseDeps,
     Dependencies,
     DependenciesRequest,
-    DepsTraversalPredicates,
 )
 from pants.option.option_types import BoolOption
 from pants.util.frozendict import FrozenDict
@@ -33,7 +33,7 @@ async def map_addresses_to_dependents(all_targets: AllUnexpandedTargets) -> Addr
         Get(
             Addresses,
             DependenciesRequest(
-                tgt.get(Dependencies), should_traverse_deps_predicate=DepsTraversalPredicates.always
+                tgt.get(Dependencies), should_traverse_deps_predicate=AlwaysTraverseDeps()
             ),
         )
         for tgt in all_targets

src/python/pants/backend/project_info/filedeps.py

@@ -12,7 +12,7 @@
 from pants.engine.goal import Goal, GoalSubsystem, LineOriented
 from pants.engine.rules import Get, MultiGet, collect_rules, goal_rule
 from pants.engine.target import (
-    DepsTraversalPredicates,
+    AlwaysTraverseDeps,
     HydratedSources,
     HydrateSourcesRequest,
     SourcesField,
@@ -75,7 +75,7 @@ async def file_deps(
         transitive_targets = await Get(
             TransitiveTargets,
             TransitiveTargetsRequest(
-                addresses, should_traverse_deps_predicate=DepsTraversalPredicates.always
+                addresses, should_traverse_deps_predicate=AlwaysTraverseDeps()
             ),
         )
         targets = transitive_targets.closure

src/python/pants/backend/project_info/paths.py

@@ -14,9 +14,9 @@
 from pants.engine.goal import Goal, GoalSubsystem, Outputting
 from pants.engine.rules import Get, MultiGet, collect_rules, goal_rule
 from pants.engine.target import (
+    AlwaysTraverseDeps,
     Dependencies,
     DependenciesRequest,
-    DepsTraversalPredicates,
     Targets,
     TransitiveTargets,
     TransitiveTargetsRequest,
@@ -117,15 +117,15 @@ async def paths(console: Console, paths_subsystem: PathsSubsystem) -> PathsGoal:
     transitive_targets = await Get(
         TransitiveTargets,
         TransitiveTargetsRequest(
-            [root.address], should_traverse_deps_predicate=DepsTraversalPredicates.always
+            [root.address], should_traverse_deps_predicate=AlwaysTraverseDeps()
         ),
     )
 
     adjacent_targets_per_target = await MultiGet(
         Get(
             Targets,
             DependenciesRequest(
-                tgt.get(Dependencies), should_traverse_deps_predicate=DepsTraversalPredicates.always
+                tgt.get(Dependencies), should_traverse_deps_predicate=AlwaysTraverseDeps()
             ),
         )
         for tgt in transitive_targets.closure

src/python/pants/backend/project_info/peek.py

@@ -19,11 +19,11 @@
 from pants.engine.internals.dep_rules import DependencyRuleApplication, DependencyRuleSet
 from pants.engine.rules import Get, MultiGet, collect_rules, goal_rule, rule
 from pants.engine.target import (
+    AlwaysTraverseDeps,
     Dependencies,
     DependenciesRequest,
     DependenciesRuleApplication,
     DependenciesRuleApplicationRequest,
-    DepsTraversalPredicates,
     Field,
     HydratedSources,
     HydrateSourcesRequest,
@@ -181,7 +181,7 @@ async def get_target_data(
         Get(
             Targets,
             DependenciesRequest(
-                tgt.get(Dependencies), should_traverse_deps_predicate=DepsTraversalPredicates.always
+                tgt.get(Dependencies), should_traverse_deps_predicate=AlwaysTraverseDeps()
             ),
         )
         for tgt in sorted_targets

src/python/pants/backend/visibility/lint.py

@@ -13,11 +13,11 @@
 from pants.engine.platform import Platform
 from pants.engine.rules import Get, MultiGet, collect_rules, rule
 from pants.engine.target import (
+    AlwaysTraverseDeps,
     Dependencies,
     DependenciesRequest,
     DependenciesRuleApplication,
     DependenciesRuleApplicationRequest,
-    DepsTraversalPredicates,
     FieldSet,
 )
 from pants.util.logging import LogLevel
@@ -44,7 +44,7 @@ async def check_visibility_rule_violations(
             Addresses,
             DependenciesRequest(
                 field_set.dependencies,
-                should_traverse_deps_predicate=DepsTraversalPredicates.always,
+                should_traverse_deps_predicate=AlwaysTraverseDeps(),
             ),
         )
         for field_set in request.elements

src/python/pants/engine/internals/graph_test.py

@@ -34,11 +34,11 @@
 from pants.engine.target import (
     AllTargets,
     AllUnexpandedTargets,
+    AlwaysTraverseDeps,
     AsyncFieldMixin,
     CoarsenedTargets,
     Dependencies,
     DependenciesRequest,
-    DepsTraversalPredicates,
     ExplicitlyProvidedDependencies,
     Field,
     FieldDefaultFactoryRequest,
@@ -55,6 +55,7 @@
     MultipleSourcesField,
     OverridesField,
     SecondaryOwnerMixin,
+    ShouldTraverseDepsPredicate,
     SingleSourceField,
     SourcesPaths,
     SourcesPathsRequest,
@@ -318,7 +319,7 @@ def get_target(name: str) -> Target:
         Targets,
         [
             DependenciesRequest(
-                root[Dependencies], should_traverse_deps_predicate=DepsTraversalPredicates.always
+                root[Dependencies], should_traverse_deps_predicate=AlwaysTraverseDeps()
             )
         ],
     )
@@ -336,7 +337,7 @@ def get_target(name: str) -> Target:
         [
             TransitiveTargetsRequest(
                 [root.address, d2.address],
-                should_traverse_deps_predicate=DepsTraversalPredicates.always,
+                should_traverse_deps_predicate=AlwaysTraverseDeps(),
             )
         ],
     )
@@ -417,13 +418,17 @@ def get_target(name: str) -> Target:
     )
     assert direct_deps == Targets([d1, d2, d3, d4])
 
+    @dataclass(frozen=True)
+    class SkipMeTagOrTraverse(ShouldTraverseDepsPredicate):
+        def __call__(self, target: Target, field: Dependencies | SpecialCasedDependencies) -> bool:
+            return "skip_deps" not in (target[Tags].value or [])
+
     transitive_targets = transitive_targets_rule_runner.request(
         TransitiveTargets,
         [
             TransitiveTargetsRequest(
                 [root.address, d2.address],
-                should_traverse_deps_predicate=lambda tgt, fld: "skip_deps"
-                not in (tgt[Tags].value or []),
+                should_traverse_deps_predicate=SkipMeTagOrTraverse(),
             )
         ],
     )

src/python/pants/engine/target.py

@@ -39,7 +39,7 @@
     get_type_hints,
 )
 
-from typing_extensions import Protocol, Self, TypeAlias, final
+from typing_extensions import Protocol, Self, final
 
 from pants.base.deprecated import warn_or_error
 from pants.engine.addresses import Address, Addresses, UnparsedAddressInputs, assert_single_address
@@ -714,33 +714,51 @@ def expect_single(self) -> Target:
         return self[0]
 
 
-# If this predicate returns false, then the target's field's deps will be ignored.
-ShouldTraverseDepsPredicate: TypeAlias = (
-    "Callable[[Target, Dependencies | SpecialCasedDependencies], bool]"
-)
+@dataclass(frozen=True)
+class ShouldTraverseDepsPredicate(metaclass=ABCMeta):
+    """This callable determines whether to traverse through deps of a given Target + Field.
 
+    This is a callable dataclass instead of a function to avoid issues with hashing closures.
+    Only the id is used when hashing a function; any closure vars are NOT accounted for.
 
-class DepsTraversalPredicates:
-    """All methods on this class are ShouldTraverseDepsPredicate implementations."""
+    NB: When subclassing a dataclass (like this one), generated methods on a dataclass are NOT
+    inherited because the @dataclass decorator only inspects the current class before generating
+    a function--the decorator does NOT inspect __mro__.
+    """
 
-    @staticmethod
-    def if_dependencies_field(
-        target: Target, field: Dependencies | SpecialCasedDependencies
-    ) -> bool:
-        """This is the default ShouldTraverseDepsPredicate implementation.
+    # This _callable field ensures that __call__ is included in the __hash__ method generated by @dataclass.
+    _callable: Callable[
+        [Target, Dependencies | SpecialCasedDependencies], bool
+    ] = dataclasses.field(init=False, repr=False)
 
-        This skips resolving dependencies for fields (like SpecialCasedDependencies) that are not
-        subclasses of Dependencies.
-        """
+    def __post_init__(self):
+        object.__setattr__(self, "_callable", type(self).__call__)
+
+    @abstractmethod
+    def __call__(self, target: Target, field: Dependencies | SpecialCasedDependencies) -> bool:
+        """If this predicate returns false, then the target's field's deps will be ignored."""
+
+
+@dataclass(frozen=True)
+class TraverseIfDependenciesField(ShouldTraverseDepsPredicate):
+    """This is the default ShouldTraverseDepsPredicate implementation.
+
+    This skips resolving dependencies for fields (like SpecialCasedDependencies) that are not
+    subclasses of Dependencies.
+    """
+
+    def __call__(self, target: Target, field: Dependencies | SpecialCasedDependencies) -> bool:
         return isinstance(field, Dependencies)
 
-    @staticmethod
-    def always(target: Target, field: Dependencies | SpecialCasedDependencies) -> bool:
-        """A predicate to use when a request needs all deps.
 
-        This includes deps from fields like SpecialCasedDependencies which are ignored in most
-        cases.
-        """
+@dataclass(frozen=True)
+class AlwaysTraverseDeps(ShouldTraverseDepsPredicate):
+    """A predicate to use when a request needs all deps.
+
+    This includes deps from fields like SpecialCasedDependencies which are ignored in most cases.
+    """
+
+    def __call__(self, target: Target, field: Dependencies | SpecialCasedDependencies) -> bool:
         return True
 
 
@@ -875,7 +893,7 @@ def __init__(
         roots: Iterable[Address],
         *,
         expanded_targets: bool = False,
-        should_traverse_deps_predicate: ShouldTraverseDepsPredicate = DepsTraversalPredicates.if_dependencies_field,
+        should_traverse_deps_predicate: ShouldTraverseDepsPredicate = TraverseIfDependenciesField(),
     ) -> None:
         object.__setattr__(self, "roots", tuple(roots))
         object.__setattr__(self, "expanded_targets", expanded_targets)
@@ -914,7 +932,7 @@ def __init__(
         self,
         roots: Iterable[Address],
         *,
-        should_traverse_deps_predicate: ShouldTraverseDepsPredicate = DepsTraversalPredicates.if_dependencies_field,
+        should_traverse_deps_predicate: ShouldTraverseDepsPredicate = TraverseIfDependenciesField(),
     ) -> None:
         object.__setattr__(self, "roots", tuple(roots))
         object.__setattr__(self, "should_traverse_deps_predicate", should_traverse_deps_predicate)
@@ -2502,9 +2520,7 @@ def unevaluated_transitive_excludes(self) -> UnparsedAddressInputs:
 @dataclass(frozen=True)
 class DependenciesRequest(EngineAwareParameter):
     field: Dependencies
-    should_traverse_deps_predicate: ShouldTraverseDepsPredicate = (
-        DepsTraversalPredicates.if_dependencies_field
-    )
+    should_traverse_deps_predicate: ShouldTraverseDepsPredicate = TraverseIfDependenciesField()
 
     def debug_hint(self) -> str:
         return self.field.address.spec