Move DepSet to blueprint

Bug: 375276086
Test: depset_test.go
Flag: EXEMPT refactor
Change-Id: I408df647fa1ee7854078468985a62019cbf8bbaf
diff --git a/android/Android.bp b/android/Android.bp
index 3b54326..05ce10a 100644
--- a/android/Android.bp
+++ b/android/Android.bp
@@ -50,7 +50,6 @@
         "deapexer.go",
         "defaults.go",
         "defs.go",
-        "depset_generic.go",
         "deptag.go",
         "dirgroup.go",
         "early_module_context.go",
@@ -123,7 +122,6 @@
         "configured_jars_test.go",
         "csuite_config_test.go",
         "defaults_test.go",
-        "depset_test.go",
         "deptag_test.go",
         "expand_test.go",
         "filegroup_test.go",
diff --git a/android/depset_generic.go b/android/depset_generic.go
deleted file mode 100644
index 6dab3b3..0000000
--- a/android/depset_generic.go
+++ /dev/null
@@ -1,265 +0,0 @@
-// Copyright 2020 Google Inc. All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package android
-
-import (
-	"fmt"
-	"iter"
-	"slices"
-
-	"github.com/google/blueprint"
-)
-
-// DepSet is designed to be conceptually compatible with Bazel's depsets:
-// https://docs.bazel.build/versions/master/skylark/depsets.html
-
-type DepSetOrder int
-
-const (
-	PREORDER DepSetOrder = iota
-	POSTORDER
-	TOPOLOGICAL
-)
-
-func (o DepSetOrder) String() string {
-	switch o {
-	case PREORDER:
-		return "PREORDER"
-	case POSTORDER:
-		return "POSTORDER"
-	case TOPOLOGICAL:
-		return "TOPOLOGICAL"
-	default:
-		panic(fmt.Errorf("Invalid DepSetOrder %d", o))
-	}
-}
-
-type depSettableType comparable
-
-// A DepSet efficiently stores a slice of an arbitrary type from transitive dependencies without
-// copying. It is stored as a DAG of DepSet nodes, each of which has some direct contents and a list
-// of dependency DepSet nodes.
-//
-// A DepSet has an order that will be used to walk the DAG when ToList() is called.  The order
-// can be POSTORDER, PREORDER, or TOPOLOGICAL.  POSTORDER and PREORDER orders return a postordered
-// or preordered left to right flattened list.  TOPOLOGICAL returns a list that guarantees that
-// elements of children are listed after all of their parents (unless there are duplicate direct
-// elements in the DepSet or any of its transitive dependencies, in which case the ordering of the
-// duplicated element is not guaranteed).
-//
-// A DepSet is created by NewDepSet or NewDepSetBuilder.Build from the slice for direct contents
-// and the *DepSets of dependencies. A DepSet is immutable once created.
-type DepSet[T depSettableType] struct {
-	handle *depSet[T]
-}
-
-type depSet[T depSettableType] struct {
-	preorder   bool
-	reverse    bool
-	order      DepSetOrder
-	direct     []T
-	transitive []DepSet[T]
-}
-
-func (d DepSet[T]) impl() *depSet[T] {
-	return d.handle
-}
-
-func (d DepSet[T]) order() DepSetOrder {
-	impl := d.impl()
-	return impl.order
-}
-
-type depSetGob[T depSettableType] struct {
-	Preorder   bool
-	Reverse    bool
-	Order      DepSetOrder
-	Direct     []T
-	Transitive []DepSet[T]
-}
-
-func (d *DepSet[T]) ToGob() *depSetGob[T] {
-	impl := d.impl()
-	return &depSetGob[T]{
-		Preorder:   impl.preorder,
-		Reverse:    impl.reverse,
-		Order:      impl.order,
-		Direct:     impl.direct,
-		Transitive: impl.transitive,
-	}
-}
-
-func (d *DepSet[T]) FromGob(data *depSetGob[T]) {
-	d.handle = &depSet[T]{
-		preorder:   data.Preorder,
-		reverse:    data.Reverse,
-		order:      data.Order,
-		direct:     data.Direct,
-		transitive: data.Transitive,
-	}
-}
-
-func (d *DepSet[T]) GobEncode() ([]byte, error) {
-	return blueprint.CustomGobEncode[depSetGob[T]](d)
-}
-
-func (d *DepSet[T]) GobDecode(data []byte) error {
-	return blueprint.CustomGobDecode[depSetGob[T]](data, d)
-}
-
-// NewDepSet returns an immutable DepSet with the given order, direct and transitive contents.
-func NewDepSet[T depSettableType](order DepSetOrder, direct []T, transitive []DepSet[T]) DepSet[T] {
-	var directCopy []T
-	var transitiveCopy []DepSet[T]
-	nonEmptyTransitiveCount := 0
-	for _, t := range transitive {
-		if t.handle != nil {
-			if t.order() != order {
-				panic(fmt.Errorf("incompatible order, new DepSet is %s but transitive DepSet is %s",
-					order, t.order()))
-			}
-			nonEmptyTransitiveCount++
-		}
-	}
-
-	if nonEmptyTransitiveCount > 0 {
-		transitiveCopy = make([]DepSet[T], 0, nonEmptyTransitiveCount)
-	}
-	var transitiveIter iter.Seq2[int, DepSet[T]]
-	if order == TOPOLOGICAL {
-		// TOPOLOGICAL is implemented as a postorder traversal followed by reversing the output.
-		// Pre-reverse the inputs here so their order is maintained in the output.
-		directCopy = ReverseSlice(direct)
-		transitiveIter = slices.Backward(transitive)
-	} else {
-		directCopy = slices.Clone(direct)
-		transitiveIter = slices.All(transitive)
-	}
-	for _, t := range transitiveIter {
-		if t.handle != nil {
-			transitiveCopy = append(transitiveCopy, t)
-		}
-	}
-
-	if len(directCopy) == 0 && len(transitive) == 0 {
-		return DepSet[T]{nil}
-	}
-
-	depSet := &depSet[T]{
-		preorder:   order == PREORDER,
-		reverse:    order == TOPOLOGICAL,
-		order:      order,
-		direct:     directCopy,
-		transitive: transitiveCopy,
-	}
-
-	return DepSet[T]{depSet}
-}
-
-// DepSetBuilder is used to create an immutable DepSet.
-type DepSetBuilder[T depSettableType] struct {
-	order      DepSetOrder
-	direct     []T
-	transitive []DepSet[T]
-}
-
-// NewDepSetBuilder returns a DepSetBuilder to create an immutable DepSet with the given order and
-// type, represented by a slice of type that will be in the DepSet.
-func NewDepSetBuilder[T depSettableType](order DepSetOrder) *DepSetBuilder[T] {
-	return &DepSetBuilder[T]{
-		order: order,
-	}
-}
-
-// DirectSlice adds direct contents to the DepSet being built by a DepSetBuilder. Newly added direct
-// contents are to the right of any existing direct contents.
-func (b *DepSetBuilder[T]) DirectSlice(direct []T) *DepSetBuilder[T] {
-	b.direct = append(b.direct, direct...)
-	return b
-}
-
-// Direct adds direct contents to the DepSet being built by a DepSetBuilder. Newly added direct
-// contents are to the right of any existing direct contents.
-func (b *DepSetBuilder[T]) Direct(direct ...T) *DepSetBuilder[T] {
-	b.direct = append(b.direct, direct...)
-	return b
-}
-
-// Transitive adds transitive contents to the DepSet being built by a DepSetBuilder. Newly added
-// transitive contents are to the right of any existing transitive contents.
-func (b *DepSetBuilder[T]) Transitive(transitive ...DepSet[T]) *DepSetBuilder[T] {
-	for _, t := range transitive {
-		if t.handle != nil && t.order() != b.order {
-			panic(fmt.Errorf("incompatible order, new DepSet is %s but transitive DepSet is %s",
-				b.order, t.order()))
-		}
-	}
-	b.transitive = append(b.transitive, transitive...)
-	return b
-}
-
-// Returns the DepSet being built by this DepSetBuilder.  The DepSetBuilder retains its contents
-// for creating more depSets.
-func (b *DepSetBuilder[T]) Build() DepSet[T] {
-	return NewDepSet(b.order, b.direct, b.transitive)
-}
-
-// walk calls the visit method in depth-first order on a DepSet, preordered if d.preorder is set,
-// otherwise postordered.
-func (d DepSet[T]) walk(visit func([]T)) {
-	visited := make(map[DepSet[T]]bool)
-
-	var dfs func(d DepSet[T])
-	dfs = func(d DepSet[T]) {
-		impl := d.impl()
-		visited[d] = true
-		if impl.preorder {
-			visit(impl.direct)
-		}
-		for _, dep := range impl.transitive {
-			if !visited[dep] {
-				dfs(dep)
-			}
-		}
-
-		if !impl.preorder {
-			visit(impl.direct)
-		}
-	}
-
-	dfs(d)
-}
-
-// ToList returns the DepSet flattened to a list.  The order in the list is based on the order
-// of the DepSet.  POSTORDER and PREORDER orders return a postordered or preordered left to right
-// flattened list.  TOPOLOGICAL returns a list that guarantees that elements of children are listed
-// after all of their parents (unless there are duplicate direct elements in the DepSet or any of
-// its transitive dependencies, in which case the ordering of the duplicated element is not
-// guaranteed).
-func (d DepSet[T]) ToList() []T {
-	if d.handle == nil {
-		return nil
-	}
-	impl := d.impl()
-	var list []T
-	d.walk(func(paths []T) {
-		list = append(list, paths...)
-	})
-	list = firstUniqueInPlace(list)
-	if impl.reverse {
-		ReverseSliceInPlace(list)
-	}
-	return list
-}
diff --git a/android/depset_test.go b/android/depset_test.go
deleted file mode 100644
index 46c5b99..0000000
--- a/android/depset_test.go
+++ /dev/null
@@ -1,307 +0,0 @@
-// Copyright 2020 Google Inc. All rights reserved.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//     http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-package android
-
-import (
-	"fmt"
-	"reflect"
-	"strings"
-	"testing"
-)
-
-func ExampleDepSet_ToList_postordered() {
-	a := NewDepSetBuilder[Path](POSTORDER).Direct(PathForTesting("a")).Build()
-	b := NewDepSetBuilder[Path](POSTORDER).Direct(PathForTesting("b")).Transitive(a).Build()
-	c := NewDepSetBuilder[Path](POSTORDER).Direct(PathForTesting("c")).Transitive(a).Build()
-	d := NewDepSetBuilder[Path](POSTORDER).Direct(PathForTesting("d")).Transitive(b, c).Build()
-
-	fmt.Println(Paths(d.ToList()).Strings())
-	// Output: [a b c d]
-}
-
-func ExampleDepSet_ToList_preordered() {
-	a := NewDepSetBuilder[Path](PREORDER).Direct(PathForTesting("a")).Build()
-	b := NewDepSetBuilder[Path](PREORDER).Direct(PathForTesting("b")).Transitive(a).Build()
-	c := NewDepSetBuilder[Path](PREORDER).Direct(PathForTesting("c")).Transitive(a).Build()
-	d := NewDepSetBuilder[Path](PREORDER).Direct(PathForTesting("d")).Transitive(b, c).Build()
-
-	fmt.Println(Paths(d.ToList()).Strings())
-	// Output: [d b a c]
-}
-
-func ExampleDepSet_ToList_topological() {
-	a := NewDepSetBuilder[Path](TOPOLOGICAL).Direct(PathForTesting("a")).Build()
-	b := NewDepSetBuilder[Path](TOPOLOGICAL).Direct(PathForTesting("b")).Transitive(a).Build()
-	c := NewDepSetBuilder[Path](TOPOLOGICAL).Direct(PathForTesting("c")).Transitive(a).Build()
-	d := NewDepSetBuilder[Path](TOPOLOGICAL).Direct(PathForTesting("d")).Transitive(b, c).Build()
-
-	fmt.Println(Paths(d.ToList()).Strings())
-	// Output: [d b c a]
-}
-
-// Tests based on Bazel's ExpanderTestBase.java to ensure compatibility
-// https://github.com/bazelbuild/bazel/blob/master/src/test/java/com/google/devtools/build/lib/collect/nestedset/ExpanderTestBase.java
-func TestDepSet(t *testing.T) {
-	a := PathForTesting("a")
-	b := PathForTesting("b")
-	c := PathForTesting("c")
-	c2 := PathForTesting("c2")
-	d := PathForTesting("d")
-	e := PathForTesting("e")
-
-	tests := []struct {
-		name                             string
-		depSet                           func(t *testing.T, order DepSetOrder) DepSet[Path]
-		postorder, preorder, topological []string
-	}{
-		{
-			name: "simple",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				return NewDepSet[Path](order, Paths{c, a, b}, nil)
-			},
-			postorder:   []string{"c", "a", "b"},
-			preorder:    []string{"c", "a", "b"},
-			topological: []string{"c", "a", "b"},
-		},
-		{
-			name: "simpleNoDuplicates",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				return NewDepSet[Path](order, Paths{c, a, a, a, b}, nil)
-			},
-			postorder:   []string{"c", "a", "b"},
-			preorder:    []string{"c", "a", "b"},
-			topological: []string{"c", "a", "b"},
-		},
-		{
-			name: "nesting",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				subset := NewDepSet[Path](order, Paths{c, a, e}, nil)
-				return NewDepSet[Path](order, Paths{b, d}, []DepSet[Path]{subset})
-			},
-			postorder:   []string{"c", "a", "e", "b", "d"},
-			preorder:    []string{"b", "d", "c", "a", "e"},
-			topological: []string{"b", "d", "c", "a", "e"},
-		},
-		{
-			name: "builderReuse",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				assertEquals := func(t *testing.T, w, g Paths) {
-					t.Helper()
-					if !reflect.DeepEqual(w, g) {
-						t.Errorf("want %q, got %q", w, g)
-					}
-				}
-				builder := NewDepSetBuilder[Path](order)
-				assertEquals(t, nil, builder.Build().ToList())
-
-				builder.Direct(b)
-				assertEquals(t, Paths{b}, builder.Build().ToList())
-
-				builder.Direct(d)
-				assertEquals(t, Paths{b, d}, builder.Build().ToList())
-
-				child := NewDepSetBuilder[Path](order).Direct(c, a, e).Build()
-				builder.Transitive(child)
-				return builder.Build()
-			},
-			postorder:   []string{"c", "a", "e", "b", "d"},
-			preorder:    []string{"b", "d", "c", "a", "e"},
-			topological: []string{"b", "d", "c", "a", "e"},
-		},
-		{
-			name: "builderChaining",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				return NewDepSetBuilder[Path](order).Direct(b).Direct(d).
-					Transitive(NewDepSetBuilder[Path](order).Direct(c, a, e).Build()).Build()
-			},
-			postorder:   []string{"c", "a", "e", "b", "d"},
-			preorder:    []string{"b", "d", "c", "a", "e"},
-			topological: []string{"b", "d", "c", "a", "e"},
-		},
-		{
-			name: "transitiveDepsHandledSeparately",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				subset := NewDepSetBuilder[Path](order).Direct(c, a, e).Build()
-				builder := NewDepSetBuilder[Path](order)
-				// The fact that we add the transitive subset between the Direct(b) and Direct(d)
-				// calls should not change the result.
-				builder.Direct(b)
-				builder.Transitive(subset)
-				builder.Direct(d)
-				return builder.Build()
-			},
-			postorder:   []string{"c", "a", "e", "b", "d"},
-			preorder:    []string{"b", "d", "c", "a", "e"},
-			topological: []string{"b", "d", "c", "a", "e"},
-		},
-		{
-			name: "nestingNoDuplicates",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				subset := NewDepSetBuilder[Path](order).Direct(c, a, e).Build()
-				return NewDepSetBuilder[Path](order).Direct(b, d, e).Transitive(subset).Build()
-			},
-			postorder:   []string{"c", "a", "e", "b", "d"},
-			preorder:    []string{"b", "d", "e", "c", "a"},
-			topological: []string{"b", "d", "c", "a", "e"},
-		},
-		{
-			name: "chain",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				c := NewDepSetBuilder[Path](order).Direct(c).Build()
-				b := NewDepSetBuilder[Path](order).Direct(b).Transitive(c).Build()
-				a := NewDepSetBuilder[Path](order).Direct(a).Transitive(b).Build()
-
-				return a
-			},
-			postorder:   []string{"c", "b", "a"},
-			preorder:    []string{"a", "b", "c"},
-			topological: []string{"a", "b", "c"},
-		},
-		{
-			name: "diamond",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				d := NewDepSetBuilder[Path](order).Direct(d).Build()
-				c := NewDepSetBuilder[Path](order).Direct(c).Transitive(d).Build()
-				b := NewDepSetBuilder[Path](order).Direct(b).Transitive(d).Build()
-				a := NewDepSetBuilder[Path](order).Direct(a).Transitive(b).Transitive(c).Build()
-
-				return a
-			},
-			postorder:   []string{"d", "b", "c", "a"},
-			preorder:    []string{"a", "b", "d", "c"},
-			topological: []string{"a", "b", "c", "d"},
-		},
-		{
-			name: "extendedDiamond",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				d := NewDepSetBuilder[Path](order).Direct(d).Build()
-				e := NewDepSetBuilder[Path](order).Direct(e).Build()
-				b := NewDepSetBuilder[Path](order).Direct(b).Transitive(d).Transitive(e).Build()
-				c := NewDepSetBuilder[Path](order).Direct(c).Transitive(e).Transitive(d).Build()
-				a := NewDepSetBuilder[Path](order).Direct(a).Transitive(b).Transitive(c).Build()
-				return a
-			},
-			postorder:   []string{"d", "e", "b", "c", "a"},
-			preorder:    []string{"a", "b", "d", "e", "c"},
-			topological: []string{"a", "b", "c", "e", "d"},
-		},
-		{
-			name: "extendedDiamondRightArm",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				d := NewDepSetBuilder[Path](order).Direct(d).Build()
-				e := NewDepSetBuilder[Path](order).Direct(e).Build()
-				b := NewDepSetBuilder[Path](order).Direct(b).Transitive(d).Transitive(e).Build()
-				c2 := NewDepSetBuilder[Path](order).Direct(c2).Transitive(e).Transitive(d).Build()
-				c := NewDepSetBuilder[Path](order).Direct(c).Transitive(c2).Build()
-				a := NewDepSetBuilder[Path](order).Direct(a).Transitive(b).Transitive(c).Build()
-				return a
-			},
-			postorder:   []string{"d", "e", "b", "c2", "c", "a"},
-			preorder:    []string{"a", "b", "d", "e", "c", "c2"},
-			topological: []string{"a", "b", "c", "c2", "e", "d"},
-		},
-		{
-			name: "orderConflict",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				child1 := NewDepSetBuilder[Path](order).Direct(a, b).Build()
-				child2 := NewDepSetBuilder[Path](order).Direct(b, a).Build()
-				parent := NewDepSetBuilder[Path](order).Transitive(child1).Transitive(child2).Build()
-				return parent
-			},
-			postorder:   []string{"a", "b"},
-			preorder:    []string{"a", "b"},
-			topological: []string{"b", "a"},
-		},
-		{
-			name: "orderConflictNested",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				a := NewDepSetBuilder[Path](order).Direct(a).Build()
-				b := NewDepSetBuilder[Path](order).Direct(b).Build()
-				child1 := NewDepSetBuilder[Path](order).Transitive(a).Transitive(b).Build()
-				child2 := NewDepSetBuilder[Path](order).Transitive(b).Transitive(a).Build()
-				parent := NewDepSetBuilder[Path](order).Transitive(child1).Transitive(child2).Build()
-				return parent
-			},
-			postorder:   []string{"a", "b"},
-			preorder:    []string{"a", "b"},
-			topological: []string{"b", "a"},
-		},
-		{
-			name: "zeroDepSet",
-			depSet: func(t *testing.T, order DepSetOrder) DepSet[Path] {
-				a := NewDepSetBuilder[Path](order).Build()
-				var b DepSet[Path]
-				c := NewDepSetBuilder[Path](order).Direct(c).Transitive(a, b).Build()
-				return c
-			},
-			postorder:   []string{"c"},
-			preorder:    []string{"c"},
-			topological: []string{"c"},
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.name, func(t *testing.T) {
-			t.Run("postorder", func(t *testing.T) {
-				depSet := tt.depSet(t, POSTORDER)
-				if g, w := Paths(depSet.ToList()).Strings(), tt.postorder; !reflect.DeepEqual(g, w) {
-					t.Errorf("expected ToList() = %q, got %q", w, g)
-				}
-			})
-			t.Run("preorder", func(t *testing.T) {
-				depSet := tt.depSet(t, PREORDER)
-				if g, w := Paths(depSet.ToList()).Strings(), tt.preorder; !reflect.DeepEqual(g, w) {
-					t.Errorf("expected ToList() = %q, got %q", w, g)
-				}
-			})
-			t.Run("topological", func(t *testing.T) {
-				depSet := tt.depSet(t, TOPOLOGICAL)
-				if g, w := Paths(depSet.ToList()).Strings(), tt.topological; !reflect.DeepEqual(g, w) {
-					t.Errorf("expected ToList() = %q, got %q", w, g)
-				}
-			})
-		})
-	}
-}
-
-func TestDepSetInvalidOrder(t *testing.T) {
-	orders := []DepSetOrder{POSTORDER, PREORDER, TOPOLOGICAL}
-
-	run := func(t *testing.T, order1, order2 DepSetOrder) {
-		defer func() {
-			if r := recover(); r != nil {
-				if err, ok := r.(error); !ok {
-					t.Fatalf("expected panic error, got %v", err)
-				} else if !strings.Contains(err.Error(), "incompatible order") {
-					t.Fatalf("expected incompatible order error, got %v", err)
-				}
-			}
-		}()
-		NewDepSet(order1, nil, []DepSet[Path]{NewDepSet[Path](order2, Paths{PathForTesting("a")}, nil)})
-		t.Fatal("expected panic")
-	}
-
-	for _, order1 := range orders {
-		t.Run(order1.String(), func(t *testing.T) {
-			for _, order2 := range orders {
-				t.Run(order2.String(), func(t *testing.T) {
-					if order1 != order2 {
-						run(t, order1, order2)
-					}
-				})
-			}
-		})
-	}
-}