tools/src/cts/query: Add Tree

A tree of query to data. Has utilities for reducing the tree based on a
custom merger function.

Bug: dawn:1342
Change-Id: If1c0503be05ee04bcf55dd5bdc9aa3caf6fb56ee
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/87222
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>

tools/src/container/set.go

@@ -14,7 +14,10 @@
 
 package container
 
-import "sort"
+import (
+	"fmt"
+	"sort"
+)
 
 // Set is a generic unordered set, which wrap's go's builtin 'map'.
 // T is the set key, which must match the 'key' constraint.
@@ -98,3 +101,24 @@ func (s Set[T]) List() []T {
 	sort.Slice(out, func(i, j int) bool { return out[i] < out[j] })
 	return out
 }
+
+// One returns a random item from the set, or an empty item if the set is empty.
+func (s Set[T]) One() T {
+	for item := range s {
+		return item
+	}
+	var zero T
+	return zero
+}
+
+// Format writes the Target to the fmt.State
+func (s Set[T]) Format(f fmt.State, verb rune) {
+	fmt.Fprint(f, "[")
+	for i, item := range s.List() {
+		if i > 0 {
+			fmt.Fprint(f, ", ")
+		}
+		fmt.Fprint(f, item)
+	}
+	fmt.Fprint(f, "]")
+}

tools/src/container/set_test.go

@@ -15,6 +15,7 @@
 package container_test
 
 import (
+	"fmt"
 	"testing"
 
 	"dawn.googlesource.com/dawn/tools/src/container"
@@ -143,3 +144,19 @@ func TestSetRemoveAll(t *testing.T) {
 	expectEq(t, "len(s)", len(s), 1)
 	expectEq(t, "s.List()", s.List(), []string{"b"})
 }
+
+func TestSetOne(t *testing.T) {
+	expectEq(t, "NewSet[string]().One()", container.NewSet[string]().One(), "")
+	expectEq(t, `NewSet("x").One()`, container.NewSet("x").One(), "x")
+	if got := container.NewSet("x", "y").One(); got != "x" && got != "y" {
+		t.Errorf(`NewSet("x", "y").One() returned "%v"`, got)
+	}
+}
+
+func TestFormat(t *testing.T) {
+	expectEq(t, "NewSet[string]()", fmt.Sprint(container.NewSet[string]()), "[]")
+	expectEq(t, `NewSet("x")`, fmt.Sprint(container.NewSet("x")), `[x]`)
+	expectEq(t, `NewSet(1)`, fmt.Sprint(container.NewSet(1)), `[1]`)
+	expectEq(t, `NewSet("y", "x")`, fmt.Sprint(container.NewSet("y", "x")), `[x, y]`)
+	expectEq(t, `NewSet(3, 1, 2)`, fmt.Sprint(container.NewSet(3, 1, 2)), `[1, 2, 3]`)
+}