benchmark: add encoding/json/v2 benchmarks

benchmark/benchmark_jsonv2_test.go

@@ -0,0 +1,146 @@
+//go:build go1.27 && goexperiment.jsonv2
+
+/*
+encoding/json/v2 benchmarks for the small/medium/large payloads.
+
+encoding/json/v2 ships enabled by default in Go 1.27 (GOEXPERIMENT=jsonv2).
+This file builds only on Go 1.27+ with the experiment on, so older toolchains
+or GOEXPERIMENT=nojsonv2 skip it:
+
+	go test -bench 'JsonV2' -benchmem ./benchmark/
+
+The payload structs have no json tags. v1 matches field names
+case-insensitively by default; v2 does not, so MatchCaseInsensitiveNames(true)
+is passed to keep the comparison with encoding/json like-for-like.
+*/
+package benchmark
+
+import (
+	jsonv2 "encoding/json/v2"
+	"testing"
+)
+
+var jsonV2Opts = jsonv2.MatchCaseInsensitiveNames(true)
+
+// Guards against the benchmarks silently decoding nothing (for example if
+// case-insensitive matching were dropped).
+// reqproof:proptest:skip benchmark sanity check for an external decoder; not a jsonparser behavior
+func TestJsonV2DecodesFixtures(t *testing.T) {
+	var small encodingJSONSmallPayload
+	if err := jsonv2.Unmarshal(smallFixture, &small, jsonV2Opts); err != nil {
+		t.Fatalf("small: %v", err)
+	}
+	if small.Uuid == "" || small.Ua == "" || small.Tz == 0 || small.St == 0 {
+		t.Fatalf("small: fields not populated: %+v", small)
+	}
+
+	var medium encodingJSONMediumPayload
+	if err := jsonv2.Unmarshal(mediumFixture, &medium, jsonV2Opts); err != nil {
+		t.Fatalf("medium: %v", err)
+	}
+	if medium.Person == nil || medium.Person.Name.FullName == "" ||
+		medium.Person.Github.Followers == 0 || len(medium.Person.Gravatar.Avatars) == 0 {
+		t.Fatalf("medium: fields not populated")
+	}
+
+	var large encodingJSONLargePayload
+	if err := jsonv2.Unmarshal(largeFixture, &large, jsonV2Opts); err != nil {
+		t.Fatalf("large: %v", err)
+	}
+	if len(large.Users) == 0 || large.Users[0].Username == "" ||
+		large.Topics == nil || len(large.Topics.Topics) == 0 || large.Topics.Topics[0].Slug == "" {
+		t.Fatalf("large: fields not populated")
+	}
+}
+
+// reqproof:proptest:skip performance benchmark; measures wall-clock time and allocations, output is non-deterministic and not comparable to an independent reference
+func BenchmarkEncodingJsonV2StructSmall(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		var data encodingJSONSmallPayload
+		jsonv2.Unmarshal(smallFixture, &data, jsonV2Opts)
+
+		nothing(data.Uuid, data.Tz, data.Ua, data.St)
+	}
+}
+
+// reqproof:proptest:skip performance benchmark; measures wall-clock time and allocations, output is non-deterministic and not comparable to an independent reference
+func BenchmarkEncodingJsonV2InterfaceSmall(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		var data any
+		jsonv2.Unmarshal(smallFixture, &data)
+		m := data.(map[string]any)
+
+		nothing(m["uuid"].(string), m["tz"].(float64), m["ua"].(string), m["st"].(float64))
+	}
+}
+
+// reqproof:proptest:skip performance benchmark; measures wall-clock time and allocations, output is non-deterministic and not comparable to an independent reference
+func BenchmarkEncodingJsonV2StructMedium(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		var data encodingJSONMediumPayload
+		jsonv2.Unmarshal(mediumFixture, &data, jsonV2Opts)
+
+		nothing(data.Person.Name.FullName, data.Person.Github.Followers, data.Company)
+
+		for _, el := range data.Person.Gravatar.Avatars {
+			nothing(el.Url)
+		}
+	}
+}
+
+// reqproof:proptest:skip performance benchmark; measures wall-clock time and allocations, output is non-deterministic and not comparable to an independent reference
+func BenchmarkEncodingJsonV2InterfaceMedium(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		var data any
+		jsonv2.Unmarshal(mediumFixture, &data)
+		m := data.(map[string]any)
+
+		person := m["person"].(map[string]any)
+		name := person["name"].(map[string]any)
+		github := person["github"].(map[string]any)
+		company := m["company"]
+		gravatar := person["gravatar"].(map[string]any)
+		avatars := gravatar["avatars"].([]any)
+
+		nothing(name["fullName"].(string), github["followers"].(float64), company)
+		for _, a := range avatars {
+			nothing(a.(map[string]any)["url"])
+		}
+	}
+}
+
+// reqproof:proptest:skip performance benchmark; measures wall-clock time and allocations, output is non-deterministic and not comparable to an independent reference
+func BenchmarkEncodingJsonV2StructLarge(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		var data encodingJSONLargePayload
+		jsonv2.Unmarshal(largeFixture, &data, jsonV2Opts)
+
+		for _, u := range data.Users {
+			nothing(u.Username)
+		}
+
+		for _, t := range data.Topics.Topics {
+			nothing(t.Id, t.Slug)
+		}
+	}
+}
+
+// reqproof:proptest:skip performance benchmark; measures wall-clock time and allocations, output is non-deterministic and not comparable to an independent reference
+func BenchmarkEncodingJsonV2InterfaceLarge(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		var data any
+		jsonv2.Unmarshal(largeFixture, &data)
+		m := data.(map[string]any)
+
+		users := m["users"].([]any)
+		for _, u := range users {
+			nothing(u.(map[string]any)["username"].(string))
+		}
+
+		topics := m["topics"].(map[string]any)["topics"].([]any)
+		for _, t := range topics {
+			tI := t.(map[string]any)
+			nothing(tI["id"].(float64), tI["slug"].(string))
+		}
+	}
+}