internal/trace: move v2 tracer into trace directory

This change moves the v2 tracer into the trace directory.

Updates #67367

Change-Id: I3657b4227002cb00fdf29c797434800ea796715e
Reviewed-on: https://go-review.googlesource.com/c/go/+/584538
Reviewed-by: Michael Knyszek <mknyszek@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/internal/trace/reader_test.go

@@ -0,0 +1,172 @@
+// Copyright 2023 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package trace_test
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"internal/trace"
+	"internal/trace/raw"
+	"internal/trace/testtrace"
+	"internal/trace/version"
+)
+
+var (
+	logEvents  = flag.Bool("log-events", false, "whether to log high-level events; significantly slows down tests")
+	dumpTraces = flag.Bool("dump-traces", false, "dump traces even on success")
+)
+
+func TestReaderGolden(t *testing.T) {
+	matches, err := filepath.Glob("./testdata/tests/*.test")
+	if err != nil {
+		t.Fatalf("failed to glob for tests: %v", err)
+	}
+	for _, testPath := range matches {
+		testPath := testPath
+		testName, err := filepath.Rel("./testdata", testPath)
+		if err != nil {
+			t.Fatalf("failed to relativize testdata path: %v", err)
+		}
+		t.Run(testName, func(t *testing.T) {
+			tr, exp, err := testtrace.ParseFile(testPath)
+			if err != nil {
+				t.Fatalf("failed to parse test file at %s: %v", testPath, err)
+			}
+			testReader(t, tr, exp)
+		})
+	}
+}
+
+func FuzzReader(f *testing.F) {
+	// Currently disabled because the parser doesn't do much validation and most
+	// getters can be made to panic. Turn this on once the parser is meant to
+	// reject invalid traces.
+	const testGetters = false
+
+	f.Fuzz(func(t *testing.T, b []byte) {
+		r, err := trace.NewReader(bytes.NewReader(b))
+		if err != nil {
+			return
+		}
+		for {
+			ev, err := r.ReadEvent()
+			if err != nil {
+				break
+			}
+
+			if !testGetters {
+				continue
+			}
+			// Make sure getters don't do anything that panics
+			switch ev.Kind() {
+			case trace.EventLabel:
+				ev.Label()
+			case trace.EventLog:
+				ev.Log()
+			case trace.EventMetric:
+				ev.Metric()
+			case trace.EventRangeActive, trace.EventRangeBegin:
+				ev.Range()
+			case trace.EventRangeEnd:
+				ev.Range()
+				ev.RangeAttributes()
+			case trace.EventStateTransition:
+				ev.StateTransition()
+			case trace.EventRegionBegin, trace.EventRegionEnd:
+				ev.Region()
+			case trace.EventTaskBegin, trace.EventTaskEnd:
+				ev.Task()
+			case trace.EventSync:
+			case trace.EventStackSample:
+			case trace.EventBad:
+			}
+		}
+	})
+}
+
+func testReader(t *testing.T, tr io.Reader, exp *testtrace.Expectation) {
+	r, err := trace.NewReader(tr)
+	if err != nil {
+		if err := exp.Check(err); err != nil {
+			t.Error(err)
+		}
+		return
+	}
+	v := testtrace.NewValidator()
+	for {
+		ev, err := r.ReadEvent()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			if err := exp.Check(err); err != nil {
+				t.Error(err)
+			}
+			return
+		}
+		if *logEvents {
+			t.Log(ev.String())
+		}
+		if err := v.Event(ev); err != nil {
+			t.Error(err)
+		}
+	}
+	if err := exp.Check(nil); err != nil {
+		t.Error(err)
+	}
+}
+
+func dumpTraceToText(t *testing.T, b []byte) string {
+	t.Helper()
+
+	br, err := raw.NewReader(bytes.NewReader(b))
+	if err != nil {
+		t.Fatalf("dumping trace: %v", err)
+	}
+	var sb strings.Builder
+	tw, err := raw.NewTextWriter(&sb, version.Current)
+	if err != nil {
+		t.Fatalf("dumping trace: %v", err)
+	}
+	for {
+		ev, err := br.ReadEvent()
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			t.Fatalf("dumping trace: %v", err)
+		}
+		if err := tw.WriteEvent(ev); err != nil {
+			t.Fatalf("dumping trace: %v", err)
+		}
+	}
+	return sb.String()
+}
+
+func dumpTraceToFile(t *testing.T, testName string, stress bool, b []byte) string {
+	t.Helper()
+
+	desc := "default"
+	if stress {
+		desc = "stress"
+	}
+	name := fmt.Sprintf("%s.%s.trace.", testName, desc)
+	f, err := os.CreateTemp("", name)
+	if err != nil {
+		t.Fatalf("creating temp file: %v", err)
+	}
+	defer f.Close()
+	if _, err := io.Copy(f, bytes.NewReader(b)); err != nil {
+		t.Fatalf("writing trace dump to %q: %v", f.Name(), err)
+	}
+	return f.Name()
+}