1 files changed, 125 insertions, 0 deletions
diff --git a/src/runtime/metrics/description_test.go b/src/runtime/metrics/description_test.go
new file mode 100644
index 0000000000..e966a281a1
--- /dev/null
+++ b/src/runtime/metrics/description_test.go
@@ -0,0 +1,125 @@
+// Copyright 2020 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 metrics_test
+
+import (
+	"bufio"
+	"os"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"runtime/metrics"
+	"strings"
+	"testing"
+)
+
+func TestDescriptionNameFormat(t *testing.T) {
+	r := regexp.MustCompile("^(?P<name>/[^:]+):(?P<unit>[^:*/]+(?:[*/][^:*/]+)*)$")
+	descriptions := metrics.All()
+	for _, desc := range descriptions {
+		if !r.MatchString(desc.Name) {
+			t.Errorf("metrics %q does not match regexp %s", desc.Name, r)
+		}
+	}
+}
+
+func extractMetricDocs(t *testing.T) map[string]string {
+	if runtime.GOOS == "android" {
+		t.Skip("no access to Go source on android")
+	}
+
+	// Get doc.go.
+	_, filename, _, _ := runtime.Caller(0)
+	filename = filepath.Join(filepath.Dir(filename), "doc.go")
+
+	f, err := os.Open(filename)
+	if err != nil {
+		t.Fatal(err)
+	}
+	const (
+		stateSearch          = iota // look for list of metrics
+		stateNextMetric             // look for next metric
+		stateNextDescription        // build description
+	)
+	state := stateSearch
+	s := bufio.NewScanner(f)
+	result := make(map[string]string)
+	var metric string
+	var prevMetric string
+	var desc strings.Builder
+	for s.Scan() {
+		line := strings.TrimSpace(s.Text())
+		switch state {
+		case stateSearch:
+			if line == "Supported metrics" {
+				state = stateNextMetric
+			}
+		case stateNextMetric:
+			// Ignore empty lines until we find a non-empty
+			// one. This will be our metric name.
+			if len(line) != 0 {
+				prevMetric = metric
+				metric = line
+				if prevMetric > metric {
+					t.Errorf("metrics %s and %s are out of lexicographical order", prevMetric, metric)
+				}
+				state = stateNextDescription
+			}
+		case stateNextDescription:
+			if len(line) == 0 || line == `*/` {
+				// An empty line means we're done.
+				// Write down the description and look
+				// for a new metric.
+				result[metric] = desc.String()
+				desc.Reset()
+				state = stateNextMetric
+			} else {
+				// As long as we're seeing data, assume that's
+				// part of the description and append it.
+				if desc.Len() != 0 {
+					// Turn previous newlines into spaces.
+					desc.WriteString(" ")
+				}
+				desc.WriteString(line)
+			}
+		}
+		if line == `*/` {
+			break
+		}
+	}
+	if state == stateSearch {
+		t.Fatalf("failed to find supported metrics docs in %s", filename)
+	}
+	return result
+}
+
+func TestDescriptionDocs(t *testing.T) {
+	docs := extractMetricDocs(t)
+	descriptions := metrics.All()
+	for _, d := range descriptions {
+		want := d.Description
+		got, ok := docs[d.Name]
+		if !ok {
+			t.Errorf("no docs found for metric %s", d.Name)
+			continue
+		}
+		if got != want {
+			t.Errorf("mismatched description and docs for metric %s", d.Name)
+			t.Errorf("want: %q, got %q", want, got)
+			continue
+		}
+	}
+	if len(docs) > len(descriptions) {
+	docsLoop:
+		for name, _ := range docs {
+			for _, d := range descriptions {
+				if name == d.Name {
+					continue docsLoop
+				}
+			}
+			t.Errorf("stale documentation for non-existent metric: %s", name)
+		}
+	}
+}