benchstat: use template to generate html

The generated html changes in a few minor ways,
either unavoidable or not worth working around:

- Trailing <td></td> at end of row no longer removed.
- <td>~</td> instead of <td>~    </td>
- Literal + escaped to &#43;

Change-Id: I73a0d1f74ff4c3597dd96b1a4dac2d6a3d5cc462
Reviewed-on: https://go-review.googlesource.com/35938Reviewed-by: Quentin Smith <quentin@golang.org>

cmd/benchstat/data.go

@@ -44,9 +44,6 @@ type Metrics struct {
 
 // FormatMean formats m.Mean using scaler.
 func (m *Metrics) FormatMean(scaler Scaler) string {
-	if m == nil {
-		return ""
-	}
 	var s string
 	if scaler != nil {
 		s = scaler(m.Mean)
@@ -59,7 +56,7 @@ func (m *Metrics) FormatMean(scaler Scaler) string {
 // FormatDiff computes and formats the percent variation of max and min compared to mean.
 // If b.Mean or b.Max is zero, FormatDiff returns an empty string.
 func (m *Metrics) FormatDiff() string {
-	if m == nil || m.Mean == 0 || m.Max == 0 {
+	if m.Mean == 0 || m.Max == 0 {
 		return ""
 	}
 	diff := 1 - m.Min/m.Mean
@@ -71,7 +68,7 @@ func (m *Metrics) FormatDiff() string {
 
 // Format returns a textual formatting of "Mean ±Diff" using scaler.
 func (m *Metrics) Format(scaler Scaler) string {
-	if m == nil {
+	if m.Unit == "" {
 		return ""
 	}
 	mean := m.FormatMean(scaler)

cmd/benchstat/html.go

@@ -6,34 +6,27 @@ package main
 
 import (
 	"bytes"
-	"fmt"
-	"html"
+	"html/template"
 )
 
+var htmlTemplate = template.Must(template.New("").Parse(
+	`{{range $i, $table := .}}{{if gt $i 0}}
+{{end}}<style>.benchstat tbody td:nth-child(1n+2) { text-align: right; padding: 0em 1em; }</style>
+<table class='benchstat'>
+{{if .OldNewDelta}}<tr><th>name</th><th>old {{.Metric}}</th><th>new {{.Metric}}</th><th>delta</th>
+{{else if eq (len .Configs) 1}}<tr><th>name</th><th>{{.Metric}}</th>
+{{else}}<tr><th>name \ {{.Metric}}</th>{{range .Configs}}<th>{{.}}</th>{{end}}
+{{end}}{{range $row := $table.Rows}}<tr><td>{{.Benchmark}}</td>{{range $m := .Metrics}}<td>{{$m.Format $row.Scaler}}</td>{{end}}{{if $table.OldNewDelta}}<td>{{.Delta}}</td><td>{{.Note}}</td>{{end}}
+{{end -}}
+</table>
+{{end}}`))
+
 // FormatHTML appends an HTML formatting of the tables to buf.
 func FormatHTML(buf *bytes.Buffer, tables []*Table) {
-	var textTables [][]*textRow
-	for _, t := range tables {
-		textTables = append(textTables, toText(t))
-	}
-
-	for i, table := range textTables {
-		if i > 0 {
-			fmt.Fprintf(buf, "\n")
-		}
-		fmt.Fprintf(buf, "<style>.benchstat tbody td:nth-child(1n+2) { text-align: right; padding: 0em 1em; }</style>\n")
-		fmt.Fprintf(buf, "<table class='benchstat'>\n")
-		printRow := func(row *textRow, tag string) {
-			fmt.Fprintf(buf, "<tr>")
-			for _, cell := range row.cols {
-				fmt.Fprintf(buf, "<%s>%s</%s>", tag, html.EscapeString(cell), tag)
-			}
-			fmt.Fprintf(buf, "\n")
-		}
-		printRow(table[0], "th")
-		for _, row := range table[1:] {
-			printRow(row, "td")
-		}
-		fmt.Fprintf(buf, "</table>\n")
+	err := htmlTemplate.Execute(buf, tables)
+	if err != nil {
+		// Only possible errors here are template not matching data structure.
+		// Don't make caller check - it's our fault.
+		panic(err)
 	}
 }

cmd/benchstat/main_test.go

@@ -22,6 +22,7 @@ func TestGolden(t *testing.T) {
 	if t.Failed() {
 		t.Fatal("skipping other tests")
 	}
+	check(t, "exampleoldhtml", "-html", "exampleold.txt")
 	check(t, "examplehtml", "-html", "exampleold.txt", "examplenew.txt")
 	if t.Failed() {
 		t.Fatal("skipping other tests")

cmd/benchstat/table.go

@@ -12,16 +12,17 @@ import (
 
 // A Table is a table for display in the benchstat output.
 type Table struct {
-	Metric  string
-	Configs []string
-	Rows    []*Row
+	Metric      string
+	OldNewDelta bool // is this an old-new-delta table?
+	Configs     []string
+	Rows        []*Row
 }
 
 // A Row is a table row for display in the benchstat output.
 type Row struct {
 	Benchmark string     // benchmark name
 	Scaler    Scaler     // formatter for stats means
-	Metrics   []*Metrics // columns of statistics (nil slice entry means no data)
+	Metrics   []*Metrics // columns of statistics
 	Delta     string     // formatted percent change
 	Note      string     // additional information
 	Same      bool       // likely no change
@@ -40,31 +41,33 @@ func (c *Collection) Tables(deltaTest DeltaTest) []*Table {
 		table := new(Table)
 		table.Configs = c.Configs
 		table.Metric = metricOf(key.Unit)
+		table.OldNewDelta = len(c.Configs) == 2
 		for _, key.Benchmark = range c.Benchmarks {
 			row := &Row{Benchmark: key.Benchmark}
 
 			for _, key.Config = range c.Configs {
 				m := c.Metrics[key]
-				row.Metrics = append(row.Metrics, m)
 				if m == nil {
+					row.Metrics = append(row.Metrics, new(Metrics))
 					continue
 				}
+				row.Metrics = append(row.Metrics, m)
 				if row.Scaler == nil {
 					row.Scaler = NewScaler(m.Mean, m.Unit)
 				}
 			}
 
 			// If there are only two configs being compared, add stats.
-			// If one is missing, omit line entirely.
-			// TODO: Control this better.
-			if len(c.Configs) == 2 {
+			if table.OldNewDelta {
 				k0 := key
 				k0.Config = c.Configs[0]
 				k1 := key
 				k1.Config = c.Configs[1]
 				old := c.Metrics[k0]
 				new := c.Metrics[k1]
-				if old == nil || new == nil {
+				// If one is missing, omit row entirely.
+				// TODO: Control this better.
+				if old == new || new == nil {
 					continue
 				}
 				pval, testerr := deltaTest(old, new)
@@ -90,7 +93,7 @@ func (c *Collection) Tables(deltaTest DeltaTest) []*Table {
 
 		if len(table.Rows) > 0 {
 			if *flagGeomean {
-				addGeomean(c, table, key.Unit, len(c.Configs) == 2)
+				addGeomean(c, table, key.Unit, table.OldNewDelta)
 			}
 			tables = append(tables, table)
 		}
@@ -128,7 +131,7 @@ func addGeomean(c *Collection, t *Table, unit string, delta bool) {
 			}
 		}
 		if len(means) == 0 {
-			row.Metrics = append(row.Metrics, nil)
+			row.Metrics = append(row.Metrics, new(Metrics))
 			delta = false
 		} else {
 			geomean := stats.GeoMean(means)

cmd/benchstat/testdata/examplehtml.golden

 <style>.benchstat tbody td:nth-child(1n+2) { text-align: right; padding: 0em 1em; }</style>
 <table class='benchstat'>
 <tr><th>name</th><th>old time/op</th><th>new time/op</th><th>delta</th>
-<tr><td>GobEncode</td><td>13.6ms ± 1%</td><td>11.8ms ± 1%</td><td>-13.31%</td><td>(p=0.016 n=4+5)</td>
-<tr><td>JSONEncode</td><td>32.1ms ± 1%</td><td>31.8ms ± 1%</td><td>~   </td><td>(p=0.286 n=4+5)</td>
+<tr><td>GobEncode</td><td>13.6ms ± 1%</td><td>11.8ms ± 1%</td><td>-13.31%</td><td>(p=0.016 n=4&#43;5)</td>
+<tr><td>JSONEncode</td><td>32.1ms ± 1%</td><td>31.8ms ± 1%</td><td>~</td><td>(p=0.286 n=4&#43;5)</td>
 </table>
 
 <style>.benchstat tbody td:nth-child(1n+2) { text-align: right; padding: 0em 1em; }</style>
 <table class='benchstat'>
 <tr><th>name</th><th>old speed</th><th>new speed</th><th>delta</th>
-<tr><td>GobEncode</td><td>56.4MB/s ± 1%</td><td>65.1MB/s ± 1%</td><td>+15.36%</td><td>(p=0.016 n=4+5)</td>
-<tr><td>JSONEncode</td><td>60.4MB/s ± 1%</td><td>61.1MB/s ± 2%</td><td>~   </td><td>(p=0.286 n=4+5)</td>
+<tr><td>GobEncode</td><td>56.4MB/s ± 1%</td><td>65.1MB/s ± 1%</td><td>&#43;15.36%</td><td>(p=0.016 n=4&#43;5)</td>
+<tr><td>JSONEncode</td><td>60.4MB/s ± 1%</td><td>61.1MB/s ± 2%</td><td>~</td><td>(p=0.286 n=4&#43;5)</td>
 </table>

cmd/benchstat/testdata/exampleoldhtml.golden

+<style>.benchstat tbody td:nth-child(1n+2) { text-align: right; padding: 0em 1em; }</style>
+<table class='benchstat'>
+<tr><th>name</th><th>time/op</th>
+<tr><td>GobEncode</td><td>13.6ms ± 1%</td>
+<tr><td>JSONEncode</td><td>32.1ms ± 1%</td>
+</table>
+
+<style>.benchstat tbody td:nth-child(1n+2) { text-align: right; padding: 0em 1em; }</style>
+<table class='benchstat'>
+<tr><th>name</th><th>speed</th>
+<tr><td>GobEncode</td><td>56.4MB/s ± 1%</td>
+<tr><td>JSONEncode</td><td>60.4MB/s ± 1%</td>
+</table>