cmd/go: write coverage to file, add percentage statistic

Move the data dumper to the testing package, where it has access
to file I/O.
Print a percentage value at the end of the run.

R=rsc, adg
CC=golang-dev
https://golang.org/cl/10264045

src/cmd/go/test.go

@@ -126,8 +126,6 @@ control the execution of any test:
 
 	-cover set,count,atomic
 	    TODO: This feature is not yet fully implemented.
-	    TODO: Must run with -v to see output.
-	    TODO: Need control over output format,
 	    Set the mode for coverage analysis for the package[s] being tested.
 	    The default is to do none.
 	    The values:
@@ -135,6 +133,11 @@ control the execution of any test:
 		count: integer: how many times does this statement execute?
 		atomic: integer: like count, but correct in multithreaded tests;
 			significantly more expensive.
+	    Sets -v. TODO: This will change.
+
+	-coverprofile cover.out
+	    Write a coverage profile to the specified file after all tests
+	    have passed.
 
 	-cpu 1,2,4
 	    Specify a list of GOMAXPROCS values for which the tests or
@@ -534,7 +537,7 @@ func (b *builder) test(p *Package) (buildAction, runAction, printAction *action,
 
 	if testCover != "" {
 		p.coverMode = testCover
-		p.coverVars = declareCoverVars(p.GoFiles...)
+		p.coverVars = declareCoverVars(p.ImportPath, p.GoFiles...)
 	}
 
 	if err := writeTestmain(filepath.Join(testDir, "_testmain.go"), p, p.coverVars); err != nil {
@@ -678,11 +681,11 @@ var coverIndex = 0
 
 // declareCoverVars attaches the required cover variables names
 // to the files, to be used when annotating the files.
-func declareCoverVars(files ...string) map[string]*CoverVar {
+func declareCoverVars(importPath string, files ...string) map[string]*CoverVar {
 	coverVars := make(map[string]*CoverVar)
 	for _, file := range files {
 		coverVars[file] = &CoverVar{
-			File: file,
+			File: filepath.Join(importPath, file),
 			Var:  fmt.Sprintf("GoCover_%d", coverIndex),
 		}
 		coverIndex++
@@ -934,9 +937,6 @@ import (
 {{if .NeedXtest}}
 	_xtest {{.Package.ImportPath | printf "%s_test" | printf "%q"}}
 {{end}}
-{{if .CoverEnabled}}
-	_fmt "fmt"
-{{end}}
 )
 
 var tests = []testing.InternalTest{
@@ -972,66 +972,46 @@ func matchString(pat, str string) (result bool, err error) {
 }
 
 {{if .CoverEnabled}}
-type coverBlock struct {
-	line0 uint32
-	col0 uint16
-	line1 uint32
-	col1 uint16
-}
 
 // Only updated by init functions, so no need for atomicity.
 var (
 	coverCounters = make(map[string][]uint32)
-	coverBlocks = make(map[string][]coverBlock)
+	coverBlocks = make(map[string][]testing.CoverBlock)
 )
 
 func init() {
 	{{range $file, $cover := .CoverVars}}
-	coverRegisterFile({{printf "%q" $file}}, _test.{{$cover.Var}}.Count[:], _test.{{$cover.Var}}.Pos[:]...)
+	coverRegisterFile({{printf "%q" $cover.File}}, _test.{{$cover.Var}}.Count[:], _test.{{$cover.Var}}.Pos[:], _test.{{$cover.Var}}.NumStmt[:])
 	{{end}}
 }
 
-func coverRegisterFile(fileName string, counter []uint32, pos ...uint32) {
-	if 3*len(counter) != len(pos) {
+func coverRegisterFile(fileName string, counter []uint32, pos []uint32, numStmts []uint16) {
+	if 3*len(counter) != len(pos) || len(counter) != len(numStmts) {
 		panic("coverage: mismatched sizes")
 	}
 	if coverCounters[fileName] != nil {
 		panic("coverage: duplicate counter array for " + fileName)
 	}
 	coverCounters[fileName] = counter
-	block := make([]coverBlock, len(counter))
+	block := make([]testing.CoverBlock, len(counter))
 	for i := range counter {
-		block[i] = coverBlock{
-			line0: pos[3*i+0],
-			col0: uint16(pos[3*i+2]),
-			line1: pos[3*i+1],
-			col1: uint16(pos[3*i+2]>>16),
+		block[i] = testing.CoverBlock{
+			Line0: pos[3*i+0],
+			Col0: uint16(pos[3*i+2]),
+			Line1: pos[3*i+1],
+			Col1: uint16(pos[3*i+2]>>16),
+			Stmts: numStmts[i],
 		}
 	}
 	coverBlocks[fileName] = block
 }
-
-func coverDump() {
-	for name, counts := range coverCounters {
-		blocks := coverBlocks[name]
-		for i, count := range counts {
-			_, err := _fmt.Printf("%s:%d.%d,%d.%d %d\n", name,
-				blocks[i].line0, blocks[i].col0,
-				blocks[i].line1, blocks[i].col1,
-				count)
-			if err != nil {
-				panic(err)
-			}
-		}
-	}
-}
 {{end}}
 
 func main() {
-	testing.Main(matchString, tests, benchmarks, examples)
 {{if .CoverEnabled}}
-	coverDump()
+	testing.RegisterCover(coverCounters, coverBlocks)
 {{end}}
+	testing.Main(matchString, tests, benchmarks, examples)
 }
 
 `))

src/cmd/go/testflag.go

@@ -27,6 +27,8 @@ var usageMessage = `Usage of go test:
   -bench="": passes -test.bench to test
   -benchmem=false: print memory allocation statistics for benchmarks
   -benchtime=1s: passes -test.benchtime to test
+  -cover="": passes -test.cover to test
+  -coverprofile="": passes -test.coverprofile to test
   -cpu="": passes -test.cpu to test
   -cpuprofile="": passes -test.cpuprofile to test
   -memprofile="": passes -test.memprofile to test
@@ -63,7 +65,6 @@ var testFlagDefn = []*testFlagSpec{
 	{name: "c", boolVar: &testC},
 	{name: "file", multiOK: true},
 	{name: "i", boolVar: &testI},
-	{name: "cover"},
 
 	// build flags.
 	{name: "a", boolVar: &buildA},
@@ -82,6 +83,8 @@ var testFlagDefn = []*testFlagSpec{
 	{name: "bench", passToTest: true},
 	{name: "benchmem", boolVar: new(bool), passToTest: true},
 	{name: "benchtime", passToTest: true},
+	{name: "cover", passToTest: true},
+	{name: "coverprofile", passToTest: true},
 	{name: "cpu", passToTest: true},
 	{name: "cpuprofile", passToTest: true},
 	{name: "memprofile", passToTest: true},
@@ -171,7 +174,7 @@ func testFlags(args []string) (packageNames, passToTest []string) {
 			testBench = true
 		case "timeout":
 			testTimeout = value
-		case "blockprofile", "cpuprofile", "memprofile":
+		case "blockprofile", "coverprofile", "cpuprofile", "memprofile":
 			testProfile = true
 		case "outputdir":
 			outputDir = value
@@ -182,6 +185,8 @@ func testFlags(args []string) (packageNames, passToTest []string) {
 			default:
 				fatalf("invalid flag argument for -cover: %q", value)
 			}
+			// Guarantee we see the coverage statistics. Doesn't turn -v on generally; tricky. TODO?
+			testV = true
 		}
 		if extraWord {
 			i++

src/pkg/testing/cover.go

@@ -0,0 +1,91 @@
+// Copyright 2013 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.
+
+// Support for test coverage.
+
+package testing
+
+import (
+	"fmt"
+	"os"
+)
+
+// CoverBlock records the coverage data for a single basic block.
+// NOTE: This struct is internal to the testing infrastructure and may change.
+// It is not covered (yet) by the Go 1 compatibility guidelines.
+type CoverBlock struct {
+	Line0 uint32
+	Col0  uint16
+	Line1 uint32
+	Col1  uint16
+	Stmts uint16
+}
+
+var (
+	coverCounters map[string][]uint32
+	coverBlocks   map[string][]CoverBlock
+)
+
+// RegisterCover records the coverage data accumulators for the tests.
+// NOTE: This struct is internal to the testing infrastructure and may change.
+// It is not covered (yet) by the Go 1 compatibility guidelines.
+func RegisterCover(c map[string][]uint32, b map[string][]CoverBlock) {
+	coverCounters = c
+	coverBlocks = b
+}
+
+// mustBeNil checks the error and, if present, reports it and exits.
+func mustBeNil(err error) {
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "testing: %s\n", err)
+		os.Exit(2)
+	}
+}
+
+// coverReport reports the coverage percentage and writes a coverage profile if requested.
+func coverReport() {
+	var f *os.File
+	var err error
+	if *coverProfile != "" {
+		f, err = os.Create(toOutputDir(*coverProfile))
+		mustBeNil(err)
+		defer func() { mustBeNil(f.Close()) }()
+	}
+
+	var active, total int64
+	packageName := ""
+	for name, counts := range coverCounters {
+		if packageName == "" {
+			// Package name ends at last slash.
+			for i, c := range name {
+				if c == '/' {
+					packageName = name[:i]
+				}
+			}
+		}
+		blocks := coverBlocks[name]
+		for i, count := range counts {
+			stmts := int64(blocks[i].Stmts)
+			total += stmts
+			if count > 0 {
+				active += stmts
+			}
+			if f != nil {
+				_, err := fmt.Fprintf(f, "%s:%d.%d,%d.%d %d %d\n", name,
+					blocks[i].Line0, blocks[i].Col0,
+					blocks[i].Line1, blocks[i].Col1,
+					stmts,
+					count)
+				mustBeNil(err)
+			}
+		}
+	}
+	if total == 0 {
+		total = 1
+	}
+	if packageName == "" {
+		packageName = "package"
+	}
+	fmt.Printf("test coverage for %s: %.1f%% of statements\n", packageName, 100*float64(active)/float64(total))
+}

src/pkg/testing/testing.go

@@ -122,6 +122,8 @@ var (
 
 	// Report as tests are run; default is silent for success.
 	chatty           = flag.Bool("test.v", false, "verbose: print additional output")
+	cover            = flag.String("test.cover", "", "cover mode: set, count, atomic; default is none")
+	coverProfile     = flag.String("test.coverprofile", "", "write a coveraage profile to the named file after execution")
 	match            = flag.String("test.run", "", "regular expression to select tests and examples to run")
 	memProfile       = flag.String("test.memprofile", "", "write a memory profile to the named file after execution")
 	memProfileRate   = flag.Int("test.memprofilerate", 0, "if >=0, sets runtime.MemProfileRate")
@@ -518,6 +520,9 @@ func after() {
 		}
 		f.Close()
 	}
+	if *cover != "" {
+		coverReport()
+	}
 }
 
 // toOutputDir returns the file name relocated, if required, to outputDir.