cmd/go, testing: streamline direct use of test binaries

Before:

        $ go test -c -cover fmt
        $ ./fmt.test -test.covermode=set
        PASS
        coverage: 65.1% of statements in strconv
        $

After:

        $ go test -c -cover fmt
        $ ./fmt.test
        PASS
        coverage: 65.1% of statements in strconv
        $

In addition to being cumbersome, the old flag didn't make sense:
the cover mode cannot be changed after the binary has been built.

Another useful effect of this CL is that if you happen to do

        $ go test -c -covermode=atomic fmt

and then forget you did that and run benchmarks,
the final line of the output (the coverage summary) reminds you
that you are benchmarking with coverage enabled, which might
not be what you want.

        $ ./fmt.test -test.bench .
        PASS
        BenchmarkSprintfEmpty	10000000	       217 ns/op
        BenchmarkSprintfString	 2000000	       755 ns/op
        BenchmarkSprintfInt	 2000000	       774 ns/op
        BenchmarkSprintfIntInt	 1000000	      1363 ns/op
        BenchmarkSprintfPrefixedInt	 1000000	      1501 ns/op
        BenchmarkSprintfFloat	 1000000	      1257 ns/op
        BenchmarkManyArgs	  500000	      5346 ns/op
        BenchmarkScanInts	    1000	   2562402 ns/op
        BenchmarkScanRecursiveInt	     500	   3189457 ns/op
        coverage: 91.4% of statements
        $

As part of passing the new mode setting in via _testmain.go, merge
the two registration mechanisms into one extensible mechanism
(a struct).

R=r
CC=golang-dev
https://golang.org/cl/11219043

src/cmd/go/doc.go

@@ -744,7 +744,6 @@ control the execution of any test:
 
 	-cover
 	    Enable coverage analysis.
-	    TODO: This feature is not yet fully implemented.
 
 	-covermode set,count,atomic
 	    Set the mode for coverage analysis for the package[s]
@@ -754,18 +753,18 @@ control the execution of any test:
 		count: int: how many times does this statement run?
 		atomic: int: count, but correct in multithreaded tests;
 			significantly more expensive.
-	    Implies -cover.
+	    Sets -cover.
 
 	-coverpkg pkg1,pkg2,pkg3
 	    Apply coverage analysis in each test to the given list of packages.
-	    If this option is not present, each test applies coverage analysis to
-	    the package being tested. Packages are specified as import paths.
-	    Implies -cover.
+	    The default is for each test to analyze only the package being tested.
+	    Packages are specified as import paths.
+	    Sets -cover.
 
 	-coverprofile cover.out
 	    Write a coverage profile to the specified file after all tests
 	    have passed.
-	    Implies -cover.
+	    Sets -cover.
 
 	-cpu 1,2,4
 	    Specify a list of GOMAXPROCS values for which the tests or

src/cmd/go/test.go

@@ -139,18 +139,18 @@ control the execution of any test:
 		count: int: how many times does this statement run?
 		atomic: int: count, but correct in multithreaded tests;
 			significantly more expensive.
-	    Implies -cover.
+	    Sets -cover.
 
 	-coverpkg pkg1,pkg2,pkg3
 	    Apply coverage analysis in each test to the given list of packages.
 	    The default is for each test to analyze only the package being tested.
 	    Packages are specified as import paths.
-	    Implies -cover.
+	    Sets -cover.
 
 	-coverprofile cover.out
 	    Write a coverage profile to the specified file after all tests
 	    have passed.
-	    Implies -cover.
+	    Sets -cover.
 
 	-cpu 1,2,4
 	    Specify a list of GOMAXPROCS values for which the tests or
@@ -1040,6 +1040,10 @@ type testFuncs struct {
 	Cover      []coverInfo
 }
 
+func (t *testFuncs) CoverMode() string {
+	return testCoverMode
+}
+
 func (t *testFuncs) CoverEnabled() bool {
 	return testCover
 }
@@ -1201,8 +1205,12 @@ func coverRegisterFile(fileName string, counter []uint32, pos []uint32, numStmts
 
 func main() {
 {{if .CoverEnabled}}
-	testing.CoveredPackage({{printf "%q" .Tested}}, {{printf "%q" .Covered}})
-	testing.RegisterCover(coverCounters, coverBlocks)
+	testing.RegisterCover(testing.Cover{
+		Mode: {{printf "%q" .CoverMode}},
+		Counters: coverCounters,
+		Blocks: coverBlocks,
+		CoveredPackages: {{printf "%q" .Covered}},
+	})
 {{end}}
 	testing.Main(matchString, tests, benchmarks, examples)
 }

src/cmd/go/testflag.go

@@ -28,7 +28,7 @@ var usageMessage = `Usage of go test:
   -benchmem=false: print memory allocation statistics for benchmarks
   -benchtime=1s: passes -test.benchtime to test
   -cover=false: enable coverage analysis
-  -covermode="set": passes -test.covermode to test if -cover
+  -covermode="set": specifies mode for coverage analysis
   -coverpkg="": comma-separated list of packages for coverage analysis
   -coverprofile="": passes -test.coverprofile to test if -cover
   -cpu="": passes -test.cpu to test
@@ -115,6 +115,7 @@ var testFlagDefn = []*testFlagSpec{
 func testFlags(args []string) (packageNames, passToTest []string) {
 	inPkg := false
 	outputDir := ""
+	testCoverMode = "set"
 	for i := 0; i < len(args); i++ {
 		if !strings.HasPrefix(args[i], "-") {
 			if !inPkg && packageNames == nil {
@@ -208,12 +209,7 @@ func testFlags(args []string) (packageNames, passToTest []string) {
 			passToTest = append(passToTest, "-test."+f.name+"="+value)
 		}
 	}
-	if testCover {
-		if testCoverMode == "" {
-			testCoverMode = "set"
-		}
-		passToTest = append(passToTest, "-test.covermode", testCoverMode)
-	}
+
 	// Tell the test what directory we're running in, so it can write the profiles there.
 	if testProfile && outputDir == "" {
 		dir, err := os.Getwd()

src/pkg/testing/cover.go

@@ -22,30 +22,23 @@ type CoverBlock struct {
 	Stmts uint16
 }
 
-var (
-	coverCounters map[string][]uint32
-	coverBlocks   map[string][]CoverBlock
-)
-
-var (
-	testedPackage  string // The package being tested.
-	coveredPackage string // List of the package[s] being covered, if distinct from the tested package.
-)
+var cover Cover
 
-// RegisterCover records the coverage data accumulators for the tests.
+// Cover records information about test coverage checking.
 // 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
+type Cover struct {
+	Mode            string
+	Counters        map[string][]uint32
+	Blocks          map[string][]CoverBlock
+	CoveredPackages string
 }
 
-// CoveredPackage records the names of the packages being tested and covered.
+// RegisterCover records the coverage data accumulators for the tests.
 // NOTE: This function is internal to the testing infrastructure and may change.
 // It is not covered (yet) by the Go 1 compatibility guidelines.
-func CoveredPackage(tested, covered string) {
-	testedPackage = tested
-	coveredPackage = covered
+func RegisterCover(c Cover) {
+	cover = c
 }
 
 // mustBeNil checks the error and, if present, reports it and exits.
@@ -63,13 +56,13 @@ func coverReport() {
 	if *coverProfile != "" {
 		f, err = os.Create(toOutputDir(*coverProfile))
 		mustBeNil(err)
-		fmt.Fprintf(f, "mode: %s\n", *coverMode)
+		fmt.Fprintf(f, "mode: %s\n", cover.Mode)
 		defer func() { mustBeNil(f.Close()) }()
 	}
 
 	var active, total int64
-	for name, counts := range coverCounters {
-		blocks := coverBlocks[name]
+	for name, counts := range cover.Counters {
+		blocks := cover.Blocks[name]
 		for i, count := range counts {
 			stmts := int64(blocks[i].Stmts)
 			total += stmts
@@ -89,5 +82,5 @@ func coverReport() {
 	if total == 0 {
 		total = 1
 	}
-	fmt.Printf("coverage: %.1f%% of statements%s\n", 100*float64(active)/float64(total), coveredPackage)
+	fmt.Printf("coverage: %.1f%% of statements%s\n", 100*float64(active)/float64(total), cover.CoveredPackages)
 }

src/pkg/testing/testing.go

@@ -122,8 +122,7 @@ var (
 
 	// Report as tests are run; default is silent for success.
 	chatty           = flag.Bool("test.v", false, "verbose: print additional output")
-	coverMode        = flag.String("test.covermode", "", "cover mode: set, count, atomic; default is none")
-	coverProfile     = flag.String("test.coverprofile", "", "write a coveraage profile to the named file after execution")
+	coverProfile     = flag.String("test.coverprofile", "", "write a coverage 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")
@@ -489,6 +488,10 @@ func before() {
 	if *blockProfile != "" && *blockProfileRate >= 0 {
 		runtime.SetBlockProfileRate(*blockProfileRate)
 	}
+	if *coverProfile != "" && cover.Mode == "" {
+		fmt.Fprintf(os.Stderr, "testing: cannot use -test.coverprofile because test binary was not built with coverage enabled\n")
+		os.Exit(2)
+	}
 }
 
 // after runs after all testing.
@@ -520,7 +523,7 @@ func after() {
 		}
 		f.Close()
 	}
-	if *coverMode != "" {
+	if cover.Mode != "" {
 		coverReport()
 	}
 }