cmd/go: add "go clean -cache"

Give users a way to remove their caches.

Change-Id: I0b041aa54b318e98605675f168fed54ab9b6fd14
Reviewed-on: https://go-review.googlesource.com/75470
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>

src/cmd/dist/deps.go

@@ -112,10 +112,11 @@ var builddeps = map[string][]string{
 	},
 
 	"cmd/go/internal/clean": {
-		"cmd/go/internal/base", // cmd/go/internal/clean
-		"cmd/go/internal/cfg",  // cmd/go/internal/clean
-		"cmd/go/internal/load", // cmd/go/internal/clean
-		"cmd/go/internal/work", // cmd/go/internal/clean
+		"cmd/go/internal/base",  // cmd/go/internal/clean
+		"cmd/go/internal/cache", // cmd/go/internal/clean
+		"cmd/go/internal/cfg",   // cmd/go/internal/clean
+		"cmd/go/internal/load",  // cmd/go/internal/clean
+		"cmd/go/internal/work",  // cmd/go/internal/clean
 		"fmt",           // cmd/go/internal/clean
 		"io/ioutil",     // cmd/go/internal/clean
 		"os",            // cmd/go/internal/clean

src/cmd/go/alldocs.go

@@ -162,7 +162,7 @@
 //
 // Usage:
 //
-// 	go clean [-i] [-r] [-n] [-x] [build flags] [packages]
+// 	go clean [-i] [-r] [-n] [-x] [-cache] [build flags] [packages]
 //
 // Clean removes object files from package source directories.
 // The go command builds most objects in a temporary directory,
@@ -200,6 +200,9 @@
 //
 // The -x flag causes clean to print remove commands as it executes them.
 //
+// The -cache flag causes clean to remove the entire go build cache,
+// in addition to cleaning specified packages (if any).
+//
 // For more about build flags, see 'go help build'.
 //
 // For more about specifying packages, see 'go help packages'.

src/cmd/go/internal/clean/clean.go

@@ -13,13 +13,14 @@ import (
 	"strings"
 
 	"cmd/go/internal/base"
+	"cmd/go/internal/cache"
 	"cmd/go/internal/cfg"
 	"cmd/go/internal/load"
 	"cmd/go/internal/work"
 )
 
 var CmdClean = &base.Command{
-	UsageLine: "clean [-i] [-r] [-n] [-x] [build flags] [packages]",
+	UsageLine: "clean [-i] [-r] [-n] [-x] [-cache] [build flags] [packages]",
 	Short:     "remove object files",
 	Long: `
 Clean removes object files from package source directories.
@@ -58,14 +59,20 @@ dependencies of the packages named by the import paths.
 
 The -x flag causes clean to print remove commands as it executes them.
 
+The -cache flag causes clean to remove the entire go build cache,
+in addition to cleaning specified packages (if any).
+
 For more about build flags, see 'go help build'.
 
 For more about specifying packages, see 'go help packages'.
 	`,
 }
 
-var cleanI bool // clean -i flag
-var cleanR bool // clean -r flag
+var (
+	cleanI     bool // clean -i flag
+	cleanR     bool // clean -r flag
+	cleanCache bool // clean -cache flag
+)
 
 func init() {
 	// break init cycle
@@ -73,6 +80,8 @@ func init() {
 
 	CmdClean.Flag.BoolVar(&cleanI, "i", false, "")
 	CmdClean.Flag.BoolVar(&cleanR, "r", false, "")
+	CmdClean.Flag.BoolVar(&cleanCache, "cache", false, "")
+
 	// -n and -x are important enough to be
 	// mentioned explicitly in the docs but they
 	// are part of the build flags.
@@ -84,6 +93,33 @@ func runClean(cmd *base.Command, args []string) {
 	for _, pkg := range load.PackagesAndErrors(args) {
 		clean(pkg)
 	}
+
+	if cleanCache {
+		var b work.Builder
+		b.Print = fmt.Print
+		dir := cache.DefaultDir()
+		if dir != "off" {
+			// Remove the cache subdirectories but not the top cache directory.
+			// The top cache directory may have been created with special permissions
+			// and not something that we want to remove. Also, we'd like to preserve
+			// the access log for future analysis, even if the cache is cleared.
+			subdirs, _ := filepath.Glob(filepath.Join(dir, "[0-9a-f][0-9a-f]"))
+			if len(subdirs) > 0 {
+				if cfg.BuildN || cfg.BuildX {
+					b.Showcmd("", "rm -r %s", strings.Join(subdirs, " "))
+				}
+				printedErrors := false
+				for _, d := range subdirs {
+					// Only print the first error - there may be many.
+					// This also mimics what os.RemoveAll(dir) would do.
+					if err := os.RemoveAll(d); err != nil && !printedErrors {
+						printedErrors = true
+						base.Errorf("go clean -cache: %v", err)
+					}
+				}
+			}
+		}
+	}
 }
 
 var cleaned = map[*load.Package]bool{}