cmd/go: add undocumented -debug-actiongraph flag to dump action graph

This will be useful for debugging but is intentionally
undocumented and not guaranteed to persist in any
particular form.

Change-Id: I60710a1e94cfc2ce31fe91fc268c51985060f8df
Reviewed-on: https://go-review.googlesource.com/69330
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/go/internal/cfg/cfg.go

@@ -37,6 +37,8 @@ var (
 	BuildV                 bool // -v flag
 	BuildWork              bool // -work flag
 	BuildX                 bool // -x flag
+
+	DebugActiongraph string // -debug-actiongraph flag (undocumented, unstable)
 )
 
 func init() {

src/cmd/go/internal/run/run.go

@@ -111,7 +111,7 @@ func runRun(cmd *base.Command, args []string) {
 	}
 	p.Internal.ExeName = src[:len(src)-len(".go")] // name temporary executable for first go file
 	a1 := b.Action(work.ModeBuild, work.ModeBuild, p)
-	a := &work.Action{Func: buildRunProgram, Args: cmdArgs, Deps: []*work.Action{a1}}
+	a := &work.Action{Mode: "go run", Func: buildRunProgram, Args: cmdArgs, Deps: []*work.Action{a1}}
 	b.Do(a)
 }
 

src/cmd/go/internal/test/test.go

@@ -522,7 +522,7 @@ func runTest(cmd *base.Command, args []string) {
 		}
 		sort.Strings(all)
 
-		a := &work.Action{}
+		a := &work.Action{Mode: "go test -i"}
 		for _, p := range load.PackagesForBuild(all) {
 			a.Deps = append(a.Deps, b.Action(work.ModeInstall, work.ModeInstall, p))
 		}
@@ -599,7 +599,7 @@ func runTest(cmd *base.Command, args []string) {
 	}
 
 	// Ultimately the goal is to print the output.
-	root := &work.Action{Deps: prints}
+	root := &work.Action{Mode: "go test", Deps: prints}
 
 	// Force the printing of results to happen in order,
 	// one at a time.
@@ -652,8 +652,8 @@ var windowsBadWords = []string{
 func builderTest(b *work.Builder, p *load.Package) (buildAction, runAction, printAction *work.Action, err error) {
 	if len(p.TestGoFiles)+len(p.XTestGoFiles) == 0 {
 		build := b.Action(work.ModeBuild, work.ModeBuild, p)
-		run := &work.Action{Package: p, Deps: []*work.Action{build}}
-		print := &work.Action{Func: builderNoTest, Package: p, Deps: []*work.Action{run}}
+		run := &work.Action{Mode: "test run", Package: p, Deps: []*work.Action{build}}
+		print := &work.Action{Mode: "test print", Func: builderNoTest, Package: p, Deps: []*work.Action{run}}
 		return build, run, print, nil
 	}
 
@@ -945,6 +945,7 @@ func builderTest(b *work.Builder, p *load.Package) (buildAction, runAction, prin
 			}
 		}
 		buildAction = &work.Action{
+			Mode:    "test build",
 			Func:    work.BuildInstallFunc,
 			Deps:    []*work.Action{buildAction},
 			Package: pmain,
@@ -953,22 +954,25 @@ func builderTest(b *work.Builder, p *load.Package) (buildAction, runAction, prin
 		runAction = buildAction // make sure runAction != nil even if not running test
 	}
 	if testC {
-		printAction = &work.Action{Package: p, Deps: []*work.Action{runAction}} // nop
+		printAction = &work.Action{Mode: "test print (nop)", Package: p, Deps: []*work.Action{runAction}} // nop
 	} else {
 		// run test
 		runAction = &work.Action{
+			Mode:       "test run",
 			Func:       builderRunTest,
 			Deps:       []*work.Action{buildAction},
 			Package:    p,
 			IgnoreFail: true,
 		}
 		cleanAction := &work.Action{
+			Mode:    "test clean",
 			Func:    builderCleanTest,
 			Deps:    []*work.Action{runAction},
 			Package: p,
 			Objdir:  testDir,
 		}
 		printAction = &work.Action{
+			Mode:    "test print",
 			Func:    builderPrintTest,
 			Deps:    []*work.Action{cleanAction},
 			Package: p,

src/cmd/go/internal/work/build.go

@@ -9,6 +9,7 @@ import (
 	"bytes"
 	"container/heap"
 	"debug/elf"
+	"encoding/json"
 	"errors"
 	"flag"
 	"fmt"
@@ -223,6 +224,9 @@ func AddBuildFlags(cmd *base.Command) {
 	cmd.Flag.Var((*base.StringsFlag)(&cfg.BuildContext.BuildTags), "tags", "")
 	cmd.Flag.Var((*base.StringsFlag)(&cfg.BuildToolexec), "toolexec", "")
 	cmd.Flag.BoolVar(&cfg.BuildWork, "work", false, "")
+
+	// Undocumented, unstable debugging flags.
+	cmd.Flag.StringVar(&cfg.DebugActiongraph, "debug-actiongraph", "", "")
 }
 
 // fileExtSplit expects a filename and returns the name
@@ -471,7 +475,7 @@ func runBuild(cmd *base.Command, args []string) {
 			a = b.libaction(libName, pkgs, ModeBuild, depMode)
 		}
 	} else {
-		a = &Action{}
+		a = &Action{Mode: "go build"}
 		for _, p := range pkgs {
 			a.Deps = append(a.Deps, b.Action(ModeBuild, depMode, p))
 		}
@@ -589,7 +593,7 @@ func InstallPackages(args []string, forGet bool) {
 			a = b.libaction(libName, pkgs, ModeInstall, ModeInstall)
 		}
 	} else {
-		a = &Action{}
+		a = &Action{Mode: "go install"}
 		var tools []*Action
 		for _, p := range pkgs {
 			// During 'go get', don't attempt (and fail) to install packages with only tests.
@@ -611,6 +615,7 @@ func InstallPackages(args []string, forGet bool) {
 		}
 		if len(tools) > 0 {
 			a = &Action{
+				Mode: "go install (tools)",
 				Deps: tools,
 			}
 		}
@@ -672,6 +677,7 @@ type Builder struct {
 
 // An Action represents a single action in the action graph.
 type Action struct {
+	Mode       string                        // description of action operation
 	Package    *load.Package                 // the package this action works on
 	Deps       []*Action                     // actions that must happen before this one
 	Func       func(*Builder, *Action) error // the action itself (nil = no-op)
@@ -692,6 +698,21 @@ type Action struct {
 	Failed   bool // whether the action failed
 }
 
+type actionJSON struct {
+	ID         int
+	Mode       string
+	Package    string
+	Deps       []int    `json:",omitempty"`
+	IgnoreFail bool     `json:",omitempty"`
+	Args       []string `json:",omitempty"`
+	Link       bool     `json:",omitempty"`
+	Objdir     string   `json:",omitempty"`
+	Target     string   `json:",omitempty"`
+	Priority   int      `json:",omitempty"`
+	Failed     bool     `json:",omitempty"`
+	Pkgfile    string   `json:",omitempty"`
+}
+
 // cacheKey is the key for the action cache.
 type cacheKey struct {
 	mode  BuildMode
@@ -699,6 +720,57 @@ type cacheKey struct {
 	shlib string
 }
 
+func actionGraphJSON(a *Action) string {
+	var workq []*Action
+	var inWorkq = make(map[*Action]int)
+
+	add := func(a *Action) {
+		if _, ok := inWorkq[a]; ok {
+			return
+		}
+		inWorkq[a] = len(workq)
+		workq = append(workq, a)
+	}
+	add(a)
+
+	for i := 0; i < len(workq); i++ {
+		for _, dep := range workq[i].Deps {
+			add(dep)
+		}
+	}
+
+	var list []*actionJSON
+	for id, a := range workq {
+		aj := &actionJSON{
+			Mode:       a.Mode,
+			ID:         id,
+			IgnoreFail: a.IgnoreFail,
+			Args:       a.Args,
+			Link:       a.Link,
+			Objdir:     a.Objdir,
+			Target:     a.Target,
+			Failed:     a.Failed,
+			Priority:   a.priority,
+		}
+		if a.Package != nil {
+			// TODO(rsc): Make this a unique key for a.Package somehow.
+			aj.Package = a.Package.ImportPath
+			aj.Pkgfile = a.Package.Internal.Pkgfile
+		}
+		for _, a1 := range a.Deps {
+			aj.Deps = append(aj.Deps, inWorkq[a1])
+		}
+		list = append(list, aj)
+	}
+
+	js, err := json.MarshalIndent(list, "", "\t")
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "go: writing debug action graph: %v\n", err)
+		return ""
+	}
+	return string(js)
+}
+
 // BuildMode specifies the build mode:
 // are we just building things or also installing the results?
 type BuildMode int
@@ -827,7 +899,7 @@ func (b *Builder) action1(mode BuildMode, depMode BuildMode, p *load.Package, lo
 		return a
 	}
 
-	a = &Action{Package: p}
+	a = &Action{Mode: "???", Package: p}
 	b.actionCache[key] = a
 
 	for _, p1 := range p.Internal.Imports {
@@ -854,11 +926,13 @@ func (b *Builder) action1(mode BuildMode, depMode BuildMode, p *load.Package, lo
 		switch p.ImportPath {
 		case "builtin", "unsafe":
 			// Fake packages - nothing to build.
+			a.Mode = "built-in package"
 			return a
 		}
 		// gccgo standard library is "fake" too.
 		if cfg.BuildToolchainName == "gccgo" {
 			// the target name is needed for cgo.
+			a.Mode = "gccgo stdlib"
 			a.Target = p.Internal.Target
 			return a
 		}
@@ -867,6 +941,7 @@ func (b *Builder) action1(mode BuildMode, depMode BuildMode, p *load.Package, lo
 	if !p.Stale && p.Internal.Target != "" {
 		// p.Stale==false implies that p.Internal.Target is up-to-date.
 		// Record target name for use by actions depending on this one.
+		a.Mode = "use installed"
 		a.Target = p.Internal.Target
 		p.Internal.Pkgfile = a.Target
 		return a
@@ -938,7 +1013,7 @@ func (b *Builder) action1(mode BuildMode, depMode BuildMode, p *load.Package, lo
 }
 
 func (b *Builder) libaction(libname string, pkgs []*load.Package, mode, depMode BuildMode) *Action {
-	a := &Action{}
+	a := &Action{Mode: "libaction???"}
 	switch mode {
 	default:
 		base.Fatalf("unrecognized mode %v", mode)
@@ -1046,7 +1121,7 @@ func (b *Builder) libaction(libname string, pkgs []*load.Package, mode, depMode
 				if p.Internal.Target == "" {
 					continue
 				}
-				shlibnameaction := &Action{}
+				shlibnameaction := &Action{Mode: "shlibname"}
 				shlibnameaction.Func = (*Builder).installShlibname
 				shlibnameaction.Target = p.Internal.Target[:len(p.Internal.Target)-2] + ".shlibname"
 				a.Deps = append(a.Deps, shlibnameaction)
@@ -1095,6 +1170,14 @@ func (b *Builder) Do(root *Action) {
 		a.priority = i
 	}
 
+	if cfg.DebugActiongraph != "" {
+		js := actionGraphJSON(root)
+		if err := ioutil.WriteFile(cfg.DebugActiongraph, []byte(js), 0666); err != nil {
+			fmt.Fprintf(os.Stderr, "go: writing action graph: %v\n", err)
+			base.SetExitStatus(1)
+		}
+	}
+
 	b.readySema = make(chan bool, len(all))
 
 	// Initialize per-action execution state.
@@ -3040,7 +3123,7 @@ func (tools gccgoToolchain) ld(b *Builder, root *Action, out, importcfg string,
 }
 
 func (tools gccgoToolchain) ldShared(b *Builder, toplevelactions []*Action, out, importcfg string, allactions []*Action) error {
-	fakeRoot := &Action{}
+	fakeRoot := &Action{Mode: "gccgo ldshared"}
 	fakeRoot.Deps = toplevelactions
 	return tools.link(b, fakeRoot, out, importcfg, allactions, "", nil, "shared", out)
 }
@@ -3673,7 +3756,7 @@ func (b *Builder) swigDoIntSize(objdir string) (intsize string, err error) {
 
 	p := load.GoFilesPackage(srcs)
 
-	if _, _, e := BuildToolchain.gc(b, &Action{Package: p, Objdir: objdir}, "", nil, false, srcs); e != nil {
+	if _, _, e := BuildToolchain.gc(b, &Action{Mode: "swigDoIntSize", Package: p, Objdir: objdir}, "", nil, false, srcs); e != nil {
 		return "32", nil
 	}
 	return "64", nil