cmd/go: propagate context into PackagesForBuild and Do for tracing

This change propagates context into PackagesForErrors and Do for
the purpose of tracing, and calls trace.StartSpan on PackagesForErrors
and Do, so that the trace now shows the broad outline of where
the "Loading" and "Execution" phases are in the build.

Updates #38714

Change-Id: Ib9a7cf7030210f68f76663d1c8a7461e0a226611
Reviewed-on: https://go-review.googlesource.com/c/go/+/238541
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

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

@@ -117,7 +117,7 @@ func runClean(ctx context.Context, cmd *base.Command, args []string) {
 	}
 
 	if cleanPkg {
-		for _, pkg := range load.PackagesAndErrors(args) {
+		for _, pkg := range load.PackagesAndErrors(ctx, args) {
 			clean(pkg)
 		}
 	}

src/cmd/go/internal/fix/fix.go

@@ -34,7 +34,7 @@ See also: go fmt, go vet.
 
 func runFix(ctx context.Context, cmd *base.Command, args []string) {
 	printed := false
-	for _, pkg := range load.Packages(args) {
+	for _, pkg := range load.Packages(ctx, args) {
 		if modload.Enabled() && pkg.Module != nil && !pkg.Module.Main {
 			if !printed {
 				fmt.Fprintf(os.Stderr, "go: not fixing packages in dependency modules\n")

src/cmd/go/internal/fmtcmd/fmt.go

@@ -64,7 +64,7 @@ func runFmt(ctx context.Context, cmd *base.Command, args []string) {
 			}
 		}()
 	}
-	for _, pkg := range load.PackagesAndErrors(args) {
+	for _, pkg := range load.PackagesAndErrors(ctx, args) {
 		if modload.Enabled() && pkg.Module != nil && !pkg.Module.Main {
 			if !printed {
 				fmt.Fprintf(os.Stderr, "go: not formatting packages in dependency modules\n")

src/cmd/go/internal/generate/generate.go

@@ -176,7 +176,7 @@ func runGenerate(ctx context.Context, cmd *base.Command, args []string) {
 
 	// Even if the arguments are .go files, this loop suffices.
 	printed := false
-	for _, pkg := range load.PackagesAndErrors(args) {
+	for _, pkg := range load.PackagesAndErrors(ctx, args) {
 		if modload.Enabled() && pkg.Module != nil && !pkg.Module.Main {
 			if !printed {
 				fmt.Fprintf(os.Stderr, "go: not generating in packages in dependency modules\n")

src/cmd/go/internal/get/get.go

@@ -172,7 +172,7 @@ func runGet(ctx context.Context, cmd *base.Command, args []string) {
 	// everything.
 	load.ClearPackageCache()
 
-	pkgs := load.PackagesForBuild(args)
+	pkgs := load.PackagesForBuild(ctx, args)
 
 	// Phase 3. Install.
 	if *getD {
@@ -182,7 +182,7 @@ func runGet(ctx context.Context, cmd *base.Command, args []string) {
 		return
 	}
 
-	work.InstallPackages(args, pkgs)
+	work.InstallPackages(ctx, args, pkgs)
 }
 
 // downloadPaths prepares the list of paths to pass to download.

src/cmd/go/internal/list/list.go

@@ -449,9 +449,9 @@ func runList(ctx context.Context, cmd *base.Command, args []string) {
 	load.IgnoreImports = *listFind
 	var pkgs []*load.Package
 	if *listE {
-		pkgs = load.PackagesAndErrors(args)
+		pkgs = load.PackagesAndErrors(ctx, args)
 	} else {
-		pkgs = load.Packages(args)
+		pkgs = load.Packages(ctx, args)
 		base.ExitIfErrors()
 	}
 
@@ -539,7 +539,7 @@ func runList(ctx context.Context, cmd *base.Command, args []string) {
 				a.Deps = append(a.Deps, b.AutoAction(work.ModeInstall, work.ModeInstall, p))
 			}
 		}
-		b.Do(a)
+		b.Do(ctx, a)
 	}
 
 	for _, p := range pkgs {

src/cmd/go/internal/load/pkg.go

@@ -7,6 +7,7 @@ package load
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -30,6 +31,7 @@ import (
 	"cmd/go/internal/par"
 	"cmd/go/internal/search"
 	"cmd/go/internal/str"
+	"cmd/go/internal/trace"
 )
 
 var (
@@ -2123,9 +2125,9 @@ func LoadImportWithFlags(path, srcDir string, parent *Package, stk *ImportStack,
 // to load dependencies of a named package, the named
 // package is still returned, with p.Incomplete = true
 // and details in p.DepsErrors.
-func Packages(args []string) []*Package {
+func Packages(ctx context.Context, args []string) []*Package {
 	var pkgs []*Package
-	for _, pkg := range PackagesAndErrors(args) {
+	for _, pkg := range PackagesAndErrors(ctx, args) {
 		if pkg.Error != nil {
 			base.Errorf("%v", pkg.Error)
 			continue
@@ -2139,7 +2141,10 @@ func Packages(args []string) []*Package {
 // *Package for every argument, even the ones that
 // cannot be loaded at all.
 // The packages that fail to load will have p.Error != nil.
-func PackagesAndErrors(patterns []string) []*Package {
+func PackagesAndErrors(ctx context.Context, patterns []string) []*Package {
+	ctx, span := trace.StartSpan(ctx, "load.PackagesAndErrors")
+	defer span.Done()
+
 	for _, p := range patterns {
 		// Listing is only supported with all patterns referring to either:
 		// - Files that are part of the same directory.
@@ -2233,8 +2238,8 @@ func ImportPaths(args []string) []*search.Match {
 // PackagesForBuild is like Packages but exits
 // if any of the packages or their dependencies have errors
 // (cannot be built).
-func PackagesForBuild(args []string) []*Package {
-	pkgs := PackagesAndErrors(args)
+func PackagesForBuild(ctx context.Context, args []string) []*Package {
+	pkgs := PackagesAndErrors(ctx, args)
 	printed := map[*PackageError]bool{}
 	for _, pkg := range pkgs {
 		if pkg.Error != nil {

src/cmd/go/internal/modget/get.go

@@ -715,8 +715,8 @@ func runGet(ctx context.Context, cmd *base.Command, args []string) {
 		return
 	}
 	work.BuildInit()
-	pkgs := load.PackagesForBuild(pkgPatterns)
-	work.InstallPackages(pkgPatterns, pkgs)
+	pkgs := load.PackagesForBuild(ctx, pkgPatterns)
+	work.InstallPackages(ctx, pkgPatterns, pkgs)
 }
 
 // runQueries looks up modules at target versions in parallel. Results will be

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

@@ -79,7 +79,7 @@ func runRun(ctx context.Context, cmd *base.Command, args []string) {
 		}
 		p = load.GoFilesPackage(files)
 	} else if len(args) > 0 && !strings.HasPrefix(args[0], "-") {
-		pkgs := load.PackagesAndErrors(args[:1])
+		pkgs := load.PackagesAndErrors(ctx, args[:1])
 		if len(pkgs) == 0 {
 			base.Fatalf("go run: no packages loaded from %s", args[0])
 		}
@@ -141,7 +141,7 @@ func runRun(ctx context.Context, cmd *base.Command, args []string) {
 	}
 	a1 := b.LinkAction(work.ModeBuild, work.ModeBuild, p)
 	a := &work.Action{Mode: "go run", Func: buildRunProgram, Args: cmdArgs, Deps: []*work.Action{a1}}
-	b.Do(a)
+	b.Do(ctx, a)
 }
 
 // buildRunProgram is the action for running a binary that has already

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

@@ -577,7 +577,7 @@ func runTest(ctx context.Context, cmd *base.Command, args []string) {
 	work.VetFlags = testVet.flags
 	work.VetExplicit = testVet.explicit
 
-	pkgs = load.PackagesForBuild(pkgArgs)
+	pkgs = load.PackagesForBuild(ctx, pkgArgs)
 	if len(pkgs) == 0 {
 		base.Fatalf("no packages to test")
 	}
@@ -659,7 +659,7 @@ func runTest(ctx context.Context, cmd *base.Command, args []string) {
 		sort.Strings(all)
 
 		a := &work.Action{Mode: "go test -i"}
-		for _, p := range load.PackagesForBuild(all) {
+		for _, p := range load.PackagesForBuild(ctx, all) {
 			if cfg.BuildToolchainName == "gccgo" && p.Standard {
 				// gccgo's standard library packages
 				// can not be reinstalled.
@@ -667,7 +667,7 @@ func runTest(ctx context.Context, cmd *base.Command, args []string) {
 			}
 			a.Deps = append(a.Deps, b.CompileAction(work.ModeInstall, work.ModeInstall, p))
 		}
-		b.Do(a)
+		b.Do(ctx, a)
 		if !testC || a.Failed {
 			return
 		}
@@ -787,7 +787,7 @@ func runTest(ctx context.Context, cmd *base.Command, args []string) {
 		}
 	}
 
-	b.Do(root)
+	b.Do(ctx, root)
 }
 
 // ensures that package p imports the named package

src/cmd/go/internal/vet/vet.go

@@ -67,7 +67,7 @@ func runVet(ctx context.Context, cmd *base.Command, args []string) {
 		}
 	}
 
-	pkgs := load.PackagesForBuild(pkgArgs)
+	pkgs := load.PackagesForBuild(ctx, pkgArgs)
 	if len(pkgs) == 0 {
 		base.Fatalf("no packages to vet")
 	}
@@ -93,5 +93,5 @@ func runVet(ctx context.Context, cmd *base.Command, args []string) {
 			root.Deps = append(root.Deps, b.VetAction(work.ModeBuild, work.ModeBuild, pxtest))
 		}
 	}
-	b.Do(root)
+	b.Do(ctx, root)
 }

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

@@ -19,6 +19,7 @@ import (
 	"cmd/go/internal/cfg"
 	"cmd/go/internal/load"
 	"cmd/go/internal/search"
+	"cmd/go/internal/trace"
 )
 
 var CmdBuild = &base.Command{
@@ -350,7 +351,7 @@ func runBuild(ctx context.Context, cmd *base.Command, args []string) {
 	var b Builder
 	b.Init()
 
-	pkgs := load.PackagesForBuild(args)
+	pkgs := load.PackagesForBuild(ctx, args)
 
 	explicitO := len(cfg.BuildO) > 0
 
@@ -379,7 +380,7 @@ func runBuild(ctx context.Context, cmd *base.Command, args []string) {
 		depMode = ModeInstall
 	}
 
-	pkgs = omitTestOnly(pkgsFilter(load.Packages(args)))
+	pkgs = omitTestOnly(pkgsFilter(load.Packages(ctx, args)))
 
 	// Special case -o /dev/null by not writing at all.
 	if cfg.BuildO == os.DevNull {
@@ -409,7 +410,7 @@ func runBuild(ctx context.Context, cmd *base.Command, args []string) {
 			if len(a.Deps) == 0 {
 				base.Fatalf("go build: no main packages to build")
 			}
-			b.Do(a)
+			b.Do(ctx, a)
 			return
 		}
 		if len(pkgs) > 1 {
@@ -422,7 +423,7 @@ func runBuild(ctx context.Context, cmd *base.Command, args []string) {
 		p.Stale = true // must build - not up to date
 		p.StaleReason = "build -o flag in use"
 		a := b.AutoAction(ModeInstall, depMode, p)
-		b.Do(a)
+		b.Do(ctx, a)
 		return
 	}
 
@@ -433,7 +434,7 @@ func runBuild(ctx context.Context, cmd *base.Command, args []string) {
 	if cfg.BuildBuildmode == "shared" {
 		a = b.buildmodeShared(ModeBuild, depMode, args, pkgs, a)
 	}
-	b.Do(a)
+	b.Do(ctx, a)
 }
 
 var CmdInstall = &base.Command{
@@ -518,7 +519,7 @@ func libname(args []string, pkgs []*load.Package) (string, error) {
 
 func runInstall(ctx context.Context, cmd *base.Command, args []string) {
 	BuildInit()
-	InstallPackages(args, load.PackagesForBuild(args))
+	InstallPackages(ctx, args, load.PackagesForBuild(ctx, args))
 }
 
 // omitTestOnly returns pkgs with test-only packages removed.
@@ -538,7 +539,10 @@ func omitTestOnly(pkgs []*load.Package) []*load.Package {
 	return list
 }
 
-func InstallPackages(patterns []string, pkgs []*load.Package) {
+func InstallPackages(ctx context.Context, patterns []string, pkgs []*load.Package) {
+	ctx, span := trace.StartSpan(ctx, "InstallPackages "+strings.Join(patterns, " "))
+	defer span.Done()
+
 	if cfg.GOBIN != "" && !filepath.IsAbs(cfg.GOBIN) {
 		base.Fatalf("cannot install, GOBIN must be an absolute path")
 	}
@@ -607,7 +611,7 @@ func InstallPackages(patterns []string, pkgs []*load.Package) {
 		a = b.buildmodeShared(ModeInstall, ModeInstall, patterns, pkgs, a)
 	}
 
-	b.Do(a)
+	b.Do(ctx, a)
 	base.ExitIfErrors()
 
 	// Success. If this command is 'go install' with no arguments

src/cmd/go/internal/work/exec.go

@@ -8,6 +8,7 @@ package work
 
 import (
 	"bytes"
+	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -31,6 +32,7 @@ import (
 	"cmd/go/internal/cfg"
 	"cmd/go/internal/load"
 	"cmd/go/internal/str"
+	"cmd/go/internal/trace"
 )
 
 // actionList returns the list of actions in the dag rooted at root
@@ -54,7 +56,10 @@ func actionList(root *Action) []*Action {
 }
 
 // do runs the action graph rooted at root.
-func (b *Builder) Do(root *Action) {
+func (b *Builder) Do(ctx context.Context, root *Action) {
+	ctx, span := trace.StartSpan(ctx, "exec.Builder.Do ("+root.Mode+" "+root.Target+")")
+	defer span.Done()
+
 	if !b.IsCmdList {
 		// If we're doing real work, take time at the end to trim the cache.
 		c := cache.Default()