cmd/go: pass package config to vet during "go vet"

After this CL, "go vet" can be guaranteed to have complete type information
about the packages being checked, even if cgo or swig is in use,
which will in turn make it reasonable for vet checks to insist on type
information. It also fixes vet's understanding of unusual import paths
like relative paths and vendored packages.

For now "go tool vet" will continue to cope without type information,
but the eventual plan is for "go tool vet" to query the go command for
what it needs, and also to be able to query alternate build systems
like bazel. But that's future work.

Fixes #4889.
Fixes #12556 (if not already fixed).
Fixes #15182.
Fixes #16086.
Fixes #17571.

Change-Id: I932626ee7da649b302cd269b82eb6fe5d7b9f0f2
Reviewed-on: https://go-review.googlesource.com/74750
Reviewed-by: Ian Lance Taylor <[email protected]>

Author: rsc

src/cmd/dist/deps.go

@@ -3763,9 +3763,11 @@ func TestBinaryOnlyPackages(t *testing.T) {
 	tg.grepStdout("hello from p1", "did not see message from p1")
 
 	tg.tempFile("src/p4/p4.go", `package main`)
+	// The odd string split below avoids vet complaining about
+	// a // +build line appearing too late in this source file.
 	tg.tempFile("src/p4/p4not.go", `//go:binary-only-package
 
-		// +build asdf
+		/`+`/ +build asdf
 
 		package main
 	`)

src/cmd/go/go_test.go

@@ -95,6 +95,7 @@ type PackageInternal struct {
 	// Unexported fields are not part of the public API.
 	Build        *build.Package
 	Imports      []*Package           // this package's direct imports
+	RawImports   []string             // this package's original imports as they appear in the text of the program
 	ForceLibrary bool                 // this package is a library (even if named "main")
 	Cmdline      bool                 // defined by files listed on command line
 	Local        bool                 // imported via local path (./ or ../)
@@ -208,6 +209,7 @@ func (p *Package) copyBuild(pp *build.Package) {
 	// We modify p.Imports in place, so make copy now.
 	p.Imports = make([]string, len(pp.Imports))
 	copy(p.Imports, pp.Imports)
+	p.Internal.RawImports = pp.Imports
 	p.TestGoFiles = pp.TestGoFiles
 	p.TestImports = pp.TestImports
 	p.XTestGoFiles = pp.XTestGoFiles

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

@@ -6,12 +6,9 @@
 package vet
 
 import (
-	"path/filepath"
-
 	"cmd/go/internal/base"
-	"cmd/go/internal/cfg"
 	"cmd/go/internal/load"
-	"cmd/go/internal/str"
+	"cmd/go/internal/work"
 )
 
 var CmdVet = &base.Command{
@@ -37,22 +34,23 @@ See also: go fmt, go fix.
 }
 
 func runVet(cmd *base.Command, args []string) {
-	vetFlags, packages := vetFlags(args)
-	for _, p := range load.Packages(packages) {
-		// Vet expects to be given a set of files all from the same package.
-		// Run once for package p and once for package p_test.
-		if len(p.GoFiles)+len(p.CgoFiles)+len(p.TestGoFiles) > 0 {
-			runVetFiles(p, vetFlags, str.StringList(p.GoFiles, p.CgoFiles, p.TestGoFiles, p.SFiles))
-		}
-		if len(p.XTestGoFiles) > 0 {
-			runVetFiles(p, vetFlags, str.StringList(p.XTestGoFiles))
-		}
+	vetFlags, pkgArgs := vetFlags(args)
+
+	work.InstrumentInit()
+	work.BuildModeInit()
+	work.VetFlags = vetFlags
+
+	pkgs := load.PackagesForBuild(pkgArgs)
+	if len(pkgs) == 0 {
+		base.Fatalf("no packages to vet")
 	}
-}
 
-func runVetFiles(p *load.Package, flags, files []string) {
-	for i := range files {
-		files[i] = filepath.Join(p.Dir, files[i])
+	var b work.Builder
+	b.Init()
+
+	root := &work.Action{Mode: "go vet"}
+	for _, p := range pkgs {
+		root.Deps = append(root.Deps, b.VetAction(work.ModeBuild, work.ModeBuild, p))
 	}
-	base.Run(cfg.BuildToolexec, base.Tool("vet"), flags, base.RelPaths(files))
+	b.Do(root)
 }

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

@@ -74,6 +74,9 @@ type Action struct {
 	built   string // the actual created package or executable
 	buildID string // build ID of action output
 
+	needVet bool       // Mode=="build": need to fill in vet config
+	vetCfg  *vetConfig // vet config
+
 	// Execution state.
 	pending  int  // number of deps yet to complete
 	priority int  // relative execution priority
@@ -349,6 +352,51 @@ func (b *Builder) CompileAction(mode, depMode BuildMode, p *load.Package) *Actio
 	return a
 }
 
+// VetAction returns the action for running go vet on package p.
+// It depends on the action for compiling p.
+// If the caller may be causing p to be installed, it is up to the caller
+// to make sure that the install depends on (runs after) vet.
+func (b *Builder) VetAction(mode, depMode BuildMode, p *load.Package) *Action {
+	// Construct vet action.
+	a := b.cacheAction("vet", p, func() *Action {
+		a1 := b.CompileAction(mode, depMode, p)
+
+		// vet expects to be able to import "fmt".
+		var stk load.ImportStack
+		stk.Push("vet")
+		p1 := load.LoadPackage("fmt", &stk)
+		stk.Pop()
+		aFmt := b.CompileAction(ModeBuild, depMode, p1)
+
+		a := &Action{
+			Mode:    "vet",
+			Package: p,
+			Deps:    []*Action{a1, aFmt},
+			Objdir:  a1.Objdir,
+		}
+		if a1.Func == nil {
+			// Built-in packages like unsafe.
+			return a
+		}
+		a1.needVet = true
+		a.Func = (*Builder).vet
+
+		// If there might be an install action, make it depend on vet,
+		// so that the temporary files generated by the build step
+		// are not deleted before vet can use them.
+		// If nothing was going to install p, calling b.CompileAction with
+		// ModeInstall here creates the action, but nothing links it into the
+		// graph, so it will still not be installed.
+		install := b.CompileAction(ModeInstall, depMode, p)
+		if install != a1 {
+			install.Deps = append(install.Deps, a)
+		}
+
+		return a
+	})
+	return a
+}
+
 // LinkAction returns the action for linking p into an executable
 // and possibly installing the result (according to mode).
 // depMode is the action (build or install) to use when compiling dependencies.

src/cmd/go/internal/work/action.go

@@ -8,6 +8,7 @@ package work
 
 import (
 	"bytes"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
@@ -254,9 +255,13 @@ func (b *Builder) buildActionID(a *Action) cache.ActionID {
 // Note that any new influence on this logic must be reported in b.buildActionID above as well.
 func (b *Builder) build(a *Action) (err error) {
 	p := a.Package
+	cached := false
 	if !p.BinaryOnly {
 		if b.useCache(a, p, b.buildActionID(a), p.Target) {
-			return nil
+			if !a.needVet {
+				return nil
+			}
+			cached = true
 		}
 	}
 
@@ -417,6 +422,34 @@ func (b *Builder) build(a *Action) (err error) {
 		}
 	}
 
+	// Prepare Go vet config if needed.
+	var vcfg *vetConfig
+	if a.needVet {
+		// Pass list of absolute paths to vet,
+		// so that vet's error messages will use absolute paths,
+		// so that we can reformat them relative to the directory
+		// in which the go command is invoked.
+		absfiles := make([]string, len(gofiles))
+		for i, f := range gofiles {
+			if !filepath.IsAbs(f) {
+				f = filepath.Join(a.Package.Dir, f)
+			}
+			absfiles[i] = f
+		}
+		vcfg = &vetConfig{
+			Compiler:    cfg.BuildToolchainName,
+			Dir:         a.Package.Dir,
+			GoFiles:     absfiles,
+			ImportMap:   make(map[string]string),
+			PackageFile: make(map[string]string),
+		}
+		a.vetCfg = vcfg
+		for i, raw := range a.Package.Internal.RawImports {
+			final := a.Package.Imports[i]
+			vcfg.ImportMap[raw] = final
+		}
+	}
+
 	// Prepare Go import config.
 	var icfg bytes.Buffer
 	for _, a1 := range a.Deps {
@@ -434,13 +467,42 @@ func (b *Builder) build(a *Action) (err error) {
 			continue
 		}
 		fmt.Fprintf(&icfg, "importmap %s=%s\n", path[i:], path)
+		if vcfg != nil {
+			vcfg.ImportMap[path[i:]] = path
+		}
 	}
+
+	// Compute the list of mapped imports in the vet config
+	// so that we can add any missing mappings below.
+	var vcfgMapped map[string]bool
+	if vcfg != nil {
+		vcfgMapped = make(map[string]bool)
+		for _, p := range vcfg.ImportMap {
+			vcfgMapped[p] = true
+		}
+	}
+
 	for _, a1 := range a.Deps {
 		p1 := a1.Package
 		if p1 == nil || p1.ImportPath == "" || a1.built == "" {
 			continue
 		}
 		fmt.Fprintf(&icfg, "packagefile %s=%s\n", p1.ImportPath, a1.built)
+		if vcfg != nil {
+			// Add import mapping if needed
+			// (for imports like "runtime/cgo" that appear only in generated code).
+			if !vcfgMapped[p1.ImportPath] {
+				vcfg.ImportMap[p1.ImportPath] = p1.ImportPath
+			}
+			vcfg.PackageFile[p1.ImportPath] = a1.built
+		}
+	}
+
+	if cached {
+		// The cached package file is OK, so we don't need to run the compile.
+		// We've only going through the motions to prepare the vet configuration,
+		// which is now complete.
+		return nil
 	}
 
 	// Compile Go.
@@ -532,6 +594,50 @@ func (b *Builder) build(a *Action) (err error) {
 	return nil
 }
 
+type vetConfig struct {
+	Compiler    string
+	Dir         string
+	GoFiles     []string
+	ImportMap   map[string]string
+	PackageFile map[string]string
+}
+
+// VetFlags are the flags to pass to vet.
+// The caller is expected to set them before executing any vet actions.
+var VetFlags []string
+
+func (b *Builder) vet(a *Action) error {
+	// a.Deps[0] is the build of the package being vetted.
+	// a.Deps[1] is the build of the "fmt" package.
+
+	vcfg := a.Deps[0].vetCfg
+	if vcfg == nil {
+		// Vet config should only be missing if the build failed.
+		if !a.Deps[0].Failed {
+			return fmt.Errorf("vet config not found")
+		}
+		return nil
+	}
+
+	if vcfg.ImportMap["fmt"] == "" {
+		a1 := a.Deps[1]
+		vcfg.ImportMap["fmt"] = "fmt"
+		vcfg.PackageFile["fmt"] = a1.built
+	}
+
+	js, err := json.MarshalIndent(vcfg, "", "\t")
+	if err != nil {
+		return fmt.Errorf("internal error marshaling vet config: %v", err)
+	}
+	js = append(js, '\n')
+	if err := b.writeFile(a.Objdir+"vet.cfg", js); err != nil {
+		return err
+	}
+
+	p := a.Package
+	return b.run(p.Dir, p.ImportPath, nil, cfg.BuildToolexec, base.Tool("vet"), VetFlags, a.Objdir+"vet.cfg")
+}
+
 // linkActionID computes the action ID for a link action.
 func (b *Builder) linkActionID(a *Action) cache.ActionID {
 	h := cache.NewHash("link")

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

@@ -1,9 +1,5 @@
 // Non-platform-specific vet whitelist. See readme.txt for details.
 
-// Issue 17580 (remove when fixed)
-cmd/go/go_test.go: +build comment must appear before package clause and be followed by a blank line
-
-
 // Real problems that we can't fix.
 
 // This is a bad WriteTo signature. Errors are being ignored!