[dev.cmdgo] cmd/go: remove modload.ModRoot function

In some cases, ModRoot was being called in a multi module context. In
those cases, pass in the correct main module. In other cases, a
mainModule variable was already available, so call MainModules.ModRoot
on that mainModule variable to make it more clear. In yet other cases
ModRoot is just needed to determine GoMod, so determine modroot from
the current directory in those cases.

For #45713

Change-Id: I8c8aa633cfae40d0c8740bdbf985f2b60c9daf2c
Reviewed-on: https://go-review.googlesource.com/c/go/+/339171
Trust: Michael Matloob <matloob@golang.org>
Run-TryBot: Michael Matloob <matloob@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>

9 files changed, 56 insertions, 43 deletions

diff --git a/src/cmd/go/internal/envcmd/env.go b/src/cmd/go/internal/envcmd/env.go
index 5c45e34330..d23d539141 100644
--- a/src/cmd/go/internal/envcmd/env.go
+++ b/src/cmd/go/internal/envcmd/env.go
@@ -148,7 +148,7 @@ func ExtraEnvVars() []cfg.EnvVar {
 	gomod := ""
 	modload.Init()
 	if modload.HasModRoot() {
-		gomod = filepath.Join(modload.ModRoot(), "go.mod")
+		gomod = modload.ModFilePath()
 	} else if modload.Enabled() {
 		gomod = os.DevNull
 	}
diff --git a/src/cmd/go/internal/modcmd/vendor.go b/src/cmd/go/internal/modcmd/vendor.go
index 774fc3052f..a51ac21751 100644
--- a/src/cmd/go/internal/modcmd/vendor.go
+++ b/src/cmd/go/internal/modcmd/vendor.go
@@ -74,7 +74,7 @@ func runVendor(ctx context.Context, cmd *base.Command, args []string) {
 	}
 	_, pkgs := modload.LoadPackages(ctx, loadOpts, "all")
 
-	vdir := filepath.Join(modload.ModRoot(), "vendor")
+	vdir := filepath.Join(modload.VendorDir())
 	if err := os.RemoveAll(vdir); err != nil {
 		base.Fatalf("go mod vendor: %v", err)
 	}
diff --git a/src/cmd/go/internal/modget/get.go b/src/cmd/go/internal/modget/get.go
index 6eae44f1a4..3d831a14d8 100644
--- a/src/cmd/go/internal/modget/get.go
+++ b/src/cmd/go/internal/modget/get.go
@@ -724,7 +724,16 @@ func (r *resolver) performLocalQueries(ctx context.Context) {
 			// restricted to matching packages in the main module.
 			pkgPattern, mainModule := modload.MainModules.DirImportPath(ctx, q.pattern)
 			if pkgPattern == "." {
-				return errSet(fmt.Errorf("%s%s is not within module rooted at %s", q.pattern, absDetail, modload.ModRoot()))
+				modload.MustHaveModRoot()
+				var modRoots []string
+				for _, m := range modload.MainModules.Versions() {
+					modRoots = append(modRoots, modload.MainModules.ModRoot(m))
+				}
+				var plural string
+				if len(modRoots) != 1 {
+					plural = "s"
+				}
+				return errSet(fmt.Errorf("%s%s is not within module%s rooted at %s", q.pattern, absDetail, plural, strings.Join(modRoots, ", ")))
 			}
 
 			match := modload.MatchInModule(ctx, pkgPattern, mainModule, imports.AnyTags())
@@ -737,7 +746,8 @@ func (r *resolver) performLocalQueries(ctx context.Context) {
 					return errSet(fmt.Errorf("no package in current directory"))
 				}
 				if !q.isWildcard() {
-					return errSet(fmt.Errorf("%s%s is not a package in module rooted at %s", q.pattern, absDetail, modload.ModRoot()))
+					modload.MustHaveModRoot()
+					return errSet(fmt.Errorf("%s%s is not a package in module rooted at %s", q.pattern, absDetail, modload.MainModules.ModRoot(mainModule)))
 				}
 				search.WarnUnmatched([]*search.Match{match})
 				return pathSet{}
diff --git a/src/cmd/go/internal/modload/build.go b/src/cmd/go/internal/modload/build.go
index 2973586479..3f2160d52d 100644
--- a/src/cmd/go/internal/modload/build.go
+++ b/src/cmd/go/internal/modload/build.go
@@ -323,7 +323,7 @@ func moduleInfo(ctx context.Context, rs *Requirements, m module.Version, mode Li
 		if filepath.IsAbs(r.Path) {
 			info.Replace.Dir = r.Path
 		} else {
-			info.Replace.Dir = filepath.Join(ModRoot(), r.Path)
+			info.Replace.Dir = filepath.Join(replacedFrom, r.Path)
 		}
 		info.Replace.GoMod = filepath.Join(info.Replace.Dir, "go.mod")
 	}
diff --git a/src/cmd/go/internal/modload/import.go b/src/cmd/go/internal/modload/import.go
index 5741299281..de47974b9b 100644
--- a/src/cmd/go/internal/modload/import.go
+++ b/src/cmd/go/internal/modload/import.go
@@ -294,7 +294,7 @@ func importFromModules(ctx context.Context, path string, rs *Requirements, mg *M
 		if mainErr != nil {
 			return module.Version{}, "", mainErr
 		}
-		readVendorList()
+		readVendorList(mainModule)
 		return vendorPkgModule[path], vendorDir, nil
 	}
 
@@ -653,11 +653,11 @@ func fetch(ctx context.Context, mod module.Version, needSum bool) (dir string, i
 	if modRoot := MainModules.ModRoot(mod); modRoot != "" {
 		return modRoot, true, nil
 	}
-	if r, _ := Replacement(mod); r.Path != "" {
+	if r, replacedFrom := Replacement(mod); r.Path != "" {
 		if r.Version == "" {
 			dir = r.Path
 			if !filepath.IsAbs(dir) {
-				dir = filepath.Join(ModRoot(), dir)
+				dir = filepath.Join(replacedFrom, dir)
 			}
 			// Ensure that the replacement directory actually exists:
 			// dirInModule does not report errors for missing modules,
diff --git a/src/cmd/go/internal/modload/init.go b/src/cmd/go/internal/modload/init.go
index 5dd946215b..1a91b83148 100644
--- a/src/cmd/go/internal/modload/init.go
+++ b/src/cmd/go/internal/modload/init.go
@@ -374,7 +374,6 @@ func Init() {
 	}
 
 	if inWorkspaceMode() {
-
 		_ = TODOWorkspaces("go.work.sum, and also allow modfetch to fall back to individual go.sums")
 		_ = TODOWorkspaces("replaces")
 		var err error
@@ -403,8 +402,7 @@ func Init() {
 		//
 		// See golang.org/issue/32027.
 	} else {
-		_ = TODOWorkspaces("Instead of modfile path, find modfile OR workfile path depending on mode")
-		modfetch.GoSumFile = strings.TrimSuffix(ModFilePath(), ".mod") + ".sum"
+		modfetch.GoSumFile = strings.TrimSuffix(modFilePath(modRoots[0]), ".mod") + ".sum"
 	}
 }
 
@@ -463,21 +461,8 @@ func Enabled() bool {
 	return modRoots != nil || cfg.ModulesEnabled
 }
 
-// ModRoot returns the root of the main module.
-// It calls base.Fatalf if there is no main module.
-func ModRoot() string {
-	if !HasModRoot() {
-		die()
-	}
-	if inWorkspaceMode() {
-		panic("ModRoot called in workspace mode")
-	}
-	// This is similar to MustGetSingleMainModule but we can't call that
-	// because MainModules may not yet exist when ModRoot is called.
-	if len(modRoots) != 1 {
-		panic("not in workspace mode but there are multiple ModRoots")
-	}
-	return modRoots[0]
+func VendorDir() string {
+	return filepath.Join(MainModules.ModRoot(MainModules.mustGetSingleMainModule()), "vendor")
 }
 
 func inWorkspaceMode() bool {
@@ -495,12 +480,21 @@ func HasModRoot() bool {
 	return modRoots != nil
 }
 
-// ModFilePath returns the effective path of the go.mod file. Normally, this
-// "go.mod" in the directory returned by ModRoot, but the -modfile flag may
-// change its location. ModFilePath calls base.Fatalf if there is no main
+// MustHaveModRoot checks that a main module or main modules are present,
+// and calls base.Fatalf if there are no main modules.
+func MustHaveModRoot() {
+	Init()
+	if !HasModRoot() {
+		die()
+	}
+}
+
+// ModFilePath returns the path that would be used for the go.mod
+// file, if in module mode. ModFilePath calls base.Fatalf if there is no main
 // module, even if -modfile is set.
 func ModFilePath() string {
-	return modFilePath(ModRoot())
+	MustHaveModRoot()
+	return modFilePath(findModuleRoot(base.Cwd()))
 }
 
 func modFilePath(modRoot string) string {
@@ -674,7 +668,7 @@ func loadModFile(ctx context.Context) (rs *Requirements, needCommit bool) {
 	mainModule := MainModules.mustGetSingleMainModule()
 
 	if cfg.BuildMod == "vendor" {
-		readVendorList()
+		readVendorList(mainModule)
 		index := MainModules.Index(mainModule)
 		modFile := MainModules.ModFile(mainModule)
 		checkVendorConsistency(index, modFile)
@@ -719,7 +713,7 @@ func CreateModFile(ctx context.Context, modPath string) {
 	modRoot := base.Cwd()
 	modRoots = []string{modRoot}
 	Init()
-	modFilePath := ModFilePath()
+	modFilePath := modFilePath(modRoot)
 	if _, err := fsys.Stat(modFilePath); err == nil {
 		base.Fatalf("go: %s already exists", modFilePath)
 	}
@@ -1344,6 +1338,7 @@ func commitRequirements(ctx context.Context, goVersion string, rs *Requirements)
 		return
 	}
 	mainModule := MainModules.Versions()[0]
+	modFilePath := modFilePath(MainModules.ModRoot(mainModule))
 	modFile := MainModules.ModFile(mainModule)
 
 	var list []*modfile.Require
@@ -1383,8 +1378,7 @@ func commitRequirements(ctx context.Context, goVersion string, rs *Requirements)
 		}
 		return
 	}
-	gomod := ModFilePath()
-	if _, ok := fsys.OverlayPath(gomod); ok {
+	if _, ok := fsys.OverlayPath(modFilePath); ok {
 		if dirty {
 			base.Fatalf("go: updates to go.mod needed, but go.mod is part of the overlay specified with -overlay")
 		}
@@ -1422,7 +1416,7 @@ func commitRequirements(ctx context.Context, goVersion string, rs *Requirements)
 
 	errNoChange := errors.New("no update needed")
 
-	err = lockedfile.Transform(ModFilePath(), func(old []byte) ([]byte, error) {
+	err = lockedfile.Transform(modFilePath, func(old []byte) ([]byte, error) {
 		if bytes.Equal(old, new) {
 			// The go.mod file is already equal to new, possibly as the result of some
 			// other process.
diff --git a/src/cmd/go/internal/modload/load.go b/src/cmd/go/internal/modload/load.go
index dd69e2afbf..cb5a2d7a35 100644
--- a/src/cmd/go/internal/modload/load.go
+++ b/src/cmd/go/internal/modload/load.go
@@ -440,7 +440,16 @@ func matchLocalDirs(ctx context.Context, m *search.Match, rs *Requirements) {
 		if !filepath.IsAbs(dir) {
 			absDir = filepath.Join(base.Cwd(), dir)
 		}
-		if search.InDir(absDir, cfg.GOROOTsrc) == "" && search.InDir(absDir, ModRoot()) == "" && pathInModuleCache(ctx, absDir, rs) == "" {
+
+		modRoot := findModuleRoot(absDir)
+		found := false
+		for _, mod := range MainModules.Versions() {
+			if MainModules.ModRoot(mod) == modRoot {
+				found = true
+				break
+			}
+		}
+		if !found && search.InDir(absDir, cfg.GOROOTsrc) == "" && pathInModuleCache(ctx, absDir, rs) == "" {
 			m.Dirs = []string{}
 			m.AddError(fmt.Errorf("directory prefix %s outside available modules", base.ShortPath(absDir)))
 			return
@@ -513,7 +522,7 @@ func resolveLocalPackage(ctx context.Context, dir string, rs *Requirements) (str
 					return "", fmt.Errorf("without -mod=vendor, directory %s has no package path", absDir)
 				}
 
-				readVendorList()
+				readVendorList(mainModule)
 				pkg := strings.TrimPrefix(suffix, "/vendor/")
 				if _, ok := vendorPkgModule[pkg]; !ok {
 					return "", fmt.Errorf("directory %s is not a package listed in vendor/modules.txt", absDir)
@@ -582,10 +591,10 @@ func pathInModuleCache(ctx context.Context, dir string, rs *Requirements) string
 	tryMod := func(m module.Version) (string, bool) {
 		var root string
 		var err error
-		if repl, _ := Replacement(m); repl.Path != "" && repl.Version == "" {
+		if repl, replModRoot := Replacement(m); repl.Path != "" && repl.Version == "" {
 			root = repl.Path
 			if !filepath.IsAbs(root) {
-				root = filepath.Join(ModRoot(), root)
+				root = filepath.Join(replModRoot, root)
 			}
 		} else if repl.Path != "" {
 			root, err = modfetch.DownloadDir(repl)
diff --git a/src/cmd/go/internal/modload/modfile.go b/src/cmd/go/internal/modload/modfile.go
index bc5c83dffc..664fc0f91b 100644
--- a/src/cmd/go/internal/modload/modfile.go
+++ b/src/cmd/go/internal/modload/modfile.go
@@ -528,7 +528,7 @@ func goModSummary(m module.Version) (*modFileSummary, error) {
 
 		// For every module other than the target,
 		// return the full list of modules from modules.txt.
-		readVendorList()
+		readVendorList(MainModules.mustGetSingleMainModule())
 
 		// We don't know what versions the vendored module actually relies on,
 		// so assume that it requires everything.
diff --git a/src/cmd/go/internal/modload/vendor.go b/src/cmd/go/internal/modload/vendor.go
index b2da3783ea..daa5888075 100644
--- a/src/cmd/go/internal/modload/vendor.go
+++ b/src/cmd/go/internal/modload/vendor.go
@@ -36,13 +36,13 @@ type vendorMetadata struct {
 }
 
 // readVendorList reads the list of vendored modules from vendor/modules.txt.
-func readVendorList() {
+func readVendorList(mainModule module.Version) {
 	vendorOnce.Do(func() {
 		vendorList = nil
 		vendorPkgModule = make(map[string]module.Version)
 		vendorVersion = make(map[string]string)
 		vendorMeta = make(map[module.Version]vendorMetadata)
-		data, err := os.ReadFile(filepath.Join(ModRoot(), "vendor/modules.txt"))
+		data, err := os.ReadFile(filepath.Join(MainModules.ModRoot(mainModule), "vendor/modules.txt"))
 		if err != nil {
 			if !errors.Is(err, fs.ErrNotExist) {
 				base.Fatalf("go: %s", err)
@@ -136,7 +136,7 @@ func readVendorList() {
 // go 1.14) or at least does not contradict (go 1.13 or earlier) the
 // requirements and replacements listed in the main module's go.mod file.
 func checkVendorConsistency(index *modFileIndex, modFile *modfile.File) {
-	readVendorList()
+	readVendorList(MainModules.mustGetSingleMainModule())
 
 	pre114 := false
 	if semver.Compare(index.goVersionV, "v1.14") < 0 {