cmd/go: move 'go install cmd@version' code into internal/load

'go run cmd@version' will use the same code.

This changes error messages a bit.

For #42088

Change-Id: Iaed3997a3d27f9fc0e868013ab765f1fb638a0b5
Reviewed-on: https://go-review.googlesource.com/c/go/+/310410
Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

3 files changed, 210 insertions, 147 deletions

diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go
index 8a74930209..98a695ca24 100644
--- a/src/cmd/go/internal/load/pkg.go
+++ b/src/cmd/go/internal/load/pkg.go
@@ -14,6 +14,7 @@ import (
 	"go/build"
 	"go/scanner"
 	"go/token"
+	"internal/goroot"
 	"io/fs"
 	"os"
 	"path"
@@ -30,6 +31,7 @@ import (
 	"cmd/go/internal/cfg"
 	"cmd/go/internal/fsys"
 	"cmd/go/internal/imports"
+	"cmd/go/internal/modfetch"
 	"cmd/go/internal/modinfo"
 	"cmd/go/internal/modload"
 	"cmd/go/internal/par"
@@ -38,6 +40,7 @@ import (
 	"cmd/go/internal/trace"
 	"cmd/internal/sys"
 
+	"golang.org/x/mod/modfile"
 	"golang.org/x/mod/module"
 )
 
@@ -2390,6 +2393,13 @@ type PackageOpts struct {
 	// of those packages could be missing, and resolving those missing dependencies
 	// could change the selected versions of modules that provide other packages.
 	ModResolveTests bool
+
+	// MainOnly is true if the caller only wants to load main packages.
+	// For a literal argument matching a non-main package, a stub may be returned
+	// with an error. For a non-literal argument (with "..."), non-main packages
+	// are not be matched, and their dependencies may not be loaded. A warning
+	// may be printed for non-literal arguments that match no main packages.
+	MainOnly bool
 }
 
 // PackagesAndErrors returns the packages named by the command line arguments
@@ -2480,6 +2490,10 @@ func PackagesAndErrors(ctx context.Context, opts PackageOpts, patterns []string)
 		}
 	}
 
+	if opts.MainOnly {
+		pkgs = mainPackagesOnly(pkgs, patterns)
+	}
+
 	// Now that CmdlinePkg is set correctly,
 	// compute the effective flags for all loaded packages
 	// (not just the ones matching the patterns but also
@@ -2528,6 +2542,51 @@ func CheckPackageErrors(pkgs []*Package) {
 	base.ExitIfErrors()
 }
 
+// mainPackagesOnly filters out non-main packages matched only by arguments
+// containing "..." and returns the remaining main packages.
+//
+// mainPackagesOnly sets a package's error if it is named by a literal argument.
+//
+// mainPackagesOnly prints warnings for non-literal arguments that only match
+// non-main packages.
+func mainPackagesOnly(pkgs []*Package, patterns []string) []*Package {
+	matchers := make([]func(string) bool, len(patterns))
+	for i, p := range patterns {
+		if strings.Contains(p, "...") {
+			matchers[i] = search.MatchPattern(p)
+		}
+	}
+
+	mainPkgs := make([]*Package, 0, len(pkgs))
+	mainCount := make([]int, len(patterns))
+	nonMainCount := make([]int, len(patterns))
+	for _, pkg := range pkgs {
+		if pkg.Name == "main" {
+			mainPkgs = append(mainPkgs, pkg)
+			for i := range patterns {
+				if matchers[i] != nil && matchers[i](pkg.ImportPath) {
+					mainCount[i]++
+				}
+			}
+		} else {
+			for i := range patterns {
+				if matchers[i] == nil && patterns[i] == pkg.ImportPath && pkg.Error == nil {
+					pkg.Error = &PackageError{Err: ImportErrorf(pkg.ImportPath, "package %s is not a main package", pkg.ImportPath)}
+				} else if matchers[i] != nil && matchers[i](pkg.ImportPath) {
+					nonMainCount[i]++
+				}
+			}
+		}
+	}
+	for i, p := range patterns {
+		if matchers[i] != nil && mainCount[i] == 0 && nonMainCount[i] > 0 {
+			fmt.Fprintf(os.Stderr, "go: warning: %q matched no main packages\n", p)
+		}
+	}
+
+	return mainPkgs
+}
+
 func setToolFlags(pkgs ...*Package) {
 	for _, p := range PackageList(pkgs) {
 		p.Internal.Asmflags = BuildAsmflags.For(p)
@@ -2624,3 +2683,131 @@ func GoFilesPackage(ctx context.Context, opts PackageOpts, gofiles []string) *Pa
 
 	return pkg
 }
+
+// PackagesAndErrorsOutsideModule is like PackagesAndErrors but runs in
+// module-aware mode and ignores the go.mod file in the current directory or any
+// parent directory, if there is one. This is used in the implementation of 'go
+// install pkg@version' and other commands that support similar forms.
+//
+// modload.ForceUseModules must be true, and modload.RootMode must be NoRoot
+// before calling this function.
+//
+// PackagesAndErrorsOutsideModule imposes several constraints to avoid
+// ambiguity. All arguments must have the same version suffix (not just a suffix
+// that resolves to the same version). They must refer to packages in the same
+// module, which must not be std or cmd. That module is not considered the main
+// module, but its go.mod file (if it has one) must not contain directives that
+// would cause it to be interpreted differently if it were the main module
+// (replace, exclude).
+func PackagesAndErrorsOutsideModule(ctx context.Context, opts PackageOpts, args []string) ([]*Package, error) {
+	if !modload.ForceUseModules {
+		panic("modload.ForceUseModules must be true")
+	}
+	if modload.RootMode != modload.NoRoot {
+		panic("modload.RootMode must be NoRoot")
+	}
+
+	// Check that the arguments satisfy syntactic constraints.
+	var version string
+	for _, arg := range args {
+		if i := strings.Index(arg, "@"); i >= 0 {
+			version = arg[i+1:]
+			if version == "" {
+				return nil, fmt.Errorf("%s: version must not be empty", arg)
+			}
+			break
+		}
+	}
+	patterns := make([]string, len(args))
+	for i, arg := range args {
+		if !strings.HasSuffix(arg, "@"+version) {
+			return nil, fmt.Errorf("%s: all arguments must have the same version (@%s)", arg, version)
+		}
+		p := arg[:len(arg)-len(version)-1]
+		switch {
+		case build.IsLocalImport(p):
+			return nil, fmt.Errorf("%s: argument must be a package path, not a relative path", arg)
+		case filepath.IsAbs(p):
+			return nil, fmt.Errorf("%s: argument must be a package path, not an absolute path", arg)
+		case search.IsMetaPackage(p):
+			return nil, fmt.Errorf("%s: argument must be a package path, not a meta-package", arg)
+		case path.Clean(p) != p:
+			return nil, fmt.Errorf("%s: argument must be a clean package path", arg)
+		case !strings.Contains(p, "...") && search.IsStandardImportPath(p) && goroot.IsStandardPackage(cfg.GOROOT, cfg.BuildContext.Compiler, p):
+			return nil, fmt.Errorf("%s: argument must not be a package in the standard library", arg)
+		default:
+			patterns[i] = p
+		}
+	}
+
+	// Query the module providing the first argument, load its go.mod file, and
+	// check that it doesn't contain directives that would cause it to be
+	// interpreted differently if it were the main module.
+	//
+	// If multiple modules match the first argument, accept the longest match
+	// (first result). It's possible this module won't provide packages named by
+	// later arguments, and other modules would. Let's not try to be too
+	// magical though.
+	allowed := modload.CheckAllowed
+	if modload.IsRevisionQuery(version) {
+		// Don't check for retractions if a specific revision is requested.
+		allowed = nil
+	}
+	noneSelected := func(path string) (version string) { return "none" }
+	qrs, err := modload.QueryPackages(ctx, patterns[0], version, noneSelected, allowed)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w", args[0], err)
+	}
+	rootMod := qrs[0].Mod
+	data, err := modfetch.GoMod(rootMod.Path, rootMod.Version)
+	if err != nil {
+		return nil, fmt.Errorf("%s: %w", args[0], err)
+	}
+	f, err := modfile.Parse("go.mod", data, nil)
+	if err != nil {
+		return nil, fmt.Errorf("%s (in %s): %w", args[0], rootMod, err)
+	}
+	directiveFmt := "%s (in %s):\n" +
+		"\tThe go.mod file for the module providing named packages contains one or\n" +
+		"\tmore %s directives. It must not contain directives that would cause\n" +
+		"\tit to be interpreted differently than if it were the main module."
+	if len(f.Replace) > 0 {
+		return nil, fmt.Errorf(directiveFmt, args[0], rootMod, "replace")
+	}
+	if len(f.Exclude) > 0 {
+		return nil, fmt.Errorf(directiveFmt, args[0], rootMod, "exclude")
+	}
+
+	// Since we are in NoRoot mode, the build list initially contains only
+	// the dummy command-line-arguments module. Add a requirement on the
+	// module that provides the packages named on the command line.
+	if _, err := modload.EditBuildList(ctx, nil, []module.Version{rootMod}); err != nil {
+		return nil, fmt.Errorf("%s: %w", args[0], err)
+	}
+
+	// Load packages for all arguments.
+	pkgs := PackagesAndErrors(ctx, opts, patterns)
+
+	// Check that named packages are all provided by the same module.
+	for _, pkg := range pkgs {
+		var pkgErr error
+		if pkg.Module == nil {
+			// Packages in std, cmd, and their vendored dependencies
+			// don't have this field set.
+			pkgErr = fmt.Errorf("package %s not provided by module %s", pkg.ImportPath, rootMod)
+		} else if pkg.Module.Path != rootMod.Path || pkg.Module.Version != rootMod.Version {
+			pkgErr = fmt.Errorf("package %s provided by module %s@%s\n\tAll packages must be provided by the same module (%s).", pkg.ImportPath, pkg.Module.Path, pkg.Module.Version, rootMod)
+		}
+		if pkgErr != nil && pkg.Error == nil {
+			pkg.Error = &PackageError{Err: pkgErr}
+		}
+	}
+
+	matchers := make([]func(string) bool, len(patterns))
+	for i, p := range patterns {
+		if strings.Contains(p, "...") {
+			matchers[i] = search.MatchPattern(p)
+		}
+	}
+	return pkgs, nil
+}
diff --git a/src/cmd/go/internal/work/build.go b/src/cmd/go/internal/work/build.go
index dcb9e3785c..a75ace7d4e 100644
--- a/src/cmd/go/internal/work/build.go
+++ b/src/cmd/go/internal/work/build.go
@@ -10,9 +10,7 @@ import (
 	"fmt"
 	"go/build"
 	exec "internal/execabs"
-	"internal/goroot"
 	"os"
-	"path"
 	"path/filepath"
 	"runtime"
 	"strings"
@@ -21,13 +19,9 @@ import (
 	"cmd/go/internal/cfg"
 	"cmd/go/internal/fsys"
 	"cmd/go/internal/load"
-	"cmd/go/internal/modfetch"
 	"cmd/go/internal/modload"
 	"cmd/go/internal/search"
 	"cmd/go/internal/trace"
-
-	"golang.org/x/mod/modfile"
-	"golang.org/x/mod/module"
 )
 
 var CmdBuild = &base.Command{
@@ -762,145 +756,27 @@ func installOutsideModule(ctx context.Context, args []string) {
 	modload.RootMode = modload.NoRoot
 	modload.AllowMissingModuleImports()
 	modload.Init()
-
-	// Check that the arguments satisfy syntactic constraints.
-	var version string
-	for _, arg := range args {
-		if i := strings.Index(arg, "@"); i >= 0 {
-			version = arg[i+1:]
-			if version == "" {
-				base.Fatalf("go install %s: version must not be empty", arg)
-			}
-			break
-		}
-	}
-	patterns := make([]string, len(args))
-	for i, arg := range args {
-		if !strings.HasSuffix(arg, "@"+version) {
-			base.Errorf("go install %s: all arguments must have the same version (@%s)", arg, version)
-			continue
-		}
-		p := arg[:len(arg)-len(version)-1]
-		switch {
-		case build.IsLocalImport(p):
-			base.Errorf("go install %s: argument must be a package path, not a relative path", arg)
-		case filepath.IsAbs(p):
-			base.Errorf("go install %s: argument must be a package path, not an absolute path", arg)
-		case search.IsMetaPackage(p):
-			base.Errorf("go install %s: argument must be a package path, not a meta-package", arg)
-		case path.Clean(p) != p:
-			base.Errorf("go install %s: argument must be a clean package path", arg)
-		case !strings.Contains(p, "...") && search.IsStandardImportPath(p) && goroot.IsStandardPackage(cfg.GOROOT, cfg.BuildContext.Compiler, p):
-			base.Errorf("go install %s: argument must not be a package in the standard library", arg)
-		default:
-			patterns[i] = p
-		}
-	}
-	base.ExitIfErrors()
 	BuildInit()
 
-	// Query the module providing the first argument, load its go.mod file, and
-	// check that it doesn't contain directives that would cause it to be
-	// interpreted differently if it were the main module.
-	//
-	// If multiple modules match the first argument, accept the longest match
-	// (first result). It's possible this module won't provide packages named by
-	// later arguments, and other modules would. Let's not try to be too
-	// magical though.
-	allowed := modload.CheckAllowed
-	if modload.IsRevisionQuery(version) {
-		// Don't check for retractions if a specific revision is requested.
-		allowed = nil
-	}
-	noneSelected := func(path string) (version string) { return "none" }
-	qrs, err := modload.QueryPackages(ctx, patterns[0], version, noneSelected, allowed)
-	if err != nil {
-		base.Fatalf("go install %s: %v", args[0], err)
-	}
-	installMod := qrs[0].Mod
-	data, err := modfetch.GoMod(installMod.Path, installMod.Version)
-	if err != nil {
-		base.Fatalf("go install %s: %v", args[0], err)
-	}
-	f, err := modfile.Parse("go.mod", data, nil)
-	if err != nil {
-		base.Fatalf("go install %s: %s: %v", args[0], installMod, err)
-	}
-	directiveFmt := "go install %s: %s\n" +
-		"\tThe go.mod file for the module providing named packages contains one or\n" +
-		"\tmore %s directives. It must not contain directives that would cause\n" +
-		"\tit to be interpreted differently than if it were the main module."
-	if len(f.Replace) > 0 {
-		base.Fatalf(directiveFmt, args[0], installMod, "replace")
-	}
-	if len(f.Exclude) > 0 {
-		base.Fatalf(directiveFmt, args[0], installMod, "exclude")
-	}
-
-	// Since we are in NoRoot mode, the build list initially contains only
-	// the dummy command-line-arguments module. Add a requirement on the
-	// module that provides the packages named on the command line.
-	if _, err := modload.EditBuildList(ctx, nil, []module.Version{installMod}); err != nil {
-		base.Fatalf("go install %s: %v", args[0], err)
-	}
-
-	// Load packages for all arguments. Ignore non-main packages.
+	// Load packages. Ignore non-main packages.
 	// Print a warning if an argument contains "..." and matches no main packages.
 	// PackagesAndErrors already prints warnings for patterns that don't match any
 	// packages, so be careful not to double print.
-	matchers := make([]func(string) bool, len(patterns))
-	for i, p := range patterns {
-		if strings.Contains(p, "...") {
-			matchers[i] = search.MatchPattern(p)
-		}
-	}
-
 	// TODO(golang.org/issue/40276): don't report errors loading non-main packages
 	// matched by a pattern.
-	pkgs := load.PackagesAndErrors(ctx, load.PackageOpts{}, patterns)
-	load.CheckPackageErrors(pkgs)
-	mainPkgs := make([]*load.Package, 0, len(pkgs))
-	mainCount := make([]int, len(patterns))
-	nonMainCount := make([]int, len(patterns))
-	for _, pkg := range pkgs {
-		if pkg.Name == "main" {
-			mainPkgs = append(mainPkgs, pkg)
-			for i := range patterns {
-				if matchers[i] != nil && matchers[i](pkg.ImportPath) {
-					mainCount[i]++
-				}
-			}
-		} else {
-			for i := range patterns {
-				if matchers[i] == nil && patterns[i] == pkg.ImportPath {
-					base.Errorf("go install: package %s is not a main package", pkg.ImportPath)
-				} else if matchers[i] != nil && matchers[i](pkg.ImportPath) {
-					nonMainCount[i]++
-				}
-			}
-		}
-	}
-	base.ExitIfErrors()
-	for i, p := range patterns {
-		if matchers[i] != nil && mainCount[i] == 0 && nonMainCount[i] > 0 {
-			fmt.Fprintf(os.Stderr, "go: warning: %q matched no main packages\n", p)
-		}
+	pkgOpts := load.PackageOpts{MainOnly: true}
+	pkgs, err := load.PackagesAndErrorsOutsideModule(ctx, pkgOpts, args)
+	if err != nil {
+		base.Fatalf("go install: %v", err)
 	}
-
-	// Check that named packages are all provided by the same module.
-	for _, pkg := range mainPkgs {
-		if pkg.Module == nil {
-			// Packages in std, cmd, and their vendored dependencies
-			// don't have this field set.
-			base.Errorf("go install: package %s not provided by module %s", pkg.ImportPath, installMod)
-		} else if pkg.Module.Path != installMod.Path || pkg.Module.Version != installMod.Version {
-			base.Errorf("go install: package %s provided by module %s@%s\n\tAll packages must be provided by the same module (%s).", pkg.ImportPath, pkg.Module.Path, pkg.Module.Version, installMod)
-		}
+	load.CheckPackageErrors(pkgs)
+	patterns := make([]string, len(args))
+	for i, arg := range args {
+		patterns[i] = arg[:strings.Index(arg, "@")]
 	}
-	base.ExitIfErrors()
 
 	// Build and install the packages.
-	InstallPackages(ctx, patterns, mainPkgs)
+	InstallPackages(ctx, patterns, pkgs)
 }
 
 // ExecCmd is the command to use to run user binaries.
diff --git a/src/cmd/go/testdata/script/mod_install_pkg_version.txt b/src/cmd/go/testdata/script/mod_install_pkg_version.txt
index c14085c4fd..3b387cd8b6 100644
--- a/src/cmd/go/testdata/script/mod_install_pkg_version.txt
+++ b/src/cmd/go/testdata/script/mod_install_pkg_version.txt
@@ -81,17 +81,17 @@ env GO111MODULE=auto
 # 'go install pkg@version' reports errors for meta packages, std packages,
 # and directories.
 ! go install std@v1.0.0
-stderr '^go install std@v1.0.0: argument must be a package path, not a meta-package$'
+stderr '^go install: std@v1.0.0: argument must be a package path, not a meta-package$'
 ! go install fmt@v1.0.0
-stderr '^go install fmt@v1.0.0: argument must not be a package in the standard library$'
+stderr '^go install: fmt@v1.0.0: argument must not be a package in the standard library$'
 ! go install example.com//cmd/a@v1.0.0
-stderr '^go install example.com//cmd/a@v1.0.0: argument must be a clean package path$'
+stderr '^go install: example.com//cmd/a@v1.0.0: argument must be a clean package path$'
 ! go install example.com/cmd/a@v1.0.0 ./x@v1.0.0
-stderr '^go install ./x@v1.0.0: argument must be a package path, not a relative path$'
+stderr '^go install: ./x@v1.0.0: argument must be a package path, not a relative path$'
 ! go install example.com/cmd/a@v1.0.0 $GOPATH/src/x@v1.0.0
-stderr '^go install '$WORK'[/\\]gopath/src/x@v1.0.0: argument must be a package path, not an absolute path$'
+stderr '^go install: '$WORK'[/\\]gopath/src/x@v1.0.0: argument must be a package path, not an absolute path$'
 ! go install example.com/cmd/a@v1.0.0 cmd/...@v1.0.0
-stderr '^go install: package cmd/go not provided by module example.com/cmd@v1.0.0$'
+stderr '^package cmd/go not provided by module example.com/cmd@v1.0.0$'
 
 # 'go install pkg@version' should accept multiple arguments but report an error
 # if the version suffixes are different, even if they refer to the same version.
@@ -106,19 +106,19 @@ stdout '^example.com/cmd v1.0.0$'
 env GO111MODULE=auto
 
 ! go install example.com/cmd/a@v1.0.0 example.com/cmd/b@latest
-stderr '^go install example.com/cmd/b@latest: all arguments must have the same version \(@v1.0.0\)$'
+stderr '^go install: example.com/cmd/b@latest: all arguments must have the same version \(@v1.0.0\)$'
 
 
 # 'go install pkg@version' should report an error if the arguments are in
 # different modules.
 ! go install example.com/cmd/a@v1.0.0 rsc.io/fortune@v1.0.0
-stderr '^go install: package rsc.io/fortune provided by module rsc.io/fortune@v1.0.0\n\tAll packages must be provided by the same module \(example.com/cmd@v1.0.0\).$'
+stderr '^package rsc.io/fortune provided by module rsc.io/fortune@v1.0.0\n\tAll packages must be provided by the same module \(example.com/cmd@v1.0.0\).$'
 
 
 # 'go install pkg@version' should report an error if an argument is not
 # a main package.
 ! go install example.com/cmd/a@v1.0.0 example.com/cmd/err@v1.0.0
-stderr '^go install: package example.com/cmd/err is not a main package$'
+stderr '^go: package example.com/cmd/err is not a main package$'
 
 # Wildcards should match only main packages. This module has a non-main package
 # with an error, so we'll know if that gets built.
@@ -137,7 +137,7 @@ rm $GOPATH/bin
 
 # If a wildcard matches no packages, we should see a warning.
 ! go install example.com/cmd/nomatch...@v1.0.0
-stderr '^go install example.com/cmd/nomatch\.\.\.@v1.0.0: module example.com/cmd@v1.0.0 found, but does not contain packages matching example.com/cmd/nomatch\.\.\.$'
+stderr '^go install: example.com/cmd/nomatch\.\.\.@v1.0.0: module example.com/cmd@v1.0.0 found, but does not contain packages matching example.com/cmd/nomatch\.\.\.$'
 go install example.com/cmd/a@v1.0.0 example.com/cmd/nomatch...@v1.0.0
 stderr '^go: warning: "example.com/cmd/nomatch\.\.\." matched no packages$'
 
@@ -159,7 +159,7 @@ cmp stderr exclude-err
 # 'go install pkg@version' should report an error if the module requires a
 # higher version of itself.
 ! go install example.com/cmd/a@v1.0.0-newerself
-stderr '^go install example.com/cmd/a@v1.0.0-newerself: version constraints conflict:\n\texample.com/cmd@v1.0.0-newerself requires example.com/cmd@v1.0.0, but example.com/cmd@v1.0.0-newerself is requested$'
+stderr '^go install: example.com/cmd/a@v1.0.0-newerself: version constraints conflict:\n\texample.com/cmd@v1.0.0-newerself requires example.com/cmd@v1.0.0, but example.com/cmd@v1.0.0-newerself is requested$'
 
 
 # 'go install pkg@version' will only match a retracted version if it's
@@ -192,12 +192,12 @@ package main
 
 func main() {}
 -- replace-err --
-go install example.com/cmd/a@v1.0.0-replace: example.com/cmd@v1.0.0-replace
+go install: example.com/cmd/a@v1.0.0-replace (in example.com/cmd@v1.0.0-replace):
 	The go.mod file for the module providing named packages contains one or
 	more replace directives. It must not contain directives that would cause
 	it to be interpreted differently than if it were the main module.
 -- exclude-err --
-go install example.com/cmd/a@v1.0.0-exclude: example.com/cmd@v1.0.0-exclude
+go install: example.com/cmd/a@v1.0.0-exclude (in example.com/cmd@v1.0.0-exclude):
 	The go.mod file for the module providing named packages contains one or
 	more exclude directives. It must not contain directives that would cause
 	it to be interpreted differently than if it were the main module.