cmd/go: add support for go get -u tool

Change-Id: I14d20c6c77d0d0a83cb547d954ba7f244166bc43
Reviewed-on: https://go-review.googlesource.com/c/go/+/563176
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>
Reviewed-by: Michael Matloob <matloob@golang.org>

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

@@ -342,6 +342,7 @@ func runGet(ctx context.Context, cmd *base.Command, args []string) {
 	r := newResolver(ctx, queries)
 	r.performLocalQueries(ctx)
 	r.performPathQueries(ctx)
+	r.performToolQueries(ctx)
 
 	for {
 		r.performWildcardQueries(ctx)
@@ -515,6 +516,7 @@ type resolver struct {
 	pathQueries       []*query // package path literal queries in original order
 	wildcardQueries   []*query // path wildcard queries in original order
 	patternAllQueries []*query // queries with the pattern "all"
+	toolQueries       []*query // queries with the pattern "tool"
 
 	// Indexed "none" queries. These are also included in the slices above;
 	// they are indexed here to speed up noneForPath.
@@ -574,6 +576,8 @@ func newResolver(ctx context.Context, queries []*query) *resolver {
 	for _, q := range queries {
 		if q.pattern == "all" {
 			r.patternAllQueries = append(r.patternAllQueries, q)
+		} else if q.pattern == "tool" {
+			r.toolQueries = append(r.toolQueries, q)
 		} else if q.patternIsLocal {
 			r.localQueries = append(r.localQueries, q)
 		} else if q.isWildcard() {
@@ -1050,6 +1054,19 @@ func (r *resolver) queryPath(ctx context.Context, q *query) {
 	})
 }
 
+// performToolQueries populates the candidates for each query whose
+// pattern is "tool".
+func (r *resolver) performToolQueries(ctx context.Context) {
+	for _, q := range r.toolQueries {
+		for tool := range modload.MainModules.Tools() {
+			q.pathOnce(tool, func() pathSet {
+				pkgMods, err := r.queryPackages(ctx, tool, q.version, r.initialSelected)
+				return pathSet{pkgMods: pkgMods, err: err}
+			})
+		}
+	}
+}
+
 // performPatternAllQueries populates the candidates for each query whose
 // pattern is "all".
 //

src/cmd/go/internal/modget/query.go

@@ -199,6 +199,9 @@ func (q *query) validate() error {
 
 	if search.IsMetaPackage(q.pattern) && q.pattern != "all" {
 		if q.pattern != q.raw {
+			if q.pattern == "tool" {
+				return fmt.Errorf("can't request explicit version of \"tool\" pattern")
+			}
 			return fmt.Errorf("can't request explicit version of standard-library pattern %q", q.pattern)
 		}
 	}

src/cmd/go/testdata/mod/example.com_tools_v1.1.0.txt

@@ -0,0 +1,12 @@
+-- .info --
+{"Version": "v1.1.0"}
+-- .mod --
+module example.com/tools
+-- cmd/hello/hello.go --
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("hello v1.1")
+}

src/cmd/go/testdata/script/mod_get_tool.txt

@@ -1,7 +1,10 @@
 # test go get -tool
-go get -tool example.com/tools/cmd/hello
+go get -tool example.com/tools/cmd/hello@v1.0.0
 cmp go.mod go.mod.want
 
+go get -u tool
+cmp go.mod go.mod.upgraded
+
 # test -tool with @none
 go get -tool example.com/tools/cmd/hello@none
 cmp go.mod go.mod.gone
@@ -19,6 +22,10 @@ stderr 'can''t request explicit version "none" of path "./cmd/..." in main modul
 ! go get -tool all
 stderr 'go get -tool does not work with "all"'
 
+# test tool@none
+! go get tool@none
+stderr 'can''t request explicit version of "tool" pattern'
+
 -- main.go --
 package main
 
@@ -36,12 +43,20 @@ go 1.24
 tool example.com/tools/cmd/hello
 
 require example.com/tools v1.0.0 // indirect
+-- go.mod.upgraded --
+module example.com/foo
+
+go 1.24
+
+tool example.com/tools/cmd/hello
+
+require example.com/tools v1.1.0 // indirect
 -- go.mod.gone --
 module example.com/foo
 
 go 1.24
 
-require example.com/tools v1.0.0 // indirect
+require example.com/tools v1.1.0 // indirect
 -- go.mod.empty --
 module example.com/foo