cmd/go: add tool names to go tool subcommand counters

When go tool <toolname> is run, increment the
go/subcommand:tool-<toolname> counter instead of just
go/subcommand:tool. go/subcommand:tool will be incremented
if go tool is run without a tool argument to list the
available tools.

Change-Id: I22b888fada1441389315a79f417c72b3f74070f8
Reviewed-on: https://go-review.googlesource.com/c/go/+/571802
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Sam Thanawalla <samthanawalla@google.com>

4 files changed, 81 insertions, 5 deletions

diff --git a/src/cmd/go/counters_test.go b/src/cmd/go/counters_test.go
index 2392b17eb9..7c73889351 100644
--- a/src/cmd/go/counters_test.go
+++ b/src/cmd/go/counters_test.go
@@ -6,7 +6,9 @@ package main_test
 
 import (
 	"cmd/go/internal/base"
+	"cmd/go/internal/cfg"
 	"flag"
+	"go/build"
 	"internal/diff"
 	"os"
 	"slices"
@@ -33,7 +35,11 @@ func TestCounterNamesUpToDate(t *testing.T) {
 	// for all subcommands, but it's also valid to invoke go help without any arguments.
 	counters = append(counters, "go/subcommand:help")
 	for _, cmd := range base.Go.Commands {
-		counters = append(counters, cmdcounters(nil, cmd)...)
+		cmdcounters, err := cmdcounters(nil, cmd)
+		if err != nil {
+			t.Fatal(err)
+		}
+		counters = append(counters, cmdcounters...)
 	}
 
 	counters = append(counters, base.RegisteredCounterNames()...)
@@ -76,7 +82,7 @@ func flagscounters(prefix string, flagSet flag.FlagSet) []string {
 	return counters
 }
 
-func cmdcounters(previous []string, cmd *base.Command) []string {
+func cmdcounters(previous []string, cmd *base.Command) ([]string, error) {
 	const subcommandPrefix = "go/subcommand:"
 	const flagPrefix = "go/flag:"
 	var counters []string
@@ -85,6 +91,19 @@ func cmdcounters(previous []string, cmd *base.Command) []string {
 		previousComponent += "-"
 	}
 	if cmd.Runnable() {
+		if cmd.Name() == "tool" {
+			// TODO(matloob): Do we expect the same tools to be present on all
+			// platforms/configurations? Should we only run this on certain
+			// platforms?
+			tools, err := toolNames()
+			if err != nil {
+				return nil, err
+			}
+			for _, t := range tools {
+				counters = append(counters, subcommandPrefix+previousComponent+cmd.Name()+"-"+t)
+			}
+			counters = append(counters, subcommandPrefix+previousComponent+cmd.Name()+"-unknown")
+		}
 		counters = append(counters, subcommandPrefix+previousComponent+cmd.Name())
 	}
 	counters = append(counters, flagscounters(flagPrefix+previousComponent+cmd.Name()+"-", cmd.Flag)...)
@@ -94,7 +113,28 @@ func cmdcounters(previous []string, cmd *base.Command) []string {
 	counters = append(counters, subcommandPrefix+"help-"+previousComponent+cmd.Name())
 
 	for _, subcmd := range cmd.Commands {
-		counters = append(counters, cmdcounters(append(slices.Clone(previous), cmd.Name()), subcmd)...)
+		subcmdcounters, err := cmdcounters(append(slices.Clone(previous), cmd.Name()), subcmd)
+		if err != nil {
+			return nil, err
+		}
+		counters = append(counters, subcmdcounters...)
 	}
-	return counters
+	return counters, nil
+}
+
+// toolNames returns the list of basenames of executables in the tool dir.
+func toolNames() ([]string, error) {
+	entries, err := os.ReadDir(build.ToolDir)
+	if err != nil {
+		return nil, err
+	}
+	var names []string
+	for _, e := range entries {
+		if e.IsDir() {
+			continue
+		}
+		name := strings.TrimSuffix(e.Name(), cfg.ToolExeSuffix())
+		names = append(names, name)
+	}
+	return names, nil
 }
diff --git a/src/cmd/go/internal/tool/tool.go b/src/cmd/go/internal/tool/tool.go
index ebe189bb81..da219f041c 100644
--- a/src/cmd/go/internal/tool/tool.go
+++ b/src/cmd/go/internal/tool/tool.go
@@ -6,6 +6,7 @@
 package tool
 
 import (
+	"cmd/internal/telemetry"
 	"context"
 	"encoding/json"
 	"flag"
@@ -57,6 +58,7 @@ func init() {
 
 func runTool(ctx context.Context, cmd *base.Command, args []string) {
 	if len(args) == 0 {
+		telemetry.Inc("go/subcommand:tool")
 		listTools()
 		return
 	}
@@ -82,12 +84,19 @@ func runTool(ctx context.Context, cmd *base.Command, args []string) {
 			//
 			// If the dist tool does not exist, impersonate this command.
 			if impersonateDistList(args[2:]) {
+				// If it becomes necessary, we could increment an additional counter to indicate
+				// that we're impersonating dist list if knowing that becomes important?
+				telemetry.Inc("go/subcommand:tool-dist")
 				return
 			}
 		}
 
+		telemetry.Inc("go/subcommand:tool-unknown")
 		// Emit the usual error for the missing tool.
 		_ = base.Tool(toolName)
+	} else {
+		// Increment a counter for the tool subcommand with the tool name.
+		telemetry.Inc("go/subcommand:tool-" + toolName)
 	}
 
 	if toolN {
diff --git a/src/cmd/go/main.go b/src/cmd/go/main.go
index 9fa9fbea5a..73fe612e75 100644
--- a/src/cmd/go/main.go
+++ b/src/cmd/go/main.go
@@ -182,7 +182,13 @@ func main() {
 		base.SetExitStatus(2)
 		base.Exit()
 	}
-	telemetry.Inc("go/subcommand:" + strings.ReplaceAll(cfg.CmdName, " ", "-"))
+	// Increment a subcommand counter for the subcommand we're running.
+	// Don't increment the counter for the tool subcommand here: we'll
+	// increment in the tool subcommand's Run function because we need
+	// to do the flag processing in invoke first.
+	if cfg.CmdName != "tool" {
+		telemetry.Inc("go/subcommand:" + strings.ReplaceAll(cfg.CmdName, " ", "-"))
+	}
 	invoke(cmd, args[used-1:])
 	base.Exit()
 }
diff --git a/src/cmd/go/testdata/counters.txt b/src/cmd/go/testdata/counters.txt
index 4482c0a915..109be96556 100644
--- a/src/cmd/go/testdata/counters.txt
+++ b/src/cmd/go/testdata/counters.txt
@@ -600,6 +600,27 @@ go/flag:test-vet
 go/flag:test-work
 go/flag:test-x
 go/subcommand:help-test
+go/subcommand:tool-addr2line
+go/subcommand:tool-asm
+go/subcommand:tool-buildid
+go/subcommand:tool-cgo
+go/subcommand:tool-compile
+go/subcommand:tool-covdata
+go/subcommand:tool-cover
+go/subcommand:tool-dist
+go/subcommand:tool-distpack
+go/subcommand:tool-doc
+go/subcommand:tool-fix
+go/subcommand:tool-link
+go/subcommand:tool-nm
+go/subcommand:tool-objdump
+go/subcommand:tool-pack
+go/subcommand:tool-pprof
+go/subcommand:tool-preprofile
+go/subcommand:tool-test2json
+go/subcommand:tool-trace
+go/subcommand:tool-vet
+go/subcommand:tool-unknown
 go/subcommand:tool
 go/flag:tool-C
 go/flag:tool-n