feat(completion): unify shell wrappers behind task __complete

cmd/task/complete_cmd.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"io"
+	"os"
+
+	"github.com/spf13/pflag"
+
+	"github.com/go-task/task/v3"
+	"github.com/go-task/task/v3/internal/complete"
+)
+
+func runComplete(args []string) error {
+	dir, entrypoint, global := extractTaskfileFlags(args)
+
+	e := task.NewExecutor(
+		task.WithDir(dir),
+		task.WithEntrypoint(entrypoint),
+		task.WithStdout(io.Discard),
+		task.WithStderr(io.Discard),
+		task.WithVersionCheck(false),
+	)
+	if global {
+		if home, err := os.UserHomeDir(); err == nil {
+			e.Options(task.WithDir(home))
+		}
+	}
+
+	// Best-effort: a missing or broken Taskfile must not break completion.
+	_ = e.Setup()
+
+	suggs, dirv := complete.Complete(e, pflag.CommandLine, args)
+	complete.Write(os.Stdout, suggs, dirv)
+	return nil
+}
+
+func extractTaskfileFlags(args []string) (dir, entrypoint string, global bool) {
+	fs := pflag.NewFlagSet("complete", pflag.ContinueOnError)
+	fs.SetOutput(io.Discard)
+	fs.ParseErrorsAllowlist.UnknownFlags = true
+	fs.Usage = func() {}
+	fs.StringVarP(&dir, "dir", "d", "", "")
+	fs.StringVarP(&entrypoint, "taskfile", "t", "", "")
+	fs.BoolVarP(&global, "global", "g", false, "")
+	_ = fs.Parse(args)
+	return
+}

cmd/task/task.go

@@ -13,6 +13,7 @@ import (
 	"github.com/go-task/task/v3/args"
 	"github.com/go-task/task/v3/errors"
 	"github.com/go-task/task/v3/experiments"
+	"github.com/go-task/task/v3/internal/complete"
 	"github.com/go-task/task/v3/internal/filepathext"
 	"github.com/go-task/task/v3/internal/flags"
 	"github.com/go-task/task/v3/internal/logger"
@@ -58,6 +59,12 @@ func emitCIErrorAnnotation(err error) {
 }
 
 func run() error {
+	// Dispatched before flag validation: the args after __complete are the
+	// user's command line, not Task's own flags.
+	if complete.IsActive() {
+		return runComplete(os.Args[2:])
+	}
+
 	log := &logger.Logger{
 		Stdout:  os.Stdout,
 		Stderr:  os.Stderr,