feat: implement --yield-deps-only and fix tag issues

main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"encoding/json"
 	"fmt"
 	"io"
 	"os"
@@ -15,10 +16,18 @@ var args struct {
 	File          string `arg:"positional" help:"if not specified, will read from stdin" default:""`
 	Outfile       string `arg:"positional" help:"if not specified, will emit to stdout" default:""`
 	Version       bool   `arg:"-v" help:"print version and exit"`
-	YieldDepsOnly bool   `arg:"--yield-deps-only" help:"print dependencies as a JSON array and exit" default:false`
-	ExposeDeps    bool   `arg:"--expose-deps" help:"expose dependencies to program" default:false`
+	YieldDepsOnly bool   `arg:"--yield-deps-only" help:"print dependencies as a JSON array and exit" default:"false"`
+	ExposeDeps    bool   `arg:"--expose-deps" help:"expose dependencies to program" default:"false"`
 	DepsVarName   string `arg:"--deps-var-name" help:"override deps variable name" default:"deps"`
-	IgnoreShebang bool   `arg:"--ignore-shebang" help:"ignore shebang requirement" default:false`
+	IgnoreShebang bool   `arg:"--ignore-shebang" help:"ignore shebang requirement" default:"false"`
+}
+
+func emit(code string) {
+	if args.Outfile == "" {
+		fmt.Printf("%s", code)
+	} else {
+		os.WriteFile(args.Outfile, []byte(code), os.FileMode(0o755))
+	}
 }
 
 func main() {
@@ -55,6 +64,24 @@ func main() {
 		panic(err)
 	}
 
+	if args.YieldDepsOnly {
+		marshaled, err := json.Marshal(found)
+		if err != nil {
+			panic(err)
+		}
+		if string(marshaled) == "null" {
+			emit("[]")
+		} else {
+			emit(string(marshaled))
+		}
+		os.Exit(0)
+	}
+
+	if len(found) == 0 {
+		emit(code)
+		os.Exit(0)
+	}
+
 	codelines := strings.Split(code, "\n")
 
 	if len(codelines) < 2 {
@@ -70,10 +97,5 @@ func main() {
 	}
 
 	gen := shebang + "\n\n" + gencode(found) + "\n\n" + strings.Join(codelines[1:], "\n")
-
-	if args.Outfile == "" {
-		fmt.Printf("%s", gen)
-	} else {
-		os.WriteFile(args.Outfile, []byte(gen), os.FileMode(0o755))
-	}
+	emit(gen)
 }