feat: add flag to add go:generate directive in the generated file

mockgen/internal/tests/add_generate_directive/import.go

@@ -0,0 +1,10 @@
+// Package add_generate_directive makes sure output places the go:generate command as a directive in the generated code.
+package add_generate_directive
+
+type Message struct {
+	Text string
+}
+
+type Foo interface {
+	Bar(channels []string, message chan<- Message)
+}

mockgen/mockgen.go

@@ -60,6 +60,7 @@ var (
 	selfPackage        = flag.String("self_package", "", "The full package import path for the generated code. The purpose of this flag is to prevent import cycles in the generated code by trying to include its own package. This can happen if the mock's package is set to one of its inputs (usually the main one) and the output is stdio so mockgen cannot detect the final output package. Setting this flag will then tell mockgen which import to exclude.")
 	writePkgComment    = flag.Bool("write_package_comment", true, "Writes package documentation comment (godoc) if true.")
 	writeSourceComment = flag.Bool("write_source_comment", true, "Writes original file (source mode) or interface names (reflect mode) comment if true.")
+  writeGenerateDirective = flag.Bool("write_generate_directive", false, "Put the //go:generate directive into the generated code")
 	copyrightFile      = flag.String("copyright_file", "", "Copyright file used to add copyright header")
 	typed              = flag.Bool("typed", false, "Generate Type-safe 'Return', 'Do', 'DoAndReturn' function")
 	imports            = flag.String("imports", "", "(source mode) Comma-separated name=path pairs of explicit imports to use.")
@@ -383,6 +384,10 @@ func (g *generator) Generate(pkg *model.Package, outputPkgName string, outputPac
 	g.out()
 	g.p(")")
 
+	if *writeGenerateDirective {
+		g.p("//go:generate %v", strings.Join(os.Args, " "))
+	}
+
 	for _, intf := range pkg.Interfaces {
 		if err := g.GenerateMockInterface(intf, outputPackagePath); err != nil {
 			return err