Add gob mode to support custom package loading techniques in place of --exec_only

mockgen/gob.go

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"encoding/gob"
+	"os"
+
+	"go.uber.org/mock/mockgen/model"
+)
+
+func gobMode(path string) (*model.Package, error) {
+	in, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer in.Close()
+	var pkg model.Package
+	if err := gob.NewDecoder(in).Decode(&pkg); err != nil {
+		return nil, err
+	}
+	return &pkg, nil
+}

mockgen/gob_test.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"encoding/gob"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGobMode(t *testing.T) {
+
+	// Encode a package to a temporary gob.
+	parser := packageModeParser{}
+	want, err := parser.parsePackage(
+		"go.uber.org/mock/mockgen/internal/tests/package_mode" /* package name */,
+		[]string{ "Human", "Earth" } /* ifaces */,
+	)
+	path := filepath.Join(t.TempDir(), "model.gob")
+	outfile, err := os.Create(path)
+	require.NoError(t, err)
+	require.NoError(t, gob.NewEncoder(outfile).Encode(want))
+	outfile.Close()
+
+	// Ensure gobMode loads it correctly.
+	got, err := gobMode(path)
+	require.NoError(t, err)
+	assert.Equal(t, want, got)
+}

mockgen/mockgen.go

@@ -69,6 +69,7 @@ var (
 	imports                = flag.String("imports", "", "(source mode) Comma-separated name=path pairs of explicit imports to use.")
 	auxFiles               = flag.String("aux_files", "", "(source mode) Comma-separated pkg=path pairs of auxiliary Go source files.")
 	excludeInterfaces      = flag.String("exclude_interfaces", "", "(source mode) Comma-separated names of interfaces to be excluded")
+	modelGob               = flag.String("model_gob", "", "Skip package/source loading entirely and use the gob encoded model.Package at the given path")
 
 	debugParser = flag.Bool("debug_parser", false, "Print out parser results only.")
 	showVersion = flag.Bool("version", false, "Print version.")
@@ -88,7 +89,9 @@ func main() {
 	var pkg *model.Package
 	var err error
 	var packageName string
-	if *source != "" {
+	if *modelGob != "" {
+		pkg, err = gobMode(*modelGob)
+	} else if *source != "" {
 		pkg, err = sourceMode(*source)
 	} else {
 		if flag.NArg() != 2 {