From b391ab3b1776e237da36a451338943bba80b8ead Mon Sep 17 00:00:00 2001
From: Hesky Fisher <hesky.fisher@gmail.com>
Date: Thu, 5 Apr 2018 21:51:19 +0000
Subject: [PATCH] Fix output for empty interfaces. Added a test.

---
 mockgen/mockgen.go                     | 10 +++++++-
 mockgen/tests/empty_interface/input.go |  4 ++++
 mockgen/tests/empty_interface/mock.go  | 32 ++++++++++++++++++++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)
 create mode 100644 mockgen/tests/empty_interface/input.go
 create mode 100644 mockgen/tests/empty_interface/mock.go

diff --git a/mockgen/mockgen.go b/mockgen/mockgen.go
index 5a88fa85..67481a64 100644
--- a/mockgen/mockgen.go
+++ b/mockgen/mockgen.go
@@ -231,7 +231,15 @@ func (g *generator) Generate(pkg *model.Package, pkgName string, outputPackagePa
 	// Get all required imports, and generate unique names for them all.
 	im := pkg.Imports()
 	im[gomockImportPath] = true
-	im["reflect"] = true
+
+	// Only import reflect if it's used. We only use reflect in mocked methods
+	// so only import if any of the mocked interfaces have methods.
+	for _, intf := range pkg.Interfaces {
+		if len(intf.Methods) > 0 {
+			im["reflect"] = true
+			break
+		}
+	}
 
 	// Sort keys to make import alias generation predictable
 	sorted_paths := make([]string, len(im), len(im))
diff --git a/mockgen/tests/empty_interface/input.go b/mockgen/tests/empty_interface/input.go
new file mode 100644
index 00000000..bbcb3fc8
--- /dev/null
+++ b/mockgen/tests/empty_interface/input.go
@@ -0,0 +1,4 @@
+//go:generate mockgen -package empty_interface -destination mock.go -source input.go
+package empty_interface
+
+type Empty interface{}
diff --git a/mockgen/tests/empty_interface/mock.go b/mockgen/tests/empty_interface/mock.go
new file mode 100644
index 00000000..0fc5b0c7
--- /dev/null
+++ b/mockgen/tests/empty_interface/mock.go
@@ -0,0 +1,32 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: input.go
+
+// Package empty_interface is a generated GoMock package.
+package empty_interface
+
+import (
+	gomock "github.com/golang/mock/gomock"
+)
+
+// MockEmpty is a mock of Empty interface
+type MockEmpty struct {
+	ctrl     *gomock.Controller
+	recorder *MockEmptyMockRecorder
+}
+
+// MockEmptyMockRecorder is the mock recorder for MockEmpty
+type MockEmptyMockRecorder struct {
+	mock *MockEmpty
+}
+
+// NewMockEmpty creates a new mock instance
+func NewMockEmpty(ctrl *gomock.Controller) *MockEmpty {
+	mock := &MockEmpty{ctrl: ctrl}
+	mock.recorder = &MockEmptyMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use
+func (m *MockEmpty) EXPECT() *MockEmptyMockRecorder {
+	return m.recorder
+}