Add -stub flag to stub func implementation (#132)

When a mock is generated with the flag enabled, it introduces the
following changes:
- Does not panic on calling the method without a mock implementation.
- Return zero values iff the implementation is not provided and the
  method has return parameters.

Co-authored-by: Scott Leuthaeuser <scott_leuthaeuser@homedepot.com>

main.go

@@ -17,6 +17,7 @@ type userFlags struct {
 	outFile   string
 	pkgName   string
 	formatter string
+	stubImpl  bool
 	args      []string
 }
 
@@ -25,6 +26,8 @@ func main() {
 	flag.StringVar(&flags.outFile, "out", "", "output file (default stdout)")
 	flag.StringVar(&flags.pkgName, "pkg", "", "package name (default will infer)")
 	flag.StringVar(&flags.formatter, "fmt", "", "go pretty-printer: gofmt (default) or goimports")
+	flag.BoolVar(&flags.stubImpl, "stubImpl", false,
+		"return zero values when no mock implementation is provided, do not panic")
 
 	flag.Usage = func() {
 		fmt.Println(`moq [flags] source-dir interface [interface2 [interface3 [...]]]`)
@@ -59,6 +62,7 @@ func run(flags userFlags) error {
 		SrcDir:    srcDir,
 		PkgName:   flags.pkgName,
 		Formatter: flags.formatter,
+		StubImpl:  flags.stubImpl,
 	})
 	if err != nil {
 		return err

pkg/moq/moq.go

@@ -19,11 +19,12 @@ import (
 
 // Mocker can generate mock structs.
 type Mocker struct {
-	srcPkg  *packages.Package
-	tmpl    *template.Template
-	pkgName string
-	pkgPath string
-	fmter   func(src []byte) ([]byte, error)
+	srcPkg   *packages.Package
+	tmpl     *template.Template
+	pkgName  string
+	pkgPath  string
+	fmter    func(src []byte) ([]byte, error)
+	stubImpl bool
 
 	imports map[string]bool
 }
@@ -34,6 +35,7 @@ type Config struct {
 	SrcDir    string
 	PkgName   string
 	Formatter string
+	StubImpl  bool
 }
 
 // New makes a new Mocker for the specified package directory.
@@ -64,12 +66,13 @@ func New(conf Config) (*Mocker, error) {
 	}
 
 	return &Mocker{
-		tmpl:    tmpl,
-		srcPkg:  srcPkg,
-		pkgName: pkgName,
-		pkgPath: pkgPath,
-		fmter:   fmter,
-		imports: make(map[string]bool),
+		tmpl:     tmpl,
+		srcPkg:   srcPkg,
+		pkgName:  pkgName,
+		pkgPath:  pkgPath,
+		fmter:    fmter,
+		stubImpl: conf.StubImpl,
+		imports:  make(map[string]bool),
 	}, nil
 }
 
@@ -107,6 +110,7 @@ func (m *Mocker) Mock(w io.Writer, names ...string) error {
 	doc := doc{
 		PackageName: m.pkgName,
 		Imports:     moqImports,
+		StubImpl:    m.stubImpl,
 	}
 
 	mocksMethods := false
@@ -246,6 +250,7 @@ type doc struct {
 	SourcePackagePrefix string
 	Objects             []obj
 	Imports             []string
+	StubImpl            bool
 }
 
 type obj struct {
@@ -275,7 +280,7 @@ func (m *method) ArgCallList() string {
 	return strings.Join(params, ", ")
 }
 
-func (m *method) ReturnArglist() string {
+func (m *method) ReturnArgTypeList() string {
 	params := make([]string, len(m.Returns))
 	for i, p := range m.Returns {
 		params[i] = p.TypeString()
@@ -286,6 +291,14 @@ func (m *method) ReturnArglist() string {
 	return strings.Join(params, ", ")
 }
 
+func (m *method) ReturnArgNameList() string {
+	params := make([]string, len(m.Returns))
+	for i, p := range m.Returns {
+		params[i] = p.Name
+	}
+	return strings.Join(params, ", ")
+}
+
 type param struct {
 	Name     string
 	Type     string

pkg/moq/moq_test.go

@@ -284,23 +284,19 @@ func TestNothingToReturn(t *testing.T) {
 }
 
 func TestChannelNames(t *testing.T) {
-	m, err := New(Config{SrcDir: "testpackages/channels"})
+	m, err := New(Config{SrcDir: "testpackages/channels", StubImpl: true})
 	if err != nil {
 		t.Fatalf("moq.New: %s", err)
 	}
+
 	var buf bytes.Buffer
-	err = m.Mock(&buf, "Queuer")
-	if err != nil {
+	if err = m.Mock(&buf, "Queuer"); err != nil {
 		t.Errorf("m.Mock: %s", err)
 	}
-	s := buf.String()
-	var strs = []string{
-		"func (mock *QueuerMock) Sub(topic string) (<-chan Queue, error)",
-	}
-	for _, str := range strs {
-		if !strings.Contains(s, str) {
-			t.Errorf("expected but missing: \"%s\"", str)
-		}
+
+	golden := filepath.Join("testpackages/channels", "queuer_moq.golden.go")
+	if err := matchGoldenFile(golden, buf.Bytes()); err != nil {
+		t.Errorf("check golden file: %s", err)
 	}
 }
 

pkg/moq/template.go

@@ -10,6 +10,7 @@ var moqTemplate = `// Code generated by moq; DO NOT EDIT.
 
 package {{.PackageName}}
 {{- $sourcePackagePrefix := .SourcePackagePrefix}}
+{{- $stubImpl := .StubImpl}}
 
 import (
 {{- range .Imports }}
@@ -29,7 +30,7 @@ var _ {{$sourcePackagePrefix}}{{.InterfaceName}} = &{{.MockName}}{}
 //
 //         // make and configure a mocked {{$sourcePackagePrefix}}{{.InterfaceName}}
 //         mocked{{.InterfaceName}} := &{{.MockName}}{ {{ range .Methods }}
-//             {{.Name}}Func: func({{ .Arglist }}) {{.ReturnArglist}} {
+//             {{.Name}}Func: func({{ .Arglist }}) {{.ReturnArgTypeList}} {
 // 	               panic("mock out the {{.Name}} method")
 //             },{{- end }}
 //         }
@@ -41,7 +42,7 @@ var _ {{$sourcePackagePrefix}}{{.InterfaceName}} = &{{.MockName}}{}
 type {{.MockName}} struct {
 {{- range .Methods }}
 	// {{.Name}}Func mocks the {{.Name}} method.
-	{{.Name}}Func func({{ .Arglist }}) {{.ReturnArglist}}
+	{{.Name}}Func func({{ .Arglist }}) {{.ReturnArgTypeList}}
 {{ end }}
 	// calls tracks calls to the methods.
 	calls struct {
@@ -61,10 +62,12 @@ type {{.MockName}} struct {
 }
 {{ range .Methods }}
 // {{.Name}} calls {{.Name}}Func.
-func (mock *{{$obj.MockName}}) {{.Name}}({{.Arglist}}) {{.ReturnArglist}} {
+func (mock *{{$obj.MockName}}) {{.Name}}({{.Arglist}}) {{.ReturnArgTypeList}} {
+{{- if not $stubImpl }}
 	if mock.{{.Name}}Func == nil {
 		panic("{{$obj.MockName}}.{{.Name}}Func: method is nil but {{$obj.InterfaceName}}.{{.Name}} was just called")
 	}
+{{- end }}
 	callInfo := struct {
 		{{- range .Params }}
 		{{ .Name | Exported }} {{ .Type }}
@@ -77,9 +80,24 @@ func (mock *{{$obj.MockName}}) {{.Name}}({{.Arglist}}) {{.ReturnArglist}} {
 	mock.lock{{.Name}}.Lock()
 	mock.calls.{{.Name}} = append(mock.calls.{{.Name}}, callInfo)
 	mock.lock{{.Name}}.Unlock()
-{{- if .ReturnArglist }}
+{{- if .Returns }}
+	{{- if $stubImpl }}
+	if mock.{{.Name}}Func == nil {
+		var (
+		{{- range .Returns }}
+			{{.Name}} {{.Type}}
+		{{- end }}
+		)
+		return {{.ReturnArgNameList}}
+	}
+	{{- end }}
 	return mock.{{.Name}}Func({{.ArgCallList}})
 {{- else }}
+	{{- if $stubImpl }}
+	if mock.{{.Name}}Func == nil {
+		return
+	}
+	{{- end }}
 	mock.{{.Name}}Func({{.ArgCallList}})
 {{- end }}
 }

pkg/moq/testpackages/channels/example.go

@@ -6,4 +6,5 @@ type Queue []string
 // Queuer provides a channel example.
 type Queuer interface {
 	Sub(topic string) (<-chan Queue, error)
+	Unsub(topic string)
 }

pkg/moq/testpackages/channels/queuer_moq.golden.go

@@ -0,0 +1,120 @@
+// Code generated by moq; DO NOT EDIT.
+// github.com/matryer/moq
+
+package channels
+
+import (
+	"sync"
+)
+
+// Ensure, that QueuerMock does implement Queuer.
+// If this is not the case, regenerate this file with moq.
+var _ Queuer = &QueuerMock{}
+
+// QueuerMock is a mock implementation of Queuer.
+//
+//     func TestSomethingThatUsesQueuer(t *testing.T) {
+//
+//         // make and configure a mocked Queuer
+//         mockedQueuer := &QueuerMock{
+//             SubFunc: func(topic string) (<-chan Queue, error) {
+// 	               panic("mock out the Sub method")
+//             },
+//             UnsubFunc: func(topic string)  {
+// 	               panic("mock out the Unsub method")
+//             },
+//         }
+//
+//         // use mockedQueuer in code that requires Queuer
+//         // and then make assertions.
+//
+//     }
+type QueuerMock struct {
+	// SubFunc mocks the Sub method.
+	SubFunc func(topic string) (<-chan Queue, error)
+
+	// UnsubFunc mocks the Unsub method.
+	UnsubFunc func(topic string)
+
+	// calls tracks calls to the methods.
+	calls struct {
+		// Sub holds details about calls to the Sub method.
+		Sub []struct {
+			// Topic is the topic argument value.
+			Topic string
+		}
+		// Unsub holds details about calls to the Unsub method.
+		Unsub []struct {
+			// Topic is the topic argument value.
+			Topic string
+		}
+	}
+	lockSub   sync.RWMutex
+	lockUnsub sync.RWMutex
+}
+
+// Sub calls SubFunc.
+func (mock *QueuerMock) Sub(topic string) (<-chan Queue, error) {
+	callInfo := struct {
+		Topic string
+	}{
+		Topic: topic,
+	}
+	mock.lockSub.Lock()
+	mock.calls.Sub = append(mock.calls.Sub, callInfo)
+	mock.lockSub.Unlock()
+	if mock.SubFunc == nil {
+		var (
+			out1 <-chan Queue
+			out2 error
+		)
+		return out1, out2
+	}
+	return mock.SubFunc(topic)
+}
+
+// SubCalls gets all the calls that were made to Sub.
+// Check the length with:
+//     len(mockedQueuer.SubCalls())
+func (mock *QueuerMock) SubCalls() []struct {
+	Topic string
+} {
+	var calls []struct {
+		Topic string
+	}
+	mock.lockSub.RLock()
+	calls = mock.calls.Sub
+	mock.lockSub.RUnlock()
+	return calls
+}
+
+// Unsub calls UnsubFunc.
+func (mock *QueuerMock) Unsub(topic string) {
+	callInfo := struct {
+		Topic string
+	}{
+		Topic: topic,
+	}
+	mock.lockUnsub.Lock()
+	mock.calls.Unsub = append(mock.calls.Unsub, callInfo)
+	mock.lockUnsub.Unlock()
+	if mock.UnsubFunc == nil {
+		return
+	}
+	mock.UnsubFunc(topic)
+}
+
+// UnsubCalls gets all the calls that were made to Unsub.
+// Check the length with:
+//     len(mockedQueuer.UnsubCalls())
+func (mock *QueuerMock) UnsubCalls() []struct {
+	Topic string
+} {
+	var calls []struct {
+		Topic string
+	}
+	mock.lockUnsub.RLock()
+	calls = mock.calls.Unsub
+	mock.lockUnsub.RUnlock()
+	return calls
+}