feat: support generic interface generation (#175)

Allow the generation of mocks for generics as introduced in golang 1.18

go.mod

@@ -1,8 +1,14 @@
 module github.com/matryer/moq
 
-go 1.14
+go 1.18
 
 require (
 	github.com/pmezard/go-difflib v1.0.0
 	golang.org/x/tools v0.1.10
 )
+
+require (
+	golang.org/x/mod v0.6.0-dev.0.20220106191415-9b9b3d81d5e3 // indirect
+	golang.org/x/sys v0.0.0-20211019181941-9d821ace8654 // indirect
+	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
+)

go.sum

@@ -1,31 +1,10 @@
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/yuin/goldmark v1.4.1/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
-golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
-golang.org/x/crypto v0.0.0-20210921155107-089bfa567519/go.mod h1:GvvjBRRGRdwPK5ydBHafDWAxML/pGHZbMvKqRZ5+Abc=
 golang.org/x/mod v0.6.0-dev.0.20220106191415-9b9b3d81d5e3 h1:kQgndtyPBW/JIYERgdxfwMYh3AVStj88WQTlNDi2a+o=
 golang.org/x/mod v0.6.0-dev.0.20220106191415-9b9b3d81d5e3/go.mod h1:3p9vT2HGsQu2K1YbXdKPJLVgG5VJdoTa1poYQBtP1AY=
-golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
-golang.org/x/net v0.0.0-20210226172049-e18ecbb05110/go.mod h1:m0MpNAwzfU5UDzcl9v0D8zg8gWTRqZa9RBIspLL5mdg=
-golang.org/x/net v0.0.0-20211015210444-4f30a5c0130f/go.mod h1:9nx3DQGgdP8bBQD5qxJ1jj9UTztislL4KSBs9R2vV5Y=
-golang.org/x/sync v0.0.0-20190423024810-112230192c58/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sync v0.0.0-20210220032951-036812b2e83c/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
-golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
-golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210423082822-04245dca01da/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20210615035016-665e8c7367d1/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.0.0-20211019181941-9d821ace8654 h1:id054HUawV2/6IGm2IV8KZQjqtwAOo2CYlOToYqa0d0=
 golang.org/x/sys v0.0.0-20211019181941-9d821ace8654/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
-golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
-golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
-golang.org/x/text v0.3.7/go.mod h1:u+2+/6zg+i71rQMx5EYifcz6MCKuco9NR6JIITiCfzQ=
-golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=
-golang.org/x/tools v0.0.0-20191119224855-298f0cb1881e/go.mod h1:b+2E5dAYhXwXZwtnZ6UAqBI28+e2cm9otk0dWdXHAEo=
 golang.org/x/tools v0.1.10 h1:QjFRCZxdOhBJ/UNgnBZLbNV13DlbnK0quyivTnXJM20=
 golang.org/x/tools v0.1.10/go.mod h1:Uh6Zz+xoGYZom868N8YTex3t7RhtHDBrE8Gzo9bV56E=
-golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 h1:go1bK/D/BFZV2I8cIQd1NKEZ+0owSTG1fDTci4IqFcE=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=

internal/registry/registry.go

@@ -52,17 +52,23 @@ func (r Registry) SrcPkgName() string {
 
 // LookupInterface returns the underlying interface definition of the
 // given interface name.
-func (r Registry) LookupInterface(name string) (*types.Interface, error) {
+func (r Registry) LookupInterface(name string) (*types.Interface, *types.TypeParamList, error) {
 	obj := r.SrcPkg().Scope().Lookup(name)
 	if obj == nil {
-		return nil, fmt.Errorf("interface not found: %s", name)
+		return nil, nil, fmt.Errorf("interface not found: %s", name)
 	}
 
 	if !types.IsInterface(obj.Type()) {
-		return nil, fmt.Errorf("%s (%s) is not an interface", name, obj.Type())
+		return nil, nil, fmt.Errorf("%s (%s) is not an interface", name, obj.Type())
 	}
 
-	return obj.Type().Underlying().(*types.Interface).Complete(), nil
+	var tparams *types.TypeParamList
+	named, ok := obj.Type().(*types.Named)
+	if ok {
+		tparams = named.TypeParams()
+	}
+
+	return obj.Type().Underlying().(*types.Interface).Complete(), tparams, nil
 }
 
 // MethodScope returns a new MethodScope.

internal/template/template.go

@@ -48,7 +48,22 @@ import (
 {{- if not $.SkipEnsure -}}
 // Ensure, that {{.MockName}} does implement {{$.SrcPkgQualifier}}{{.InterfaceName}}.
 // If this is not the case, regenerate this file with moq.
-var _ {{$.SrcPkgQualifier}}{{.InterfaceName}} = &{{.MockName}}{}
+var _ {{$.SrcPkgQualifier}}{{.InterfaceName -}} 
+	{{- if .TypeParams }}[
+		{{- range $index, $param := .TypeParams}}
+			{{- if $index}}, {{end -}}
+			{{if $param.Constraint}}{{$param.Constraint.String}}{{else}}{{$param.TypeString}}{{end}}
+		{{- end -}}
+		]
+	{{- end }} = &{{.MockName}}
+	 {{- if .TypeParams }}[
+		{{- range $index, $param := .TypeParams}}
+			{{- if $index}}, {{end -}}
+			{{if $param.Constraint}}{{$param.Constraint.String}}{{else}}{{$param.TypeString}}{{end}}
+		{{- end -}}
+		]
+	{{- end -}}
+{}
 {{- end}}
 
 // {{.MockName}} is a mock implementation of {{$.SrcPkgQualifier}}{{.InterfaceName}}.
@@ -68,7 +83,12 @@ var _ {{$.SrcPkgQualifier}}{{.InterfaceName}} = &{{.MockName}}{}
 // 		// and then make assertions.
 //
 // 	}
-type {{.MockName}} struct {
+type {{.MockName}} 
+{{- if .TypeParams -}}
+	[{{- range $index, $param := .TypeParams}}
+			{{- if $index}}, {{end}}{{$param.Name | Exported}} {{$param.TypeString}}
+	{{- end -}}]
+{{- end }} struct {
 {{- range .Methods}}
 	// {{.Name}}Func mocks the {{.Name}} method.
 	{{.Name}}Func func({{.ArgList}}) {{.ReturnArgTypeList}}
@@ -91,7 +111,13 @@ type {{.MockName}} struct {
 }
 {{range .Methods}}
 // {{.Name}} calls {{.Name}}Func.
-func (mock *{{$mock.MockName}}) {{.Name}}({{.ArgList}}) {{.ReturnArgTypeList}} {
+func (mock *{{$mock.MockName}}
+{{- if $mock.TypeParams -}}
+	[{{- range $index, $param := $mock.TypeParams}}
+		{{- if $index}}, {{end}}{{$param.Name | Exported}}
+	{{- end -}}]
+{{- end -}}	
+) {{.Name}}({{.ArgList}}) {{.ReturnArgTypeList}} {
 {{- if not $.StubImpl}}
 	if mock.{{.Name}}Func == nil {
 		panic("{{$mock.MockName}}.{{.Name}}Func: method is nil but {{$mock.InterfaceName}}.{{.Name}} was just called")
@@ -134,7 +160,13 @@ func (mock *{{$mock.MockName}}) {{.Name}}({{.ArgList}}) {{.ReturnArgTypeList}} {
 // {{.Name}}Calls gets all the calls that were made to {{.Name}}.
 // Check the length with:
 //     len(mocked{{$mock.InterfaceName}}.{{.Name}}Calls())
-func (mock *{{$mock.MockName}}) {{.Name}}Calls() []struct {
+func (mock *{{$mock.MockName}}
+{{- if $mock.TypeParams -}}
+	[{{- range $index, $param := $mock.TypeParams}}
+		{{- if $index}}, {{end}}{{$param.Name | Exported}}
+	{{- end -}}]
+{{- end -}}	
+) {{.Name}}Calls() []struct {
 		{{- range .Params}}
 		{{.Name | Exported}} {{.TypeString}}
 		{{- end}}

internal/template/template_data.go

@@ -2,6 +2,7 @@ package template
 
 import (
 	"fmt"
+	"go/types"
 	"strings"
 
 	"github.com/matryer/moq/internal/registry"
@@ -33,6 +34,7 @@ func (d Data) MocksSomeMethod() bool {
 type MockData struct {
 	InterfaceName string
 	MockName      string
+	TypeParams    []TypeParamData
 	Methods       []MethodData
 }
 
@@ -87,6 +89,11 @@ func (m MethodData) ReturnArgNameList() string {
 	return strings.Join(params, ", ")
 }
 
+type TypeParamData struct {
+	ParamData
+	Constraint types.Type
+}
+
 // ParamData is the data which represents a parameter to some method of
 // an interface.
 type ParamData struct {

pkg/moq/moq.go

@@ -3,6 +3,7 @@ package moq
 import (
 	"bytes"
 	"errors"
+	"go/token"
 	"go/types"
 	"io"
 	"strings"
@@ -57,7 +58,7 @@ func (m *Mocker) Mock(w io.Writer, namePairs ...string) error {
 	mocks := make([]template.MockData, len(namePairs))
 	for i, np := range namePairs {
 		name, mockName := parseInterfaceName(np)
-		iface, err := m.registry.LookupInterface(name)
+		iface, tparams, err := m.registry.LookupInterface(name)
 		if err != nil {
 			return err
 		}
@@ -71,6 +72,7 @@ func (m *Mocker) Mock(w io.Writer, namePairs ...string) error {
 			InterfaceName: name,
 			MockName:      mockName,
 			Methods:       methods,
+			TypeParams:    m.typeParams(tparams),
 		}
 	}
 
@@ -110,6 +112,43 @@ func (m *Mocker) Mock(w io.Writer, namePairs ...string) error {
 	return nil
 }
 
+func (m *Mocker) typeParams(tparams *types.TypeParamList) []template.TypeParamData {
+	var tpd []template.TypeParamData
+	if tparams == nil {
+		return tpd
+	}
+
+	tpd = make([]template.TypeParamData, tparams.Len())
+
+	scope := m.registry.MethodScope()
+	for i := 0; i < len(tpd); i++ {
+		tp := tparams.At(i)
+		typeParam := types.NewParam(token.Pos(i), tp.Obj().Pkg(), tp.Obj().Name(), tp.Constraint())
+		tpd[i] = template.TypeParamData{
+			ParamData:  template.ParamData{Var: scope.AddVar(typeParam, "")},
+			Constraint: explicitConstraintType(typeParam),
+		}
+	}
+
+	return tpd
+}
+
+func explicitConstraintType(typeParam *types.Var) (t types.Type) {
+	underlying := typeParam.Type().Underlying().(*types.Interface)
+	// check if any of the embedded types is either a basic type or a union,
+	// because the generic type has to be an alias for one of those types then
+	for j := 0; j < underlying.NumEmbeddeds(); j++ {
+		t := underlying.EmbeddedType(j)
+		switch t := t.(type) {
+		case *types.Basic:
+			return t
+		case *types.Union: // only unions of basic types are allowed, so just take the first one as a valid type constraint
+			return t.Term(0).Type()
+		}
+	}
+	return nil
+}
+
 func (m *Mocker) methodData(f *types.Func) template.MethodData {
 	sig := f.Type().(*types.Signature)
 

pkg/moq/moq_test.go

@@ -383,6 +383,12 @@ func TestMockGolden(t *testing.T) {
 			interfaces: []string{"ShadowTypes"},
 			goldenFile: filepath.Join("testpackages/shadowtypes", "shadowtypes_moq.golden.go"),
 		},
+		{
+			name:       "Generics",
+			cfg:        Config{SrcDir: "testpackages/generics"},
+			interfaces: []string{"GenericStore1", "GenericStore2", "AliasStore"},
+			goldenFile: filepath.Join("testpackages/generics", "generics_moq.golden.go"),
+		},
 	}
 	for _, tc := range cases {
 		t.Run(tc.name, func(t *testing.T) {

pkg/moq/testpackages/generics/generics.go

@@ -0,0 +1,32 @@
+package generics
+
+import (
+	"context"
+	"fmt"
+)
+
+type GenericStore1[T Key1, S any] interface {
+	Get(ctx context.Context, id T) (S, error)
+	Create(ctx context.Context, id T, value S) error
+}
+
+type GenericStore2[T Key2, S any] interface {
+	Get(ctx context.Context, id T) (S, error)
+	Create(ctx context.Context, id T, value S) error
+}
+
+type AliasStore GenericStore1[KeyImpl, bool]
+
+type Key1 interface {
+	fmt.Stringer
+}
+
+type Key2 interface {
+	~[]byte | string
+}
+
+type KeyImpl []byte
+
+func (x KeyImpl) String() string {
+	return string(x)
+}