Add unexported analyzer

Author: uudashr

.golangci.yml

@@ -10,7 +10,6 @@ linters:
     - copyloopvar
     - decorder
     - dogsled
-    - dupl
     - dupword
     - durationcheck
     - err113

README.md

@@ -8,6 +8,7 @@ It consists of several analyzers:
 1. `unused`: Identifies interfaces that are not used anywhere in the same package where the interface is defined.
 2. `identical`: Identifies interfaces in the same package with identical methods or constraints.
 3. `opaque`: Identifies functions that return interfaces, but the actual returned value is always a single concrete implementation.
+4. `unexported`: Identifies interfaces that are not exported but are used in exported functions or methods.
 
 ## Usage
 
@@ -21,6 +22,7 @@ To install individual linter, use the following command:
 go install github.com/uudashr/iface/unused/cmd/unusediface@latest
 go install github.com/uudashr/iface/identical/cmd/identicaliface@latest
 go install github.com/uudashr/iface/opaque/cmd/opaqueiface@latest
+go install github.com/uudashr/iface/unexported/cmd/unexportediface@latest
 ```
 
 Run the linter

cmd/ifacecheck/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"github.com/uudashr/iface/identical"
 	"github.com/uudashr/iface/opaque"
+	"github.com/uudashr/iface/unexported"
 	"github.com/uudashr/iface/unused"
 	"golang.org/x/tools/go/analysis/multichecker"
 )
@@ -12,5 +13,6 @@ func main() {
 		unused.Analyzer,
 		identical.Analyzer,
 		opaque.Analyzer,
+		unexported.Analyzer,
 	)
 }

unexported/cmd/unexportediface/main.go

@@ -0,0 +1,10 @@
+package main
+
+import (
+	"github.com/uudashr/iface/unexported"
+	"golang.org/x/tools/go/analysis/singlechecker"
+)
+
+func main() {
+	singlechecker.Main(unexported.Analyzer)
+}

unexported/doc.go

@@ -0,0 +1,3 @@
+// Package unexported defines an Analyzer that identifies interfaces that are
+// not exported but are used in exported functions or methods.
+package unexported

unexported/testdata/src/a/a.go

@@ -0,0 +1,103 @@
+package a
+
+import (
+	"io"
+)
+
+// unexportedReader is an unexported interface.
+type unexportedReader interface {
+	Read([]byte) (int, error)
+}
+
+// ExportedWriter is an exported interface.
+type ExportedWriter interface {
+	Write([]byte) (int, error)
+}
+
+// 1. Function with unexported arg type interface
+func ReadAll(r unexportedReader) ([]byte, error) { // want "unexported interface 'unexportedReader' used as parameter in exported function 'ReadAll'"
+	buf := make([]byte, 1024)
+	_, err := r.Read(buf)
+	return buf, err
+}
+
+// 2. Function with exported arg type interface
+func WriteHello(w ExportedWriter) error {
+	_, err := w.Write([]byte("hello"))
+	return err
+}
+
+// 3. Function with unexported return type interface
+func NewUnexportedReader() unexportedReader { // want "unexported interface 'unexportedReader' used as return value in exported function 'NewUnexportedReader'"
+	return nil // stub
+}
+
+// 4. Function with exported return type interface
+func NewWriter() ExportedWriter {
+	return nil // stub
+}
+
+// 5. Function with both unexported arg and return type interface
+func WrapReader(r unexportedReader) unexportedReader { // want "unexported interface 'unexportedReader' used as parameter in exported function 'WrapReader'" "unexported interface 'unexportedReader' used as return value in exported function 'WrapReader'"
+	return r
+}
+
+// 6. Function with both exported arg and return type interface
+func WrapWriter(w ExportedWriter) ExportedWriter {
+	return w
+}
+
+// 7. Function with unexported arg type interface and exported return type interface
+func PromoteReader(r unexportedReader) ExportedWriter { // want "unexported interface 'unexportedReader' used as parameter in exported function 'PromoteReader'"
+	return nil // stub
+}
+
+// 8. Function with exported arg type interface and unexported return type interface
+func DemoteWriter(w ExportedWriter) unexportedReader { // want "unexported interface 'unexportedReader' used as return value in exported function 'DemoteWriter'"
+	return nil // stub
+}
+
+// 9. Function with external arg type interface (io.Writer)
+func WriteToExternal(w io.Writer) error {
+	_, err := w.Write([]byte("external"))
+	return err
+}
+
+// 10. Function with external return type interface (io.Writer)
+func NewExternalWriter() io.Writer {
+	return nil // stub
+}
+
+// 11. Function with both external arg and return type interface (io.Writer)
+func WrapExternalWriter(w io.Writer) io.Writer {
+	return w
+}
+
+// 12. Function with any arg type
+func Print(a any) {
+}
+
+// 13. Function witn interface{} arg type
+func Write(i interface{}) {
+}
+
+// 14. Function with error arg type
+func Capture(err error) {}
+
+// 15. Function with no arg and no return type interface
+func Ping() {}
+
+// 16. Function with primitive arg type
+func AddOne(x int) int {
+	return x + 1
+}
+
+// 17. Function with primitive return type
+func GetZero() int {
+	return 0
+}
+
+// 18. Function with both primitive arg and return type
+func Double(x int) int {
+	return x * 2
+}

unexported/testdata/src/b/b.go

@@ -0,0 +1,104 @@
+package b
+
+import "io"
+
+// unexportedReader is an unexported interface.
+type unexportedReader interface {
+	Read([]byte) (int, error)
+}
+
+// ExportedWriter is an exported interface.
+type ExportedWriter interface {
+	Write([]byte) (int, error)
+}
+
+// ExportedType is an exported struct type.
+type ExportedType struct{}
+
+// 1. Method with unexported arg type interface
+func (e *ExportedType) ReadAll(r unexportedReader) ([]byte, error) { // want "unexported interface 'unexportedReader' used as parameter in exported method 'ExportedType.ReadAll'"
+	buf := make([]byte, 1024)
+	_, err := r.Read(buf)
+	return buf, err
+}
+
+// 2. Method with exported arg type interface
+func (e *ExportedType) WriteHello(w ExportedWriter) error {
+	_, err := w.Write([]byte("hello"))
+	return err
+}
+
+// 3. Method with unexported return type interface
+func (e *ExportedType) NewUnexportedReader() unexportedReader { // want "unexported interface 'unexportedReader' used as return value in exported method 'ExportedType.NewUnexportedReader'"
+	return nil // stub
+}
+
+// 4. Method with exported return type interface
+func (e *ExportedType) NewWriter() ExportedWriter {
+	return nil // stub
+}
+
+// 5. Method with both unexported arg and return type interface
+func (e *ExportedType) WrapReader(r unexportedReader) unexportedReader { // want "unexported interface 'unexportedReader' used as parameter in exported method 'ExportedType.WrapReader'" "unexported interface 'unexportedReader' used as return value in exported method 'ExportedType.WrapReader'"
+	return r
+}
+
+// 6. Method with both exported arg and return type interface
+func (e *ExportedType) WrapWriter(w ExportedWriter) ExportedWriter {
+	return w
+}
+
+// 7. Method with unexported arg type interface and exported return type interface
+func (e *ExportedType) PromoteReader(r unexportedReader) ExportedWriter { // want "unexported interface 'unexportedReader' used as parameter in exported method 'ExportedType.PromoteReader'"
+	return nil // stub
+}
+
+// 8. Method with exported arg type interface and unexported return type interface
+func (e *ExportedType) DemoteWriter(w ExportedWriter) unexportedReader { // want "unexported interface 'unexportedReader' used as return value in exported method 'ExportedType.DemoteWriter'"
+	return nil // stub
+}
+
+// 9. Method with external arg type interface (io.Writer)
+func (e *ExportedType) WriteToExternal(w io.Writer) error {
+	_, err := w.Write([]byte("external"))
+	return err
+}
+
+// 10. Method with external return type interface (io.Writer)
+func (e *ExportedType) NewExternalWriter() io.Writer {
+	return nil // stub
+}
+
+// 11. Method with both external arg and return type interface (io.Writer)
+func (e *ExportedType) WrapExternalWriter(w io.Writer) io.Writer {
+	return w
+}
+
+// 13. Method with any arg type
+func (e *ExportedType) Print(a any) {
+}
+
+// 14. Method with interface{} arg type
+func (e *ExportedType) Write(i interface{}) {
+}
+
+// 15. Method with error arg type
+func (e *ExportedType) Capture(err error) {}
+
+// 16. Method with no arg and no return type interface
+func (e *ExportedType) Ping() {}
+
+// 17. Method with primitive arg type
+func (e *ExportedType) AddOne(x int) int {
+	return x + 1
+}
+
+// 18. Method with primitive return type
+func (e *ExportedType) GetZero() int {
+	return 0
+}
+
+// 19. Method with both primitive arg and return type
+func (e *ExportedType) Double(x int) int {
+	return x * 2
+}