chore(lint): add ireturn linter

- Return concrete structs
- Accept interfaces
- Define narrow interfaces locally where needed

pkg/publicip/dns/dns.go

@@ -1,18 +1,11 @@
 package dns
 
 import (
-	"context"
 	"net"
 
 	"github.com/miekg/dns"
 )
 
-type Fetcher interface {
-	IP(ctx context.Context) (publicIP net.IP, err error)
-	IP4(ctx context.Context) (publicIP net.IP, err error)
-	IP6(ctx context.Context) (publicIP net.IP, err error)
-}
-
 type fetcher struct {
 	ring    ring
 	client  Client
@@ -26,7 +19,7 @@ type ring struct {
 	providers []Provider
 }
 
-func New(options ...Option) (f Fetcher, err error) {
+func New(options ...Option) (f *fetcher, err error) {
 	settings := newDefaultSettings()
 	for _, option := range options {
 		if err := option(&settings); err != nil {

pkg/publicip/dns/dns_test.go

@@ -11,12 +11,9 @@ import (
 func Test_New(t *testing.T) {
 	t.Parallel()
 
-	intf, err := New(SetTimeout(time.Hour))
+	impl, err := New(SetTimeout(time.Hour))
 	require.NoError(t, err)
 
-	impl, ok := intf.(*fetcher)
-	require.True(t, ok)
-
 	assert.NotNil(t, impl.ring.counter)
 	assert.NotEmpty(t, impl.ring.providers)
 	assert.NotNil(t, impl.client)

pkg/publicip/http/http.go

@@ -1,20 +1,12 @@
 package http
 
 import (
-	"context"
-	"net"
 	"net/http"
 	"time"
 
 	"github.com/qdm12/ddns-updater/pkg/publicip/ipversion"
 )
 
-type Fetcher interface {
-	IP(ctx context.Context) (publicIP net.IP, err error)
-	IP4(ctx context.Context) (publicIP net.IP, err error)
-	IP6(ctx context.Context) (publicIP net.IP, err error)
-}
-
 type fetcher struct {
 	client  *http.Client
 	timeout time.Duration
@@ -28,7 +20,7 @@ type urlsRing struct {
 	urls    []string
 }
 
-func New(client *http.Client, options ...Option) (f Fetcher, err error) {
+func New(client *http.Client, options ...Option) (f *fetcher, err error) {
 	settings := newDefaultSettings()
 	for _, option := range options {
 		if err := option(&settings); err != nil {

pkg/publicip/http/http_test.go

@@ -75,18 +75,16 @@ func Test_New(t *testing.T) {
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 
-			f, err := New(client, testCase.options...)
+			fetcher, err := New(client, testCase.options...)
 
 			if testCase.err != nil {
 				require.Error(t, err)
 				assert.Equal(t, testCase.err.Error(), err.Error())
-				assert.Nil(t, f)
+				assert.Nil(t, fetcher)
 				return
 			}
 			assert.NoError(t, err)
-			implementation, ok := f.(*fetcher)
-			require.True(t, ok)
-			assert.Equal(t, testCase.fetcher, implementation)
+			assert.Equal(t, testCase.fetcher, fetcher)
 		})
 	}
 }

pkg/publicip/publicip.go

@@ -9,7 +9,7 @@ import (
 	"github.com/qdm12/ddns-updater/pkg/publicip/http"
 )
 
-type Fetcher interface {
+type ipFetcher interface {
 	IP(ctx context.Context) (ip net.IP, err error)
 	IP4(ctx context.Context) (ipv4 net.IP, err error)
 	IP6(ctx context.Context) (ipv6 net.IP, err error)
@@ -17,14 +17,14 @@ type Fetcher interface {
 
 type fetcher struct {
 	settings settings
-	fetchers []Fetcher
+	fetchers []ipFetcher
 	// Cycling effect if both are enabled
 	counter *uint32 // 32 bit for 32 bit systems
 }
 
 var ErrNoFetchTypeSpecified = errors.New("at least one fetcher type must be specified")
 
-func NewFetcher(dnsSettings DNSSettings, httpSettings HTTPSettings) (f Fetcher, err error) {
+func NewFetcher(dnsSettings DNSSettings, httpSettings HTTPSettings) (f *fetcher, err error) {
 	settings := settings{
 		dns:  dnsSettings,
 		http: httpSettings,

pkg/publicip/subfetcher.go

@@ -4,7 +4,7 @@ import (
 	"sync/atomic"
 )
 
-func (f *fetcher) getSubFetcher() Fetcher {
+func (f *fetcher) getSubFetcher() ipFetcher { //nolint:ireturn
 	fetcher := f.fetchers[0]
 	if len(f.fetchers) > 1 { // cycling effect
 		index := int(atomic.AddUint32(f.counter, 1)) % len(f.fetchers)