Fix dropped notification errors and switch to errors.Join

notify/email.go accumulated multi-recipient errors with
multierror.Append(fmt.Errorf(...)) instead of
multierror.Append(result, ...), so the accumulator was overwritten each
iteration and only the last failing recipient's error survived; earlier
failures were silently dropped. The telegram notifier did it correctly.

Replace hashicorp/go-multierror with the stdlib errors.Join everywhere
it was used (notify/email.go, notify/telegram.go, rest/api/rest_private.go,
store/service/service.go, store/image/image.go and store/engine/bolt.go),
which fixes the bug and drops the direct dependency. It stays indirect
because go-pkgz/lcw/v2 still imports it. A regression test in
email_test.go now sends two failing recipients and asserts both errors
are reported.

backend/_example/memory_store/go.mod

@@ -21,8 +21,6 @@ require (
 	github.com/go-pkgz/rest v1.22.0 // indirect
 	github.com/go-pkgz/routegroup v1.6.0 // indirect
 	github.com/gorilla/css v1.0.1 // indirect
-	github.com/hashicorp/errwrap v1.1.0 // indirect
-	github.com/hashicorp/go-multierror v1.1.1 // indirect
 	github.com/kr/text v0.2.0 // indirect
 	github.com/microcosm-cc/bluemonday v1.0.27 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect

backend/_example/memory_store/go.sum

@@ -27,11 +27,6 @@ github.com/go-pkgz/routegroup v1.6.0 h1:44XHZgF6JIIldRlv+zjg6SygULASmjifnfIQjwCT
 github.com/go-pkgz/routegroup v1.6.0/go.mod h1:Pmu04fhgWhRtBMIJ8HXppnnzOPjnL/IEPBIdO2zmeqg=
 github.com/gorilla/css v1.0.1 h1:ntNaBIghp6JmvWnxbZKANoLyuXTPZ4cAMlo6RyhlbO8=
 github.com/gorilla/css v1.0.1/go.mod h1:BvnYkspnSzMmwRK+b8/xgNPLiIuNZr6vbZBTPQ2A3b0=
-github.com/hashicorp/errwrap v1.0.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
-github.com/hashicorp/errwrap v1.1.0 h1:OxrOeh75EUXMY8TBjag2fzXGZ40LB6IKw45YeGUDY2I=
-github.com/hashicorp/errwrap v1.1.0/go.mod h1:YH+1FKiLXxHSkmPseP+kNlulaMuP3n2brvKWEqk/Jc4=
-github.com/hashicorp/go-multierror v1.1.1 h1:H5DkEtf6CXdFp0N0Em5UCwQpXMWke8IA0+lD48awMYo=
-github.com/hashicorp/go-multierror v1.1.1/go.mod h1:iw975J/qwKPdAO1clOe2L8331t/9/fmwbPZ6JB6eMoM=
 github.com/hexops/gotextdiff v1.0.3 h1:gitA9+qJrrTCsiCl7+kh75nPqQt1cx4ZkudSTLoUqJM=
 github.com/hexops/gotextdiff v1.0.3/go.mod h1:pSWU5MAI3yDq+fZBTazCSJysOMbxWL1BSow5/V2vxeg=
 github.com/jessevdk/go-flags v1.6.1 h1:Cvu5U8UGrLay1rZfv/zP7iLpSHGUZ/Ou68T0iX1bBK4=

backend/app/notify/email.go

@@ -3,6 +3,7 @@ package notify
 import (
 	"bytes"
 	"context"
+	"errors"
 	"fmt"
 	"html/template"
 	"net/url"
@@ -11,7 +12,6 @@ import (
 	log "github.com/go-pkgz/lgr"
 	ntf "github.com/go-pkgz/notify"
 	"github.com/go-pkgz/repeater/v2"
-	"github.com/hashicorp/go-multierror"
 	"github.com/microcosm-cc/bluemonday"
 
 	"github.com/umputun/remark42/backend/app/templates"
@@ -160,23 +160,23 @@ func (e *Email) Send(ctx context.Context, req Request) error {
 	default:
 	}
 
-	result := new(multierror.Error)
+	var errs []error
 
 	for _, email := range req.Emails {
 		err := e.buildAndSendMessage(ctx, req, email, false)
 		if err != nil {
-			result = multierror.Append(fmt.Errorf("problem sending user email notification to %q: %w", email, err))
+			errs = append(errs, fmt.Errorf("problem sending user email notification to %q: %w", email, err))
 		}
 	}
 
 	for _, email := range e.AdminEmails {
 		err := e.buildAndSendMessage(ctx, req, email, true)
 		if err != nil {
-			result = multierror.Append(fmt.Errorf("problem sending admin email notification to %q: %w", email, err))
+			errs = append(errs, fmt.Errorf("problem sending admin email notification to %q: %w", email, err))
 		}
 	}
 
-	return result.ErrorOrNil()
+	return errors.Join(errs...)
 }
 
 func (e *Email) buildAndSendMessage(ctx context.Context, req Request, email string, forAdmin bool) error {

backend/app/notify/email_test.go

@@ -110,10 +110,10 @@ func TestEmailSendErrors(t *testing.T) {
 	e.msgTmpl, err = template.New("test").Parse("{{.Test}}")
 	assert.NoError(t, err)
 	assert.EqualError(t, e.Send(context.Background(), Request{Comment: store.Comment{ID: "999"}, parent: store.Comment{User: store.User{ID: "test"}}, Emails: []string{"bad@example.org"}}),
-		"1 error occurred:\n\t* problem sending user email notification to \"bad@example.org\": "+
+		"problem sending user email notification to \"bad@example.org\": "+
 			"error executing template to build comment reply message: "+
 			"template: test:1:2: executing \"test\" at <.Test>: "+
-			"can't evaluate field Test in type notify.msgTmplData\n\n")
+			"can't evaluate field Test in type notify.msgTmplData")
 
 	ctx, cancel := context.WithCancel(context.Background())
 	cancel()
@@ -121,8 +121,14 @@ func TestEmailSendErrors(t *testing.T) {
 		"sending email messages about comment \"999\" aborted due to canceled context")
 
 	assert.EqualError(t, e.Send(context.Background(), Request{Comment: store.Comment{ID: "999"}, parent: store.Comment{User: store.User{ID: "error"}}, Emails: []string{"bad@example.org"}}),
-		"1 error occurred:\n\t* problem sending user email notification to \"bad@example.org\":"+
-			" error creating token for unsubscribe link: token generation error\n\n")
+		"problem sending user email notification to \"bad@example.org\":"+
+			" error creating token for unsubscribe link: token generation error")
+
+	// errors for all failed recipients are reported, not just the last one
+	assert.EqualError(t, e.Send(context.Background(),
+		Request{Comment: store.Comment{ID: "999"}, parent: store.Comment{User: store.User{ID: "error"}}, Emails: []string{"bad1@example.org", "bad2@example.org"}}),
+		"problem sending user email notification to \"bad1@example.org\": error creating token for unsubscribe link: token generation error\n"+
+			"problem sending user email notification to \"bad2@example.org\": error creating token for unsubscribe link: token generation error")
 }
 
 func TestEmailSend_ExitConditions(t *testing.T) {

backend/app/notify/telegram.go

@@ -2,12 +2,12 @@ package notify
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"time"
 
 	log "github.com/go-pkgz/lgr"
 	ntf "github.com/go-pkgz/notify"
-	"github.com/hashicorp/go-multierror"
 )
 
 const commentTextLengthLimit = 100
@@ -47,14 +47,14 @@ func NewTelegram(params TelegramParams) (*Telegram, error) {
 // Send to telegram recipients
 func (t *Telegram) Send(ctx context.Context, req Request) error {
 	log.Printf("[DEBUG] send telegram notification for comment ID %s", req.Comment.ID)
-	result := new(multierror.Error)
+	var errs []error
 
 	msg := t.buildMessage(req)
 
 	if t.AdminChannelID != "" {
 		err := t.Telegram.Send(ctx, fmt.Sprintf("telegram:%s?parseMode=HTML", t.AdminChannelID), msg)
 		if err != nil {
-			result = multierror.Append(result,
+			errs = append(errs,
 				fmt.Errorf("problem sending admin telegram notification about comment ID %s to %s: %w",
 					req.Comment.ID, t.AdminChannelID, err,
 				),
@@ -66,7 +66,7 @@ func (t *Telegram) Send(ctx context.Context, req Request) error {
 		for _, user := range req.Telegrams {
 			err := t.Telegram.Send(ctx, fmt.Sprintf("telegram:%s?parseMode=HTML", user), msg)
 			if err != nil {
-				result = multierror.Append(result,
+				errs = append(errs,
 					fmt.Errorf("problem sending user telegram notification about comment ID %s to %q: %w",
 						req.Comment.ID, user, err,
 					),
@@ -74,7 +74,7 @@ func (t *Telegram) Send(ctx context.Context, req Request) error {
 			}
 		}
 	}
-	return result.ErrorOrNil()
+	return errors.Join(errs...)
 }
 
 // buildMessage generates message for generic notification about new comment

backend/app/notify/telegram_test.go

@@ -30,7 +30,6 @@ func TestTelegram_Send(t *testing.T) {
 
 	err := tb.Send(context.Background(), Request{Comment: c, parent: cp, Telegrams: []string{"test_user_channel"}})
 	assert.Error(t, err)
-	assert.Contains(t, err.Error(), "2 errors occurred")
 	assert.Contains(t, err.Error(), "problem sending user telegram notification about comment ID 999 to \"test_user_channel\"")
 	assert.Contains(t, err.Error(), "problem sending admin telegram notification about comment ID 999 to remark_test")
 

backend/app/rest/api/rest_private.go

@@ -21,7 +21,6 @@ import (
 	log "github.com/go-pkgz/lgr"
 	R "github.com/go-pkgz/rest"
 	"github.com/golang-jwt/jwt/v5"
-	"github.com/hashicorp/go-multierror"
 
 	"github.com/umputun/remark42/backend/app/notify"
 	"github.com/umputun/remark42/backend/app/rest"
@@ -663,10 +662,8 @@ func (s *private) userAllDataCtrl(w http.ResponseWriter, r *http.Request) {
 		return e
 	}
 
-	var merr error
-	merr = multierror.Append(merr, write([]byte(`{"info": `)))     // send user prefix
-	merr = multierror.Append(merr, write(userB))                   // send user info
-	merr = multierror.Append(merr, write([]byte(`, "comments":`))) // send comments prefix
+	// send user prefix, user info and comments prefix
+	errs := []error{write([]byte(`{"info": `)), write(userB), write([]byte(`, "comments":`))}
 
 	// get comments in 100 in each paginated request
 	for i := range 100 {
@@ -681,15 +678,15 @@ func (s *private) userAllDataCtrl(w http.ResponseWriter, r *http.Request) {
 			return
 		}
 
-		merr = multierror.Append(merr, write(b))
+		errs = append(errs, write(b))
 		if len(comments) != 100 {
 			break
 		}
 	}
 
-	merr = multierror.Append(merr, write([]byte(`}`)))
-	if merr.(*multierror.Error).ErrorOrNil() != nil {
-		rest.SendErrorJSON(w, r, http.StatusInternalServerError, merr, "can't write user info", rest.ErrInternal)
+	errs = append(errs, write([]byte(`}`)))
+	if err := errors.Join(errs...); err != nil {
+		rest.SendErrorJSON(w, r, http.StatusInternalServerError, err, "can't write user info", rest.ErrInternal)
 		return
 	}
 }

backend/app/store/engine/bolt.go

@@ -9,7 +9,6 @@ import (
 	"time"
 
 	log "github.com/go-pkgz/lgr"
-	"github.com/hashicorp/go-multierror"
 	bolt "go.etcd.io/bbolt"
 	berrors "go.etcd.io/bbolt/errors"
 
@@ -415,14 +414,14 @@ func (b *BoltDB) Delete(req DeleteRequest) error {
 
 // Close boltdb store
 func (b *BoltDB) Close() error {
-	errs := new(multierror.Error)
+	var errs []error
 	for site, db := range b.dbs {
 		err := db.Close()
 		if err != nil {
-			errs = multierror.Append(errs, fmt.Errorf("can't close site %s: %w", site, err))
+			errs = append(errs, fmt.Errorf("can't close site %s: %w", site, err))
 		}
 	}
-	return errs.ErrorOrNil()
+	return errors.Join(errs...)
 }
 
 // Last returns up to max last comments for given siteID

backend/app/store/image/fs_store.go

@@ -147,8 +147,8 @@ func (f *FileSystem) Cleanup(_ context.Context, ttl time.Duration) error {
 		age := time.Since(info.ModTime())
 		if age > (ttl + 100*time.Millisecond) { // delay cleanup triggering to allow commit
 			log.Printf("[INFO] remove staging image %s, age %v", fpath, age)
-			rmErr := os.Remove(fpath)             //nolint:gosec // staging dir is server-only, no untrusted symlinks land here
-			_ = os.Remove(path.Dir(fpath))        //nolint:gosec // same staging dir
+			rmErr := os.Remove(fpath)      //nolint:gosec // staging dir is server-only, no untrusted symlinks land here
+			_ = os.Remove(path.Dir(fpath)) //nolint:gosec // same staging dir
 			return rmErr
 		}
 		return nil

backend/app/store/image/image.go

@@ -11,6 +11,7 @@ import (
 	"context"
 	"crypto/sha1" //nolint:gosec // not used for cryptography
 	"encoding/base64"
+	"errors"
 	"fmt"
 	"image"
 	_ "image/gif"  // register gif decoder
@@ -27,7 +28,6 @@ import (
 
 	"github.com/PuerkitoBio/goquery"
 	log "github.com/go-pkgz/lgr"
-	"github.com/hashicorp/go-multierror"
 	"github.com/rs/xid"
 	"golang.org/x/image/draw"
 	_ "golang.org/x/image/webp" // register webp decoder so DecodeConfig accepts what readAndValidateImage allows
@@ -91,14 +91,14 @@ func NewService(s Store, p ServiceParams) *Service {
 
 // Commit multiple ids immediately
 func (s *Service) Commit(idsFn func() []string) error {
-	errs := new(multierror.Error)
+	var errs []error
 	for _, id := range idsFn() {
 		err := s.store.Commit(id)
 		if err != nil {
-			errs = multierror.Append(errs, fmt.Errorf("failed to commit image %s: %w", id, err))
+			errs = append(errs, fmt.Errorf("failed to commit image %s: %w", id, err))
 		}
 	}
-	return errs.ErrorOrNil()
+	return errors.Join(errs...)
 }
 
 // Submit multiple ids via function for delayed commit

backend/app/store/service/service.go

@@ -3,6 +3,7 @@
 package service
 
 import (
+	"errors"
 	"fmt"
 	"math"
 	"slices"
@@ -14,7 +15,6 @@ import (
 	"github.com/go-pkgz/lcw/v2"
 	log "github.com/go-pkgz/lgr"
 	"github.com/google/uuid"
-	"github.com/hashicorp/go-multierror"
 	bf "github.com/russross/blackfriday/v2"
 
 	"github.com/umputun/remark42/backend/app/store"
@@ -249,18 +249,18 @@ func (s *DataStore) ResubmitStagingImages(sites []string) error {
 	if ts.IsZero() {
 		return nil
 	}
-	result := new(multierror.Error)
+	var errs []error
 	for _, site := range sites {
 		locator := store.Locator{SiteID: site}
 		comments, err := s.FindSince(locator, "time", store.User{}, ts)
 		if err != nil {
-			result = multierror.Append(result, fmt.Errorf("problem finding comments for site %s: %w", site, err))
+			errs = append(errs, fmt.Errorf("problem finding comments for site %s: %w", site, err))
 		}
 		for _, c := range comments {
 			s.submitImages(c)
 		}
 	}
-	return result.ErrorOrNil()
+	return errors.Join(errs...)
 }
 
 // submitImages initiated delayed commit of all images from the comment uploaded to remark42
@@ -915,32 +915,32 @@ func (s *DataStore) Metas(siteID string) (umetas []UserMetaData, pmetas []PostMe
 
 // SetMetas saves metadata for users and posts
 func (s *DataStore) SetMetas(siteID string, umetas []UserMetaData, pmetas []PostMetaData) (err error) {
-	errs := new(multierror.Error)
+	var errs []error
 
 	// save posts metas
 	for _, pm := range pmetas {
 		if pm.ReadOnly {
-			errs = multierror.Append(errs, s.SetReadOnly(store.Locator{SiteID: siteID, URL: pm.URL}, true))
+			errs = append(errs, s.SetReadOnly(store.Locator{SiteID: siteID, URL: pm.URL}, true))
 		}
 	}
 
 	// save users metas
 	for _, um := range umetas {
 		if um.Blocked.Status {
-			errs = multierror.Append(errs, s.SetBlock(siteID, um.ID, true, time.Until(um.Blocked.Until)))
+			errs = append(errs, s.SetBlock(siteID, um.ID, true, time.Until(um.Blocked.Until)))
 		}
 		if um.Verified {
-			errs = multierror.Append(errs, s.SetVerified(siteID, um.ID, true))
+			errs = append(errs, s.SetVerified(siteID, um.ID, true))
 		}
 		// this code doesn't delete user details in case they are not set in import but present in DB already
 		if um.Details.Email != "" {
 			req := engine.UserDetailRequest{Locator: store.Locator{SiteID: siteID}, UserID: um.ID, Detail: engine.UserEmail, Update: um.Details.Email}
 			_, err := s.Engine.UserDetail(req)
-			errs = multierror.Append(errs, err)
+			errs = append(errs, err)
 		}
 	}
 
-	return errs.ErrorOrNil()
+	return errors.Join(errs...)
 }
 
 // User gets comment for given userID on siteID
@@ -972,15 +972,15 @@ func (s *DataStore) Last(siteID string, limit int, since time.Time, user store.U
 
 // Close store service
 func (s *DataStore) Close() error {
-	errs := new(multierror.Error)
+	var errs []error
 	if s.repliesCache.LoadingCache != nil {
-		errs = multierror.Append(errs, s.repliesCache.Close())
+		errs = append(errs, s.repliesCache.Close())
 	}
 	if s.TitleExtractor != nil {
-		errs = multierror.Append(errs, s.TitleExtractor.Close())
+		errs = append(errs, s.TitleExtractor.Close())
 	}
-	errs = multierror.Append(errs, s.Engine.Close())
-	return errs.ErrorOrNil()
+	errs = append(errs, s.Engine.Close())
+	return errors.Join(errs...)
 }
 
 func (s *DataStore) upsAndDowns(c store.Comment) (ups, downs int) {

backend/go.mod

@@ -19,7 +19,6 @@ require (
 	github.com/golang-jwt/jwt/v5 v5.3.1
 	github.com/google/uuid v1.6.0
 	github.com/gorilla/feeds v1.2.0
-	github.com/hashicorp/go-multierror v1.1.1
 	github.com/jessevdk/go-flags v1.6.1
 	github.com/kyokomi/emoji/v2 v2.2.13
 	github.com/microcosm-cc/bluemonday v1.0.27
@@ -51,6 +50,7 @@ require (
 	github.com/gorilla/css v1.0.1 // indirect
 	github.com/gorilla/websocket v1.5.3 // indirect
 	github.com/hashicorp/errwrap v1.1.0 // indirect
+	github.com/hashicorp/go-multierror v1.1.1 // indirect
 	github.com/hashicorp/golang-lru/v2 v2.0.7 // indirect
 	github.com/klauspost/compress v1.18.7 // indirect
 	github.com/montanaflynn/stats v0.9.0 // indirect