From 3c953af882ba45faa8fd6ece30f17015c8060218 Mon Sep 17 00:00:00 2001
From: Dmitry <dmitry.eremenko@ferretdb.io>
Date: Fri, 3 Mar 2023 15:20:50 +0000
Subject: [PATCH] Fix `$mul` operator handling dot notation (#2094)

Closes #1744.
---
 integration/shareddata/composites.go    |  5 +++++
 integration/update_field_compat_test.go | 16 +++++++---------
 internal/handlers/common/update.go      | 16 +++++++++++++++-
 internal/types/path.go                  |  9 ++++-----
 4 files changed, 31 insertions(+), 15 deletions(-)

diff --git a/integration/shareddata/composites.go b/integration/shareddata/composites.go
index 367821a7f4fd..e9ce98f82d49 100644
--- a/integration/shareddata/composites.go
+++ b/integration/shareddata/composites.go
@@ -40,6 +40,11 @@ var Composites = &Values[string]{
 			{"42", "foo"},
 			{"foo", int32(42)},
 		},
+		"document-composite-numerical-field-name": bson.D{
+			{"foo", int32(42)},
+			{"42", "foo"},
+			{"array", bson.D{{"42", int32(42)}}},
+		},
 		"document-null":  bson.D{{"foo", nil}},
 		"document-empty": bson.D{},
 
diff --git a/integration/update_field_compat_test.go b/integration/update_field_compat_test.go
index 2bd224136bad..5b8fab67ad79 100644
--- a/integration/update_field_compat_test.go
+++ b/integration/update_field_compat_test.go
@@ -1202,17 +1202,15 @@ func TestUpdateFieldCompatMul(t *testing.T) {
 		"DotNotationMissingField": {
 			update:     bson.D{{"$mul", bson.D{{"v..", int32(45)}}}},
 			resultType: emptyResult,
-			skip:       "https://github.com/FerretDB/FerretDB/issues/1744",
-		},
-		"DotNotationNegativeIndex": {
-			update:     bson.D{{"$mul", bson.D{{"v.-1.bar", int32(45)}}}},
-			resultType: emptyResult,
-			skip:       "https://github.com/FerretDB/FerretDB/issues/2050",
 		},
 		"DotNotationIndexExceedsArrayLength": {
-			update:     bson.D{{"$mul", bson.D{{"v.100.bar", int32(45)}}}},
-			resultType: emptyResult,
-			skip:       "https://github.com/FerretDB/FerretDB/issues/1744",
+			update: bson.D{{"$mul", bson.D{{"v.100.bar", int32(45)}}}},
+		},
+		"DotNotationFieldNumericName": {
+			update: bson.D{{"$mul", bson.D{{"v.array.42", int32(42)}}}},
+		},
+		"DotNotationNegativeIndex": {
+			update: bson.D{{"$mul", bson.D{{"v.array.-1", int32(42)}}}},
 		},
 	}
 
diff --git a/internal/handlers/common/update.go b/internal/handlers/common/update.go
index fd52a6cb4d56..54dbf0b84def 100644
--- a/internal/handlers/common/update.go
+++ b/internal/handlers/common/update.go
@@ -583,7 +583,21 @@ func processMulFieldExpression(doc *types.Document, updateV any) (bool, error) {
 
 		path, err = types.NewPathFromString(mulKey)
 		if err != nil {
-			return false, lazyerrors.Error(err)
+			var pathErr *types.DocumentPathError
+
+			if errors.As(err, &pathErr) {
+				switch pathErr.Code() {
+				case types.ErrDocumentPathEmptyKey:
+					return false, commonerrors.NewWriteErrorMsg(
+						commonerrors.ErrEmptyName,
+						fmt.Sprintf("Cannot apply $mul to a value of non-numeric type. "+
+							"{_id: %s} has the field '%s' of non-numeric type object",
+							must.NotFail(doc.Get("_id")),
+							mulKey,
+						),
+					)
+				}
+			}
 		}
 
 		if !doc.HasByPath(path) {
diff --git a/internal/types/path.go b/internal/types/path.go
index 0c68359306e8..5baf7a15eebb 100644
--- a/internal/types/path.go
+++ b/internal/types/path.go
@@ -15,6 +15,7 @@
 package types
 
 import (
+	"errors"
 	"fmt"
 	"math"
 	"strconv"
@@ -23,7 +24,6 @@ import (
 
 	"golang.org/x/exp/slices"
 
-	"github.com/FerretDB/FerretDB/internal/util/lazyerrors"
 	"github.com/FerretDB/FerretDB/internal/util/must"
 )
 
@@ -41,6 +41,8 @@ const (
 	ErrDocumentPathIndexOutOfBound
 	// ErrDocumentPathCannotCreateField indicates that it's impossible to create a specific field.
 	ErrDocumentPathCannotCreateField
+	// ErrDocumentPathEmptyKey indicates that provided path contains empty key.
+	ErrDocumentPathEmptyKey
 )
 
 // DocumentPathError describes an error that could occur on document path related operations.
@@ -84,13 +86,10 @@ func NewPathFromString(s string) (Path, error) {
 	var res Path
 
 	path := strings.Split(s, ".")
-	if len(path) == 0 {
-		return res, lazyerrors.New("empty path")
-	}
 
 	for _, s := range path {
 		if s == "" {
-			return res, lazyerrors.New("path element must not be empty")
+			return res, newDocumentPathError(ErrDocumentPathEmptyKey, errors.New("path element must not be empty"))
 		}
 	}