fix validation error position for container type (#716)

Author: goccy

decode.go

@@ -1453,7 +1453,10 @@ func (d *Decoder) decodeStruct(ctx context.Context, dst reflect.Value, src ast.N
 					node, exists := keyToNodeMap[structField.RenderName]
 					if exists {
 						// TODO: to make FieldError message cutomizable
-						return errors.ErrSyntax(fmt.Sprintf("%s", err), node.GetToken())
+						return errors.ErrSyntax(
+							fmt.Sprintf("%s", err),
+							d.getParentMapTokenIfExistsForValidationError(node.Type(), node.GetToken()),
+						)
 					} else if t := src.GetToken(); t != nil && t.Prev != nil && t.Prev.Prev != nil {
 						// A missing required field will not be in the keyToNodeMap
 						// the error needs to be associated with the parent of the source node
@@ -1467,6 +1470,37 @@ func (d *Decoder) decodeStruct(ctx context.Context, dst reflect.Value, src ast.N
 	return nil
 }
 
+// getParentMapTokenIfExists if the NodeType is a container type such as MappingType or SequenceType,
+// it is necessary to return the parent MapNode's colon token to represent the entire container.
+func (d *Decoder) getParentMapTokenIfExistsForValidationError(typ ast.NodeType, tk *token.Token) *token.Token {
+	if tk == nil {
+		return nil
+	}
+	if typ == ast.MappingType {
+		// map:
+		//   key: value
+		//      ^ current token ( colon )
+		if tk.Prev == nil {
+			return tk
+		}
+		key := tk.Prev
+		if key.Prev == nil {
+			return tk
+		}
+		return key.Prev
+	}
+	if typ == ast.SequenceType {
+		// map:
+		//   - value
+		//   ^ current token ( sequence entry )
+		if tk.Prev == nil {
+			return tk
+		}
+		return tk.Prev
+	}
+	return tk
+}
+
 func (d *Decoder) decodeArray(ctx context.Context, dst reflect.Value, src ast.Node) error {
 	d.stepIn()
 	defer d.stepOut()

testdata/validate_test.go

@@ -174,6 +174,37 @@ lt10: 20
 				Inner `yaml:",inline"`
 			}{},
 		},
+		{
+			TestName: "Test map",
+			YAMLContent: `
+map:
+  hello: hello
+  hello2: hello`,
+			ExpectedErr: `[2:4] Key: 'Map' Error:Field validation for 'Map' failed on the 'eq' tag
+>  2 | map:
+          ^
+   3 |   hello: hello
+   4 |   hello2: hello`,
+			Instance: &struct {
+				// Make sure that this map is not set
+				Map map[string]string `yaml:"map" validate:"eq=0"`
+			}{},
+		},
+		{
+			TestName: "Test sequence",
+			YAMLContent: `
+map:
+  - value
+`,
+			ExpectedErr: `[2:4] Key: 'Map' Error:Field validation for 'Map' failed on the 'eq' tag
+>  2 | map:
+          ^
+   3 |   - value`,
+			Instance: &struct {
+				// Make sure that this map is not set
+				Map []string `yaml:"map" validate:"eq=0"`
+			}{},
+		},
 	}
 
 	for _, tc := range cases {