Add support for delete by value

README.md

@@ -34,6 +34,15 @@ go get -u github.com/evanphx/json-patch
   functionality can be disabled by setting `jsonpatch.SupportNegativeIndices =
   false`.
 
+* There is a global configuration variable `jsonpatch.SupportDeleteByValue`.
+  This defaults to `true` and enables the support for the non-standard
+  practice of deleting from an array with value. This functionality
+  can be disabled by setting `jsonpatch.SupportNegativeIndices = false`.
+  This can be used by using `-` instead of the array index and specifying the
+  value to remove in "value". For example:
+  `[{ "op": "remove", "path": "/foo/-", "value": "qux"}]` will delete
+  value `qux` from the array `foo`. This works also with values that are objects.
+
 * There is a global configuration variable `jsonpatch.AccumulatedCopySizeLimit`,
   which limits the total size increase in bytes caused by "copy" operations in a
   patch. It defaults to 0, which means there is no limit.

patch.go

@@ -24,6 +24,9 @@ var (
 	// AccumulatedCopySizeLimit limits the total size increase in bytes caused by
 	// "copy" operations in a patch.
 	AccumulatedCopySizeLimit int64 = 0
+	// SupportDeleteByValue decides whether to support non-standard practice of
+	// allowing deleting from array with value.
+	SupportDeleteByValue bool = true
 )
 
 var (
@@ -505,6 +508,16 @@ func (d *partialArray) remove(key string) error {
 
 }
 
+func (d *partialArray) removeByValue(key *lazyNode) error {
+	for i, v := range *d {
+		if key.equal(v) {
+			return d.remove(strconv.Itoa(i))
+		}
+	}
+
+	return errors.Wrapf(ErrInvalidIndex, "value not found")
+}
+
 func (p Patch) add(doc *container, op Operation) error {
 	path, err := op.Path()
 	if err != nil {
@@ -537,7 +550,18 @@ func (p Patch) remove(doc *container, op Operation) error {
 		return errors.Wrapf(ErrMissing, "remove operation does not apply: doc is missing path: \"%s\"", path)
 	}
 
-	err = con.remove(key)
+	if key == "-" && SupportDeleteByValue {
+		value := op.value()
+		switch v := con.(type) {
+		case *partialArray:
+			err = v.removeByValue(value)
+		default:
+			return errors.Wrapf(ErrInvalid, "cannot delete by value from a non-array")
+		}
+	} else {
+		err = con.remove(key)
+	}
+
 	if err != nil {
 		return errors.Wrapf(err, "error in remove for path: '%s'", path)
 	}

patch_test.go

@@ -90,6 +90,21 @@ var Cases = []Case{
 		`[ { "op": "remove", "path": "/foo/1" } ]`,
 		`{ "foo": [ "bar", "baz" ] }`,
 	},
+	{
+		`{ "foo": [ "bar", "qux", "baz" ] }`,
+		`[ { "op": "remove", "path": "/foo/-" , "value": "qux" }]`,
+		`{ "foo": [ "bar", "baz" ] }`,
+	},
+	{
+		`{ "foo": [ "3", "2", "1" ] }`,
+		`[ { "op": "remove", "path": "/foo/-" , "value": "1" }]`,
+		`{ "foo": [ "3", "2" ] }`,
+	},
+	{
+		`{ "foo": [ [ "bar", "qux", "baz" ], [ "bar", "baz" ], "1" ] }`,
+		`[ { "op": "remove", "path": "/foo/-" , "value": [ "bar", "baz" ] }]`,
+		`{ "foo": [ [ "bar", "qux", "baz" ], "1" ] }`,
+	},
 	{
 		`{ "baz": "qux", "foo": "bar" }`,
 		`[ { "op": "replace", "path": "/baz", "value": "boo" } ]`,
@@ -295,6 +310,10 @@ var BadCases = []BadCase{
 		`{ "foo": []}`,
 		`[ {"op": "remove", "path": "/foo/-"}]`,
 	},
+	{
+		`{ "foo": []}`,
+		`[ {"op": "remove", "path": "/foo/-", "value": "asd"}]`,
+	},
 	{
 		`{ "foo": []}`,
 		`[ {"op": "remove", "path": "/foo/-1"}]`,