TextFormat decoding options to skip unknown fields/extensions.

Modeled after the upstream C++, provide two new decoding options to skip
unknown fields while decoding TextFormat.

Sources/SwiftProtobuf/DoubleParser.swift

@@ -18,9 +18,12 @@ import Foundation
 internal class DoubleParser {
  // Temporary buffer so we can null-terminate the UTF-8 string
  // before calling the C standard library to parse it.
+ //
  // In theory, JSON writers should be able to represent any IEEE Double
  // in at most 25 bytes, but many writers will emit more digits than
- // necessary, so we size this generously.
+ // necessary, so we size this generously; but we could still fail to
+ // parse if someone crafts something really long (especially for
+ // TextFormat due to overflows (see below)).
  private var work =
  UnsafeMutableBufferPointer<Int8>.allocate(capacity: 128)
 
@@ -49,6 +52,15 @@ internal class DoubleParser {
 
  // Fail if strtod() did not consume everything we expected
  // or if strtod() thought the number was out of range.
+ //
+ // NOTE: TextFormat specifically calls out handling for overflows
+ // for float/double fields:
+ // https://protobuf.dev/reference/protobuf/textformat-spec/#value
+ //
+ // > Overflows are treated as infinity or -infinity.
+ //
+ // But the JSON protobuf spec doesn't mention anything:
+ // https://protobuf.dev/programming-guides/proto3/#json
  if e != work.baseAddress! + bytes.count || !d.isFinite {
  return nil
  }

Sources/SwiftProtobuf/TextFormatDecoder.swift

@@ -27,6 +27,10 @@ internal struct TextFormatDecoder: Decoder {
  private var fieldNameMap: _NameMap?
  private var messageType: any Message.Type
 
+ internal var options: TextFormatDecodingOptions {
+ return scanner.options
+ }
+
  internal var complete: Bool {
  mutating get {
  return scanner.complete
@@ -63,27 +67,17 @@ internal struct TextFormatDecoder: Decoder {
  }
 
  mutating func nextFieldNumber() throws -> Int? {
- // Per https://protobuf.dev/reference/protobuf/textformat-spec/#fields, every field can be
- // followed by a field separator, so if we've seen a field, remove the separator before
- // checking for the terminator.
  if fieldCount > 0 {
  scanner.skipOptionalSeparator()
  }
- if let terminator = terminator,
- scanner.skipOptionalObjectEnd(terminator) {
- return nil
- }
- if let fieldNumber = try scanner.nextFieldNumber(names: fieldNameMap!, messageType: messageType) {
+ if let fieldNumber = try scanner.nextFieldNumber(names: fieldNameMap!,
+ messageType: messageType,
+ terminator: terminator) {
  fieldCount += 1
  return fieldNumber
- } else if terminator == nil {
- return nil
  } else {
- // If this decoder is looking for at a terminator, then if the scanner failed to
- // find a field number, something went wrong (end of stream).
- throw TextFormatDecodingError.truncated
+ return nil
  }
-
  }
 
  mutating func decodeSingularFloatField(value: inout Float) throws {
@@ -559,6 +553,7 @@ internal struct TextFormatDecoder: Decoder {
  var keyField: KeyType.BaseType?
  var valueField: ValueType.BaseType?
  let terminator = try scanner.skipObjectStart()
+ let ignoreExtensionFields = options.ignoreUnknownExtensionFields
  while true {
  if scanner.skipOptionalObjectEnd(terminator) {
  if let keyField = keyField, let valueField = valueField {
@@ -568,14 +563,20 @@ internal struct TextFormatDecoder: Decoder {
  throw TextFormatDecodingError.malformedText
  }
  }
- if let key = try scanner.nextKey() {
+ if let key = try scanner.nextKey(allowExtensions: ignoreExtensionFields) {
  switch key {
  case "key", "1":
  try KeyType.decodeSingular(value: &keyField, from: &self)
  case "value", "2":
  try ValueType.decodeSingular(value: &valueField, from: &self)
  default:
- throw TextFormatDecodingError.unknownField
+ if ignoreExtensionFields && key.hasPrefix("[") {
+ try scanner.skipUnknownFieldValue()
+ } else if options.ignoreUnknownFields && !key.hasPrefix("[") {
+ try scanner.skipUnknownFieldValue()
+ } else {
+ throw TextFormatDecodingError.unknownField
+ }
  }
  scanner.skipOptionalSeparator()
  } else {
@@ -608,6 +609,7 @@ internal struct TextFormatDecoder: Decoder {
  var keyField: KeyType.BaseType?
  var valueField: ValueType?
  let terminator = try scanner.skipObjectStart()
+ let ignoreExtensionFields = options.ignoreUnknownExtensionFields
  while true {
  if scanner.skipOptionalObjectEnd(terminator) {
  if let keyField = keyField, let valueField = valueField {
@@ -617,14 +619,20 @@ internal struct TextFormatDecoder: Decoder {
  throw TextFormatDecodingError.malformedText
  }
  }
- if let key = try scanner.nextKey() {
+ if let key = try scanner.nextKey(allowExtensions: ignoreExtensionFields) {
  switch key {
  case "key", "1":
  try KeyType.decodeSingular(value: &keyField, from: &self)
  case "value", "2":
  try decodeSingularEnumField(value: &valueField)
  default:
- throw TextFormatDecodingError.unknownField
+ if ignoreExtensionFields && key.hasPrefix("[") {
+ try scanner.skipUnknownFieldValue()
+ } else if options.ignoreUnknownFields && !key.hasPrefix("[") {
+ try scanner.skipUnknownFieldValue()
+ } else {
+ throw TextFormatDecodingError.unknownField
+ }
  }
  scanner.skipOptionalSeparator()
  } else {
@@ -657,6 +665,7 @@ internal struct TextFormatDecoder: Decoder {
  var keyField: KeyType.BaseType?
  var valueField: ValueType?
  let terminator = try scanner.skipObjectStart()
+ let ignoreExtensionFields = options.ignoreUnknownExtensionFields
  while true {
  if scanner.skipOptionalObjectEnd(terminator) {
  if let keyField = keyField, let valueField = valueField {
@@ -666,14 +675,20 @@ internal struct TextFormatDecoder: Decoder {
  throw TextFormatDecodingError.malformedText
  }
  }
- if let key = try scanner.nextKey() {
+ if let key = try scanner.nextKey(allowExtensions: ignoreExtensionFields) {
  switch key {
  case "key", "1":
  try KeyType.decodeSingular(value: &keyField, from: &self)
  case "value", "2":
  try decodeSingularMessageField(value: &valueField)
  default:
- throw TextFormatDecodingError.unknownField
+ if ignoreExtensionFields && key.hasPrefix("[") {
+ try scanner.skipUnknownFieldValue()
+ } else if options.ignoreUnknownFields && !key.hasPrefix("[") {
+ try scanner.skipUnknownFieldValue()
+ } else {
+ throw TextFormatDecodingError.unknownField
+ }
  }
  scanner.skipOptionalSeparator()
  } else {

Sources/SwiftProtobuf/TextFormatDecodingOptions.swift

@@ -21,5 +21,19 @@ public struct TextFormatDecodingOptions: Sendable {
  /// while parsing.
  public var messageDepthLimit: Int = 100
 
+ /// If unknown fields in the TextFormat should be ignored. If they aren't
+ /// ignored, an error will be raised if one is encountered.
+ ///
+ /// Note: This is a lossy option, enabling it means part of the TextFormat
+ /// is silently skipped.
+ public var ignoreUnknownFields: Bool = false
+
+ /// If unknown extension fields in the TextFormat should be ignored. If they
+ /// aren't ignored, an error will be raised if one is encountered.
+ ///
+ /// Note: This is a lossy option, enabling it means part of the TextFormat
+ /// is silently skipped.
+ public var ignoreUnknownExtensionFields: Bool = false
+
  public init() {}
 }