Merge pull request dart-lang/yaml#107 from DanTup/recover
Attempt to recover from invalid YAML
diff --git a/pkgs/yaml/lib/src/error_listener.dart b/pkgs/yaml/lib/src/error_listener.dart
new file mode 100644
index 0000000..dac7d63
--- /dev/null
+++ b/pkgs/yaml/lib/src/error_listener.dart
@@ -0,0 +1,19 @@
+// Copyright (c) 2021, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'yaml_exception.dart';
+
+/// A listener that is notified of [YamlError]s during scanning/parsing.
+abstract class ErrorListener {
+ /// This method is invoked when an [error] has been found in the YAML.
+ void onError(YamlException error);
+}
+
+/// An [ErrorListener] that collects all errors into [errors].
+class ErrorCollector extends ErrorListener {
+ final List<YamlException> errors = [];
+
+ @override
+ void onError(YamlException error) => errors.add(error);
+}
diff --git a/pkgs/yaml/lib/src/loader.dart b/pkgs/yaml/lib/src/loader.dart
index 7333227..0056a64 100644
--- a/pkgs/yaml/lib/src/loader.dart
+++ b/pkgs/yaml/lib/src/loader.dart
@@ -4,6 +4,7 @@
import 'package:charcode/ascii.dart';
import 'package:source_span/source_span.dart';
+import 'package:yaml/src/error_listener.dart';
import 'equality.dart';
import 'event.dart';
@@ -30,8 +31,10 @@
FileSpan _span;
/// Creates a loader that loads [source].
- factory Loader(String source, {Uri? sourceUrl}) {
- var parser = Parser(source, sourceUrl: sourceUrl);
+ factory Loader(String source,
+ {Uri? sourceUrl, bool recover = false, ErrorListener? errorListener}) {
+ var parser = Parser(source,
+ sourceUrl: sourceUrl, recover: recover, errorListener: errorListener);
var event = parser.parse();
assert(event.type == EventType.streamStart);
return Loader._(parser, event.span);
diff --git a/pkgs/yaml/lib/src/parser.dart b/pkgs/yaml/lib/src/parser.dart
index 3443e2e..aeeda4e 100644
--- a/pkgs/yaml/lib/src/parser.dart
+++ b/pkgs/yaml/lib/src/parser.dart
@@ -4,6 +4,7 @@
import 'package:source_span/source_span.dart';
import 'package:string_scanner/string_scanner.dart';
+import 'package:yaml/src/error_listener.dart';
import 'event.dart';
import 'scanner.dart';
@@ -35,8 +36,18 @@
bool get isDone => _state == _State.END;
/// Creates a parser that parses [source].
- Parser(String source, {Uri? sourceUrl})
- : _scanner = Scanner(source, sourceUrl: sourceUrl);
+ ///
+ /// If [recover] is true, will attempt to recover from parse errors and may return
+ /// invalid or synthetic nodes. If [errorListener] is also supplied, its onError
+ /// method will be called for each error recovered from. It is not valid to
+ /// provide [errorListener] if [recover] is false.
+ Parser(String source,
+ {Uri? sourceUrl, bool recover = false, ErrorListener? errorListener})
+ : assert(recover || errorListener == null),
+ _scanner = Scanner(source,
+ sourceUrl: sourceUrl,
+ recover: recover,
+ errorListener: errorListener);
/// Consumes and returns the next event.
Event parse() {
diff --git a/pkgs/yaml/lib/src/scanner.dart b/pkgs/yaml/lib/src/scanner.dart
index a9f64be..5cb329a 100644
--- a/pkgs/yaml/lib/src/scanner.dart
+++ b/pkgs/yaml/lib/src/scanner.dart
@@ -5,6 +5,7 @@
import 'package:collection/collection.dart';
import 'package:source_span/source_span.dart';
import 'package:string_scanner/string_scanner.dart';
+import 'package:yaml/src/error_listener.dart';
import 'style.dart';
import 'token.dart';
@@ -89,6 +90,12 @@
static const LETTER_CAP_X = 0x58;
static const LETTER_CAP_Z = 0x5A;
+ /// Whether this scanner should attempt to recover when parsing invalid YAML.
+ final bool _recover;
+
+ /// A listener to report YAML errors to.
+ final ErrorListener? _errorListener;
+
/// The underlying [SpanScanner] used to read characters from the source text.
///
/// This is also used to track line and column information and to generate
@@ -288,8 +295,11 @@
}
/// Creates a scanner that scans [source].
- Scanner(String source, {Uri? sourceUrl})
- : _scanner = SpanScanner.eager(source, sourceUrl: sourceUrl);
+ Scanner(String source,
+ {Uri? sourceUrl, bool recover = false, ErrorListener? errorListener})
+ : _recover = recover,
+ _errorListener = errorListener,
+ _scanner = SpanScanner.eager(source, sourceUrl: sourceUrl);
/// Consumes and returns the next token.
Token scan() {
@@ -486,7 +496,9 @@
if (key.line == _scanner.line) continue;
if (key.required) {
- throw YamlException("Expected ':'.", _scanner.emptySpan);
+ _reportError(YamlException("Expected ':'.", _scanner.emptySpan));
+ _tokens.insert(key.tokenNumber - _tokensParsed,
+ Token(TokenType.key, key.location.pointSpan() as FileSpan));
}
_simpleKeys[i] = null;
@@ -1624,6 +1636,15 @@
_scanner.readChar();
}
}
+
+ /// Reports a [YamlException] to [_errorListener] if [_recover] is true,
+ /// otherwise throws the exception.
+ void _reportError(YamlException exception) {
+ if (!_recover) {
+ throw exception;
+ }
+ _errorListener?.onError(exception);
+ }
}
/// A record of the location of a potential simple key.
diff --git a/pkgs/yaml/lib/yaml.dart b/pkgs/yaml/lib/yaml.dart
index f80489a..d150725 100644
--- a/pkgs/yaml/lib/yaml.dart
+++ b/pkgs/yaml/lib/yaml.dart
@@ -2,6 +2,7 @@
// for details. All rights reserved. Use of this source code is governed by a
// BSD-style license that can be found in the LICENSE file.
+import 'src/error_listener.dart';
import 'src/loader.dart';
import 'src/style.dart';
import 'src/yaml_document.dart';
@@ -30,24 +31,41 @@
///
/// If [sourceUrl] is passed, it's used as the URL from which the YAML
/// originated for error reporting.
-dynamic loadYaml(String yaml, {Uri? sourceUrl}) =>
- loadYamlNode(yaml, sourceUrl: sourceUrl).value;
+///
+/// If [recover] is true, will attempt to recover from parse errors and may return
+/// invalid or synthetic nodes. If [errorListener] is also supplied, its onError
+/// method will be called for each error recovered from. It is not valid to
+/// provide [errorListener] if [recover] is false.
+dynamic loadYaml(String yaml,
+ {Uri? sourceUrl, bool recover = false, ErrorListener? errorListener}) =>
+ loadYamlNode(yaml,
+ sourceUrl: sourceUrl,
+ recover: recover,
+ errorListener: errorListener)
+ .value;
/// Loads a single document from a YAML string as a [YamlNode].
///
/// This is just like [loadYaml], except that where [loadYaml] would return a
/// normal Dart value this returns a [YamlNode] instead. This allows the caller
/// to be confident that the return value will always be a [YamlNode].
-YamlNode loadYamlNode(String yaml, {Uri? sourceUrl}) =>
- loadYamlDocument(yaml, sourceUrl: sourceUrl).contents;
+YamlNode loadYamlNode(String yaml,
+ {Uri? sourceUrl, bool recover = false, ErrorListener? errorListener}) =>
+ loadYamlDocument(yaml,
+ sourceUrl: sourceUrl,
+ recover: recover,
+ errorListener: errorListener)
+ .contents;
/// Loads a single document from a YAML string as a [YamlDocument].
///
/// This is just like [loadYaml], except that where [loadYaml] would return a
/// normal Dart value this returns a [YamlDocument] instead. This allows the
/// caller to access document metadata.
-YamlDocument loadYamlDocument(String yaml, {Uri? sourceUrl}) {
- var loader = Loader(yaml, sourceUrl: sourceUrl);
+YamlDocument loadYamlDocument(String yaml,
+ {Uri? sourceUrl, bool recover = false, ErrorListener? errorListener}) {
+ var loader = Loader(yaml,
+ sourceUrl: sourceUrl, recover: recover, errorListener: errorListener);
var document = loader.load();
if (document == null) {
return YamlDocument.internal(YamlScalar.internalWithSpan(null, loader.span),
diff --git a/pkgs/yaml/test/utils.dart b/pkgs/yaml/test/utils.dart
index ce05481..f90ac5b 100644
--- a/pkgs/yaml/test/utils.dart
+++ b/pkgs/yaml/test/utils.dart
@@ -22,6 +22,14 @@
return map;
}
+/// Asserts that an error has the given message and starts at the given line/col.
+void expectErrorAtLineCol(
+ YamlException error, String message, int line, int col) {
+ expect(error.message, equals(message));
+ expect(error.span!.start.line, equals(line));
+ expect(error.span!.start.column, equals(col));
+}
+
/// Asserts that a string containing a single YAML document produces a given
/// value when loaded.
void expectYamlLoads(expected, String source) {
diff --git a/pkgs/yaml/test/yaml_test.dart b/pkgs/yaml/test/yaml_test.dart
index a0fb8f1..dffb9d5 100644
--- a/pkgs/yaml/test/yaml_test.dart
+++ b/pkgs/yaml/test/yaml_test.dart
@@ -3,6 +3,7 @@
// BSD-style license that can be found in the LICENSE file.
import 'package:test/test.dart';
+import 'package:yaml/src/error_listener.dart';
import 'package:yaml/yaml.dart';
import 'utils.dart';
@@ -61,6 +62,84 @@
});
});
+ group('recovers', () {
+ var collector = ErrorCollector();
+ setUp(() {
+ collector = ErrorCollector();
+ });
+
+ test('from incomplete leading keys', () {
+ final yaml = cleanUpLiteral(r'''
+ dependencies:
+ zero
+ one: any
+ ''');
+ var result = loadYaml(yaml, recover: true, errorListener: collector);
+ expect(
+ result,
+ deepEquals({
+ 'dependencies': {
+ 'zero': null,
+ 'one': 'any',
+ }
+ }));
+ expect(collector.errors.length, equals(1));
+ // These errors are reported at the start of the next token (after the
+ // whitespace/newlines).
+ expectErrorAtLineCol(collector.errors[0], "Expected ':'.", 2, 2);
+ // Skipped because this case is not currently handled. If it's the first
+ // package without the colon, because the value is indented from the line
+ // above, the whole `zero\n one` is treated as a scalar value.
+ }, skip: true);
+ test('from incomplete keys', () {
+ final yaml = cleanUpLiteral(r'''
+ dependencies:
+ one: any
+ two
+ three:
+ four
+ five:
+ 1.2.3
+ six: 5.4.3
+ ''');
+ var result = loadYaml(yaml, recover: true, errorListener: collector);
+ expect(
+ result,
+ deepEquals({
+ 'dependencies': {
+ 'one': 'any',
+ 'two': null,
+ 'three': null,
+ 'four': null,
+ 'five': '1.2.3',
+ 'six': '5.4.3',
+ }
+ }));
+
+ expect(collector.errors.length, equals(2));
+ // These errors are reported at the start of the next token (after the
+ // whitespace/newlines).
+ expectErrorAtLineCol(collector.errors[0], "Expected ':'.", 3, 2);
+ expectErrorAtLineCol(collector.errors[1], "Expected ':'.", 5, 2);
+ });
+ test('from incomplete trailing keys', () {
+ final yaml = cleanUpLiteral(r'''
+ dependencies:
+ six: 5.4.3
+ seven
+ ''');
+ var result = loadYaml(yaml, recover: true);
+ expect(
+ result,
+ deepEquals({
+ 'dependencies': {
+ 'six': '5.4.3',
+ 'seven': null,
+ }
+ }));
+ });
+ });
+
test('includes source span information', () {
var yaml = loadYamlNode(r'''
- foo:
