# YAML Test Matrix

--- &test-ZL4Z
  Title: Invalid nested mapping
  Tags: [ error, mapping ]

YAML

---
a: 'b': c

Expected Events

+STR
+DOC ---
+MAP
=VAL :a
=VAL 'b

Expected JSON



hs-reference-yeast

 invalid_incorrect
Line  Col Char Byte Token|Content
   1    0    0    0 +DOC |
   1    0    0    0 =HEAD|---
   1    3    3    3 +NODE|
   1    3    3    3 =EOL |\x0a
   2    0    4    4 +MAP |
   2    0    4    4 +PAIR|
   2    0    4    4 +NODE|
   2    0    4    4 +VAL |
   2    0    4    4 =TEXT|a
   2    1    5    5 -VAL |
   2    1    5    5 -NODE|
   2    1    5    5 =SYNX|:
   2    2    6    6 =WSPC|.
   2    3    7    7 +NODE|
   2    3    7    7 +VAL |
   2    3    7    7 =SYNX|'
   2    4    8    8 =TEXT|b
   2    5    9    9 =SYNX|'
   2    6   10   10 -VAL |
   2    6   10   10 -NODE|
   2    6   10   10 =ERR |Expected.start.of.line
   2    6   10   10 =REST|:.c
   2    9   13   13 =REST|\x0a
   3    0   14   14 -PAIR|
   3    0   14   14 -MAP |
   3    0   14   14 -NODE|
   3    0   14   14 -DOC |

c-libfyaml-event

 invalid_correct
stdin:2:7: error: invalid nested block mapping on the same line
a: 'b': c
      ^
+STR
+DOC ---
+MAP
=VAL :a
=VAL 'b

c-libfyaml-json

 invalid_correct
stdin:2:7: error: invalid nested block mapping on the same line
a: 'b': c
      ^

c-libyaml-event

 invalid_correct
Parse error: mapping values are not allowed in this context
+STR
+DOC ---
+MAP
=VAL :a
=VAL 'b

cpp-rapidyaml-event

 invalid_correct
/tmp/rapidyaml-0.4.0-src/src/c4/yml/parse.cpp:3563:check failed: m_state->flags & SSCL
Aborted (core dumped)

cpp-yamlcpp-event

 invalid_correct
Exception:
yaml-cpp: error at line 2, column 7: illegal map value
+STR
+DOC
+MAP
=VAL :a
=VAL :b

dotnet-yamldotnet-event

 invalid_correct
Unhandled exception. YamlDotNet.Core.SyntaxErrorException: (Line: 2, Col: 7, Idx: 10) - (Line: 2, Col: 7, Idx: 10): Mapping values are not allowed in this context.
   at YamlDotNet.Core.Parser.ParseBlockMappingKey(Boolean isFirst)
   at YamlDotNet.Core.Parser.StateMachine()
   at YamlDotNet.Core.Parser.MoveNext()
   at YamlDotNet.RepresentationModel.LibYamlEventStream.WriteTo(TextWriter textWriter)
   at Program.Main(String[] commandLineArguments)
Aborted (core dumped)
+STR
+DOC ---
+MAP
=VAL :a
=VAL 'b

dotnet-yamldotnet-json

 invalid_correct
Unhandled exception. YamlDotNet.Core.SyntaxErrorException: (Line: 2, Col: 7, Idx: 10) - (Line: 2, Col: 7, Idx: 10): Mapping values are not allowed in this context.
   at YamlDotNet.Core.Parser.ParseBlockMappingKey(Boolean isFirst)
   at YamlDotNet.Core.Parser.StateMachine()
   at YamlDotNet.Core.Parser.MoveNext()
   at YamlDotNet.Core.ParserExtensions.TryConsume[T](IParser parser, T& event)
   at YamlDotNet.Serialization.NodeDeserializers.ScalarNodeDeserializer.YamlDotNet.Serialization.INodeDeserializer.Deserialize(IParser parser, Type expectedType, Func`3 nestedObjectDeserializer, Object& value)
   at YamlDotNet.Serialization.ValueDeserializers.NodeValueDeserializer.DeserializeValue(IParser parser, Type expectedType, SerializerState state, IValueDeserializer nestedObjectDeserializer)
   at YamlDotNet.Serialization.ValueDeserializers.AliasValueDeserializer.DeserializeValue(IParser parser, Type expectedType, SerializerState state, IValueDeserializer nestedObjectDeserializer)
   at YamlDotNet.Serialization.ValueDeserializers.NodeValueDeserializer.<>c__DisplayClass3_0.<DeserializeValue>b__0(IParser r, Type t)
   at YamlDotNet.Serialization.NodeDeserializers.DictionaryNodeDeserializer.DeserializeHelper(Type tKey, Type tValue, IParser parser, Func`3 nestedObjectDeserializer, IDictionary result)
   at YamlDotNet.Serialization.NodeDeserializers.DictionaryNodeDeserializer.YamlDotNet.Serialization.INodeDeserializer.Deserialize(IParser parser, Type expectedType, Func`3 nestedObjectDeserializer, Object& value)
   at YamlDotNet.Serialization.ValueDeserializers.NodeValueDeserializer.DeserializeValue(IParser parser, Type expectedType, SerializerState state, IValueDeserializer nestedObjectDeserializer)
   at YamlDotNet.Serialization.ValueDeserializers.AliasValueDeserializer.DeserializeValue(IParser parser, Type expectedType, SerializerState state, IValueDeserializer nestedObjectDeserializer)
   at YamlDotNet.Serialization.Deserializer.Deserialize(IParser parser, Type type)
   at YamlDotNet.Serialization.Deserializer.Deserialize(TextReader input, Type type)
   at YamlDotNet.Serialization.Deserializer.Deserialize(TextReader input)
   at Program.Main(String[] commandLineArguments)
Aborted (core dumped)

go-yaml-json

 invalid_correct
yaml: line 2: mapping values are not allowed in this context

hs-hsyaml-event

 invalid_correct
Parsing error near byte offset Pos {posByteOffset = 10, posCharOffset = 10, posLine = 2, posColumn = 6} (Expected start of line)
+STR
+DOC ---
+MAP
=VAL :a
=VAL 'b

hs-hsyaml-json

 invalid_correct
hsyaml-parser: user error (Expected start of line)

js-jsyaml-json

 invalid_correct
/node/node_modules/js-yaml/lib/loader.js:187
  throw generateError(state, message);
  ^
YAMLException: bad indentation of a mapping entry (2:7)

 1 | ---
 2 | a: 'b': c
-----------^
    at generateError (/node/node_modules/js-yaml/lib/loader.js:183:10)
    at throwError (/node/node_modules/js-yaml/lib/loader.js:187:9)
    at readBlockMapping (/node/node_modules/js-yaml/lib/loader.js:1182:7)
    at composeNode (/node/node_modules/js-yaml/lib/loader.js:1441:12)
    at readDocument (/node/node_modules/js-yaml/lib/loader.js:1625:3)
    at loadDocuments (/node/node_modules/js-yaml/lib/loader.js:1688:5)
    at Object.loadAll (/node/node_modules/js-yaml/lib/loader.js:1701:19)
    at Object.<anonymous> (/yaml/bin/js-jsyaml-json:7:13)
    at Module._compile (node:internal/modules/cjs/loader:1358:14)
    at Module._extensions..js (node:internal/modules/cjs/loader:1416:10) {
  reason: 'bad indentation of a mapping entry',
  mark: {
    name: null,
    buffer: "---\na: 'b': c\n",
    position: 10,
    line: 1,
    column: 6,
    snippet: " 1 | ---\n 2 | a: 'b': c\n-----------^"
  }
}

Node.js v20.13.1

js-yaml-event

 invalid_correct
Nested mappings are not allowed in compact mappings at line 2, column 4:

a: 'b': c
   ^
+STR
+DOC ---
+MAP
=VAL :a

js-yaml-json

 invalid_correct
/yaml/bin/js-yaml-json:9
    if (doc.errors.length !== 0) throw doc.errors[0]
                                 ^

YAMLParseError: Nested mappings are not allowed in compact mappings at line 2, column 4:

a: 'b': c
   ^

    at Composer.onError (/node/node_modules/yaml/dist/compose/composer.js:69:34)
    at Object.resolveBlockMap (/node/node_modules/yaml/dist/compose/resolve-block-map.js:76:21)
    at resolveCollection (/node/node_modules/yaml/dist/compose/compose-collection.js:13:27)
    at Object.composeCollection (/node/node_modules/yaml/dist/compose/compose-collection.js:47:16)
    at Object.composeNode (/node/node_modules/yaml/dist/compose/compose-node.js:31:38)
    at Object.composeDoc (/node/node_modules/yaml/dist/compose/compose-doc.js:34:23)
    at Composer.next (/node/node_modules/yaml/dist/compose/composer.js:149:40)
    at next (<anonymous>)
    at Composer.compose (/node/node_modules/yaml/dist/compose/composer.js:131:25)
    at compose.next (<anonymous>) {
  code: 'BLOCK_AS_IMPLICIT_KEY',
  pos: [ 7, 8 ],
  linePos: [ { line: 2, col: 4 }, { line: 2, col: 5 } ]
}

Node.js v20.13.1

lua-lyaml-json

 invalid_correct
luajit: 2:4: mapping values are not allowed in this context
stack traceback:
	[C]: in function 'error'
	/usr/local/share/lua/5.1/lyaml/init.lua:306: in function 'error'
	/usr/local/share/lua/5.1/lyaml/init.lua:325: in function 'parse'
	/usr/local/share/lua/5.1/lyaml/init.lua:443: in function 'load_node'
	/usr/local/share/lua/5.1/lyaml/init.lua:340: in function 'load_node'
	/usr/local/share/lua/5.1/lyaml/init.lua:497: in function 'load'
	/yaml/bin/lua-lyaml-json:6: in main chunk
	[C]: at 0x55ca2c3d4ed0

nim-nimyaml-event

 invalid_correct
/tmp/NimYAML-0.16.0/yaml/stream.nim(134) nimyaml_event
/tmp/NimYAML-0.16.0/yaml/stream.nim(106) next
Error: unhandled exception: Compact notation not allowed after implicit key [YamlStreamError]
+STR
+DOC ---
+MAP
=VAL :a

perl-pp-event

 invalid_correct
Line      : 2
Column    : 7
Expected  : EOL
Got       : COLON
Where     : /perl5/lib/perl5/YAML/PP/Parser.pm line 392
YAML      : ": c\n"
  at /yaml/bin/perl-pp-event line 46.
+STR
+DOC ---
+MAP
=VAL :a

perl-pp-json

 invalid_correct
Line      : 2
Column    : 7
Expected  : EOL
Got       : COLON
Where     : /perl5/lib/perl5/YAML/PP/Parser.pm line 392
YAML      : ": c\n"
  at /perl5/lib/perl5/YAML/PP/Loader.pm line 94.

perl-pp-perl

 invalid_correct
Line      : 2
Column    : 7
Expected  : EOL
Got       : COLON
Where     : /perl5/lib/perl5/YAML/PP/Parser.pm line 392
YAML      : ": c\n"
  at /perl5/lib/perl5/YAML/PP/Loader.pm line 94.

perl-pplibyaml-json

 invalid_correct
YAML::PP::LibYAML Error: The problem:

    mapping values are not allowed in this context

was found at , line: 2, column: 7

perl-pplibyaml-perl

 invalid_correct
YAML::PP::LibYAML Error: The problem:

    mapping values are not allowed in this context

was found at , line: 2, column: 7

perl-refparser-event

 invalid_correct
Parser finished before end of input at /perl5/lib/perl5/YAML/Parser.pm line 4056, <> line 1.

perl-syck-json

 invalid_correct
Syck parser (line 2, column 7): syntax error at /perl5/lib/perl5/x86_64-linux-thread-multi/YAML/Syck.pm line 60, <> line 1.

perl-syck-perl

 invalid_correct
Syck parser (line 2, column 7): syntax error at /perl5/lib/perl5/x86_64-linux-thread-multi/YAML/Syck.pm line 60, <> line 1.

perl-tiny-json

 invalid_correct
YAML::Tiny does not support a feature in line ''b': c' at /yaml/bin/perl-tiny-json line 12.

perl-tiny-perl

 invalid_correct
YAML::Tiny does not support a feature in line ''b': c' at /yaml/bin/perl-tiny-perl line 15.

perl-xs-json

 invalid_correct
YAML::XS::Load Error: The problem:

    mapping values are not allowed in this context

was found at document: 1, line: 2, column: 7

perl-xs-perl

 invalid_correct
YAML::XS::Load Error: The problem:

    mapping values are not allowed in this context

was found at document: 1, line: 2, column: 7

perl-yaml-json

 invalid_correct
YAML Error: Couldn't parse single line value
   Code: YAML_PARSE_ERR_SINGLE_LINE
   Line: 2
   Document: 1
 at /perl5/lib/perl5/YAML/Loader.pm line 164.

perl-yaml-perl

 invalid_correct
YAML Error: Couldn't parse single line value
   Code: YAML_PARSE_ERR_SINGLE_LINE
   Line: 2
   Document: 1
 at /perl5/lib/perl5/YAML/Loader.pm line 164.

py-pyyaml-event

 invalid_correct
Traceback (most recent call last):
  File "/yaml/bin/py-pyyaml-event", line 7, in <module>
    for event in yaml.parse(sys.stdin.read()):
  File "/python/lib/python3.12/site-packages/yaml/__init__.py", line 75, in parse
    while loader.check_event():
          ^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/parser.py", line 98, in check_event
    self.current_event = self.state()
                         ^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/parser.py", line 428, in parse_block_mapping_key
    if self.check_token(KeyToken):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/scanner.py", line 116, in check_token
    self.fetch_more_tokens()
  File "/python/lib/python3.12/site-packages/yaml/scanner.py", line 223, in fetch_more_tokens
    return self.fetch_value()
           ^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/scanner.py", line 577, in fetch_value
    raise ScannerError(None, None,
yaml.scanner.ScannerError: mapping values are not allowed here
  in "<unicode string>", line 2, column 7:
    a: 'b': c
          ^
+STR
+DOC ---
+MAP
=VAL :a
=VAL 'b

py-pyyaml-json

 invalid_correct
Traceback (most recent call last):
  File "/yaml/bin/py-pyyaml-json", line 19, in <module>
    for doc in yaml.load_all(sys.stdin.read(), Loader=yaml.FullLoader):
  File "/python/lib/python3.12/site-packages/yaml/__init__.py", line 130, in load_all
    yield loader.get_data()
          ^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/constructor.py", line 45, in get_data
    return self.construct_document(self.get_node())
                                   ^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/composer.py", line 27, in get_node
    return self.compose_document()
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/composer.py", line 55, in compose_document
    node = self.compose_node(None, None)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/composer.py", line 84, in compose_node
    node = self.compose_mapping_node(anchor)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/composer.py", line 127, in compose_mapping_node
    while not self.check_event(MappingEndEvent):
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/parser.py", line 98, in check_event
    self.current_event = self.state()
                         ^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/parser.py", line 428, in parse_block_mapping_key
    if self.check_token(KeyToken):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/scanner.py", line 116, in check_token
    self.fetch_more_tokens()
  File "/python/lib/python3.12/site-packages/yaml/scanner.py", line 223, in fetch_more_tokens
    return self.fetch_value()
           ^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/scanner.py", line 577, in fetch_value
    raise ScannerError(None, None,
yaml.scanner.ScannerError: mapping values are not allowed here
  in "<unicode string>", line 2, column 7:
    a: 'b': c
          ^

py-pyyaml-py

 invalid_correct
Traceback (most recent call last):
  File "/yaml/bin/py-pyyaml-py", line 36, in <module>
    for doc in yaml.load_all(sys.stdin.read(), Loader=yaml.FullLoader):
  File "/python/lib/python3.12/site-packages/yaml/__init__.py", line 130, in load_all
    yield loader.get_data()
          ^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/constructor.py", line 45, in get_data
    return self.construct_document(self.get_node())
                                   ^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/composer.py", line 27, in get_node
    return self.compose_document()
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/composer.py", line 55, in compose_document
    node = self.compose_node(None, None)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/composer.py", line 84, in compose_node
    node = self.compose_mapping_node(anchor)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/composer.py", line 127, in compose_mapping_node
    while not self.check_event(MappingEndEvent):
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/parser.py", line 98, in check_event
    self.current_event = self.state()
                         ^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/parser.py", line 428, in parse_block_mapping_key
    if self.check_token(KeyToken):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/scanner.py", line 116, in check_token
    self.fetch_more_tokens()
  File "/python/lib/python3.12/site-packages/yaml/scanner.py", line 223, in fetch_more_tokens
    return self.fetch_value()
           ^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/yaml/scanner.py", line 577, in fetch_value
    raise ScannerError(None, None,
yaml.scanner.ScannerError: mapping values are not allowed here
  in "<unicode string>", line 2, column 7:
    a: 'b': c
          ^

py-ruamel-event

 invalid_correct
Traceback (most recent call last):
  File "/yaml/bin/py-ruamel-event", line 9, in <module>
    for event in yaml.parse(sys.stdin.read()):
  File "/python/lib/python3.12/site-packages/ruamel/yaml/main.py", line 371, in parse
    while parser.check_event():
          ^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/parser.py", line 141, in check_event
    self.current_event = self.state()
                         ^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/parser.py", line 600, in parse_block_mapping_key
    if self.scanner.check_token(KeyToken):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/scanner.py", line 170, in check_token
    self.fetch_more_tokens()
  File "/python/lib/python3.12/site-packages/ruamel/yaml/scanner.py", line 278, in fetch_more_tokens
    return self.fetch_value()
           ^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/scanner.py", line 628, in fetch_value
    raise ScannerError(
ruamel.yaml.scanner.ScannerError: mapping values are not allowed here
  in "<unicode string>", line 2, column 7:
    a: 'b': c
          ^ (line: 2)
+STR
+DOC ---
+MAP
=VAL :a
=VAL 'b

py-ruamel-json

 invalid_correct
Traceback (most recent call last):
  File "/yaml/bin/py-ruamel-json", line 21, in <module>
    for doc in yaml.load_all(sys.stdin.read()):
  File "/python/lib/python3.12/site-packages/ruamel/yaml/main.py", line 476, in load_all
    yield constructor.get_data()
          ^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/constructor.py", line 110, in get_data
    return self.construct_document(self.composer.get_node())
                                   ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/composer.py", line 63, in get_node
    return self.compose_document()
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/composer.py", line 94, in compose_document
    node = self.compose_node(None, None)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/composer.py", line 130, in compose_node
    node = self.compose_mapping_node(anchor)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/composer.py", line 204, in compose_mapping_node
    while not self.parser.check_event(MappingEndEvent):
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/parser.py", line 141, in check_event
    self.current_event = self.state()
                         ^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/parser.py", line 600, in parse_block_mapping_key
    if self.scanner.check_token(KeyToken):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/scanner.py", line 170, in check_token
    self.fetch_more_tokens()
  File "/python/lib/python3.12/site-packages/ruamel/yaml/scanner.py", line 278, in fetch_more_tokens
    return self.fetch_value()
           ^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/scanner.py", line 628, in fetch_value
    raise ScannerError(
ruamel.yaml.scanner.ScannerError: mapping values are not allowed here
  in "<unicode string>", line 2, column 7:
    a: 'b': c
          ^ (line: 2)

py-ruamel-py

 invalid_correct
Traceback (most recent call last):
  File "/yaml/bin/py-ruamel-py", line 38, in <module>
    for doc in yaml.load_all(sys.stdin.read()):
  File "/python/lib/python3.12/site-packages/ruamel/yaml/main.py", line 476, in load_all
    yield constructor.get_data()
          ^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/constructor.py", line 110, in get_data
    return self.construct_document(self.composer.get_node())
                                   ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/composer.py", line 63, in get_node
    return self.compose_document()
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/composer.py", line 94, in compose_document
    node = self.compose_node(None, None)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/composer.py", line 130, in compose_node
    node = self.compose_mapping_node(anchor)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/composer.py", line 204, in compose_mapping_node
    while not self.parser.check_event(MappingEndEvent):
              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/parser.py", line 141, in check_event
    self.current_event = self.state()
                         ^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/parser.py", line 600, in parse_block_mapping_key
    if self.scanner.check_token(KeyToken):
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/scanner.py", line 170, in check_token
    self.fetch_more_tokens()
  File "/python/lib/python3.12/site-packages/ruamel/yaml/scanner.py", line 278, in fetch_more_tokens
    return self.fetch_value()
           ^^^^^^^^^^^^^^^^^^
  File "/python/lib/python3.12/site-packages/ruamel/yaml/scanner.py", line 628, in fetch_value
    raise ScannerError(
ruamel.yaml.scanner.ScannerError: mapping values are not allowed here
  in "<unicode string>", line 2, column 7:
    a: 'b': c
          ^ (line: 2)

ruby-psych-json

 invalid_correct
/ruby/gems/psych/lib/psych.rb:458:in `parse': (<unknown>): mapping values are not allowed in this context at line 2 column 7 (Psych::SyntaxError)
	from /ruby/gems/psych/lib/psych.rb:458:in `parse_stream'
	from /ruby/gems/psych/lib/psych.rb:632:in `load_stream'
	from /yaml/bin/ruby-psych-json:6:in `<main>'

rust-yamlrust-event

 invalid_correct
Error: ScanError { mark: Marker { index: 10, line: 2, col: 6 }, info: "mapping values are not allowed in this context" }
+STR
+DOC
+MAP
=VAL :a
=VAL 'b