# YAML Test Matrix

--- &test-5U3A
  Title: Sequence on same Line as Mapping Key
  Tags: [ error, mapping, sequence ]

YAML

key: - a
     - b

Expected Events

+STR
+DOC
+MAP
=VAL :key

Expected JSON



perl-syck-json

 invalid_incorrect
{
   "key" : [
      "a",
      "b"
   ]
}

perl-syck-perl

 invalid_incorrect
{
  'key' => [
             'a',
             'b'
           ]
}

c-libfyaml-event

 invalid_correct
stdin:1:6: error: block sequence on the same line as a mapping key
key: - a
     ^
[NOT]: fy_fetch_block_entry() failed
[NOT]: fy_fetch_tokens() failed
[NOT]: failed to peek token
+STR
+DOC
+MAP
=VAL :key

c-libfyaml-json

 invalid_correct
stdin:1:6: error: block sequence on the same line as a mapping key
key: - a
     ^
[NOT]: fy_fetch_block_entry() failed
[NOT]: fy_fetch_tokens() failed
[NOT]: failed to peek token

c-libyaml-event

 invalid_correct
Parse error: block sequence entries are not allowed in this context
+STR
+DOC
+MAP
=VAL :key

cpp-yamlcpp-event

 invalid_correct
Exception:
yaml-cpp: error at line 1, column 6: illegal block entry
+STR
+DOC
+MAP
=VAL :key

dotnet-yamldotnet-event

 invalid_correct
Unhandled exception. YamlDotNet.Core.SemanticErrorException: (Line: 1, Col: 6, Idx: 5) - (Line: 1, Col: 6, Idx: 5): Block sequence entries are not allowed in this context.
   at YamlDotNet.Core.Parser.ParseNode(Boolean isBlock, Boolean isIndentlessSequence)
   at YamlDotNet.Core.Parser.ParseBlockMappingValue()
   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 :key

dotnet-yamldotnet-json

 invalid_correct
Unhandled exception. YamlDotNet.Core.SemanticErrorException: (Line: 1, Col: 6, Idx: 5) - (Line: 1, Col: 6, Idx: 5): Block sequence entries are not allowed in this context.
   at YamlDotNet.Core.Parser.ParseNode(Boolean isBlock, Boolean isIndentlessSequence)
   at YamlDotNet.Core.Parser.ParseBlockMappingValue()
   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)

hs-hsyaml-event

 invalid_correct
Parsing error near byte offset Pos {posByteOffset = 4, posCharOffset = 4, posLine = 1, posColumn = 4} (Lexical error near " - a")
+STR
+DOC
+MAP
=VAL :key
=VAL :

hs-hsyaml-json

 invalid_correct
hsyaml-parser: user error (Lexical error near " - a")

java-snakeyaml-event

 invalid_correct
Exception in thread "main" sequence entries are not allowed here
 in 'reader', line 1, column 6:
    key: - a
         ^

	at org.yaml.snakeyaml.scanner.ScannerImpl.fetchBlockEntry(ScannerImpl.java:797)
	at org.yaml.snakeyaml.scanner.ScannerImpl.fetchMoreTokens(ScannerImpl.java:336)
	at org.yaml.snakeyaml.scanner.ScannerImpl.checkToken(ScannerImpl.java:248)
	at org.yaml.snakeyaml.parser.ParserImpl$ParseBlockMappingValue.produce(ParserImpl.java:665)
	at org.yaml.snakeyaml.parser.ParserImpl.peekEvent(ParserImpl.java:165)
	at org.yaml.snakeyaml.Yaml$3.hasNext(Yaml.java:677)
	at org.yaml.editor.Snake2Events.yamlToEvents(Snake2Events.java:111)
	at org.yaml.editor.Snake2Events.main(Snake2Events.java:119)

java-snakeyaml-json

 invalid_correct
Exception in thread "main" sequence entries are not allowed here
 in 'reader', line 1, column 6:
    key: - a
         ^

	at org.yaml.snakeyaml.scanner.ScannerImpl.fetchBlockEntry(ScannerImpl.java:797)
	at org.yaml.snakeyaml.scanner.ScannerImpl.fetchMoreTokens(ScannerImpl.java:336)
	at org.yaml.snakeyaml.scanner.ScannerImpl.checkToken(ScannerImpl.java:248)
	at org.yaml.snakeyaml.parser.ParserImpl$ParseBlockMappingValue.produce(ParserImpl.java:665)
	at org.yaml.snakeyaml.parser.ParserImpl.peekEvent(ParserImpl.java:165)
	at org.yaml.snakeyaml.comments.CommentEventsCollector$1.peek(CommentEventsCollector.java:59)
	at org.yaml.snakeyaml.comments.CommentEventsCollector$1.peek(CommentEventsCollector.java:45)
	at org.yaml.snakeyaml.comments.CommentEventsCollector.collectEvents(CommentEventsCollector.java:140)
	at org.yaml.snakeyaml.comments.CommentEventsCollector.collectEvents(CommentEventsCollector.java:119)
	at org.yaml.snakeyaml.composer.Composer.composeScalarNode(Composer.java:214)
	at org.yaml.snakeyaml.composer.Composer.composeNode(Composer.java:184)
	at org.yaml.snakeyaml.composer.Composer.composeKeyNode(Composer.java:310)
	at org.yaml.snakeyaml.composer.Composer.composeMappingChildren(Composer.java:301)
	at org.yaml.snakeyaml.composer.Composer.composeMappingNode(Composer.java:286)
	at org.yaml.snakeyaml.composer.Composer.composeNode(Composer.java:188)
	at org.yaml.snakeyaml.composer.Composer.getNode(Composer.java:115)
	at org.yaml.snakeyaml.constructor.BaseConstructor.getData(BaseConstructor.java:135)
	at org.yaml.snakeyaml.Yaml$1.next(Yaml.java:514)
	at org.yaml.editor.Snake2Json.yamlToJson(Snake2Json.java:18)
	at org.yaml.editor.Snake2Json.main(Snake2Json.java:25)

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 (1:6)

 1 | key: - a
----------^
 2 |      - b
    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 (internal/modules/cjs/loader.js:778:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:789:10)

js-yaml-event

 invalid_correct
Implicit keys need to be on a single line at line 1, column 8:

key: - a
       ^
+STR
+DOC
+MAP
=VAL :key
+SEQ

js-yaml-json

 invalid_correct
/yaml/bin/js-yaml-json:8
  if (doc.errors.length !== 0) throw doc.errors[0]
                               ^

YAMLParseError: Implicit keys need to be on a single line at line 1, column 8:

key: - a
       ^

    at Composer.onError (/node/node_modules/yaml/dist/compose/composer.js:71:34)
    at Object.resolveBlockMap (/node/node_modules/yaml/dist/compose/resolve-block-map.js:45:13)
    at Object.composeCollection (/node/node_modules/yaml/dist/compose/compose-collection.js:13:36)
    at Object.composeNode (/node/node_modules/yaml/dist/compose/compose-node.js:30:38)
    at Object.composeDoc (/node/node_modules/yaml/dist/compose/compose-doc.js:31:23)
    at Composer.next (/node/node_modules/yaml/dist/compose/composer.js:152:40)
    at next (<anonymous>)
    at Composer.compose (/node/node_modules/yaml/dist/compose/composer.js:134:25)
    at compose.next (<anonymous>)
    at Function.from (<anonymous>)

lua-lyaml-json

 invalid_correct
luajit: 1:1: block sequence entries 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:378: 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 0x5578a7c59f97

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 :key

perl-pp-event

 invalid_correct
Line      : 1
Column    : 6
Expected  : ALIAS BLOCK_SCALAR DOC_END FLOWMAP_START FLOWSEQ_START PLAIN PLAIN_MULTI QUOTED QUOTED_MULTILINE
Got       : DASH
Where     : /perl5/lib/perl5/YAML/PP/Parser.pm line 392
YAML      : "- a\n"
  at /yaml/bin/perl-pp-event line 25.
+STR
+DOC
+MAP
=VAL :key

perl-pp-json

 invalid_correct
Line      : 1
Column    : 6
Expected  : ALIAS BLOCK_SCALAR DOC_END FLOWMAP_START FLOWSEQ_START PLAIN PLAIN_MULTI QUOTED QUOTED_MULTILINE
Got       : DASH
Where     : /perl5/lib/perl5/YAML/PP/Parser.pm line 392
YAML      : "- a\n"
  at /perl5/lib/perl5/YAML/PP/Loader.pm line 94.

perl-pp-perl

 invalid_correct
Line      : 1
Column    : 6
Expected  : ALIAS BLOCK_SCALAR DOC_END FLOWMAP_START FLOWSEQ_START PLAIN PLAIN_MULTI QUOTED QUOTED_MULTILINE
Got       : DASH
Where     : /perl5/lib/perl5/YAML/PP/Parser.pm line 392
YAML      : "- a\n"
  at /perl5/lib/perl5/YAML/PP/Loader.pm line 94.

perl-pplibyaml-event

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

    block sequence entries are not allowed in this context

was found at , line: 1, column: 6

perl-pplibyaml-json

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

    block sequence entries are not allowed in this context

was found at , line: 1, column: 6

perl-pplibyaml-perl

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

    block sequence entries are not allowed in this context

was found at , line: 1, column: 6

perl-refparser-event

 invalid_correct
Parser finished before end of input at /perl5/lib/perl5/YAML/Parser.pm line 4047, <> line 1.

perl-tiny-json

 invalid_correct
YAML::Tiny found illegal characters in plain scalar: '- a' at /yaml/bin/perl-tiny-json line 12.

perl-tiny-perl

 invalid_correct
YAML::Tiny found illegal characters in plain scalar: '- a' at /yaml/bin/perl-tiny-perl line 15.

perl-xs-json

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

    block sequence entries are not allowed in this context

was found at document: 1, line: 1, column: 6

perl-xs-perl

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

    block sequence entries are not allowed in this context

was found at document: 1, line: 1, column: 6

perl-yaml-json

 invalid_correct
YAML Error: Inconsistent indentation level
   Code: YAML_PARSE_ERR_INCONSISTENT_INDENTATION
   Line: 2
   Document: 1
 at /perl5/lib/perl5/YAML/Loader.pm line 804.

perl-yaml-perl

 invalid_correct
YAML Error: Inconsistent indentation level
   Code: YAML_PARSE_ERR_INCONSISTENT_INDENTATION
   Line: 2
   Document: 1
 at /perl5/lib/perl5/YAML/Loader.pm line 804.

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/python3.7/site-packages/yaml/__init__.py", line 75, in parse
    while loader.check_event():
  File "/python/lib/python3.7/site-packages/yaml/parser.py", line 98, in check_event
    self.current_event = self.state()
  File "/python/lib/python3.7/site-packages/yaml/parser.py", line 449, in parse_block_mapping_value
    if not self.check_token(KeyToken, ValueToken, BlockEndToken):
  File "/python/lib/python3.7/site-packages/yaml/scanner.py", line 116, in check_token
    self.fetch_more_tokens()
  File "/python/lib/python3.7/site-packages/yaml/scanner.py", line 215, in fetch_more_tokens
    return self.fetch_block_entry()
  File "/python/lib/python3.7/site-packages/yaml/scanner.py", line 493, in fetch_block_entry
    self.get_mark())
yaml.scanner.ScannerError: sequence entries are not allowed here
  in "<unicode string>", line 1, column 6:
    key: - a
         ^
+STR
+DOC
+MAP
=VAL :key

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/python3.7/site-packages/yaml/__init__.py", line 130, in load_all
    yield loader.get_data()
  File "/python/lib/python3.7/site-packages/yaml/constructor.py", line 45, in get_data
    return self.construct_document(self.get_node())
  File "/python/lib/python3.7/site-packages/yaml/composer.py", line 27, in get_node
    return self.compose_document()
  File "/python/lib/python3.7/site-packages/yaml/composer.py", line 55, in compose_document
    node = self.compose_node(None, None)
  File "/python/lib/python3.7/site-packages/yaml/composer.py", line 84, in compose_node
    node = self.compose_mapping_node(anchor)
  File "/python/lib/python3.7/site-packages/yaml/composer.py", line 133, in compose_mapping_node
    item_value = self.compose_node(node, item_key)
  File "/python/lib/python3.7/site-packages/yaml/composer.py", line 64, in compose_node
    if self.check_event(AliasEvent):
  File "/python/lib/python3.7/site-packages/yaml/parser.py", line 98, in check_event
    self.current_event = self.state()
  File "/python/lib/python3.7/site-packages/yaml/parser.py", line 449, in parse_block_mapping_value
    if not self.check_token(KeyToken, ValueToken, BlockEndToken):
  File "/python/lib/python3.7/site-packages/yaml/scanner.py", line 116, in check_token
    self.fetch_more_tokens()
  File "/python/lib/python3.7/site-packages/yaml/scanner.py", line 215, in fetch_more_tokens
    return self.fetch_block_entry()
  File "/python/lib/python3.7/site-packages/yaml/scanner.py", line 493, in fetch_block_entry
    self.get_mark())
yaml.scanner.ScannerError: sequence entries are not allowed here
  in "<unicode string>", line 1, column 6:
    key: - a
         ^

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/python3.7/site-packages/yaml/__init__.py", line 130, in load_all
    yield loader.get_data()
  File "/python/lib/python3.7/site-packages/yaml/constructor.py", line 45, in get_data
    return self.construct_document(self.get_node())
  File "/python/lib/python3.7/site-packages/yaml/composer.py", line 27, in get_node
    return self.compose_document()
  File "/python/lib/python3.7/site-packages/yaml/composer.py", line 55, in compose_document
    node = self.compose_node(None, None)
  File "/python/lib/python3.7/site-packages/yaml/composer.py", line 84, in compose_node
    node = self.compose_mapping_node(anchor)
  File "/python/lib/python3.7/site-packages/yaml/composer.py", line 133, in compose_mapping_node
    item_value = self.compose_node(node, item_key)
  File "/python/lib/python3.7/site-packages/yaml/composer.py", line 64, in compose_node
    if self.check_event(AliasEvent):
  File "/python/lib/python3.7/site-packages/yaml/parser.py", line 98, in check_event
    self.current_event = self.state()
  File "/python/lib/python3.7/site-packages/yaml/parser.py", line 449, in parse_block_mapping_value
    if not self.check_token(KeyToken, ValueToken, BlockEndToken):
  File "/python/lib/python3.7/site-packages/yaml/scanner.py", line 116, in check_token
    self.fetch_more_tokens()
  File "/python/lib/python3.7/site-packages/yaml/scanner.py", line 215, in fetch_more_tokens
    return self.fetch_block_entry()
  File "/python/lib/python3.7/site-packages/yaml/scanner.py", line 493, in fetch_block_entry
    self.get_mark())
yaml.scanner.ScannerError: sequence entries are not allowed here
  in "<unicode string>", line 1, column 6:
    key: - a
         ^

py-ruamel-event

 invalid_correct
Traceback (most recent call last):
  File "/yaml/bin/py-ruamel-event", line 7, in <module>
    for event in ruamel.yaml.parse(sys.stdin.read()):
  File "/python/lib/python3.7/site-packages/ruamel/yaml/main.py", line 907, in parse
    while loader._parser.check_event():
  File "/python/lib/python3.7/site-packages/ruamel/yaml/parser.py", line 140, in check_event
    self.current_event = self.state()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/parser.py", line 603, in parse_block_mapping_value
    if self.scanner.check_token(ValueToken):
  File "/python/lib/python3.7/site-packages/ruamel/yaml/scanner.py", line 170, in check_token
    self.fetch_more_tokens()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/scanner.py", line 275, in fetch_more_tokens
    return self.fetch_block_entry()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/scanner.py", line 569, in fetch_block_entry
    None, None, 'sequence entries are not allowed here', self.reader.get_mark()
ruamel.yaml.scanner.ScannerError: sequence entries are not allowed here
  in "<unicode string>", line 1, column 6:
    key: - a
         ^ (line: 1)
+STR
+DOC
+MAP
=VAL :key

py-ruamel-json

 invalid_correct
Traceback (most recent call last):
  File "/yaml/bin/py-ruamel-json", line 19, in <module>
    for doc in ruamel.yaml.load_all(sys.stdin.read(), Loader=ruamel.yaml.Loader):
  File "/python/lib/python3.7/site-packages/ruamel/yaml/main.py", line 976, in load_all
    yield loader._constructor.get_data()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/constructor.py", line 106, in get_data
    return self.construct_document(self.composer.get_node())
  File "/python/lib/python3.7/site-packages/ruamel/yaml/composer.py", line 68, in get_node
    return self.compose_document()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/composer.py", line 101, in compose_document
    node = self.compose_node(None, None)
  File "/python/lib/python3.7/site-packages/ruamel/yaml/composer.py", line 138, in compose_node
    node = self.compose_mapping_node(anchor)
  File "/python/lib/python3.7/site-packages/ruamel/yaml/composer.py", line 218, in compose_mapping_node
    item_value = self.compose_node(node, item_key)
  File "/python/lib/python3.7/site-packages/ruamel/yaml/composer.py", line 111, in compose_node
    if self.parser.check_event(AliasEvent):
  File "/python/lib/python3.7/site-packages/ruamel/yaml/parser.py", line 140, in check_event
    self.current_event = self.state()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/parser.py", line 603, in parse_block_mapping_value
    if self.scanner.check_token(ValueToken):
  File "/python/lib/python3.7/site-packages/ruamel/yaml/scanner.py", line 170, in check_token
    self.fetch_more_tokens()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/scanner.py", line 275, in fetch_more_tokens
    return self.fetch_block_entry()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/scanner.py", line 569, in fetch_block_entry
    None, None, 'sequence entries are not allowed here', self.reader.get_mark()
ruamel.yaml.scanner.ScannerError: sequence entries are not allowed here
  in "<unicode string>", line 1, column 6:
    key: - a
         ^ (line: 1)

py-ruamel-py

 invalid_correct
Traceback (most recent call last):
  File "/yaml/bin/py-ruamel-py", line 36, in <module>
    for doc in ruamel.yaml.load_all(sys.stdin.read(), Loader=ruamel.yaml.Loader):
  File "/python/lib/python3.7/site-packages/ruamel/yaml/main.py", line 976, in load_all
    yield loader._constructor.get_data()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/constructor.py", line 106, in get_data
    return self.construct_document(self.composer.get_node())
  File "/python/lib/python3.7/site-packages/ruamel/yaml/composer.py", line 68, in get_node
    return self.compose_document()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/composer.py", line 101, in compose_document
    node = self.compose_node(None, None)
  File "/python/lib/python3.7/site-packages/ruamel/yaml/composer.py", line 138, in compose_node
    node = self.compose_mapping_node(anchor)
  File "/python/lib/python3.7/site-packages/ruamel/yaml/composer.py", line 218, in compose_mapping_node
    item_value = self.compose_node(node, item_key)
  File "/python/lib/python3.7/site-packages/ruamel/yaml/composer.py", line 111, in compose_node
    if self.parser.check_event(AliasEvent):
  File "/python/lib/python3.7/site-packages/ruamel/yaml/parser.py", line 140, in check_event
    self.current_event = self.state()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/parser.py", line 603, in parse_block_mapping_value
    if self.scanner.check_token(ValueToken):
  File "/python/lib/python3.7/site-packages/ruamel/yaml/scanner.py", line 170, in check_token
    self.fetch_more_tokens()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/scanner.py", line 275, in fetch_more_tokens
    return self.fetch_block_entry()
  File "/python/lib/python3.7/site-packages/ruamel/yaml/scanner.py", line 569, in fetch_block_entry
    None, None, 'sequence entries are not allowed here', self.reader.get_mark()
ruamel.yaml.scanner.ScannerError: sequence entries are not allowed here
  in "<unicode string>", line 1, column 6:
    key: - a
         ^ (line: 1)

ruby-psych-json

 invalid_correct
/usr/lib/ruby/2.5.0/psych.rb:405:in `parse': (<unknown>): block sequence entries are not allowed in this context at line 1 column 6 (Psych::SyntaxError)
	from /usr/lib/ruby/2.5.0/psych.rb:405:in `parse_stream'
	from /usr/lib/ruby/2.5.0/psych.rb:488:in `load_stream'
	from /yaml/bin/ruby-psych-json:6:in `<main>'