= Bugs in YAML specification =

[[PageOutline]]

== Bugs in the Type Library ==

'''`!!float`''': The regular expression matches a single dot "`.`".

'''`!!bool`''': Single characters y, Y, n, N are still present as values for bool

== Bugs in Examples ==

''Example 2.17. Hex'': decimal instead of hex format
{{{
hexesc:  "\x13\x10 is \r\n"
}}}
Correct:
{{{
hexesc:  "\x0D\x0A is \r\n"
}}}

''Example 2.19. Integers'': invalid comma in
{{{
decimal: +12,345
}}}
Correct:
{{{
decimal: +12_345
}}}

''Example 2.20. Floating Point'': invalid comma in
{{{
fixed: 1,230.15
}}}
Correct:
{{{
fixed: 1_230.15
}}}

''Example 10.7. Flow Mapping Keys'': missing comma in
{{{
{
?° : value # Empty key
}}}
and
{{{
simple key : value
}}}


''Example 9.33. Final Empty Lines'': extra '''!!seq [''' in
{{{
---
!!seq [
  !!str "folded line\n\
}}}
The same bug in
 * ''Example 9.25. Literal Scalar'',
 * ''Example 9.29. Folded Scalar'',
 * ''Example 9.30. Folded Lines'',
 * ''Example 9.31. Spaced Lines'',
 * ''Example 9.32. Empty Separation Lines''.


''Example 8.1. Node Properties'': a simple key should be limited to a single line:
{{{
!!str
 &a1
  "foo" : !!str bar
}}}

''Example 8.15. Completely Empty Block Nodes'':
Either remove '''seq:''' from the left side, or add it to the right side.

The same example: extra comma in
{{{
  : bar,
}}}

''Example 5.3. Block Structure Indicators'':
{{{
  ? sky
  : blue
  ? sea : green
}}}
is interpreted as
{{{
  !!map {
    ? !!str "sky" : !!str "blue",
    ? !!str "sea" : !!str "green",
  }
}}}
Correct:
{{{
  !!map {
    ? !!str "sky" : !!str "blue",
    ? !!map { ? !!str "sea" : !!str "green" } : !!null "",
  }
}}}

''Example 6.7. Empty Lines'': invalid indicators in
{{{
!!seq {
}}}

''Example 7.8. Tag Handles'': missing comma in
{{{
  !<tag:yaml.org,2002:str> "string"
}}}

''Example 8.1. Node Properties'': different case of anchor and alias:
{{{
  ? &A1 !!str "foo"
}}}
and
{{{
  : *a1
}}}
Anchors are case sensitive, right?

''Example 8.9. Flow Content'': the '''sequence''' sequence is invalid:
{{{
    ? !!str "sequence" : !!seq [
      ? !!str "entry",
      : !!map {
        ? !!str "key" : !!str "value"
    } ],
}}}
Correct:
{{{
    ? !!str "sequence" : !!seq [
      !!str "entry",
      !!map {
        ? !!str "key" : !!str "value"
    } ],
}}}


''Example 8.9. Flow Content'': extra ''':''' in
{{{
  ? !!str "collections": : !!map {
}}}
and in
{{{
    ? !!str "mapping": : !!map {
}}}

''Example 8.13. Completely Empty Flow Nodes'': extra comma in
{{{
  ? !!str "",
  : !!str "bar",
}}}

''Example 8.15. Completely Empty Block Nodes'': extra comma in
{{{
    ? !!str "",
    : !!str "bar",
}}}

''Example 9.15. Document Marker Scalar Content'': extra comma in
{{{
  ? !!str "...",
  : !!str "bar"
}}}

''Example 9.23. Block Scalar Chomping'': should be '''!!map {''' instead of '''!seq [''' in
{{{
!!seq [
  ? !!str "strip"
  : !!str "# text",
}}}

''Example 9.24. Empty Scalar Chomping'': should be '''!!map {''' instead of '''!seq [''' in
{{{
!!seq [
  ? !!str "strip"
  : !!str "",
}}}

''Example 10.5. Block Sequence Entry Types'': missing comma after ''']''' in
{{{
    !!str "two",
  ]
  !!map {
}}}

''Example 10.12. Block Mappings'': extra comma in
{{{
    ? !!str "key",
}}}

''Example 10.15. In-Line Block Mappings'': Right side - '''{''' instead of '''[''':
{{{
%YAML 1.1
---
!!seq {
}}}

''Example 5.14. Escaped Characters'':
Right side - should be '''\x0C''' in the line
{{{
 \x22 \x07 \x08 \x1B \0C
}}}

''Example 10.10. Flow Mapping Key: Value Pairs'':
The tag for empty scalars should be '''!null''', not '''!str'''. Compare:
{{{
? explicit key3,     # Empty value
}}}
with
{{{
  ? !!str "explicit key3"
  : !!str "",
}}}

Correct:
{{{
  ? !!str "explicit key3"
  : !!null "",
}}}

The same problem in
 * ''Example 7.10. Documents'',
 * ''Example 8.13. Completely Empty Flow Nodes'',
 * ''Example 8.15. Completely Empty Block Nodes'',
 * ''Example 10.5. Block Sequence Entry Types'',
 * ''Example 10.7. Flow Mapping Keys'',
 * ''Example 10.9. Flow Mapping Values'',
 * ''Example 10.11. Single Pair Mappings'',
 * ''Example 10.13. Explicit Block Mapping Entries'',
 * ''Example 10.14. Simple Block Mapping Entries'',


''Example 9.12. Plain Characters'':
Left side has not comma before '''and'''. Compare
{{{
- Up, up and away!
}}}
with
{{{
!!str "Up, up, and away!",
}}}

Correct:
{{{
- Up, up, and away!
}}}

== Not bugs, but might be invalid in the future ==

''Example 9.12. Plain Characters''. ''':''' might be prohibited for plain scalars in the flow context:
{{{
# Outside flow collection:
- ::std::vector
- Up, up and away!
- -123
# Inside flow collection:
- [ ::std::vector,
  "Up, up and away!",
  -123 ]
}}}

Empty content might be prohibited in the flow context.

''Example 8.12. Flow Nodes in Flow Context'':
{{{
[
  Without properties,
  &anchor "Anchored",
  !!str 'Tagged',
  *anchor, # Alias node
  !!str,   # Empty plain scalar
]
}}}

''Example 10.7. Flow Mapping Keys''
{{{
{
?° : value # Empty key
? explicit
 key: value,
simple key : value
[ collection, simple, key ]: value
}
}}}

There is a problem when you allow constructions like
{{{
{ !!str, }
}}}
because URIs may include the ''',''' and ''':''' characters. Suppose that we use a Perl-specific tag
like '''!!perl/ref/YAML::Parser''' in
{{{
{ !!perl/ref/YAML::Parser, }
}}}
How it should be interpreted? Is '''::''' a delimiter or a part of the URI?
The above examples may be easily rewritten
{{{
{
? ~ : value # Empty key
}
}}}

{{{
[
  *anchor, # Alias node
  '',   # Empty plain scalar
]
}}}

== Anchors and Tags eat too much ==

It's easier to see this problem for Anchors. Problematic rules are:

{{{
c-ns-alias-node  	 ::=   	 “*”  ns-anchor-name
c-ns-anchor-property  	 ::=   	 “&”  ns-anchor-name
ns-anchor-name  	 ::=   	 ns-char+
}}}

'''ns-char''' will eat too much. It's bad, especially for flow collections because it may eat the delimiter comma.

The following example clearly shows the ambiguity:

{{{
[ &alias, value ]
}}}

It can be parsed both as '''["", "value"]''' and as '''["value"]'''.

Compare it with an example from the spec:

''Example 8.12. Flow Nodes in Flow Context:''
{{{
[
  Without properties,
  &anchor "Anchored",
  !!str 'Tagged',
  *anchor, # Alias node
  !!str,   # Empty plain scalar
]
}}}

Solution: restrict '''ns-anchor-name'''.

The '''ns-uri-char''' definition allows commas so Tags have the same problem.
Unfortunately you cannot just forbid commas because of the tags like '''!<tag:yaml.org,2002:str>'''.

A probable solution is to allow commas only between '''<''' and '''>'''. Another solution is to forbid
empty plain scalars in flow context.

Another solution: require '''s-separate''' after Tags, Anchors, and Aliases. It's not really intuitive since
it will force you to write '''[ *alias_, foo]''' instead of '''[ *alias, foo]'''.

Now I think the best solution is to restrict '''ns-anchor-name''' to '''nb-plain-char-in+'''
and to forbid empty scalar content in flow collections. So you should write
{{{
[
  Without properties,
  &anchor "Anchored",
  !!str 'Tagged',
  *anchor, # Alias node
  !!str '',   # Empty plain scalar
]
}}}

== Line break is required before block collections ==

According to the spec, a document must have at least one leading line break before the real
content. It makes simple documents such as ''Example 2.1'' invalid:
{{{
- Mark McGwire
- Sammy Sosa
- Ken Griffey
}}}

The relevant production rules:

{{{
l-implicit-document       ::= s-ignored-space*
                              ns-l+block-node(-1,block-in)
                              l-document-suffix?

ns-l+block-node(n,c)      ::= ns-l+block-in-block(n,c)
                            | ns-l+flow-in-block(n,c)

ns-l+block-in-block(n,c)  ::= ( c-ns-properties(n+1,c) s-separate(n+1,c) )?
                              c-l+block-content(n,c)

c-l+block-content(n,c)    ::= c-l+block-scalar(n)
                            | c-l-block-collection(>n,c)

c-l-block-collection(n,c) ::= c-l-block-sequence(n,c) | c-l-block-mapping(n)

c-l-block-sequence(n,c)   ::= c-l-comments l-block-seq-entry(n,c)+
}}}

The last rule is the one that requires a line break since '''c-l-comments'''
always ended with a line break.