65 lines
2.2 KiB
Markdown
65 lines
2.2 KiB
Markdown
|
# Differences between D:YAML and the YAML specification
|
||
|
|
|
||
|
|
There are some differences between D:YAML and the YAML 1.1
|
||
|
|
specification. Some are caused by difficulty of implementation of some
|
||
|
|
features, such as multiple Unicode encodings within single stream, and
|
||
|
|
some by unnecessary restrictions or ambiguities in the specification.
|
||
|
|
|
||
|
|
Still, D:YAML tries to be as close to the specification as possible. It
|
||
|
|
should never load documents with different meaning than according to the
|
||
|
|
specification, and documents that fail to load should be very rare (for
|
||
|
|
instance, very few files use multiple Unicode encodings).
|
||
|
|
|
||
|
|
## List of known differences:
|
||
|
|
|
||
|
|
Differences that can cause valid YAML documents not to load:
|
||
|
|
|
||
|
|
- No support for byte order marks and multiple Unicode encodings in a
|
||
|
|
stream.
|
||
|
|
|
||
|
|
- Plain scalars in flow context cannot contain `,`, `:` and `?`. This
|
||
|
|
might change with `:` in the future. See
|
||
|
|
<http://pyyaml.org/wiki/YAMLColonInFlowContext> for details.
|
||
|
|
|
||
|
|
- The specification does not restrict characters for anchors and
|
||
|
|
aliases. This may lead to problems, for instance, the document:
|
||
|
|
|
||
|
|
[ *alias, value ]
|
||
|
|
|
||
|
|
can be interpteted in two ways, as:
|
||
|
|
|
||
|
|
[ "value" ]
|
||
|
|
|
||
|
|
and:
|
||
|
|
|
||
|
|
[ *alias , "value" ]
|
||
|
|
|
||
|
|
Therefore we restrict aliases and anchors to ASCII alphanumeric
|
||
|
|
characters.
|
||
|
|
|
||
|
|
- The specification is confusing about tabs in plain scalars. We don't
|
||
|
|
use tabs in plain scalars at all.
|
||
|
|
|
||
|
|
- There is no support for recursive data structures in DYAML.
|
||
|
|
|
||
|
|
Other differences:
|
||
|
|
|
||
|
|
- Indentation is ignored in the flow context, which is less
|
||
|
|
restrictive than the specification. This allows code such as:
|
||
|
|
|
||
|
|
key: {
|
||
|
|
}
|
||
|
|
|
||
|
|
- Indentation rules for quoted scalars are loosed: They don't need to
|
||
|
|
adhere indentation as `"` and `'` clearly mark the beginning and the
|
||
|
|
end of them.
|
||
|
|
|
||
|
|
- We allow `_` in tag handles.
|
||
|
|
|
||
|
|
- Right now, two mappings with the same contents but different
|
||
|
|
orderings are considered unequal, even if they are unordered
|
||
|
|
mappings. This is because all mappings are ordered in the D:YAML
|
||
|
|
implementation. This should change in future, once D associative
|
||
|
|
arrays work with variant types or a map class or struct appears in
|
||
|
|
Phobos.
|