Feature Request: JSON-compatible dumper settings

[tom-tan]

YAML 1.1 is almost a superset of JSON and therefore D-YAML can read most of existing JSON files via Loader.

D-YAML also provides Dumper to dump a YAML object to an output range (of course it dumps in YAML format) and we can customize its output format with Dumper#defaultCollectionStyle and Dumper#defaultScalarStyle.

However, we cannot dump a YAML object to an output range in JSON-compatible format due to the following reasons:

• defaultCollectionStyle and defaultScalarStyle seems to be used only if nodes are not generated via Loader.fromString nor Loader.fromFile to keep the original collection and scalar styles and I did not find a way to overwrite the original styles. It would be nice if we have an option to overwrite styles.

  • PoC:

    
    import dyaml;
    import std: appender, stdout;

  enum str = q"EOS

  • hello
  • world EOS";

  auto root = Loader.fromString(str).load; auto dumper = dumper(); dumper.YAMLVersion = null; dumper.defaultCollectionStyle = CollectionStyle.flow;

  dumper.dump(stdout.lockingTextWriter, root);

  - Expected output:
  ```yaml
  [hello, world]

  • Actual output:

  • hello
  • world

• CollectionStyle (type of defaultCollectionStyle) has flow member for flow (i.e., JSON-compatible) style output for sequences and mappings but there are no corresponding members in ScalarStyle to dump an object in JSON-compatible format for scalar types. It would be nice if ScalaStyle has a member for JSON-compatible style for scalar types.

[Herringway]

Currently, the Loader retains the styles of loaded YAML, and the default setting is only used when the nodes do not have styles. It is currently possible to get most of the way there by manually setting the styles on the nodes yourself - see Node.collectionStyle and Node.scalarStyle.

YAML 1.2 support should make this a lot easier though, via schemas (the json schema in particular, naturally).

[Herringway]

Also, JSON scalars use both plain and double quoted styles, depending on their types

[tom-tan]

Thank you for your suggestion!

It is currently possible to get most of the way there by manually setting the styles on the nodes yourself - see Node.collectionStyle and Node.scalarStyle.

Unfortunately they are not available for user code because they have package visibility. Can we make them public?

[Herringway]

Unfortunately they are not available for user code because they have package visibility. Can we make them public?

Whoops! I meant Node.setStyle.

[tom-tan]

I meant Node.setStyle.

Oh, I missed it. I can use it to make a custom dumper for JSON-compatible output.

Thanks!