dump_yaml

A spec-compliant YAML dumper that prioritizes clean YAML documents as its default configuration. It supports all features implemented in most (if not all) YAML parsers.

Principles

1. 100% spec-compliant - All supported features are included in the YAML spec and vice versa (all YAML features are supported).
2. Simplicity - No YAML features are shoved into your files unless you explicitly use them.
3. Configurability - The dumper includes features you can use to accurately control the final output of your YAML files. (See next section).

What's Included

Dumping YAML is tricky but incredibly satisfying when gotten right. The YamlDumper exposed is built for configurability and reusability. The dumper accepts a config with 2 options:

• styling - Controls the node styles used when dumping.
• formatting - Controls the final YAML output.

Styling

The package also exposes additional utility classes:

• TreeBuilder - builds the YAML representation tree that is dumped.
• DumpableView - a mutable lightweight wrapper class that exposes all the YAML features you may require for a node.

Formatting

Use this option to configure:

1. Starting indent.
2. Indentation step for nested nodes of a collection.
3. Line ending used for your files.

Usage

Dumper oneliner

print(dumpAsYaml(['hello', 'there']));

- hello
- there

Streaming support

Tweak the dumper to match your requirements. A simple example:

final someLazyStream = StreamController<String>();

final dumper = YamlDumper(
  config: Config.defaults(),
  buffer: YamlBuffer.toStream(someLazyStream),
);

dumper.dump([
  'I',
  'love',
  {'streaming': 'things'},
  'lazily',
]);

someLazyStream.close();
final chunks = await someLazyStream.stream.toList();

/*
 * Lazy chunks as the dumper walks the YAML representation tree for your
 * object.

[, -,  , I,
, , -,  , love,
, , -,  , streaming, :,  , things,
, , -,  , lazily,
]

*/
print(chunks);

/*
- I
- love
- streaming: things
- lazily
*/
print(chunks.join());

Support for YAML features

• A bit sophisticated. A DumpableView provides granular control over the TreeBuilder but still relies on the same builder for housekeeping. For example, ScalarStyle.literal is not allowed in flow styles in YAML.

final configurable = [
  ScalarView('hello YAML, from world')
    ..anchor = 'scalar'
    ..scalarStyle = ScalarStyle.literal // Not allowed in YAML flow.
    ..commentStyle = CommentStyle.trailing
    ..comments.addAll(['trailing', 'comments']),

  YamlMapping({'key': 24, 'next': Alias('scalar')})
      ..forceInline = true
      ..commentStyle = CommentStyle.block
      ..comments.addAll(['block', 'comments'])
];

print(
  dumpAsYaml(
    configurable,
    config: Config.yaml(
      includeYamlDirective: true,
      styling: TreeConfig.flow(
        forceInline: false,
        scalarStyle: ScalarStyle.doubleQuoted,
        includeSchemaTag: true,
      ),
      formatting: Formatter.config(rootIndent: 3, indentationStep: 1),
    ),
  ),
);

%YAML 1.2
---
   !!seq [
    &scalar "hello YAML, from world" # trailing
                                     # comments
    ,
    # block
    # comments
    {!!str "key": !!int "24", !!str "next": *scalar}
   ]

Documentation & Examples (Still in progress 🏗️)

• The docs folder in the repository. Use the table of contents as a guide.
• Visit pub guide which provides an automatic guided order for the docs above.

Contribution

All contributions are welcome.

• Create an issue if you need help or any features you'd like.
• See guide on how to make contributions to this repository.