Introduction to Tags topic

Tags are also node properties declared in tandem with an anchor but never with an alias. The package has an expressive way to write tags in Dart (in line with the spec). They form the backbone of the custom resolvers this package allows. Do not skip this section (compacted version of the spec). You can use this as a reference to read the spec (Create an issue if there is an error).

Every node tag begins with the ! indicator. This signifies the start of a node tag's tag handle. There are 3 types of tag handles in YAML.

Primary Tag Handle !

Has a single !. You can use this to declare your own tags without declaring a global tag to resolve them.

Secondary Tag Handle !!

Declared as !!. Reserved to tags that instruct the parser on how these node's can be represented based on the YAML spec. To that effect, tags with this handle are restricted to those the spec recognizes and are always resolved to the official YAML global tag prefix, tag:yaml.org,2002:. This handle can be overriden by a custom global tag prefix. See the supported tags section.

Named Tag Handle

Starts with a ! + a custom name + ! closing indicator. This handle must have a corresponding global tag (more on this later).

%TAG !example! !named-must-have-global
---
[
  !my-tag scalar, # Custom primary tag

  !!int 24, # Secondary tag supported by yaml

  # Named tag resolved to "!named-must-have-global-tag"
  !example!-tag just-a-value,
]