Crate serde_tagged

Tagging values for de-/serialization

serde does not provide a way to store type-information during serialization, thus de-/serializing trait-objects requires a considerable amount of boilerplate code to work. This library aims to help with that by providing multiple ways to store information, i.e. a tag, associated with a value and later retreive that information during deserialization. The retreived tag information can then be used to select a type-specific deserializer.

A tag can be almost any type, its requirements mainly depend on what you want to use it for. It should implement Serialize and Deserialize (otherwise it would of course be impossible to de-/serialize it). It should also provide means for comparison, which is required to access the specific deserializer associated with that tag (unless the tag serves another purpose). Further restrictions on the tag type may be imposed by the data- and tag-format you choose (e.g. JSON only allows strings as keys in JSON-objects).

This library provides multiple formats to store (and retreive) tags, that are somewhat similar to the way enums can be tagged in serde. The (currently) supported formats are:

• externally tagged, as in { <tag> => <value> }
• internally tagged (i.e. embedded in the value)
• adjacently tagged using tuples, as in ( <tag>, <value> )
• adjacently tagged using maps, as in { <tag-key> => <tag>, <value-key> => <value> }
• adjacently tagged using structs, as in { <tag-key>: <tag>, <value-key>: <value> }

A quick overview

This crate is separated into two main modules: ser for serialization and de for deserialization. Both modules contain further submodules, each representing a separate tagging-format.

Serialization

For each tagging-format both, a serialize function and a Serializer are provided, which allow for values to be serialized with a pre-existing serializer defining the data format, a tag, and possibly further format-specific parameters. You should always prefer the serialize function to the Serializer as it, in most cases, allows for a better performance.

Note: Tagged serialization requires access to a Serializer, however some data formats do not provide direct access to the serializer. In such a case you could create a wrapper-type with a custom Serialize implementation.

Deserialization

For deserialization, the deserialize function (and in some cases also variants of it) are provided in the respective format-modules. Have a look the respective function documentation for more details.

Examples

For some examples have a look at the examples directory in the repository.

Modules

• de
  Deserialization of tagged values.
• ser
  Serialization of tagged values.
• util
  Utilities for de-/serialization.