2019-05-13 17:01:24 +03:00
The Unison codebase format needs to be able to store metadata about definitions it contains, such as:
* Author, copyright holder
* Creation date
* License
* API docs
* Boolean indicating whether a definition is a test, needed to support incremental test evaluation
* Comments that annotate subpaths of the definition
* ...
Some desired features:
* We probably won't know all the kinds of metadata in advance, so having it be extensible would be good.
* Metadata should probably be versioned. (Example: what if you want to change the license of a definition?)
A simple proposal is to just add metadata information at each level of the versioned namespace tree:
```Haskell
-- Metadata is always just a link to some other term
newtype Metadata = Metadata Reference
newtype MetadataType = MetadataType Text -- "License", "Creation date", etc
data Branch0 =
Branch0 { _terms :: Relation NameSegment Referent
, _types :: Relation NameSegment Reference
, _edits :: ...
, _metadata :: Relation (MetadataType, Referent) Metadata }
```
That's it. Metadata is just a "link", a lightweight reference to some other definition.
We don't try to make `MetadataType` more strongly typed. It's just a string, its meaning determined by convention. For instance, the default CLI viewer can look for an "API docs" key, and use that in its display.
2019-05-13 20:11:59 +03:00
Nothing special for the on disk format, it can just be encoded the same way as the other relations in the Branch0.
