Re:Decoding JSON sum types in Go without panicking
by mccanne on Thursday March 20, 2025 @11:09AM
(#43424471)
And somewhat ironically here, SuperDB not only implements sum-type decoding of JSON in package unpack, but it also implements native sum types in a superset of JSON that we call Super JSON (with a query language that understands how to rip and stitch sum types for columnar analytics... work in progress)
Decoding sum types into Go interface values is obviously tricky stuff, but it gets even harder when you have recursive data structures as in an abstract syntax tree (AST). The article doesn't address this. Since there wasn't anything out there to do this, we built a little package called "unpack" as part of the SuperDB project.
The package is here...
https://github.com/brimdata/super/blob/main/pkg/unpack/refle...
and an example use in SuperDB is here...
https://github.com/brimdata/super/blob/main/compiler/ast/unp...
Sorry it's not very well documented, but once we got it working, we found the approach quite powerful and easy.