internal/core/adt: "fix" disjunction resolution

The recent performance improvement eliminated disjuncts
too aggressively, causing some disjuncts to disappear.
Early elimination prevents exponential blowup, but of course
it should not make it incorrect.

Note that for most common uses, like protobuf and K8s
structs with discriminator fields, special optimizations exist
that make this linear. But this has not been implemented yet.

Now this fix exposed another bug. This bug was deliberate to
work around a limitation of default values when representing
oneOf fields. We planned to introduce a "required field" annotation
which would also allow to represent these kind of semantics
much more elegantly.

For now, though, we are stuck in a position that more than one
oneOf field cannot be represented properly with defaults.
We fix it for now in an even more AWFUL way, and instead work
towards a proper solution based on required fields.

Issue #726

Change-Id: Id4bcd0445612e12fba48a744654de4e1852c552e
Reviewed-by: Paul Jolly <>
Reviewed-by: Marcel van Lohuizen <>
6 files changed
tree: a2d932a4cacdbb36e7c7a04aaad184b570221ef2
  1. .dockerignore
  2. .gitattributes
  3. .github/
  4. .gitignore
  5. .goreleaser.yml
  8. Dockerfile
  11. _scripts/
  12. cmd/
  13. codereview.cfg
  14. cue.mod/
  15. cue/
  16. cuego/
  17. doc/
  18. encoding/
  19. go.mod
  20. go.sum
  21. internal/
  22. pkg/
  23. tools.go
  24. tools/

Go Reference Github GolangCI Go 1.13+ platforms

The CUE Data Constraint Language

Configure, Unify, Execute

CUE is an open source data constraint language which aims to simplify tasks involving defining and using data.

It is a superset of JSON, allowing users familiar with JSON to get started quickly.

What is it for?

You can use CUE to

  • define a detailed validation schema for your data (manually or automatically from data)
  • reduce boilerplate in your data (manually or automatically from schema)
  • extract a schema from code
  • generate type definitions and validation code
  • merge JSON in a principled way
  • define and run declarative scripts


CUE merges the notion of schema and data. The same CUE definition can simultaneously be used for validating data and act as a template to reduce boilerplate. Schema definition is enriched with fine-grained value definitions and default values. At the same time, data can be simplified by removing values implied by such detailed definitions. The merging of these two concepts enables many tasks to be handled in a principled way.

Constraints provide a simple and well-defined, yet powerful, alternative to inheritance, a common source of complexity with configuration languages.

CUE Scripting

The CUE scripting layer defines declarative scripting, expressed in CUE, on top of data. This solves three problems: working around the closedness of CUE definitions (we say CUE is hermetic), providing an easy way to share common scripts and workflows for using data, and giving CUE the knowledge of how data is used to optimize validation.

There are many tools that interpret data or use a specialized language for a specific domain (Kustomize, Ksonnet). This solves dealing with data on one level, but the problem it solves may repeat itself at a higher level when integrating other systems in a workflow. CUE scripting is generic and allows users to define any workflow.


CUE is designed for automation. Some aspects of this are:

  • convert existing YAML and JSON
  • automatically simplify configurations
  • rich APIs designed for automated tooling
  • formatter
  • arbitrary-precision arithmetic
  • generate CUE templates from source code
  • generate source code from CUE definitions (TODO)

Download and Install

Install using Homebrew

Using Homebrew, you can install using the CUE Homebrew tap:

brew install cuelang/tap/cue

Install From Source

If you already have Go installed, the short version is:

go get -u

This will install the cue command line tool.

For more details see Installing CUE.

Learning CUE

The fastest way to learn the basics is to follow the tutorial on basic language constructs.

A more elaborate tutorial demonstrating of how to convert and restructure an existing set of Kubernetes configurations is available in written form.



Our canonical Git repository is located at

To contribute, please read the Contribution Guide.

To report issues or make a feature request, use the issue tracker.

Changes can be contributed using Gerrit or Github pull requests.


You can get in touch with the cuelang community in the following ways:

Unless otherwise noted, the CUE source files are distributed under the Apache 2.0 license found in the LICENSE file.

This is not an officially supported Google product.