v0.4.2

Rego

This release changes the Rego syntax. The two main changes are:

• Expressions are now separated by semicolons (instead of commas). When writing rules, the semicolons are optional.
• Rules are no longer written in the form: head :- body. Instead they are written as head { body }.

Also:

• Set, array, and object literals now support trailing commas.
• To declare a set literal with one element, you must include a trailing comma, e.g., { foo, }.
• Arithmetic and set operations can now be performed with infix notation, e.g., x = 2 + 1.
• Sets can be referred to like objects and arrays now (#243). E.g., p[_].foo = 1 # check if element in has attr foo equal to 1.

Evaluation

This release changes the evaluation behaviour for packages. Previously, if a package contained no rules OR all of the rules were undefined when evaluated, a query against the package path would return undefined. As of v0.4.2 the query will return an empty object.

REST API

This release changes the Data API to return an HTTP 200 response if the document is undefined. The message body will contain an object without the result property.

Fixes

• Allow sets to be treated like objects/arrays

Miscellaneous

• Added high level API for Go users. See github.com/open-policy-agent/opa/rego package.
• Improved expression String() function to handle infix operators better.
• Added support for set intersection and union built-ins. See language docs.