aeson-match-qq

Declarative JSON matchers.

Motivation

When testing an HTTP service that spouts JSON documents, it's often inconvenient to write out the whole response as the expected value. Sometimes, you only care about a couple specific properties, or simply want to ensure that the response has certain structure. This package provides a quasiquoter to define declarative matchers using a variation of the familiar syntax.

Features

Basic JSON construction

Since this package is heavily inspired by aeson-qq, the parser tries to follow its behavior and has support for optional quotes for simple keys and the #{exp} syntax for Haskell expression interpolation. It currently does not support variable keys though and there are no plans to add them.

Spread-like syntax for arrays and objects

This syntax allows you to match only the part of the structure you care about:

[match| [1, 2, 3, ...] |] matches arrays starting with [1, 2, 3]
[match| {foo: 1, bar: 2, ...} |] matches objects that are supersets of {foo: 1, bar: 2}

Holes

Holes are placeholders that match anything:

[match| _ |] matches any JSON document
[match| {foo: _} |] matches any object that has the foo property.

If a hole is named, its value will be returned from match

[match| {foo: {bar: _n} |] will return {n: 4} if matched with {foo: {bar: 4}}

Case-insensitive strings

A small addition to the JSON syntax that allows string matches that ignore case:

[match| (ci) "foo" |] matches any of "Foo", "fOO", or "FOO".

Unordered arrays

A small addition to the JSON syntax that allows array matches that ignore the order of the elements, for example:

[match| (unordered) [1,2,3] |] matches [3, 1, 2].