GraphQL::SchemaComparator

GraphQL::SchemaComparator is a GraphQL Schema comparator. What does that mean? GraphQL::SchemaComparator takes two GraphQL schemas and outputs a list of changes between versions. This is useful for many things:

Breaking Change detection
Applying custom rules to schema changes
Building automated tools like linters

Installation

Add this line to your application's Gemfile:

gem 'graphql-schema_comparator'

And then execute:

$ bundle

Or install it yourself as:

$ gem install graphql-schema_comparator

CLI

GraphQL::SchemaComparator comes with a handy CLI to help compare two schemas using the command line.

After a gem install graphql-schema_comparator, use the CLI this way:

Commands:
  schema_comparator compare OLD_SCHEMA NEW_SCHEMA  # Compares OLD_SCHEMA with NEW_SCHEMA and returns a list of changes
  schema_comparator help [COMMAND]                 # Describe available commands or one specific command

Where OLD_SCHEMA and NEW_SCHEMA can be a string containing a schema IDL or a filename where that IDL is located.

Example

$ ./bin/schema_comparator compare "type Query { a: A } type A { a: String } enum B { A_VALUE }" "type Query { a: A } type A { b: String } enum B { A_VALUE ANOTHER_VALUE }"
⏳  Checking for changes...
🎉  Done! Result:

Detected the following changes between schemas:

🛑  Field `a` was removed from object type `A`
⚠️  Enum value `ANOTHER_VALUE` was added to enum `B`
✅  Field `b` was added to object type `A`

Usage

GraphQL::SchemaComparator, provides a simple api for Ruby applications to use.

Docs

http://www.rubydoc.info/github/xuorig/graphql-schema_comparator/master/GraphQL/SchemaComparator

GraphQL::SchemaComparator.compare

The compare method takes two arguments, old_schema and new_schema, the two schemas to compare.

You may provide schema IDL as strings, or provide instances of GraphQL::Schema.

The result of compare returns a SchemaComparator::Result object, from which you can access information on the changes between the two schemas.

result.breaking? returns true if any breaking changes were found between the two schemas
result.identical? returns true if the two schemas were identical
result.breaking_changes returns the list of breaking changes found between schemas.
result.non_breaking_changes returns the list of non-breaking changes found between schemas.
result.dangerous_changes returns the list of dangerous changes found between schemas.
result.changes returns the full list of change objects.

Change Objects

GraphQL::SchemaComparator returns a list of change objects. These change objects all inherit from Changes::AbstractChange

Possible changes are all found in changes.rb.

Change Criticality

Each change object has a #criticality method which returns a Changes::Criticality object. This objects defines how dangerous a change is to a schema.

The different levels of criticality (non_breaking, dangerous, breaking) are explained here: https://github.com/xuorig/graphql-schema_comparator/blob/master/lib/graphql/schema_comparator/changes/criticality.rb#L6-L19

The gem is available as open source under the terms of the MIT License.

TheMetalCode/graphql-schema_comparator