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 schemasresult.identical?returns true if the two schemas were identicalresult.breaking_changesreturns the list of breaking changes found between schemas.result.non_breaking_changesreturns the list of non-breaking changes found between schemas.result.dangerous_changesreturns the list of dangerous changes found between schemas.result.changesreturns 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.