schemadiff

schemadiff is a lib that shows you the difference between two GraphQL Schemas. It takes two schemas from a string or a file and gives you a list of changes between both versions. This might be useful for:

• Detecting breaking changes before they reach the api clients
• Integrating into CI pipelines to control your api evolution
• Document your api changes and submit them for an approval along with your pull requests.
• Restricting unwanted changes

Installation

The lib requires python3.6 or greater to work. In order to install it run

$ python3 -m pip install graphql-schema-diff

Usage

You can use this package as a lib or as a CLI. You can choose what better suits your needs

As a Lib

from schemadiff import diff, diff_from_file, print_diff

old_schema = """
schema {
    query: Query
} 

type Query {
    a: Int!,
    sum(start: Float=0): Int
}
"""

new_schema = """
schema {
    query: Query
} 

type Query {
    b: String,
    sum(start: Float=1): Int
}
"""

changes = diff(old_schema, new_schema)
print_diff(changes)                   # Pretty print difference
any(change.breaking or change.dangerous for change in changes)    # Check if there was any breaking or dangerous change

# You can also compare from schema files
with open('old_schema.gql', 'w') as f:
    f.write(old_schema)

with open('new_schema.gql', 'w') as f:
    f.write(new_schema)

changes = diff_from_file('old_schema.gql', 'new_schema.gql')
print_diff(changes)

CLI

Inside your virtualenv you can invoke the entrypoint to see its usage options

$ schemadiff -h
Usage: schemadiff [-h] -o OLD_SCHEMA -n NEW_SCHEMA [-j] [-a ALLOW_LIST] [-t] [-r] [-s]

Schema comparator

optional arguments:
  -h, --help            show this help message and exit
  -o OLD_SCHEMA, --old-schema OLD_SCHEMA
                        Path to old graphql schema file
  -n NEW_SCHEMA, --new-schema NEW_SCHEMA
                        Path to new graphql schema file
  -j, --as-json         Output a detailed summary of changes in json format
  -a ALLOW_LIST, --allow-list ALLOW_LIST
                        Path to the allowed list of changes
  -t, --tolerant        Tolerant mode. Error out only if there's a breaking
                        change but allow dangerous changes
  -r, --restrictions    Restricted mode. Error out on restricted changes.
  -s, --strict          Strict mode. Error out on dangerous and breaking
                        changes.

Examples

# Compare schemas and output diff to stdout
schemadiff -o tests/data/simple_schema.gql -n tests/data/new_schema.gql

# Pass a evaluation flag (mixing long arg name and short arg name)
schemadiff --old-schema tests/data/simple_schema.gql -n tests/data/new_schema.gql --strict

# Print output as json with details of each change
schemadiff -o tests/data/simple_schema.gql -n tests/data/new_schema.gql --as-json

# Save output to a json file
schemadiff -o tests/data/simple_schema.gql -n tests/data/new_schema.gql --as-json > changes.json

# Compare schemas ignoring allowed changes
schemadiff -o tests/data/simple_schema.gql -n tests/data/new_schema.gql -a allowlist.json

# Compare schemas restricting adding new types without description
schemadiff -o tests/data/simple_schema.gql -n simple_schema_new_type_without_description.gql -r add-type-without-description

If you run the cli and see a replacement character (�) or a square box (□) instead of the emojis run

$ sudo apt install fonts-noto-color-emoji
$ vim ~/.config/fontconfig/fonts.conf # and paste https://gist.github.com/Ambro17/80bce76d07a6eb74323db2ca9b887263
$ fc-cache -f -v

That should install noto emoji fonts and set is as the fallback font to render emojis 😎

Restricting changes

You can use this library to validate whether your schema matches a set of rules.

Built-in restrictions

The library has its own built-in restrictions ready-to-use. Just append them to the -r command in CLI. You can add as many as you want.

• add-type-without-description Restrict adding new GraphQL types without entering a non-empty description.

• remove-type-description Restrict removing the description from an existing GraphQL type.

• add-field-without-description Restrict adding fields without description.

• remove-field-description Restrict removing the description from an existing GraphQL field.

• add-enum-value-without-description Restrict adding enum value without description.

• remove-enum-value-description Restrict adding enum value without description.

Running the following command, you could restrict type additions without entering a nice description.

# Compare schemas restricting adding new types without description
schemadiff -o tests/data/simple_schema.gql -n simple_schema_new_type_without_description.gql -r add-type-without-description

API Reference

You can also read the API Reference if you want to get a better understanding of the inner workings of the lib

Credits

Implementation was heavily inspired by Marc Giroux ruby version and Kamil Kisiela js implementation.

Logo arrows were adapted from the work of Paul Verhulst @ The Noun Project

Contributors

• @Checho3388: Added the whole evaluate_diff functionality. Thank you!

You can contribute reporting bugs, writing issues or pull requests for any new features!