Introducing new transform to override schema field config

[santino]

Description

GraphQL Mesh, and underlying GraphQL Tools, make it easy and convenient to extend schemas, merge schemas and types, add middlewares to resolvers (composers), and much more.

However, it seems there is not really a way to override parts of a schema, such as overriding types for fields.
This transform introduces this functionality.
The transform was initially meant to hoist fields, but during development, it became much more than that.

You can transform a field by selecting the base type and field name (current) and the target type and field name (to be).
This is very simple when you want to hoist fields.
However, the transform also allows you to pass additional typeDefs so that you can create new GraphQL Types to be used as a target (to be).
The transform provides built-in functionality to hoist field values or replace the entire fieldConfig (including the resolver function) with the targeted one.
However, it also allows adding a composer to each rule so that custom logic can be built on each resolver function.
The composer is fundamental for instance when hoisting values for fields that have been renamed, especially on a bare schema, because the transform cannot be aware of the shape of the raw resolver result; so manual adjustments are necessary.
Obviously, the composer can be used to completely ignore the original resolver for a field and execute a new resolver function instead; which might be necessary when overriding fields in general (so beyond the hoisting scope).

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

I have added unit tests for the new transform.
These make a good example of how the transform can be used.

I plan to add more unit tests to cover scenarios where multiple config options are combined together.

Checklist:

• I have followed the CONTRIBUTING doc and the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests and linter rules pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Further comments

This PR is still a draft as it requires an agreement to be reached on the proposed transform.
Current transform only implements bare mode, we should define if wrap is required and estimate effort to get it working.

I believe this transform has huge potential.
Moving forward we can extend functionalities to override input types and arguments for instance.

[changeset-bot]

🦋 Changeset detected

Latest commit: b7f244a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 74 packages

Name	Type
@graphql-mesh/replace-field	Minor
@graphql-mesh/types	Minor
@graphql-mesh/website	Minor
@graphql-mesh/config	Patch
@graphql-mesh/runtime	Patch
@graphql-mesh/utils	Patch
@graphql-mesh/cache-file	Patch
@graphql-mesh/cache-inmemory-lru	Patch
@graphql-mesh/cache-localforage	Patch
@graphql-mesh/cache-redis	Patch
@graphql-mesh/cache-store	Patch
@graphql-mesh/graphql	Patch
@graphql-mesh/grpc	Patch
@graphql-mesh/json-schema	Patch
@graphql-mesh/mongoose	Patch
@graphql-mesh/mysql	Patch
@graphql-mesh/neo4j	Patch
@graphql-mesh/odata	Patch
@graphql-mesh/openapi	Patch
@graphql-mesh/postgraphile	Patch
@graphql-mesh/soap	Patch
@graphql-mesh/thrift	Patch
@graphql-mesh/tuql	Patch
@graphql-mesh/transform-cache	Patch
@graphql-mesh/transform-encapsulate	Patch
@graphql-mesh/transform-extend	Patch
@graphql-mesh/transform-federation	Patch
@graphql-mesh/transform-filter-schema	Patch
@graphql-mesh/transform-mock	Patch
@graphql-mesh/transform-naming-convention	Patch
@graphql-mesh/transform-prefix	Patch
@graphql-mesh/transform-rename	Patch
@graphql-mesh/transform-resolvers-composition	Patch
@graphql-mesh/transform-snapshot	Patch
@graphql-mesh/transform-type-merging	Patch
@graphql-mesh/merger-bare	Patch
@graphql-mesh/merger-federation	Patch
@graphql-mesh/merger-stitching	Patch
@graphql-mesh/cli	Patch
@graphql-mesh/container	Patch
odata-msgraph-programmatic-ts	Patch
odata-msgraph-programmatic	Patch
postgres-geodb-example	Patch
typescript-location-weather-example	Patch
openapi-react-weatherbit	Patch
json-machete	Patch
@graphql-mesh/store	Patch
neo4j-example	Patch
federation-handler-example	Patch
graphql-file-upload-example	Patch
covid-mesh	Patch
type-merging-batching-example	Patch
grpc-example	Patch
grpc-reflection-example	Patch
hasura-openbrewery-geodb	Patch
json-schema-hello-world	Patch
json-schema-example	Patch
json-schema-fhir	Patch
json-schema-subscriptions	Patch
mongoose-example	Patch
mysql-employees	Patch
mysql-rfam	Patch
odata-microsoft-graph-example	Patch
odata-trippin-example	Patch
javascript-wiki	Patch
openapi-stackexchange	Patch
openapi-stripe	Patch
openapi-subscriptions	Patch
openapi-youtrack	Patch
country-info-example	Patch
soap-demo	Patch
soap-netsuite	Patch
thrift-calculator	Patch
chinook	Patch

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[ardatan]

@santino I think we can merge this :) You can add a changeset so we can release

[santino]

Hey @ardatan,
I have added changeset and introduced documentation for this new transform.

Currently, this supports only bare mode.
We should work on potentially introducing wrap mode, but I figured out it requires a lot of custom code, and probably would be better to introduce a transform in graphql-tools (or in mesh, but still graphql-tools like) to cover this functionality.

In the meantime, this can be merged and released.

[ardatan]

Thanks @santino !