Merge pull request #794 from snewcomer/rfc-642

Simplifying Schema Definition Service type signatures

Author: snewcomer

text/0794-ember-data-schema-definition-service-simplify.md

@@ -0,0 +1,66 @@
+---
+Stage: Accepted
+Start Date: 2022-02-12
+Release Date: Unreleased
+Release Versions:
+  ember-source: vX.Y.Z
+  ember-data: vX.Y.Z
+Relevant Team(s): ember-data 
+RFC PR: https://github.com/emberjs/rfcs/pull/794
+---
+
+# Simplify Schema Definition Service methods in Ember Data
+
+## Summary
+
+This RFC is an amendment to the Custom Model Classes RFC (https://github.com/emberjs/rfcs/pull/487).
+Based on implementation feedback, we discovered we could simplify the arguments to
+`attributesDefinitionFor` and `relationshipsDefinitionFor` to drop the string argument and always
+pass in an object.
+
+
+## Motivation
+
+When implementing a schema service, code ends up easier and cleaner if it does not have to deal with
+both a raw string and an object.
+
+## Detailed design
+
+The original RFC proposed the following interface:
+
+```typescript
+interface SchemaDefinitionService {
+  // Following the existing RD implementation 
+  attributesDefinitionFor(identifier: RecordIdentifier | type: string): AttributesDefinition
+  
+  // Following the existing RD implementation
+  relationshipsDefinitionFor(identifier: RecordIdentifier | type: string): RelationshipsDefinition
+  doesTypeExist(type: string): boolean
+}
+```
+
+We can simplify `attributesDefinitionFor` and `relationshipsDefinitionFor` methods to always accept an object.
+
+```typescript
+interface SchemaDefinitionService {
+  // Following the existing RD implementation 
+  attributesDefinitionFor(identifier: RecordIdentifier | { type: string }): AttributesDefinition
+  
+  // Following the existing RD implementation
+  relationshipsDefinitionFor(identifier: RecordIdentifier | { type: string }): RelationshipsDefinition
+
+  doesTypeExist(type: string): boolean
+}
+```
+
+## How we teach this
+
+It simplifies the types passed in, so should be easier to teach.
+
+
+## Drawbacks
+
+
+## Alternatives
+
+Keeping the existing design per the original RFC.