feat(endpoint): allow shared Collection context keys

.changeset/collection-context-detection.md

@@ -0,0 +1,24 @@
+---
+'@data-client/endpoint': minor
+'@data-client/rest': minor
+'@data-client/graphql': minor
+'@data-client/normalizr': minor
+'@data-client/core': minor
+'@data-client/react': minor
+'@data-client/vue': minor
+---
+
+Allow one `Collection` schema to be used both top-level and nested.
+
+Before:
+
+```ts
+const getTodos = new Collection([Todo], { argsKey });
+const userTodos = new Collection([Todo], { nestKey });
+```
+
+After:
+
+```ts
+const userTodos = new Collection([Todo], { argsKey, nestKey });
+```

.cursor/skills/data-client-schema/SKILL.md

@@ -105,7 +105,7 @@ export const EventResource = resource({
 
 ### pk routing
 
-`pk()` uses `argsKey(...args)` or `nestKey(parent, key)`, then serializes the result. Without either option, it defaults to `argsKey: params => ({ ...params })`, using all endpoint args as the collection key.
+`pk()` uses `nestKey(parent, key)` when nested in an Entity and available; otherwise it uses `argsKey(...args)`, then serializes the result. Without options, it defaults to `argsKey: params => ({ ...params })`, using all endpoint args as the collection key. Provide both `argsKey` and `nestKey` to reuse one Collection definition top-level and nested.
 
 - `argsKey` — derive pk from endpoint arguments (default)
 - `nestKey` — derive pk from parent entity for nested shared-state collections

.cursor/skills/data-client-v0.17-migration/SKILL.md

@@ -146,6 +146,44 @@ These are rare; do them by hand:
 
 `Schema.normalize()` and the `visit()` callback gain an optional trailing `parentEntity` parameter — the nearest enclosing entity-like schema, tracked automatically by the visit walker. Existing schemas don't need changes; new schemas can opt in.
 
+### Optional Collection cleanup
+
+`Collection` can now define both `argsKey` and `nestKey` on the same instance. During normalization it uses `argsKey` when top-level and `nestKey` when nested in an Entity, so paired definitions can be consolidated:
+
+```ts
+// before: two separate but equivalent Collections
+export const getTodos = new RestEndpoint({
+  path: '/todos',
+  searchParams: {} as { userId?: string },
+  schema: new Collection([Todo]),
+});
+
+class User extends Entity {
+  static schema = {
+    todos: new Collection([Todo], {
+      nestKey: parent => ({ userId: parent.id }),
+    }),
+  };
+}
+
+// after: one shared Collection
+export const userTodos = new Collection([Todo], {
+  nestKey: parent => ({ userId: parent.id }),
+});
+
+export const getTodos = new RestEndpoint({
+  path: '/todos',
+  searchParams: {} as { userId?: string },
+  schema: userTodos,
+});
+
+class User extends Entity {
+  static schema = {
+    todos: userTodos,
+  };
+}
+```
+
 ## Where to find affected code
 
 Search for these patterns in your codebase:

docs/rest/api/Collection.md

@@ -60,7 +60,7 @@ delay: 150,
 },
 ]}>
 
-```ts title="api/Todo" {15} collapsed
+```ts title="api/Todo" {15-18,24} collapsed
 import { Entity, RestEndpoint, Collection } from '@data-client/rest';
 
 export class Todo extends Entity {
@@ -72,16 +72,20 @@ export class Todo extends Entity {
   static key = 'Todo';
 }
 
+export const userTodos = new Collection([Todo], {
+  nestKey: (parent: { id: string }) => ({ userId: parent.id }),
+});
+
 export const getTodos = new RestEndpoint({
   path: '/todos',
   searchParams: {} as { userId?: string },
-  schema: new Collection([Todo]),
+  schema: userTodos,
 });
 ```
 
-```ts title="api/User" {13-17} collapsed
+```ts title="api/User" {13} collapsed
 import { Entity, RestEndpoint, Collection } from '@data-client/rest';
-import { Todo } from './Todo';
+import { Todo, userTodos } from './Todo';
 
 export class User extends Entity {
   id = '';
@@ -92,11 +96,7 @@ export class User extends Entity {
 
   static key = 'User';
   static schema = {
-    todos: new Collection([Todo], {
-      nestKey: (parent, key) => ({
-        userId: parent.id,
-      }),
-    }),
+    todos: userTodos,
   };
 }
 
@@ -247,7 +247,10 @@ await ctrl.fetch(StatsResource.getList.assign, {
 
 ## Options
 
-One of `argsKey` or `nestKey` is used to compute the `Collection's` [pk](#pk).
+`argsKey` and `nestKey` compute the `Collection's` [pk](#pk). `argsKey` is used
+when the Collection is normalized as a top-level endpoint result; `nestKey` is
+used when the same Collection is nested in an [Entity](./Entity.md). Provide both
+to reuse one Collection definition in both contexts.
 
 ### argsKey(...args): Object {#argsKey}
 
@@ -257,36 +260,37 @@ on Endpoint arguments.
 ```ts {7-9}
 import { RestEndpoint, Collection } from '@data-client/rest';
 
+const userTodos = new Collection([Todo], {
+  argsKey: (urlParams: { userId?: string }) => ({
+    ...urlParams,
+  }),
+  nestKey: (parent: { id: string }) => ({
+    userId: parent.id,
+  }),
+});
+
 const getTodos = new RestEndpoint({
   path: '/todos',
   searchParams: {} as { userId?: string },
-  schema: new Collection([Todo], {
-    argsKey: (urlParams: { userId?: string }) => ({
-      ...urlParams,
-    }),
-  }),
+  schema: userTodos,
 });
 ```
 
+When omitted, `argsKey` defaults to `params => ({ ...params })`.
+
 ### nestKey(parent, key): Object {#nestKey}
 
 Returns a serializable Object whose members uniquely define this collection based
 on the parent it is nested inside.
 
 Nested `Collection's` [pk](#pk) are better defined by what they are nested inside. This allows
 the nested Collection to share its state with other instances whose key has the same value.
+When `argsKey` and `nestKey` return the same object shape, top-level and nested
+reads resolve to the same collection state.
 
-```ts {28-30}
-import { Collection, Entity } from '@data-client/rest';
-
-class Todo extends Entity {
-  id = '';
-  userId = '';
-  title = '';
-  completed = false;
-
-  static key = 'Todo';
-}
+```ts {13}
+import { Entity } from '@data-client/rest';
+import { Todo, userTodos } from './Todo';
 
 class User extends Entity {
   id = '';
@@ -297,17 +301,21 @@ class User extends Entity {
 
   static key = 'User';
   static schema = {
-    todos: new Collection([Todo], {
-      nestKey: (parent, key) => ({
-        userId: parent.id,
-      }),
-    }),
+    todos: userTodos,
   };
 }
 ```
 
 In this case, `user.todos` and getTodos() response (from the argsKey example) will always
-be the same (referentially equal) Array.
+be the same (referentially equal) Array. Add both key functions to the shared
+Collection definition:
+
+```ts
+const userTodos = new Collection([Todo], {
+  argsKey: ({ userId }: { userId?: string }) => ({ userId }),
+  nestKey: (parent: User) => ({ userId: parent.id }),
+});
+```
 
 ### nonFilterArgumentKeys? {#nonFilterArgumentKeys}
 
@@ -684,16 +692,24 @@ static mergeWithStore(
 
 `mergeWithStore()` is called during normalization when a processed entity is already found in the store.
 
-### pk: (parent?, key?, args?): pk? {#pk}
+### pk: (parent?, key?, args?, parentEntity?): pk? {#pk}
 
-`pk()` calls [argsKey](#argsKey) or [nestKey](#nestKey) depending on which are specified, and
-then serializes the result for the pk string.
+`pk()` calls [nestKey](#nestKey) when nested in an Entity and available;
+otherwise it calls [argsKey](#argsKey). It then serializes the result for the pk
+string.
 
 ```ts
-pk(value: any, parent: any, key: string, args: readonly any[]) {
-  const obj = this.argsKey
-    ? this.argsKey(...args)
-    : this.nestKey(parent, key);
+pk(
+  value: any,
+  parent: any,
+  key: string,
+  args: readonly any[],
+  parentEntity?: any,
+) {
+  const obj =
+    parentEntity && this.nestKey
+      ? this.nestKey(parent, key)
+      : this.argsKey(...args);
   for (const key in obj) {
     if (typeof obj[key] !== 'string') obj[key] = `${obj[key]}`;
   }

packages/endpoint/src/schemaTypes.ts

@@ -88,21 +88,30 @@ export interface CollectionInterface<
   /**
    * A unique identifier for each Collection
    *
-   * Calls argsKey or nestKey depending on which are specified, and then serializes the result for the pk string.
+   * Calls nestKey when nested in an Entity and available; otherwise calls
+   * argsKey. The resulting object is serialized for the pk string.
    *
    * @param [parent] When normalizing, the object which included the entity
    * @param [key] When normalizing, the key where this entity was found
    * @param [args] ...args sent to Endpoint
+   * @param [parentEntity] Entity class containing this Collection when nested
    * @see https://dataclient.io/docs/api/Collection#pk
    */
-  pk(value: any, parent: any, key: string, args: any[]): string;
+  pk(
+    value: any,
+    parent: any,
+    key: string,
+    args: any[],
+    parentEntity?: any,
+  ): string;
   normalize(
     input: any,
     parent: Parent,
     key: string,
     args: any[],
     visit: (...args: any) => any,
     delegate: INormalizeDelegate,
+    parentEntity?: any,
   ): string;
 
   /** Creates new instance copying over defined values of arguments