fix(kitsu-core): Deserialize and link nested relations (#601)

* fix(kistu-core): Deserialize and link nested relations

* fix(kitsu-core): Run linter and add jsdoc definitions for previouslyLinked

* refactor: remove default value of previouslyLinked in link()

Empty object is passed down from root linkRelationships

* ci(size-limit): increase warning threshold by 1 kB for CommonJS output

* test: check circular JSON exists in output

* docs: note previouslyLinked param on linkRelationships is only used internally

JSDoc doesn't have anything for this type of thing it seems.

Co-authored-by: wopian <james.harris@trutify.com>
Co-authored-by: James Harris <wopian@wopian.me>

Author: 3 people

package.json

@@ -47,6 +47,7 @@
     "eslint": "~7.32.0",
     "eslint-config-wopian": "~2.1.0",
     "jest": "~27.2.0",
+    "json-stringify-safe": "~5.0.1",
     "lerna": "^3.0.0",
     "rollup": "~2.58.0",
     "rollup-plugin-delete": "~2.0.0",

packages/kitsu-core/src/linkRelationships/index.js

@@ -9,11 +9,16 @@ import { filterIncludes } from '../filterIncludes'
  * @param {string} resource.type Resource type
  * @param {Object} [resource.meta] Meta information
  * @param {Object[]} included The response included object
+ * @param {Object} [previouslyLinked] A mapping of already visited resources
  * @private
  */
-function link ({ id, type, meta }, included) {
+function link ({ id, type, meta }, included, previouslyLinked) {
   const filtered = filterIncludes(included, { id, type })
-  if (filtered.relationships) linkRelationships(filtered, included)
+  previouslyLinked[`${type}#${id}`] = filtered
+
+  if (filtered.relationships) {
+    linkRelationships(filtered, included, previouslyLinked)
+  }
   if (meta) filtered.meta = meta
 
   return deattribute(filtered)
@@ -25,14 +30,16 @@ function link ({ id, type, meta }, included) {
  * @param {Object} data The response data object
  * @param {Object[]} included The response included object
  * @param {string} key Name of the relationship item
+ * @param {Object} previouslyLinked A mapping of already visited resources
  * @private
  */
-function linkArray (data, included, key) {
+function linkArray (data, included, key, previouslyLinked) {
   data[key] = {}
   if (data.relationships[key].links) data[key].links = data.relationships[key].links
   data[key].data = []
   for (const resource of data.relationships[key].data) {
-    data[key].data.push(link(resource, included))
+    const cache = previouslyLinked[`${resource.type}#${resource.id}`]
+    data[key].data.push(cache || link(resource, included, previouslyLinked))
   }
   delete data.relationships[key]
 }
@@ -43,11 +50,14 @@ function linkArray (data, included, key) {
  * @param {Object} data The response data object
  * @param {Object[]} included The response included object
  * @param {string} key Name of the relationship item
+ * @param {Object} previouslyLinked A mapping of already visited resources
  * @private
  */
-function linkObject (data, included, key) {
+function linkObject (data, included, key, previouslyLinked) {
   data[key] = {}
-  data[key].data = link(data.relationships[key].data, included)
+  const resource = data.relationships[key].data
+  const cache = previouslyLinked[`${resource.type}#${resource.id}`]
+  data[key].data = cache || link(resource, included, previouslyLinked)
   if (data.relationships[key].links) data[key].links = data.relationships[key].links
   delete data.relationships[key]
 }
@@ -70,6 +80,7 @@ function linkAttr (data, key) {
  *
  * @param {Object} data The response data object
  * @param {Object[]} [included] The response included object
+ * @param {Object} [previouslyLinked] A mapping of already visited resources (internal use only)
  * @returns Parsed data
  *
  * @example
@@ -94,16 +105,16 @@ function linkAttr (data, key) {
  * //   }
  * // }
  */
-export function linkRelationships (data, included = []) {
+export function linkRelationships (data, included = [], previouslyLinked = {}) {
   const { relationships } = data
 
   for (const key in relationships) {
     // Relationship contains collection of resources
     if (Array.isArray(relationships[key]?.data)) {
-      linkArray(data, included, key)
+      linkArray(data, included, key, previouslyLinked)
     // Relationship contains a single resource
     } else if (relationships[key].data) {
-      linkObject(data, included, key)
+      linkObject(data, included, key, previouslyLinked)
     } else {
       linkAttr(data, key)
     }

packages/kitsu-core/src/linkRelationships/index.spec.js

@@ -1,3 +1,4 @@
+import stringify from 'json-stringify-safe'
 import { linkRelationships } from './'
 
 describe('kitsu-core', () => {
@@ -88,6 +89,91 @@ describe('kitsu-core', () => {
         })
     })
 
+    it('caches relationships that were previously linked', () => {
+      expect.assertions(1)
+
+      const data = {
+        id: '1',
+        type: 'user',
+        attributes: {
+          name: 'A user'
+        },
+        relationships: {
+          current_song: {
+            data: {
+              id: '1',
+              type: 'song'
+            }
+          }
+        }
+      }
+
+      const included = [
+        {
+          id: '1',
+          type: 'album',
+          attributes: {
+            name: 'Mezmerize'
+          },
+          relationships: {
+            songs: {
+              data: [
+                {
+                  id: '1',
+                  type: 'song'
+                }
+              ]
+            }
+          }
+        },
+        {
+          id: '1',
+          type: 'song',
+          attributes: {
+            title: 'Revenga'
+          },
+          relationships: {
+            album: {
+              data: {
+                id: '1',
+                type: 'album'
+              }
+            }
+          }
+        }
+      ]
+
+      const circularResult = linkRelationships(data, included)
+      const result = JSON.parse(stringify(circularResult))
+
+      expect(result).toEqual({
+        id: '1',
+        type: 'user',
+        attributes: {
+          name: 'A user'
+        },
+        current_song: {
+          data: {
+            id: '1',
+            type: 'song',
+            album: {
+              data: {
+                id: '1',
+                name: 'Mezmerize',
+                type: 'album',
+                songs: {
+                  data: [
+                    '[Circular ~.current_song.data]'
+                  ]
+                }
+              }
+            },
+            title: 'Revenga'
+          }
+        }
+      })
+    })
+
     it('does not deattribute key if theres a relationship (single) with same name (handle invalid JSON:API)', () => {
       expect.assertions(1)
       const data = {

packages/kitsu/package.json

@@ -56,7 +56,7 @@
   "size-limit": [
     {
       "path": "./dist/index.js",
-      "limit": "10 kb",
+      "limit": "11 kb",
       "brotli": true
     },
     {