feat(pinia-orm): hydrate recursively discriminated models

Discriminated models can now be nested over multiple levels (e.g.
Document -> File -> Video). When hydrating a record, the type keys are
walked down the hierarchy and an instance of the most specific matching
type is created. make() now also resolves discriminated types, and
nested type models are registered to the database.

closes #1995

Author: CodeDredd

docs/content/1.guide/2.model/7.single-table-inheritance.md

@@ -196,6 +196,72 @@ const people = useRepo(Person).all()
 */
 ```
 
+### Nested Discriminators
+
+Discriminated models can be nested over multiple levels. A derived model may define its own `typeKey` and `types()` map — when hydrating a record, Pinia ORM walks the type keys down the hierarchy and creates an instance of the most specific matching type.
+
+```js
+class Animal extends Model {
+  static entity = 'animals'
+
+  static types () {
+    return {
+      animal: Animal,
+      dog: Dog,
+    }
+  }
+
+  static fields () {
+    return {
+      id: this.attr(null),
+      type: this.attr('animal'),
+    }
+  }
+}
+
+class Dog extends Animal {
+  static entity = 'dogs'
+
+  static baseEntity = 'animals'
+
+  // Second discriminator level with its own type key.
+  static typeKey = 'race'
+
+  static types () {
+    return {
+      labrador: Dog,
+      terrier: Terrier,
+    }
+  }
+
+  static fields () {
+    return {
+      ...super.fields(),
+      type: this.attr('dog'),
+      race: this.attr('labrador'),
+    }
+  }
+}
+
+class Terrier extends Dog {
+  static entity = 'terriers'
+
+  static baseEntity = 'animals'
+
+  static fields () {
+    return {
+      ...super.fields(),
+      race: this.attr('terrier'),
+      speed: this.attr(0),
+    }
+  }
+}
+
+const animal = useRepo(Animal).make({ id: 1, type: 'dog', race: 'terrier', speed: 42 })
+
+animal instanceof Terrier // true
+```
+
 ### Exposing the Discriminator Field
 
 Note that if the `static fields` method doesn't expose the discriminator field (default or custom one), it will not be exposed in the results when fetching data. If you want to be able to read the discriminator field, you'll need to add it to the `fields` method **on the base entity**:

packages/pinia-orm/src/composables/useRepo.ts

@@ -26,9 +26,20 @@ export function useRepo (
     : new Repository(database, pinia).initialize(ModelOrRepository)
 
   try {
-    const typeModels = Object.values(repository.getModel().$types())
-    if (typeModels.length > 0) {
-      typeModels.forEach(typeModel => repository.database.register(typeModel.newRawInstance()))
+    const registerTypeModels = (model: Model, registered: Set<string>) => {
+      Object.values(model.$types()).forEach((typeModel) => {
+        if (registered.has(typeModel.modelEntity())) { return }
+
+        registered.add(typeModel.modelEntity())
+        const instance = typeModel.newRawInstance()
+        repository.database.register(instance)
+        // Also register nested discriminated models (e.g. Document -> File -> Video).
+        registerTypeModels(instance, registered)
+      })
+    }
+
+    if (Object.values(repository.getModel().$types()).length > 0) {
+      registerTypeModels(repository.getModel(), new Set())
     } else {
       repository.database.register(repository.getModel())
     }

packages/pinia-orm/src/model/Model.ts

@@ -709,6 +709,30 @@ export class Model {
     return this.$self().types()
   }
 
+  /**
+   * Resolve the most specific discriminated model for the given record by
+   * walking nested type keys (e.g. Document -> File -> Video).
+   */
+  $getDiscriminatedModel (record: Element): typeof Model | undefined {
+    let modelByType = this.$types()[record[this.$typeKey()]]
+
+    if (!modelByType) { return undefined }
+
+    const visited = new Set<typeof Model>([modelByType])
+
+    while (true) {
+      const instance = modelByType.newRawInstance()
+      const nextModel = instance.$types()[record[instance.$typeKey()]]
+
+      if (!nextModel || visited.has(nextModel)) { break }
+
+      visited.add(nextModel)
+      modelByType = nextModel
+    }
+
+    return modelByType
+  }
+
   /**
    * Get the pinia options for this model.
    */

packages/pinia-orm/src/query/Query.ts

@@ -1086,7 +1086,7 @@ export class Query<M extends Model = Model> {
       savedHydratedModel
     ) { return savedHydratedModel }
 
-    const modelByType = this.model.$types()[record[this.model.$typeKey()]]
+    const modelByType = this.model.$getDiscriminatedModel(record)
     const getNewInsance = (newOptions?: ModelOptions) => (modelByType ? modelByType.newRawInstance() as M : this.model)
       .$newInstance(record, { relations: false, ...(options || {}), ...newOptions })
     const hydratedModel = getNewInsance()

packages/pinia-orm/src/repository/Repository.ts

@@ -404,12 +404,13 @@ export class Repository<M extends Model = Model> {
   make (record?: Element): M
   make (records?: Element | Element[]): M | M[] {
     if (isArray(records)) {
-      return records.map(record => this.getModel().$newInstance(record, {
-        relations: true,
-      }))
+      return records.map(record => this.make(record))
     }
 
-    return this.getModel().$newInstance(records, {
+    const model = this.getModel()
+    const typeModel = records ? model.$getDiscriminatedModel(records) : undefined
+
+    return (typeModel ? typeModel.newRawInstance() as M : model).$newInstance(records, {
       relations: true,
     })
   }

packages/pinia-orm/tests/unit/model/Model_STI.spec.ts

@@ -389,4 +389,99 @@ describe('unit/model/Model_STI', () => {
     expect(personneMoraleRepo.all().length).toBe(1)
     expect(personneRepo.all().length).toBe(2)
   })
+
+  it('hydrates recursively discriminated models to the most specific type', () => {
+    class Animal extends Model {
+      static entity = 'animals'
+
+      static fields () {
+        return {
+          id: this.attr(null),
+          type: this.attr('animal'),
+        }
+      }
+
+      static types () {
+        return {
+          animal: Animal,
+          dog: Dog,
+        }
+      }
+    }
+
+    class Dog extends Animal {
+      static entity = 'dogs'
+
+      static baseEntity = 'animals'
+
+      static typeKey = 'race'
+
+      static fields () {
+        return {
+          ...super.fields(),
+          type: this.attr('dog'),
+          race: this.attr('labrador'),
+        }
+      }
+
+      static types () {
+        return {
+          labrador: Dog,
+          terrier: Terrier,
+        }
+      }
+    }
+
+    class Terrier extends Dog {
+      static entity = 'terriers'
+
+      static baseEntity = 'animals'
+
+      static fields () {
+        return {
+          ...super.fields(),
+          race: this.attr('terrier'),
+          speed: this.attr(0),
+        }
+      }
+    }
+
+    const animalsRepo = useRepo(Animal)
+
+    const terrier = animalsRepo.make({
+      id: 1,
+      type: 'dog',
+      race: 'terrier',
+      speed: 42,
+    })
+
+    expect(terrier).toBeInstanceOf(Terrier)
+    expect((terrier as Terrier).speed).toBe(42)
+
+    const labrador = animalsRepo.make({
+      id: 2,
+      type: 'dog',
+      race: 'labrador',
+    })
+
+    expect(labrador).toBeInstanceOf(Dog)
+    expect(labrador).not.toBeInstanceOf(Terrier)
+
+    const animal = animalsRepo.make({
+      id: 3,
+      type: 'animal',
+    })
+
+    expect(animal).toBeInstanceOf(Animal)
+    expect(animal).not.toBeInstanceOf(Dog)
+
+    animalsRepo.save({
+      id: 4,
+      type: 'dog',
+      race: 'terrier',
+      speed: 10,
+    })
+
+    expect(animalsRepo.find(4)).toBeInstanceOf(Terrier)
+  })
 })