Add iterable handlers (ending mutators)

lib/mutation.mjs

@@ -104,6 +104,9 @@ function prepareContext (context, unwrapOptions) {
     commitMode: mutentOptions.commitMode !== undefined
       ? parseCommitMode(mutentOptions.commitMode)
       : context.commitMode,
+    handlers: context.handlers.concat(
+      normalizeMutators(mutentOptions.handlers)
+    ),
     hooks: mergeHooks(context.hooks, normalizeHooks(mutentOptions.hooks)),
     intent,
     multiple: isMultiple(intent, argument),
@@ -121,12 +124,23 @@ function prepareContext (context, unwrapOptions) {
   }
 }
 
-async function * iterateMethod (context, mutators) {
-  const { adapter, argument, intent, multiple, options } = context
-
-  const iterable = context.mutators.concat(mutators).reduce(
-    (accumulator, mutator) => mutator(accumulator, context),
-    iterateEntities(iterateContext(context), context)
+async function * iterateMethod (ctx, mutators) {
+  const { adapter, argument, intent, multiple, options } = ctx
+
+  const chain = [
+    // Plugins' mutators
+    ...ctx.mutators,
+    // Local chain mutators
+    ...mutators,
+    // Internal end/safe mutator
+    mutatorClose,
+    // Plugins' handlers (end mutators)
+    ...ctx.handlers
+  ]
+
+  const iterable = chain.reduce(
+    (acc, mutator) => mutator(acc, ctx),
+    iterateEntities(iterateContext(ctx), ctx)
   )
 
   let count = 0

lib/mutation.spec.mjs

@@ -9,6 +9,7 @@ function buildMutation (intent, argument, context = {}) {
     adapter: {},
     argument,
     commitMode: 'AUTO',
+    handlers: [],
     intent,
     mutators: [],
     writeMode: 'AUTO',

lib/store.mjs

@@ -13,6 +13,7 @@ export class Store {
     const {
       adapter,
       commitMode,
+      handlers,
       hooks,
       mutators,
       plugins,
@@ -27,13 +28,21 @@ export class Store {
     // Save (valid) defaults
     this.adapter = adapter
     this.commitMode = 'AUTO'
+    this.handlers = []
     this.hooks = normalizeHooks()
     this.mutators = []
     this.writeMode = 'AUTO'
     this.writeSize = 16
 
     // Parse and save submitted options
-    this.register({ commitMode, hooks, mutators, writeMode, writeSize })
+    this.register({
+      commitMode,
+      handlers,
+      hooks,
+      mutators,
+      writeMode,
+      writeSize
+    })
 
     // Register plugins
     if (Array.isArray(plugins)) {
@@ -50,6 +59,7 @@ export class Store {
   register (plugin) {
     const {
       commitMode,
+      handlers,
       hooks,
       mutators,
       writeMode,
@@ -59,6 +69,9 @@ export class Store {
     if (commitMode !== undefined) {
       this.commitMode = parseCommitMode(commitMode)
     }
+    if (handlers !== undefined) {
+      this.handlers = this.handlers.concat(normalizeMutators(handlers))
+    }
     if (hooks !== undefined) {
       this.hooks = mergeHooks(this.hooks, normalizeHooks(hooks))
     }
@@ -92,6 +105,7 @@ export class Store {
       adapter: this.adapter,
       argument,
       commitMode: this.commitMode,
+      handlers: this.handlers,
       hooks: this.hooks,
       intent,
       mutators: this.mutators,

mutent.spec.mjs

@@ -778,3 +778,24 @@ test('bulkEntities over bulk', async t => {
     'SECOND_UPDATE'
   ])
 })
+
+test('store handlers', async t => {
+  t.plan(3)
+
+  const store = new Store({
+    adapter: {},
+    handlers: [
+      async function * (iterable, ctx) {
+        t.like(ctx, { multiple: false })
+        try {
+          yield * iterable
+        } catch (err) {
+          t.like(err, { code: 'EMUT_PARTIAL_ADAPTER' })
+        }
+      }
+    ]
+  })
+
+  const result = await store.create('Oh no').unwrap()
+  t.is(result, null)
+})