Fix createStaticFacet triggering NO_VALUE (#164)

* Fix createStaticFacet triggering NO_VALUE

* Unit test createFacet to check parity

Author: pirelenito

packages/@react-facet/core/src/facet/createFacet.spec.ts

@@ -235,3 +235,12 @@ describe('setWithCallback', () => {
     expect(listenerMock).not.toHaveBeenCalled()
   })
 })
+
+it('avoids triggering the listener if initialized with NO_VALUE', () => {
+  const update = jest.fn()
+  const initialValue = NO_VALUE
+  const mock = createFacet({ initialValue })
+
+  mock.observe(update)
+  expect(update).not.toHaveBeenCalled()
+})

packages/@react-facet/core/src/facet/createStaticFacet.spec.ts

@@ -1,27 +1,35 @@
+import { NO_VALUE } from '../types'
 import { createStaticFacet } from './createStaticFacet'
 
-describe('createStaticFacet', () => {
-  it(`it can be read but not mutated`, () => {
-    const initialValue = {}
-    const mock = createStaticFacet(initialValue)
+it('allows reading, but not mutation', () => {
+  const initialValue = {}
+  const mock = createStaticFacet(initialValue)
 
-    expect(mock.get()).toBe(initialValue)
-    expect('set' in mock).toBe(false)
-  })
+  expect(mock.get()).toBe(initialValue)
+  expect('set' in mock).toBe(false)
+})
+
+it('responds with the same value if you observe it and warns you in a non-production environment', () => {
+  const update = jest.fn()
+  const initialValue = {}
+  const mock = createStaticFacet(initialValue)
 
-  it(`it responds with the same value if you observe it and warns you in a non-production environment`, () => {
-    const update = jest.fn()
-    const initialValue = {}
-    const mock = createStaticFacet(initialValue)
+  mock.observe(update)
+  expect(update).toHaveBeenCalledTimes(1)
+  expect(update).toHaveBeenCalledWith(initialValue)
 
-    mock.observe(update)
-    expect(update).toHaveBeenCalledTimes(1)
-    expect(update).toHaveBeenCalledWith(initialValue)
+  update.mockClear()
+
+  mock.observe(update)
+  expect(update).toHaveBeenCalledTimes(1)
+  expect(update).toHaveBeenCalledWith(initialValue)
+})
 
-    update.mockClear()
+it('avoids triggering the listener if initialized with NO_VALUE', () => {
+  const update = jest.fn()
+  const initialValue = NO_VALUE
+  const mock = createStaticFacet(initialValue)
 
-    mock.observe(update)
-    expect(update).toHaveBeenCalledTimes(1)
-    expect(update).toHaveBeenCalledWith(initialValue)
-  })
+  mock.observe(update)
+  expect(update).not.toHaveBeenCalled()
 })

packages/@react-facet/core/src/facet/createStaticFacet.ts

@@ -1,4 +1,4 @@
-import { Facet } from '../types'
+import { Facet, NO_VALUE } from '../types'
 /**
  * Creates a nonwritable barebones static facet to be used when you need an initial facet value outside the react context
  * that's meant to be replaced later by a real facet. Ex: with `createContext()`
@@ -7,7 +7,9 @@ export function createStaticFacet<T>(value: T): Facet<T> {
   const facet: Facet<T> = {
     get: () => value,
     observe: (listener) => {
-      listener(value)
+      if (value !== NO_VALUE) {
+        listener(value)
+      }
       return () => {}
     },
   }