Force strict comparison (eqeqeq eslint rule)

.eslintrc.js

@@ -28,6 +28,7 @@ module.exports = {
     'import/no-cycle': 'error',
     'no-unreachable': 'error',
     'no-undef': 'error',
+    'eqeqeq': 'error',
     'react-hooks/rules-of-hooks': 'error',
     'react-hooks/exhaustive-deps': 'error',
     'react/jsx-uses-react': 'error',

examples/benchmarking/src/listMemoFacet.tsx

@@ -18,7 +18,7 @@ export const Performance = () => {
 
     const tick = () => {
       setDataFacet((data) => {
-        if (data == NO_VALUE) return []
+        if (data === NO_VALUE) return []
 
         data[0].health = data[0].health === 10 ? 5 : 10
         return data
@@ -50,6 +50,7 @@ const ListItem = ({ item }: { item: Facet<Data> }) => {
   useFacetEffect(
     (health) => {
       randomWork(health)
+      return undefined
     },
     [],
     [health],
@@ -58,6 +59,7 @@ const ListItem = ({ item }: { item: Facet<Data> }) => {
   useFacetEffect(
     (name) => {
       randomWork(name)
+      return undefined
     },
     [],
     [name],
@@ -66,6 +68,7 @@ const ListItem = ({ item }: { item: Facet<Data> }) => {
   useFacetEffect(
     (name) => {
       randomWork(name)
+      return undefined
     },
     [],
     [name],
@@ -74,6 +77,7 @@ const ListItem = ({ item }: { item: Facet<Data> }) => {
   useFacetEffect(
     (name) => {
       randomWork(name)
+      return undefined
     },
     [],
     [name],

packages/@react-facet/core/src/components/Map.tsx

@@ -17,7 +17,7 @@ export const Map = <T,>({ array, children, equalityCheck }: MapProps<T>) => {
     <>
       {times(
         (index) =>
-          equalityCheck != null ? (
+          equalityCheck !== undefined ? (
             <MapChildMemo<T>
               key={index}
               arrayFacet={array}

packages/@react-facet/core/src/components/With.tsx

@@ -13,7 +13,7 @@ const hasData = <T,>(_: Facet<T | null | undefined>, shouldRender: boolean | NoV
 }
 
 export const With = <T,>({ data, children }: WithProps<T>) => {
-  const shouldRenderFacet = useFacetMap((data) => data != null, [], [data])
+  const shouldRenderFacet = useFacetMap((data) => data !== null && data !== undefined, [], [data])
   const shouldRender = useFacetUnwrap(shouldRenderFacet)
   return hasData(data, shouldRender) ? children(data) : null
 }

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

@@ -10,8 +10,8 @@ export const createNullableEqualityCheck = <T>(comparator: EqualityCheck<T>) =>
   let previous: T | null | undefined | NoValue = NO_VALUE
 
   return (value: T | null | undefined) => {
-    if (value == null || previous == null) {
-      if (value != previous) {
+    if (value === undefined || value === null || previous === undefined || previous === null) {
+      if (value !== previous) {
         previous = value
         return false
       } else {
@@ -90,7 +90,7 @@ export const createUniformArrayEqualityCheck =
 
       let isEquals = true
       for (let i = 0; i < longestLength; i++) {
-        if (previous[i] == null) {
+        if (previous[i] === undefined) {
           previous[i] = comparator()
         }
         if (!previous[i](current[i])) {
@@ -158,7 +158,7 @@ export const createOptionalValueEqualityCheck =
     let initializedComparator = comparator()
 
     return (current: T | undefined | null) => {
-      if (current == null) {
+      if (current === undefined || current === null) {
         if (previousWasNullish) {
           return true
         }

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

@@ -22,7 +22,7 @@ export function createFacet<V>({
   const checker = equalityCheck?.()
 
   const update = (newValue: V) => {
-    if (equalityCheck != null) {
+    if (equalityCheck !== undefined) {
       // we optimize for the most common scenario of using the defaultEqualityCheck (by inline its implementation)
       if (equalityCheck === defaultEqualityCheck) {
         const typeofValue = typeof newValue
@@ -37,7 +37,7 @@ export function createFacet<V>({
           return
         }
       } else {
-        if (checker != null && checker(newValue)) {
+        if (checker !== undefined && checker(newValue)) {
           return
         }
       }

packages/@react-facet/core/src/helpers/hasDefinedValue.ts

@@ -1,3 +1,4 @@
 import { NoValue, NO_VALUE, Value } from '../types'
 
-export const hasDefinedValue = (value: Value | NoValue): value is Value => value != null && value !== NO_VALUE
+export const hasDefinedValue = (value: Value | NoValue): value is Value =>
+  value !== undefined && value !== null && value !== NO_VALUE

packages/@react-facet/core/src/helpers/multiObserve.ts

@@ -26,10 +26,10 @@ export function multiObserve<Y extends Facet<unknown>[], T extends [...Y]>(
   for (let i = 0; i < facets.length; i++) {
     unsubscribes[i] = facets[i].observe((value) => {
       values[i] = value
-      hasAllDependencies = hasAllDependencies || values.every((value) => value != NO_VALUE)
+      hasAllDependencies = hasAllDependencies || values.every((value) => value !== NO_VALUE)
 
       if (hasAllDependencies) {
-        if (cleanup != null) {
+        if (cleanup !== undefined) {
           cleanup()
         }
 
@@ -42,7 +42,7 @@ export function multiObserve<Y extends Facet<unknown>[], T extends [...Y]>(
     for (let index = 0; index < unsubscribes.length; index++) {
       unsubscribes[index]()
     }
-    if (cleanup != null) {
+    if (cleanup !== undefined) {
       cleanup()
     }
   }

packages/@react-facet/core/src/hooks/useFacetCallback.spec.tsx

@@ -104,6 +104,7 @@ it('should work with uninitialized values', () => {
     useFacetEffect(
       () => {
         handler()
+        return undefined
       },
       [handler],
       [internalDemoFacet],

packages/@react-facet/core/src/hooks/useFacetCallback.ts

@@ -70,7 +70,7 @@ export function useFacetCallback<M, Y extends Facet<unknown>[], T extends [...Y]
       const values = facets.map((facet) => facet.get())
 
       for (const value of values) {
-        if (value === NO_VALUE) return defaultReturnValue != null ? defaultReturnValue : NO_VALUE
+        if (value === NO_VALUE) return defaultReturnValue !== undefined ? defaultReturnValue : NO_VALUE
       }
 
       return callbackMemoized(...(values as ExtractFacetValues<T>))(...(args as K))

packages/@react-facet/core/src/hooks/useFacetEffect.spec.tsx

@@ -42,6 +42,7 @@ it('triggers the effect when a dependency changes', () => {
     useFacetEffect(
       (value) => {
         callback(`${value} ${dependency}`)
+        return undefined
       },
       [dependency],
       [demoFacet],

packages/@react-facet/core/src/hooks/useFacetEffect.tsx

@@ -4,19 +4,19 @@ import { cancelScheduledTask, scheduleTask } from '../scheduler'
 
 export const createUseFacetEffect = (useHook: typeof useEffect | typeof useLayoutEffect) => {
   return function <Y extends Facet<unknown>[], T extends [...Y]>(
-    effect: (...args: ExtractFacetValues<T>) => void | Cleanup,
+    effect: (...args: ExtractFacetValues<T>) => undefined | Cleanup,
     dependencies: unknown[],
     facets: T,
   ) {
     // eslint-disable-next-line react-hooks/exhaustive-deps
     const effectMemoized = useCallback(effect as (...args: unknown[]) => ReturnType<typeof effect>, dependencies)
 
     useHook(() => {
-      let cleanup: void | Cleanup
+      let cleanup: undefined | Cleanup
 
       if (facets.length === 1) {
         const unsubscribe = facets[0].observe((value) => {
-          if (cleanup != null) {
+          if (cleanup !== undefined) {
             cleanup()
           }
 
@@ -25,7 +25,7 @@ export const createUseFacetEffect = (useHook: typeof useEffect | typeof useLayou
 
         return () => {
           unsubscribe()
-          if (cleanup != null) {
+          if (cleanup !== undefined) {
             cleanup()
           }
         }
@@ -36,10 +36,10 @@ export const createUseFacetEffect = (useHook: typeof useEffect | typeof useLayou
       const values: unknown[] = facets.map(() => NO_VALUE)
 
       const task = () => {
-        hasAllDependencies = hasAllDependencies || values.every((value) => value != NO_VALUE)
+        hasAllDependencies = hasAllDependencies || values.every((value) => value !== NO_VALUE)
 
         if (hasAllDependencies) {
-          if (cleanup != null) {
+          if (cleanup !== undefined) {
             cleanup()
           }
 
@@ -61,7 +61,7 @@ export const createUseFacetEffect = (useHook: typeof useEffect | typeof useLayou
       return () => {
         cancelScheduledTask(task)
         unsubscribes.forEach((unsubscribe) => unsubscribe())
-        if (cleanup != null) {
+        if (cleanup !== undefined) {
           cleanup()
         }
       }

packages/@react-facet/core/src/hooks/useFacetMap.spec.tsx

@@ -105,6 +105,7 @@ describe('multiple dependencies', () => {
       useFacetEffect(
         (value) => {
           mock(value.name)
+          return undefined
         },
         [],
         [adaptValue],
@@ -147,6 +148,7 @@ describe('multiple dependencies', () => {
       useFacetEffect(
         (value) => {
           mock(value)
+          return undefined
         },
         [],
         [adaptValue],
@@ -189,6 +191,7 @@ describe('multiple dependencies', () => {
       useFacetEffect(
         (value) => {
           mock(value)
+          return undefined
         },
         [],
         [adaptValue],
@@ -231,6 +234,7 @@ describe('multiple dependencies', () => {
       useFacetEffect(
         (value) => {
           mock(value)
+          return undefined
         },
         [],
         [adaptValue],
@@ -388,6 +392,7 @@ describe('single dependency', () => {
       useFacetEffect(
         (value) => {
           mock(value.name)
+          return undefined
         },
         [],
         [adaptValue],
@@ -429,6 +434,7 @@ describe('single dependency', () => {
       useFacetEffect(
         (value) => {
           mock(value)
+          return undefined
         },
         [],
         [adaptValue],
@@ -470,6 +476,7 @@ describe('single dependency', () => {
       useFacetEffect(
         (value) => {
           mock(value)
+          return undefined
         },
         [],
         [adaptValue],
@@ -511,6 +518,7 @@ describe('single dependency', () => {
       useFacetEffect(
         (value) => {
           mock(value)
+          return undefined
         },
         [],
         [adaptValue],

packages/@react-facet/core/src/hooks/useFacetMemo.spec.tsx

@@ -105,6 +105,7 @@ describe('multiple dependencies', () => {
       useFacetEffect(
         (value) => {
           mock(value.name)
+          return undefined
         },
         [],
         [adaptValue],
@@ -147,6 +148,7 @@ describe('multiple dependencies', () => {
       useFacetEffect(
         (value) => {
           mock(value)
+          return undefined
         },
         [],
         [adaptValue],
@@ -189,6 +191,7 @@ describe('multiple dependencies', () => {
       useFacetEffect(
         (value) => {
           mock(value)
+          return undefined
         },
         [],
         [adaptValue],
@@ -231,6 +234,7 @@ describe('multiple dependencies', () => {
       useFacetEffect(
         (value) => {
           mock(value)
+          return undefined
         },
         [],
         [adaptValue],
@@ -388,6 +392,7 @@ describe('single dependency', () => {
       useFacetEffect(
         (value) => {
           mock(value.name)
+          return undefined
         },
         [],
         [adaptValue],
@@ -429,6 +434,7 @@ describe('single dependency', () => {
       useFacetEffect(
         (value) => {
           mock(value)
+          return undefined
         },
         [],
         [adaptValue],
@@ -470,6 +476,7 @@ describe('single dependency', () => {
       useFacetEffect(
         (value) => {
           mock(value)
+          return undefined
         },
         [],
         [adaptValue],
@@ -511,6 +518,7 @@ describe('single dependency', () => {
       useFacetEffect(
         (value) => {
           mock(value)
+          return undefined
         },
         [],
         [adaptValue],

packages/@react-facet/core/src/hooks/useFacetPropSetter.ts

@@ -22,7 +22,7 @@ export function useFacetPropSetter<T extends Record<string, any>, Prop extends k
 ): PropSetter<T, Prop> {
   return useMemo(
     () => (value: T[Prop]) => {
-      facet.setWithCallback((prev) => ({ ...(prev != NO_VALUE ? prev : {}), [prop]: value } as unknown as T))
+      facet.setWithCallback((prev) => ({ ...(prev !== NO_VALUE ? prev : {}), [prop]: value } as unknown as T))
     },
     [facet, prop],
   )

packages/@react-facet/core/src/hooks/useFacetRef.ts

@@ -6,14 +6,15 @@ export function useFacetRef<T>(facet: Facet<T>): MutableRefObject<Option<T>>
 export function useFacetRef<T>(facet: Facet<T>, defaultValue: T): MutableRefObject<T>
 export function useFacetRef<T>(facet: Facet<T>, defaultValue?: T): MutableRefObject<T> {
   let value = facet.get()
-  if (value === NO_VALUE && defaultValue != undefined) {
+  if (value === NO_VALUE && defaultValue !== undefined) {
     value = defaultValue
   }
 
   const ref = useRef<Option<T>>(value)
   useFacetEffect(
     (value) => {
       ref.current = value
+      return undefined
     },
     [],
     [facet],