Better React 18 support (#3590)

Author: urugator

.changeset/brown-seals-worry.md

@@ -0,0 +1,5 @@
+---
+"mobx": minor
+---
+
+Better support for React 18: Mobx now keeps track of a global state version, which updates with each mutation.

.changeset/early-terms-bow.md

@@ -0,0 +1,6 @@
+---
+"mobx-react-lite": major
+---
+
+Components now use `useSyncExternalStore`, which should prevent tearing - you have to update mobx, otherwise it should behave as previously.<br>
+Improved displayName/name handling as discussed in #3438.<br>

.changeset/wise-waves-jam.md

@@ -0,0 +1,12 @@
+---
+"mobx-react": major
+---
+
+Functional components now use `useSyncExternalStore`, which should prevent tearing - you have to update mobx, otherwise it should behave as previously.<br>
+Improved displayName/name handling of functional components as discussed in #3438.<br>
+Reactions of uncommited class components are now correctly disposed, fixes #3492.<br>
+Reactions don't notify uncommited class components, avoiding the warning, fixes #3492.<br>
+Removed symbol "polyfill" and replaced with actual Symbols.<br>
+Removed `this.render` replacement detection + warning. `this.render` is no longer configurable/writable (possibly BC).<br>
+Class component instance is no longer exposed as `component[$mobx]["reactcomponent"]` (possibly BC).<br>
+Deprecated `disposeOnUnmount`, it's not compatible with remounting.<br>

.vscode/settings.json

@@ -1,9 +1,11 @@
 {
     "[typescript]": {
+        "editor.defaultFormatter": "esbenp.prettier-vscode",
         "editor.formatOnSave": true,
         "editor.formatOnPaste": false
     },
     "[javascript]": {
+        "editor.defaultFormatter": "esbenp.prettier-vscode",
         "editor.formatOnSave": true,
         "editor.formatOnPaste": false
     },

packages/mobx-react-lite/__tests__/api.test.ts

@@ -18,7 +18,8 @@ test("correct api should be exposed", function () {
             "useObserver",
             "isObserverBatched",
             "observerBatching",
-            "useStaticRendering"
+            "useStaticRendering",
+            "_observerFinalizationRegistry"
         ].sort()
     )
 })

packages/mobx-react-lite/__tests__/observer.test.tsx

@@ -618,12 +618,15 @@ it("should hoist known statics only", () => {
     expect(wrapped.render).toBe(undefined)
 })
 
-it("should have the correct displayName", () => {
-    const TestComponent = observer(function MyComponent() {
+it("should inherit original name/displayName #3438", () => {
+    function Name() {
         return null
-    })
+    }
+    Name.displayName = "DisplayName"
+    const TestComponent = observer(Name)
 
-    expect((TestComponent as any).type.displayName).toBe("MyComponent")
+    expect((TestComponent as any).type.name).toBe("Name")
+    expect((TestComponent as any).type.displayName).toBe("DisplayName")
 })
 
 test("parent / childs render in the right order", done => {

packages/mobx-react-lite/__tests__/strictAndConcurrentModeUsingFinalizationRegistry.test.tsx

@@ -1,4 +1,4 @@
-import { cleanup, render } from "@testing-library/react"
+import { cleanup, render, waitFor } from "@testing-library/react"
 import * as mobx from "mobx"
 import * as React from "react"
 import { useObserver } from "../src/useObserver"
@@ -43,10 +43,17 @@ test("uncommitted components should not leak observations", async () => {
 
     // Allow gc to kick in in case to let finalization registry cleanup
     gc()
-    await sleep(50)
-
-    // count1 should still be being observed by Component1,
-    // but count2 should have had its reaction cleaned up.
-    expect(count1IsObserved).toBeTruthy()
-    expect(count2IsObserved).toBeFalsy()
+    // Can take a while (especially on CI) before gc actually calls the registry
+    await waitFor(
+        () => {
+            // count1 should still be being observed by Component1,
+            // but count2 should have had its reaction cleaned up.
+            expect(count1IsObserved).toBeTruthy()
+            expect(count2IsObserved).toBeFalsy()
+        },
+        {
+            timeout: 2000,
+            interval: 200
+        }
+    )
 })

packages/mobx-react-lite/package.json

@@ -38,7 +38,7 @@
     "homepage": "https://mobx.js.org",
     "dependencies": {},
     "peerDependencies": {
-        "mobx": "^6.1.0",
+        "mobx": "^6.9.0",
         "react": "^16.8.0 || ^17 || ^18"
     },
     "peerDependenciesMeta": {
@@ -51,7 +51,8 @@
     },
     "devDependencies": {
         "mobx": "^6.8.0",
-        "expose-gc": "^1.0.0"
+        "expose-gc": "^1.0.0",
+        "use-sync-external-store": "^1.2.0"
     },
     "keywords": [
         "mobx",

packages/mobx-react-lite/src/index.ts

@@ -16,6 +16,7 @@ export { useLocalObservable } from "./useLocalObservable"
 export { useLocalStore } from "./useLocalStore"
 export { useAsObservableSource } from "./useAsObservableSource"
 
+export { observerFinalizationRegistry as _observerFinalizationRegistry }
 export const clearTimers = observerFinalizationRegistry["finalizeAllImmediately"] ?? (() => {})
 
 export function useObserver<T>(fn: () => T, baseComponentName: string = "observed"): T {

packages/mobx-react-lite/src/observer.ts

@@ -104,11 +104,13 @@ export function observer<P extends object, TRef = {}>(
         return useObserver(() => render(props, ref), baseComponentName)
     }
 
-    // Don't set `displayName` for anonymous components,
-    // so the `displayName` can be customized by user, see #3192.
-    if (baseComponentName !== "") {
-        ;(observerComponent as React.FunctionComponent).displayName = baseComponentName
-    }
+    // Inherit original name and displayName, see #3438
+    ;(observerComponent as React.FunctionComponent).displayName = baseComponent.displayName
+    Object.defineProperty(observerComponent, "name", {
+        value: baseComponent.name,
+        writable: true,
+        configurable: true
+    })
 
     // Support legacy context: `contextTypes` must be applied before `memo`
     if ((baseComponent as any).contextTypes) {
@@ -136,7 +138,7 @@ export function observer<P extends object, TRef = {}>(
             set() {
                 throw new Error(
                     `[mobx-react-lite] \`${
-                        this.displayName || this.type?.displayName || "Component"
+                        this.displayName || this.type?.displayName || this.type?.name || "Component"
                     }.contextTypes\` must be set before applying \`observer\`.`
                 )
             }