Various TypeScript improvements (#2309)

- Use Mithril.Attributes as base for ComponentAttrs, remove =any from class signature for Component
- Convert Alert to TypeScript, introduce AlertAttrs interface
- Convert AlertManagerState to TypeScript, add overload signatures for `show`, introduce AlertState interface for stored Alerts.
- Set ComponentAttrs as default T for Component
- Make attrs in AlertAttrs optional
- Add AlertIdentifier interface, simplify show type signature
- Remove mithril patch shim, as all patches onto m are now deprecated
- Use Mithril.Static for shim

js/shims.d.ts

@@ -1,6 +1,5 @@
 // Mithril
-import * as Mithril from 'mithril';
-import Stream from 'mithril/stream';
+import Mithril from 'mithril';
 
 // Other third-party libs
 import * as _dayjs from 'dayjs';
@@ -9,13 +8,6 @@ import * as _$ from 'jquery';
 // Globals from flarum/core
 import Application from './src/common/Application';
 
-/**
- * Helpers that flarum/core patches into Mithril
- */
-interface m extends Mithril.Static {
-  prop: typeof Stream;
-}
-
 /**
  * Export Mithril typings globally.
  *
@@ -36,7 +28,7 @@ export as namespace Mithril;
  */
 declare global {
   const $: typeof _$;
-  const m: m;
+  const m: Mithril.Static;
   const dayjs: typeof _dayjs;
 }
 

js/src/common/Component.ts

@@ -3,11 +3,7 @@ import * as Mithril from 'mithril';
 let deprecatedPropsWarned = false;
 let deprecatedInitPropsWarned = false;
 
-export type ComponentAttrs = {
-  className?: string;
-
-  [key: string]: any;
-};
+export interface ComponentAttrs extends Mithril.Attributes {}
 
 /**
  * The `Component` class defines a user interface 'building block'. A component
@@ -36,7 +32,7 @@ export type ComponentAttrs = {
  *
  * @see https://mithril.js.org/components.html
  */
-export default abstract class Component<T extends ComponentAttrs = any> implements Mithril.ClassComponent<T> {
+export default abstract class Component<T extends ComponentAttrs = ComponentAttrs> implements Mithril.ClassComponent<T> {
   /**
    * The root DOM element for the component.
    */

js/src/common/components/Alert.tsx

@@ -1,31 +1,33 @@
-import Component from '../Component';
+import Component, { ComponentAttrs } from '../Component';
 import Button from './Button';
 import listItems from '../helpers/listItems';
 import extract from '../utils/extract';
+import Mithril from 'mithril';
+
+export interface AlertAttrs extends ComponentAttrs {
+  /** The type of alert this is. Will be used to give the alert a class name of `Alert--{type}`. */
+  type?: string;
+  /** An array of controls to show in the alert. */
+  controls?: Mithril.Children;
+  /** Whether or not the alert can be dismissed. */
+  dismissible?: boolean;
+  /** A callback to run when the alert is dismissed */
+  ondismiss?: Function;
+}
 
 /**
  * The `Alert` component represents an alert box, which contains a message,
  * some controls, and may be dismissible.
- *
- * ### Attrs
- *
- * - `type` The type of alert this is. Will be used to give the alert a class
- *   name of `Alert--{type}`.
- * - `controls` An array of controls to show in the alert.
- * - `dismissible` Whether or not the alert can be dismissed.
- * - `ondismiss` A callback to run when the alert is dismissed.
- *
- * All other attrs will be assigned as attributes on the DOM element.
  */
-export default class Alert extends Component {
-  view(vnode) {
+export default class Alert<T extends AlertAttrs = AlertAttrs> extends Component<T> {
+  view(vnode: Mithril.Vnode) {
     const attrs = Object.assign({}, this.attrs);
 
     const type = extract(attrs, 'type');
     attrs.className = 'Alert Alert--' + type + ' ' + (attrs.className || '');
 
     const content = extract(attrs, 'content') || vnode.children;
-    const controls = extract(attrs, 'controls') || [];
+    const controls = (extract(attrs, 'controls') || []) as Mithril.ChildArray;
 
     // If the alert is meant to be dismissible (which is the case by default),
     // then we will create a dismiss button to append as the final control in

js/src/common/states/AlertManagerState.ts

@@ -1,10 +1,20 @@
-import Alert from '../components/Alert';
+import Mithril from 'mithril';
+import Alert, { AlertAttrs } from '../components/Alert';
+
+/**
+ * Returned by `AlertManagerState.show`. Used to dismiss alerts.
+ */
+export type AlertIdentifier = number;
+
+export interface AlertState {
+  componentClass: typeof Alert;
+  attrs: AlertAttrs;
+  children: Mithril.Children;
+}
 
 export default class AlertManagerState {
-  constructor() {
-    this.activeAlerts = {};
-    this.alertId = 0;
-  }
+  protected activeAlerts: { [id: number]: AlertState } = {};
+  protected alertId = 0;
 
   getActiveAlerts() {
     return this.activeAlerts;
@@ -12,19 +22,27 @@ export default class AlertManagerState {
 
   /**
    * Show an Alert in the alerts area.
+   *
+   * @returns The alert's ID, which can be used to dismiss the alert.
    */
-  show(arg1, arg2, arg3) {
+  show(children: Mithril.Children): AlertIdentifier;
+  show(attrs: AlertAttrs, children: Mithril.Children): AlertIdentifier;
+  show(componentClass: Alert, attrs: AlertAttrs, children: Mithril.Children): AlertIdentifier;
+
+  show(arg1: any, arg2?: any, arg3?: any) {
+    // Assigns variables as per the above signatures
     let componentClass = Alert;
-    let attrs = {};
-    let children;
+    let attrs: AlertAttrs = {};
+    let children: Mithril.Children;
+
     if (arguments.length == 1) {
-      children = arg1;
+      children = arg1 as Mithril.Children;
     } else if (arguments.length == 2) {
-      attrs = arg1;
-      children = arg2;
+      attrs = arg1 as AlertAttrs;
+      children = arg2 as Mithril.Children;
     } else if (arguments.length == 3) {
-      componentClass = arg1;
-      attrs = arg2;
+      componentClass = arg1 as typeof Alert;
+      attrs = arg2 as AlertAttrs;
       children = arg3;
     }
 
@@ -45,7 +63,7 @@ export default class AlertManagerState {
   /**
    * Dismiss an alert.
    */
-  dismiss(key) {
+  dismiss(key: AlertIdentifier): void {
     if (!key || !(key in this.activeAlerts)) return;
 
     delete this.activeAlerts[key];
@@ -54,10 +72,8 @@ export default class AlertManagerState {
 
   /**
    * Clear all alerts.
-   *
-   * @public
    */
-  clear() {
+  clear(): void {
     this.activeAlerts = {};
     m.redraw();
   }