From 580be37eb45f57ba1b5446824c3a53f56e32eac7 Mon Sep 17 00:00:00 2001
From: Alexander Skvortsov <38059171+askvortsov1@users.noreply.github.com>
Date: Sun, 12 Dec 2021 14:51:05 -0500
Subject: [PATCH] `listItems` typing fix (#3176)

Co-authored-by: David Wheatley <hi@davwheat.dev>
---
 js/src/common/helpers/listItems.tsx | 87 +++++++++++++++++------------
 1 file changed, 52 insertions(+), 35 deletions(-)

diff --git a/js/src/common/helpers/listItems.tsx b/js/src/common/helpers/listItems.tsx
index 20a2b985b..e4b39d225 100644
--- a/js/src/common/helpers/listItems.tsx
+++ b/js/src/common/helpers/listItems.tsx
@@ -3,29 +3,41 @@ import Component, { ComponentAttrs } from '../Component';
 import Separator from '../components/Separator';
 import classList from '../utils/classList';
 
-export interface ModdedVnodeAttrs {
+type ModdedVnodeAttrs = {
   itemClassName?: string;
   key?: string;
-}
-
-export type ModdedVnode<Attrs> = Mithril.Vnode<ModdedVnodeAttrs, Component<Attrs> | {}> & {
-  itemName?: string;
-  itemClassName?: string;
-  tag: Mithril.Vnode['tag'] & {
-    isListItem?: boolean;
-    isActive?: (attrs: ComponentAttrs) => boolean;
-  };
 };
 
-function isSeparator<Attrs>(item: ModdedVnode<Attrs>): boolean {
-  return item.tag === Separator;
+type ModdedTag = Mithril.Vnode['tag'] & {
+  isListItem?: boolean;
+  isActive?: (attrs: ComponentAttrs) => boolean;
+};
+
+type ModdedVnode = Mithril.Vnode<ModdedVnodeAttrs> & { itemName?: string; itemClassName?: string; tag: ModdedTag };
+
+type ModdedChild = ModdedVnode | string | number | boolean | null | undefined;
+type ModdedChildArray = ModdedChildren[];
+type ModdedChildren = ModdedChild | ModdedChildArray;
+
+/**
+ * This type represents an element of a list returned by `ItemList.toArray()`,
+ * coupled with some static properties used on various components.
+ */
+export type ModdedChildrenWithItemName = ModdedChildren & { itemName?: string };
+
+function isVnode(item: ModdedChildren): item is Mithril.Vnode {
+  return typeof item === 'object' && item !== null && 'tag' in item;
 }
 
-function withoutUnnecessarySeparators<Attrs>(items: ModdedVnode<Attrs>[]): ModdedVnode<Attrs>[] {
-  const newItems: ModdedVnode<Attrs>[] = [];
-  let prevItem: ModdedVnode<Attrs>;
+function isSeparator(item: ModdedChildren): boolean {
+  return isVnode(item) && item.tag === Separator;
+}
 
-  items.filter(Boolean).forEach((item: Mithril.Vnode, i: number) => {
+function withoutUnnecessarySeparators(items: ModdedChildrenWithItemName[]): ModdedChildrenWithItemName[] {
+  const newItems: ModdedChildrenWithItemName[] = [];
+  let prevItem: ModdedChildren;
+
+  items.filter(Boolean).forEach((item, i: number) => {
     if (!isSeparator(item) || (prevItem && !isSeparator(prevItem) && i !== items.length - 1)) {
       prevItem = item;
       newItems.push(item);
@@ -42,38 +54,43 @@ function withoutUnnecessarySeparators<Attrs>(items: ModdedVnode<Attrs>[]): Modde
  * By default, this tag is an `<li>` tag, but this is customisable through the
  * second function parameter, `customTag`.
  */
-export default function listItems<Attrs extends Record<string, unknown>>(
-  rawItems: ModdedVnode<Attrs> | ModdedVnode<Attrs>[],
-  customTag: string | Component<Attrs> = 'li',
+export default function listItems<Attrs extends ComponentAttrs>(
+  rawItems: ModdedChildrenWithItemName[],
+  customTag: VnodeElementTag<Attrs> = 'li',
   attributes: Attrs = {} as Attrs
 ): Mithril.Vnode[] {
   const items = rawItems instanceof Array ? rawItems : [rawItems];
   const Tag = customTag;
 
-  return withoutUnnecessarySeparators(items).map((item: ModdedVnode<Attrs>) => {
-    const isListItem = item.tag?.isListItem;
-    const active = item.tag?.isActive?.(item.attrs);
-    const className = item.attrs?.itemClassName || item.itemClassName;
+  return withoutUnnecessarySeparators(items).map((item) => {
+    const classes = [item.itemName && `item-${item.itemName}`];
 
-    if (isListItem) {
+    if (!isVnode(item)) {
+      return (
+        <Tag className={classList(classes)} {...attributes}>
+          {item}
+        </Tag>
+      );
+    }
+
+    if (item.tag.isListItem) {
       item.attrs = item.attrs || {};
       item.attrs.key = item.attrs.key || item.itemName;
       item.key = item.attrs.key;
+
+      return item;
     }
 
-    const node: Mithril.Vnode = isListItem ? (
-      item
-    ) : (
-      // @ts-expect-error `Component` does not have any construct or call signatures
-      <Tag
-        className={classList([className, item.itemName && `item-${item.itemName}`, active && 'active'])}
-        key={item?.attrs?.key || item.itemName}
-        {...attributes}
-      >
+    classes.push(item.attrs?.itemClassName || item.itemClassName);
+
+    if (item.tag.isActive?.(item.attrs)) {
+      classes.push('active');
+    }
+
+    return (
+      <Tag className={classList(classes)} key={item?.attrs?.key || item.itemName} {...attributes}>
         {item}
       </Tag>
     );
-
-    return node;
   });
 }