Improve typescript null checking in places (#10073 (#10073

* Improve typescript null checking in places

* Iterate

* Fix Timer.ts

src/editor/caret.ts

@@ -32,7 +32,7 @@ export function setSelection(editor: HTMLDivElement, model: EditorModel, selecti
 }
 
 function setDocumentRangeSelection(editor: HTMLDivElement, model: EditorModel, range: Range): void {
-    const sel = document.getSelection();
+    const sel = document.getSelection()!;
     sel.removeAllRanges();
     const selectionRange = document.createRange();
     const start = getNodeAndOffsetForPosition(editor, model, range.start);
@@ -50,7 +50,7 @@ export function setCaretPosition(editor: HTMLDivElement, model: EditorModel, car
     range.setStart(node, offset);
     range.collapse(true);
 
-    const sel = document.getSelection();
+    const sel = document.getSelection()!;
     if (sel.rangeCount === 1) {
         const existingRange = sel.getRangeAt(0);
         if (
@@ -124,7 +124,7 @@ function findNodeInLineForPart(parts: Part[], partIndex: number): { lineIndex: n
     let lineIndex = 0;
     let nodeIndex = -1;
 
-    let prevPart = null;
+    let prevPart: Part | undefined;
     // go through to parts up till (and including) the index
     // to find newline parts
     for (let i = 0; i <= partIndex; ++i) {
@@ -132,7 +132,7 @@ function findNodeInLineForPart(parts: Part[], partIndex: number): { lineIndex: n
         if (part.type === Type.Newline) {
             lineIndex += 1;
             nodeIndex = -1;
-            prevPart = null;
+            prevPart = undefined;
         } else {
             nodeIndex += 1;
             if (needsCaretNodeBefore(part, prevPart)) {

src/editor/deserialize.ts

@@ -51,7 +51,7 @@ export function longestBacktickSequence(text: string): number {
 }
 
 function isListChild(n: Node): boolean {
-    return LIST_TYPES.includes(n.parentNode?.nodeName);
+    return LIST_TYPES.includes(n.parentNode?.nodeName || "");
 }
 
 function parseAtRoomMentions(text: string, pc: PartCreator, opts: IParseOptions): Part[] {

src/editor/history.ts

@@ -31,7 +31,7 @@ export default class HistoryManager {
     private newlyTypedCharCount = 0;
     private currentIndex = -1;
     private changedSinceLastPush = false;
-    private lastCaret: Caret = null;
+    private lastCaret: Caret | null = null;
     private nonWordBoundarySinceLastPush = false;
     private addedSinceLastPush = false;
     private removedSinceLastPush = false;
@@ -65,7 +65,7 @@ export default class HistoryManager {
             // as long as you've only been adding or removing since the last push
             if (this.addedSinceLastPush !== this.removedSinceLastPush) {
                 // add steps by word boundary, up to MAX_STEP_LENGTH characters
-                const str = diff.added ? diff.added : diff.removed;
+                const str = diff.added ? diff.added : diff.removed!;
                 const isWordBoundary = str === " " || str === "\t" || str === "\n";
                 if (this.nonWordBoundarySinceLastPush && isWordBoundary) {
                     return true;

src/editor/model.ts

@@ -51,13 +51,13 @@ type ManualTransformCallback = () => Caret;
 export default class EditorModel {
     private _parts: Part[];
     private readonly _partCreator: PartCreator;
-    private activePartIdx: number = null;
-    private _autoComplete: AutocompleteWrapperModel = null;
-    private autoCompletePartIdx: number = null;
+    private activePartIdx: number | null = null;
+    private _autoComplete: AutocompleteWrapperModel | null = null;
+    private autoCompletePartIdx: number | null = null;
     private autoCompletePartCount = 0;
-    private transformCallback: TransformCallback = null;
+    private transformCallback: TransformCallback | null = null;
 
-    public constructor(parts: Part[], partCreator: PartCreator, private updateCallback: UpdateCallback = null) {
+    public constructor(parts: Part[], partCreator: PartCreator, private updateCallback: UpdateCallback | null = null) {
         this._parts = parts;
         this._partCreator = partCreator;
         this.transformCallback = null;

src/editor/parts.ts

@@ -455,7 +455,7 @@ class AtRoomPillPart extends RoomPillPart {
 }
 
 class UserPillPart extends PillPart {
-    public constructor(userId, displayName, private member: RoomMember) {
+    public constructor(userId, displayName, private member?: RoomMember) {
         super(userId, displayName);
     }
 
@@ -625,7 +625,7 @@ export class PartCreator {
 
     public userPill(displayName: string, userId: string): UserPillPart {
         const member = this.room.getMember(userId);
-        return new UserPillPart(userId, displayName, member);
+        return new UserPillPart(userId, displayName, member || undefined);
     }
 
     private static isRegionalIndicator(c: string): boolean {

src/editor/position.ts

@@ -79,6 +79,8 @@ export default class DocumentPosition implements IPosition {
                 offset = 0;
             }
         }
+
+        return this; // impossible but Typescript doesn't believe us
     }
 
     public backwardsWhile(model: EditorModel, predicate: Predicate): DocumentPosition {
@@ -104,6 +106,8 @@ export default class DocumentPosition implements IPosition {
                 offset = parts[index].text.length;
             }
         }
+
+        return this; // impossible but Typescript doesn't believe us
     }
 
     public asOffset(model: EditorModel): DocumentOffset {

src/editor/render.ts

@@ -18,7 +18,7 @@ limitations under the License.
 import { Part, Type } from "./parts";
 import EditorModel from "./model";
 
-export function needsCaretNodeBefore(part: Part, prevPart: Part): boolean {
+export function needsCaretNodeBefore(part: Part, prevPart?: Part): boolean {
     const isFirst = !prevPart || prevPart.type === Type.Newline;
     return !part.acceptsCaret && (isFirst || !prevPart.acceptsCaret);
 }
@@ -30,9 +30,9 @@ export function needsCaretNodeAfter(part: Part, isLastOfLine: boolean): boolean
 function insertAfter(node: HTMLElement, nodeToInsert: HTMLElement): void {
     const next = node.nextSibling;
     if (next) {
-        node.parentElement.insertBefore(nodeToInsert, next);
+        node.parentElement!.insertBefore(nodeToInsert, next);
     } else {
-        node.parentElement.appendChild(nodeToInsert);
+        node.parentElement!.appendChild(nodeToInsert);
     }
 }
 
@@ -58,11 +58,11 @@ function updateCaretNode(node: HTMLElement): void {
     }
 }
 
-export function isCaretNode(node: HTMLElement): boolean {
-    return node && node.tagName === "SPAN" && node.className === "caretNode";
+export function isCaretNode(node?: Node | null): node is HTMLElement {
+    return !!node && node instanceof HTMLElement && node.tagName === "SPAN" && node.className === "caretNode";
 }
 
-function removeNextSiblings(node: ChildNode): void {
+function removeNextSiblings(node: ChildNode | null): void {
     if (!node) {
         return;
     }
@@ -83,13 +83,13 @@ function removeChildren(parent: HTMLElement): void {
 }
 
 function reconcileLine(lineContainer: ChildNode, parts: Part[]): void {
-    let currentNode;
-    let prevPart;
+    let currentNode: ChildNode | null = null;
+    let prevPart: Part | undefined;
     const lastPart = parts[parts.length - 1];
 
     for (const part of parts) {
         const isFirst = !prevPart;
-        currentNode = isFirst ? lineContainer.firstChild : currentNode.nextSibling;
+        currentNode = isFirst ? lineContainer.firstChild : currentNode!.nextSibling;
 
         if (needsCaretNodeBefore(part, prevPart)) {
             if (isCaretNode(currentNode)) {
@@ -109,18 +109,18 @@ function reconcileLine(lineContainer: ChildNode, parts: Part[]): void {
         if (currentNode && part) {
             part.updateDOMNode(currentNode);
         } else if (part) {
-            currentNode = part.toDOMNode();
+            currentNode = part.toDOMNode() as ChildNode;
             // hooks up nextSibling for next iteration
             lineContainer.appendChild(currentNode);
         }
 
         if (needsCaretNodeAfter(part, part === lastPart)) {
-            if (isCaretNode(currentNode.nextSibling)) {
-                currentNode = currentNode.nextSibling;
-                updateCaretNode(currentNode);
+            if (isCaretNode(currentNode?.nextSibling)) {
+                currentNode = currentNode!.nextSibling;
+                updateCaretNode(currentNode as HTMLElement);
             } else {
                 const caretNode = createCaretNode();
-                insertAfter(currentNode, caretNode);
+                insertAfter(currentNode as HTMLElement, caretNode);
                 currentNode = caretNode;
             }
         }
@@ -150,7 +150,7 @@ function reconcileEmptyLine(lineContainer: HTMLElement): void {
 }
 
 export function renderModel(editor: HTMLDivElement, model: EditorModel): void {
-    const lines = model.parts.reduce(
+    const lines = model.parts.reduce<Part[][]>(
         (linesArr, part) => {
             if (part.type === Type.Newline) {
                 linesArr.push([]);