refactor(treewide): Enable strict null checking

Typescript defaults to treating null/undefined in a way that can leak
them throughout code, and will also cause type issues (unexpected
undefineds/anys) if you use them explicitly

To avoid an unreviewable mess I have either widened types to allow null
(where we own the type) or added non-null assertions (where we do not).
This is preferable to not discerning nulls at all, and while it still
creates a large (by LOC) change, it's hopefully not large (by variation
of things) - and should transpile identically to JavaScript.

There is one point where the code does not transpile identically to
JavaScript. This is because it directly set something that we don't own
which shouldn't be undefined to undefined. This is clearly incorrect,
and I've replaced it with setting to an empty string instead.

If it seems like this is bad practice, that's because it is. You
shouldn't add non-null assertions all over the place because it makes
typescript lie to you. It's of similar badness to adding `as x`
everywhere. Unfortunately, worse practice would be mandating that
typescript lie to you about nulls and undefineds everywhere, as our
tsconfig has been doing. It's far better to limit the lie to these ~850
places where I've had to explicitly tell typescript "the world isn't
actually like this - that's OK, carry on anyway".

If you're worried about blames from this change - first: I believe it's
worth it, second: this change should only affect single lines, so using
--ignore-rev should work very well on it

In the future, probably we should remove some of these assertions,
although some changes we'll have to make to remove them are likely
either tedious or dangerous.

Signed-off-by: Skyler Grey <[email protected]>
Change-Id: I1770a1a8be3f45b45bda0fd2bcd57563add25924

browser/.betterer.js

@@ -7,6 +7,10 @@ const eslintIgnorePath = resolve(__dirname, ".eslintignore");
 const eslintTypescriptIncludes = async () => (await globby).globbySync(["**/*.ts"], { ignoreFiles: eslintIgnorePath });
 
 module.exports = {
+	'avoid non-null assertions': async () =>
+		eslintBetter({
+			'@typescript-eslint/no-non-null-assertion': 'error',
+		}).include(await eslintTypescriptIncludes()),
 	'avoid expressions which have no effect': async () =>
 		eslintBetter({
 			'@typescript-eslint/no-unused-expressions': 'error',

browser/.eslintrc

@@ -53,6 +53,7 @@
         "no-constant-condition": "off",
         "@typescript-eslint/triple-slash-reference": "off",
 
+        "@typescript-eslint/no-non-null-assertion": "off", // improving in .betterer.ts
         "@typescript-eslint/no-unused-expressions": "off" // improving in .betterer.ts
       }
     }

browser/src/app/GraphicSelectionMiddleware.ts

@@ -11,10 +11,10 @@
  */
 
 class GraphicSelection {
-	public static rectangle: cool.SimpleRectangle = null;
+	public static rectangle: cool.SimpleRectangle | null = null;
 	public static extraInfo: any = null;
 	public static selectionAngle: number = 0;
-	public static handlesSection: ShapeHandlesSection = null;
+	public static handlesSection: ShapeHandlesSection | null = null;
 
 	public static hasActiveSelection() {
 		return this.rectangle !== null;
@@ -43,8 +43,8 @@ class GraphicSelection {
 		var videoDesc = JSON.parse(textMsg);
 
 		if (this.hasActiveSelection()) {
-			videoDesc.width = this.rectangle.cWidth;
-			videoDesc.height = this.rectangle.cHeight;
+			videoDesc.width = this.rectangle!.cWidth;
+			videoDesc.height = this.rectangle!.cHeight;
 		}
 
 		// proxy cannot identify RouteToken if it is encoded
@@ -82,8 +82,8 @@ class GraphicSelection {
 	}
 
 	static renderDarkOverlay() {
-		var topLeft = new L.Point(this.rectangle.pX1, this.rectangle.pY1);
-		var bottomRight = new L.Point(this.rectangle.pX2, this.rectangle.pY2);
+		var topLeft = new L.Point(this.rectangle!.pX1, this.rectangle!.pY1);
+		var bottomRight = new L.Point(this.rectangle!.pX2, this.rectangle!.pY2);
 
 		if (app.map._docLayer.isCalcRTL()) {
 			// Dark overlays (like any other overlay) need regular document coordinates.
@@ -138,7 +138,7 @@ class GraphicSelection {
 		);
 
 		if (hasGridOffset)
-			this.rectangle.moveBy([
+			this.rectangle!.moveBy([
 				app.map._docLayer._shapeGridOffset.x,
 				app.map._docLayer._shapeGridOffset.y,
 			]);
@@ -177,10 +177,13 @@ class GraphicSelection {
 				app.sectionContainer.addSection(this.handlesSection);
 			}
 
-			this.handlesSection.setPosition(this.rectangle.pX1, this.rectangle.pY1);
+			this.handlesSection!.setPosition(
+				this.rectangle!.pX1,
+				this.rectangle!.pY1,
+			);
 			extraInfo.hasTableSelection = app.map._docLayer.hasTableSelection(); // scaleSouthAndEastOnly
-			this.handlesSection.refreshInfo(this.extraInfo);
-			this.handlesSection.setShowSection(true);
+			this.handlesSection!.refreshInfo(this.extraInfo);
+			this.handlesSection!.setShowSection(true);
 			app.sectionContainer.requestReDraw();
 		} else if (
 			this.handlesSection &&