refactor(treewide): Enable strict null checking

Makefile.am

@@ -718,6 +718,12 @@ prettier: browser/node_modules
 prettier-write: browser/node_modules
 	@make -C browser prettier-write
 
+betterer: browser/node_modules
+	@make -C browser betterer
+
+betterer-write: browser/node_modules
+	@make -C browser betterer-write
+
 install-exec-hook:
 	cd $(DESTDIR)$(bindir) && \
 	$(LN_S) coolconfig loolconfig && \
@@ -761,7 +767,7 @@ check-for-system-nss:
 
 check-recursive: eslint
 
-check: check-for-system-nss prettier eslint check-recursive
+check: check-for-system-nss prettier eslint betterer check-recursive
 	$(GEN_COVERAGE_COMMAND)
 
 coverage-report:

browser/.betterer.js

@@ -0,0 +1,18 @@
+const { eslint: eslintBetter } = require('@betterer/eslint');
+const globby = import('globby');
+const { resolve } = require('path');
+
+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',
+		}).include(await eslintTypescriptIncludes()),
+};

browser/.eslintrc

@@ -51,7 +51,10 @@
         "@typescript-eslint/no-namespace": "off",
         "no-inner-declarations": "off",
         "no-constant-condition": "off",
-        "@typescript-eslint/triple-slash-reference": "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/Makefile.am

@@ -606,6 +606,10 @@ define global_file
 		@$(NODE) node_modules/uglify-js/bin/uglifyjs $< --output $@)
 endef
 
+define run_betterer_check
+	node_modules/@betterer/cli/bin/betterer -c ./.betterer.js $(1)
+endef
+
 define run_eslint_check
 	@$(NODE) node_modules/eslint/bin/eslint.js \
 		--resolve-plugins-relative-to $(abs_builddir) \
@@ -703,6 +707,7 @@ $(INTERMEDIATE_DIR)/cool-src.js: tscompile.done $(call prereq_cool) $(COOL_JS_DS
 	@printf "Checking for obsolete JS build intermediates in this makefile... "
 	@if ! test "z$(COOL_ASSERT_INTERSECT)" == "z"; then echo; echo "Error: please remove obsolete files:"; echo "$(COOL_ASSERT_INTERSECT)"; exit 1; else echo "clean"; fi
 	@echo "Checking for cool JS errors..."
+	$(call run_betterer_check,ci) || echo "Betterer doesn't have the latest state of the project. To fix it, you can run 'make betterer-write'"
 	$(call run_eslint_check,$(srcdir)/src $(srcdir)/js)
 	$(call run_prettier_check,--debug-check $(srcdir)/src $(srcdir)/js/global.js)
 	@echo "Bundling cool..."
@@ -1152,6 +1157,12 @@ prettier-write:
 		$(srcdir)/js \
 		$(srcdir)/admin/src)
 
+betterer:
+	$(call run_betterer_check,ci) || (echo "Betterer doesn't have the latest state of the project. To fix it, you can run 'make betterer-write'" && exit 1)
+
+betterer-write:
+	$(call run_betterer_check,run)
+
 MOCHA_TEST_LOG = "`pwd`/mocha.log"
 DUPLICATION_TEST_LOG = "`pwd`/duplication.log"
 check-local: $(MOCHA_TS_JS_FILES)

browser/package.json

@@ -3,6 +3,8 @@
   "version": "0.8.0-dev",
   "description": "Collabora Online front-end",
   "devDependencies": {
+    "@betterer/cli": "^5.4.0",
+    "@betterer/eslint": "^5.4.0",
     "@braintree/sanitize-url": "6.0.2",
     "@types/jquery": "^3.5.29",
     "@types/jquery.contextmenu": "^1.7.38",
@@ -52,11 +54,13 @@
   ],
   "license": "BSD-2-Clause",
   "dependencies": {
+    "globby": "^14.0.2",
     "jsdom": "^16.4.0"
   },
   "scripts": {
     "test": "mocha 'mocha_tests/**/*.js'",
     "test-single": "mocha",
-    "duplication": "jscpd ./src/ --exitCode 1 --min-lines 17"
+    "duplication": "jscpd ./src/ --exitCode 1 --min-lines 17",
+    "betterer": "betterer -c ./.betterer.js"
   }
 }

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 &&