After upgrading to Angular 9, I keep getting errors in TypeScript error console... but no errors exist when i run tsc in command line Package Version. my tsconfig { "compileOnSave": false, "angularCompilerOptions": { "fullTemplateTypeCheck": true, "preserveWhitespaces": true }, "compilerOptions": { "baseUrl": "./", "outDir": "./dist/out-tsc", "sourceMap": true, "declaration": false, "module": "esnext", "moduleResolution": "node", "emitDecoratorMetadata": true, "experimentalDecorators": true, "importHelpers": true, "target": "es2015", "paths": { "sax": [ "node_modules/sax" ], "timers": [ "node_modules/timers" ], "stream": [ "node_modules/stream" ] }, "typeRoots": [ "node_modules/@types" ], "lib": [ "es2018", "dom" ] } } and my tsconfig.app.json { "extends": "./tsconfig.json", "compilerOptions": { "outDir": "./out-tsc/app", "types": [], "module": "esnext", "moduleResolution": "node" }, "include": [ "src/**/*.ts" ], "exclude": [ "src/test.ts", "tmp/**/", "tmp/**/*.ts", "src/**/*.spec.ts" ] } Continue reading...