Many "Circular source file mapping dependency" warnings on first build

🐞 Bug report

Command (mark with an x)

• new
• build
• serve
• test
• e2e
• generate
• add
• update
• lint
• xi18n
• run
• config
• help
• version
• doc

Is this a regression?

Yes

Yes, the previous version in which this bug was not present was: ....

10.0.2

Description

A clear and concise description of the problem...

After updating a very simple, almost stock 'ng new’d application to 10.0.2, upon first build (ng serve), lots of these circular dependency warnings appeared during the first pass (building for es2015)

Compiling @angular/core : es2015 as esm2015
Compiling @angular/cdk/keycodes : es2015 as esm2015
Compiling @angular/animations : es2015 as esm2015
Compiling @angular/compiler/testing : es2015 as esm2015
Warning: Unable to fully load /Users/johntsombakos/Dev/ng9-test/node_modules/@angular/cdk/keycodes/index.d.ts for source-map flattening: Circular source file mapping dependency: /Users/johntsombakos/Dev/ng9-test/node_modules/@angular/cdk/keycodes/index.d.ts.map -> /Users/johntsombakos/Dev/ng9-test/node_modules/@angular/cdk/keycodes/index.d.ts.map
Compiling @angular/animations/browser : es2015 as esm2015
Compiling @angular/cdk/observers : es2015 as esm2015
Compiling @angular/cdk/collections : es2015 as esm2015
Compiling @angular/common : es2015 as esm2015
Compiling @angular/core/testing : es2015 as esm2015
Warning: Unable to fully load /Users/johntsombakos/Dev/ng9-test/node_modules/@angular/cdk/collections/unique-selection-dispatcher.d.ts for source-map flattening: Circular source file mapping dependency: /Users/johntsombakos/Dev/ng9-test/node_modules/@angular/cdk/collections/unique-selection-dispatcher.d.ts.map -> /Users/johntsombakos/Dev/ng9-test/node_modules/@angular/cdk/collections/unique-selection-dispatcher.d.ts.map
Warning: Unable to fully load /Users/johntsombakos/Dev/ng9-test/node_modules/@angular/cdk/collections/index.d.ts for source-map flattening: Circular source file mapping dependency: /Users/johntsombakos/Dev/ng9-test/node_modules/@angular/cdk/collections/index.d.ts.map -> /Users/johntsombakos/Dev/ng9-test/node_modules/@angular/cdk/collections/index.d.ts.map

🔬 Minimal Reproduction

🔥 Exception or Error

Warning: Unable to fully load /Users/johntsombakos/Dev/ng9-test/node_modules/@angular/cdk/keycodes/index.d.ts for source-map flattening: Circular source file mapping dependency: /Users/johntsombakos/Dev/ng9-

🌍 Your Environment

     _                      _                 ____ _     ___
    / \   _ __   __ _ _   _| | __ _ _ __     / ___| |   |_ _|
   / △ \ | '_ \ / _` | | | | |/ _` | '__|   | |   | |    | |
  / ___ \| | | | (_| | |_| | | (_| | |      | |___| |___ | |
 /_/   \_\_| |_|\__, |\__,_|_|\__,_|_|       \____|_____|___|
                |___/


Angular CLI: 10.0.2
Node: 14.5.0
OS: darwin x64

Angular: 10.0.3
... animations, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router
Ivy Workspace: Yes

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.1000.2
@angular-devkit/build-angular     0.1000.2
@angular-devkit/build-optimizer   0.1000.2
@angular-devkit/build-webpack     0.1000.2
@angular-devkit/core              10.0.2
@angular-devkit/schematics        10.0.2
@angular/cdk                      10.0.1
@angular/cli                      10.0.2
@angular/material                 10.0.1
@ngtools/webpack                  10.0.2
@schematics/angular               10.0.2
@schematics/update                0.1000.2
rxjs                              6.6.0
typescript                        3.9.6
webpack                           4.43.0

Anything else relevant?

[petebacondarwin]

You must delete and reinstall node_modules

[GeorgeTailor]

@petebacondarwin do an update from 9 to 10, this is the case when this error pops up.