Junctions (linked folders) in the assets folder are only partially copied to the build output

Start by reproducing the Windows 10 case with a junction under src/assets, then compare the build and serve handling of the linked folder with the dist/assets output. Done means nested folders and files such as myFolder/does not work.txt are copied, not just files directly under the junction.

🐞 Bug report

Command

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

Is this a regression?

Did not work with ng 8 and does not work with ng 10. Did not check with 9 or anything before 8.

Description

When creating a junction inside the src/assets folder to another folder somewhere in the filesystem, the compiled output only contains the files that are directly beneath the linked folder. Any sub-folders in this linked folder are ignored by the compiler.

🔬 Minimal Reproduction

Tested on Windows 10:

1. Create an empty angular app with ng new assetsBugApp,
2. create a folder outside the application like "testAssets"
3. Inside "testAssets" create a textfile "works.txt"
4. Inside "testAssets" create a folder "myFolder"
5. Inside "testAssets/myFolder" create a textfile "does not work.txt"
6. Create a junction from "assetsBugApp/src/assets/test" to "testAssets" (eg mklink /J C:\tmp\assetsBugApp\src\assets\test C:\tmp\testAssets)
7. Run ng build
8. Look in the dist/assets folder. You will find the folder "test" containing "works.txt" but no "myFolder" and no "does not work.txt"

🌍 Your Environment

Angular CLI: 10.1.4
Node: 12.18.3
OS: win32 x64

Angular: 10.1.4
... animations, cli, common, compiler, compiler-cli, core
... elements, forms, platform-browser, platform-browser-dynamic
... router
Ivy Workspace: Yes

Package                            Version
------------------------------------------------------------
@angular-devkit/architect          0.1001.4
@angular-devkit/build-angular      0.1001.4
@angular-devkit/build-ng-packagr   0.1001.4
@angular-devkit/core               10.1.1
@angular-devkit/schematics         10.1.4
@angular/cdk                       10.2.3
@angular/language-service          10.1.1
@angular/material                  10.2.3
@schematics/angular                10.1.4
@schematics/update                 0.1001.4
ng-packagr                         10.1.2
rxjs                               6.6.3
typescript                         3.9.7

Anything else relevant?
Might be isolated to Windows environments.

Would be great to have this resolved, copying assets from A to B is less fun than linking them... :)