Compilation breaks after update to 9.0.0-rc.13: Duplicate identifier 'ɵngcc0'

[cyrilletuzi]

🐞 bug report

Affected Package

I think the issue is in @angular/compiler-cli as it's about ngcc, but not sure.

Is this a regression?

Yes, it was OK in previous RC (rc.12 and below).

Reproduction

• npm install @angular/cli@next -g
• ng new helloworld --skipGit (git is disabled to avoid ng commands blocking because repo is not clean, otherwise you have to commit every change)
• cd helloworld
• npm install @angular/{animations,common,compiler,core,forms,platform-browser,platform-browser-dynamic,router,compiler-cli,language-service}@9.0.0-rc.12 (rollback to rc.12, as CLI installed rc.13)
• add any library, for example: ng add @angular/material@next and add MatCardModule in AppModule imports
• npm start (to run the compilation with rc.12)
• ng update @angular/core --next (will update to rc.13)
• npm start

🔥 Exception or Error

Compilation breaks with a lot of errors like this one (it's just an example):

import * as ɵngcc0 from '@angular/core';
                   ~~~~~~
    node_modules/@angular/material/core/selection/pseudo-checkbox/pseudo-checkbox.d.ts:13:13 -
error TS2300: Duplicate identifier 'ɵngcc0'.

🌍 Your Environment

Angular Version:

Angular CLI: 9.0.0-rc.12
Node: 12.14.1
OS: darwin x64

Angular: 9.0.0-rc.13
... animations, common, compiler, compiler-cli, core, forms
... language-service, platform-browser, platform-browser-dynamic
... router
Ivy Workspace: Yes

Package                           Version
-----------------------------------------------------------
@angular-devkit/architect         0.900.0-rc.12
@angular-devkit/build-angular     0.900.0-rc.12
@angular-devkit/build-optimizer   0.900.0-rc.12
@angular-devkit/build-webpack     0.900.0-rc.12
@angular-devkit/core              9.0.0-rc.12
@angular-devkit/schematics        9.0.0-rc.12
@angular/cdk                      9.0.0-rc.9
@angular/cli                      9.0.0-rc.12
@angular/material                 9.0.0-rc.9
@ngtools/webpack                  9.0.0-rc.12
@schematics/angular               9.0.0-rc.12
@schematics/update                0.900.0-rc.12
rxjs                              6.5.4
typescript                        3.7.5
webpack                           4.41.2

Anything else relevant?
Quite sure the issue comes from #35079. Before rc.13, when ng updating, next compilation would be blocked, asking to clean up node_moddules (#35082).

With rc.13, compilation is not blocked anymore, Angular do a new ngcc compilation (Compiling @angular/core : es2015 as esm2015), but then fails because of old artifacts. If you clean node_modules (npm ci), then compilation works again.

Also note that:

• if you have no library at all, the issue doesn't happen,
• it's not specific to Material, it happens with all librairies.

So I think #35079 does not clean up libraries packages.

[IgorMinar]

I've tried to repro this in #35101 but so far I'm not having luck.

[cyrilletuzi]

Repro: https://github.com/cyrilletuzi/ngcc-cleanup

To reproduce:

git clone https://github.com/cyrilletuzi/ngcc-cleanup
cd ngcc-cleanup
npm run issue

[gkalpak]

Thx for the repro, @cyrilletuzi. It really helped the to the bottom of it more quickly 💯

So, it turns out we are not invalidating our FileSystem cache correctly when moving a file or when removing a directory during clean-up. I have verified the fix against your repro - PR incoming 🚀

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