Instead of deleting the whole node_modules folders, just rename it and try

npm install 
sudo npm install --unsafe-perm //for macOS

Please find below my angular packages versions -

"@angular-devkit/build-angular": "0.802.0",
"@angular-devkit/core": "8.2.0",
"@angular/animations": "8.2.0",
"@angular/cli": "8.2.0",
"@angular/common": "8.2.0",
"@angular/compiler": "8.2.0",
"@angular/compiler-cli": "8.2.0",
"@angular/core": "8.2.0",

I had the same issue and solved it by downgrading @angular-devkit/build-angular. version to 0.803.24 as Occian Fumnanya Dia said in his answer above If after downgrading the version you still get the same error, try deleting the folder platforms and re-run with ionic cordova run <platform>. Replace <platform> with android or ios.

It will recreate the folder plaforms with new things.

Hope it helps.

This command fixes the situation temporarily:

npm i @angular-devkit/build-angular@0.803.24

My Jenkins build requires me to run the npm audit fix command to download dependencyes. This command makes the same error appear again. Anyone have any idea how to make the audit command ignore angula-devkit?

It seems to be an issue with @angular-devkit/build-angular.. Try downgrading it to a specific version:

npm i @angular-devkit/build-angular@0.803.24

Run also npm i @angular-builders/custom-webpack@8.4.1 --save

For me Occian's answer was not enough, I also had to change @angular-builders/custom-webpack from latest to 8.4.1, because it had build-angular dependency too. This is how to figure it out:

npm list @angular-devkit/build-angular

reports-web-client@0.0.0 C:\projects\2778\reports-web-client
+-- @angular-builders/custom-webpack@9.1.0
| `-- @angular-devkit/build-angular@0.901.1
`-- @angular-devkit/build-angular@0.803.8

Which meant, I had 2 versions of the package, and that's why the error would still show up.

If you use npm audit fix, find the package which you tried to fix and restore to a stable version and be aware with vulnerabilities.

From my experience a new module that you are using is designed for angular9 and you should upgrade your imports if possible to:

 "dependencies": {
    "@angular/animations": "^9.1.9",
    "@angular/cdk": "^9.2.4",
    "@angular/common": "^9.1.9",
    "@angular/compiler": "^9.1.9",
    "@angular/core": "^9.1.9",
    "@angular/forms": "^9.1.9",
    "@angular/platform-browser": "^9.1.9",
    "@angular/platform-browser-dynamic": "^9.1.9",
    "@angular/router": "^9.1.9",
 ...
}
"devDependencies": {
    "@angular-devkit/build-angular": "^0.901.7",
    "@angular/cli": "^9.1.7",
    "@angular/compiler-cli": "^9.1.9",
    "@angular/language-service": "^9.1.9",
   ...
}

Personally, the best solution is:

ng update @angular/cli @angular/core

Why? Because sooner or later, you need to upgrade to Angular 9+ and the other solutions are only to downgrade it.

I was facing the same issue today until I used this solution and this one works perfectly well.

This cmd fixes the problems

npm i @angular-devkit/build-angular@0.803.24

i fixed it by open

package.json file

and update on the next line

@angular-devkit/build-angular": "^0.803.8"

then run

npm i

Just install the @angular-devkit/build-angular according to your version like if you have angular V.8 then try this or find your version and install it according to your angular version.

npm i @angular-devkit/build-angular@0.803.29

Use below version for current angular version:

@angular-devkit/build-angular@0.8.9 v6-lts

@angular-devkit/build-angular@0.13.10 v7-lts

@angular-devkit/build-angular@0.803.29 v8-lts

@angular-devkit/build-angular@0.901.13 v9-lts

@angular-devkit/build-angular@0.1002.1 v10-lts

see last current tags version @angular-devkit/build-angular