Why do I get this error on npm install in my angular project?

Question

I have an Angular 7 project, and recently when I run npm install in my project I get this error:

npm ERR! code ERESOLVE
npm ERR! ERESOLVE unable to resolve dependency tree
npm ERR! 
npm ERR! While resolving: mat-silabo@0.0.0
npm ERR! Found: @angular/core@7.1.4
npm ERR! node_modules/@angular/core
npm ERR!   @angular/core@"~7.1.0" from the root project
npm ERR! 
npm ERR! Could not resolve dependency:
npm ERR! peer @angular/core@"^9.0.0 || ^10.0.0-0" from @angular/material-moment-   adapter@9.2.4
npm ERR! node_modules/@angular/material-moment-adapter
npm ERR!   @angular/material-moment-adapter@"^9.1.2" from the root project
npm ERR! 
npm ERR! Fix the upstream dependency conflict, or retry
npm ERR! this command with --force, or --legacy-peer-deps
npm ERR! to accept an incorrect (and potentially broken) dependency resolution.
npm ERR! 
npm ERR! See /home/userName/.npm/eresolve-report.txt for a full report.

npm ERR! A complete log of this run can be found in:
npm ERR!     /home/userName/.npm/_logs/2021-05-07T13_24_16_492Z-debug.log

It is a big project and I don't know how to resolve this package conflict. Here is my package.json file:

{
  "name": "mat-silabo",
  "version": "0.0.0",
  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
  "private": true,
  "dependencies": {
    "@angular/animations": "~7.1.0",
    "@angular/cdk": "~7.3.6",
    "@angular/common": "~7.1.0",
    "@angular/compiler": "~7.1.0",
    "@angular/core": "~7.1.0",
    "@angular/flex-layout": "^7.0.0-beta.24",
    "@angular/forms": "~7.1.0",
    "@angular/material": "^7.3.6",
    "@angular/material-moment-adapter": "^9.1.2",
    "@angular/platform-browser": "~7.1.0",
    "@angular/platform-browser-dynamic": "~7.1.0",
    "@angular/router": "~7.1.0",
    "core-js": "^2.5.4",
    "file-saver": "^2.0.2",
    "hammerjs": "^2.0.8",
    "jspdf": "^1.5.3",
    "moment": "^2.24.0",
    "rxjs": "~6.3.3",
    "tslib": "^1.9.0",
    "xlsx": "^0.16.3",
    "zone.js": "~0.8.26"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "~0.11.0",
    "@angular/cli": "~7.1.3",
    "@angular/compiler-cli": "~7.1.0",
    "@angular/language-service": "~7.1.0",
    "@types/node": "~8.9.4",
    "@types/jasmine": "~2.8.8",
    "@types/jasminewd2": "~2.0.3",
    "codelyzer": "~4.5.0",
    "jasmine-core": "~2.99.1",
    "jasmine-spec-reporter": "~4.2.1",
    "karma": "~3.1.1",
    "karma-chrome-launcher": "~2.2.0",
    "karma-coverage-istanbul-reporter": "~2.0.1",
    "karma-jasmine": "~1.1.2",
    "karma-jasmine-html-reporter": "^0.2.2",
    "protractor": "~5.4.0",
    "ts-node": "~7.0.0",
    "tslint": "~5.11.0",
    "typescript": "~3.1.6"
  }
}

OS: Debian 10

Global Angular version: 11

If you need any other details please let me know. I am tired of this package dependency, and I want the project to be clean, so we can install it without npm install --force

thanks

Answer 1

It seems "@angular/material-moment-adapter": "^9.1.2", wants Angular 9 and you have Angular 7. Change this package to "@angular/material-moment-adapter": "~7.1.0", and do a fresh npm install . That should hopefully fix it.

Answer 2

The compiler is complaining that it can't resolve @angular/core 9/10 which is a peer dependency of @angular/material-moment-adapter.

If you are upgrading to Angular 7, you should roll back this dependency to:

"@angular/material-moment-adapter": "~7.3.7"