ng generate: An unhandled exception occurred: The "path" argument must be of type string. Received undefined

Issue

When I run ng g foo or ng g library foo, I get

An unhandled exception occurred: The "path" argument must be of type string. Received undefined

My log has,

[error] TypeError [ERR_INVALID_ARG_TYPE]: The "path" argument must be of type string. Received undefined
    at validateString (internal/validators.js:124:11)
    at Object.resolve (path.js:1074:7)
    at isInside (/home/ecarroll/cp/js/cjt3/node_modules/@angular/cli/utilities/config.js:211:35)
    at /home/ecarroll/cp/js/cjt3/node_modules/@angular/cli/utilities/config.js:221:28
    at Array.filter (<anonymous>)
    at findProjectByPath (/home/ecarroll/cp/js/cjt3/node_modules/@angular/cli/utilities/config.js:221:10)
    at Object.getProjectByCwd (/home/ecarroll/cp/js/cjt3/node_modules/@angular/cli/utilities/config.js:250:21)
    at GenerateCommand.getDefaultSchematicCollection (/home/ecarroll/cp/js/cjt3/node_modules/@angular/cli/models/schematic-command.js:304:38)
    at async GenerateCommand.parseSchematicInfo (/home/ecarroll/cp/js/cjt3/node_modules/@angular/cli/commands/generate-impl.js:70:30)
    at async GenerateCommand.initialize (/home/ecarroll/cp/js/cjt3/node_modules/@angular/cli/commands/generate-impl.js:17:49)

---

Versions.

Angular CLI: 12.1.1
Node: 14.17.3
Angular: 11.2.14

Solution

For me this was because I had a specific unrelated project in my angular.json that lacked

"projects": {
  "demo-app": {
    "projectType": "application"
  },
}

This could be fixed by either deleting the entry for demo-app or adding the root entry,

"projects": {
  "demo-app": {
    "projectType": "application"
    "root": "projects/demo-app"
  },
}

---

I've opened up issue #21310 to track this

Answered By - Evan Carroll