Firebase cannot understand what targets to deploy

Faced similar issue. In firebase.json file (in hosting parameter), we have to give the name of directory that we want to deploy (in my case, I was already in the directory, which I wanted to deploy, hence I put "." in hosting specification). It solved the error for me.

{
  "hosting": {
    "public": ".",
    "ignore": [
      "firebase.json",
      "**/.*",
      "**/node_modules/**"
    ]
  }
}

it would be better to pre-populate the firebase with the default options. I choose that I wanted to use only hosting the firebase.json should have be created with the default hosting option.

{
  "hosting": {
    "public": "public"
  }
}

or you try run firebase init again.