Database emulator does not support .indexOn

[REQUIRED] Environment info

firebase-tools: 3.3.0

Platform: Windows

[REQUIRED] Test case

I used the official docs example for orderByChild https://firebase.google.com/docs/database/security/indexing-data?authuser=0.

// client code
      db.ref('dinosaurs').set({
        "lambeosaurus": {
          "height": 2.1,
          "length": 12.5,
          "weight": 5000
        },
        "stegosaurus": {
          "height": 4,
          "length": 9,
          "weight": 2500
        }
      }).then(()=>{
        db.ref('dinosaurs').orderByChild('height').startAt(3).once('value').then(s => console.log(s.val()));
      })

// security rules
{
  "rules": {
    ".read": true,
    ".write": true,
    "dinosaurs": {
      ".indexOn": [
        "height",
        "length"
      ]
    }
  }
}

[REQUIRED] Steps to reproduce

Running the code above against a real database shows stegosaurus: {height: 4, length: 9, weight: 2500}.

Running it against the emulator shows both stegosaurus: {height: 4, length: 9, weight: 2500} and a warning:

logger.ts:86 [2020-02-18T17:08:23.851Z]  @firebase/database: FIREBASE WARNING: Using an unspecified index. Your data will be downloaded and filtered on the client. Consider adding ".indexOn": "height" at /dinosaurs to your security rules for better performance. 

[REQUIRED] Expected behavior

I expected .indexOn to be supported, or perhaps for the emulator to mention it was not using the index, or for this limitation to be listed somewhere. Maybe it’s already documented but I couldn’t find it in the official docs or the issue tracker.

[REQUIRED] Actual behavior

The emulator silently ignores the index and the client warns that there is no index.

[yuchenshi]

Could you please check if the rules are properly loaded in the the emulator by curl localhost:9000/.settings/rules.json?ns=your-database-name -H 'Authorization: Bearer owner'? (Replace localhost:9000 with your emulator host/port and your-database-name with your database name).

Also, please double check that you’re connecting to the same database in your web app as specified to Firebase CLI. On the web app, make sure you’re specifying the db name like databaseURL: "http://localhost:9000/?ns=foo" (note the ns parameter). And when starting Firebase CLI, make sure to use firebase emulators:start --project foo, because Firebase CLI automatically set the security rules only for the database whose name matches the project ID. If you are accessing a different database, that database will have the default open security rules and no index entries.

[samtstern]

I am going to send a PR to add explicit encoding to all readFileSync calls in this codebase.

Also I think it should be utf8 not utf-8 but I guess Node is forgiving?