vault write --format=json auth/approle/login ... does not return auth.entity_id field

[yeonwoonj]

Describe the bug
vault write --format=json auth/approle/login role_id=<role_id> secret_id=<secret_id> does not return auth.entity_id whereas curl -X POST ... $VAULT_ADDR/v1/auth/approle/login does.

To Reproduce

1. setup an approle according to https://learn.hashicorp.com/vault/identity-access-management/iam-authentication#steps
2. use vault to login with your role_id and secret_id as follows:

$ vault write --format=json auth/approle/login role_id=<role_id> secret_id=<secret_id> | jq .auth
{
  "client_token": "...",
  "accessor": "...",
  "policies": [
    "default",
    "..."
  ],
  "token_policies": [
    "default",
    "..."
  ],
  "identity_policies": null,
  "metadata": {
    "role_name": "..."
  },
  "orphan": true,
  "lease_duration": 3600,
  "renewable": true
}

3. There you can't find entity_id field.
4. use curl to directly send a request for REST API

curl --request POST --data '{"role_id": "<role_id>", "secret_id": "<secret_id>"}' $VAULT_ADDR/v1/auth/approle/login | jq .auth
{
  "client_token": "...",
  "accessor": "...",
  "policies": [
    "default",
    "..."
  ],
  "token_policies": [
    "default",
    "..."
  ],
  "metadata": {
    "role_name": "..."
  },
  "lease_duration": 3600,
  "renewable": true,
  "entity_id": "...",
  "token_type": "service",
  "orphan": true
}

5. response body contains entity_id

Expected behavior
entity_id field is included in the output of the vault write --format=json auth/approle/login ... too.

Environment:

• Vault Server Version (retrieve with vault status): Version 1.1.2
• Vault CLI Version (retrieve with vault version): Vault v1.1.2 ('0082501623c0b704b87b1fbc84c2d725994bac54')
• Server Operating System/Architecture: Linux/amd64

Vault server configuration file(s):

listener "tcp" {
  address     = "<hostname>:8200"
  tls_disable = 0
  tls_cert_file = "/config/cert.pem"
  tls_key_file = "/config/cert.key"
}

storage "file" {
  path = "/vault/file/data"
}

Additional context

Otherwise, getting the entity id of an approle is not possible from the vault cli (automatically in a script) as far as I can see.