This is a JSON configuration file for LoopBack. The intention of determining whether the database exists or not is to either create it if does not via LoopBack's autoMigrate() function and update it if does via LoopBack's autoUpdate() function.

datasources.json

{
    "db": {
        "connector": "memory",
        "name": "db"
    },
    "mctAudit": {
        "connector": "mssql",
        "port": "{{ grains['audit_dbms_port'] }}",
        "host": "{{ grains['audit_dbms_hostname'] }}",
        "database": "{{ grains['audit_dbms_db'] }}",
        "user": "{{ grains['audit_dbms_username'] }}",
        "password": "{{ grains['audit_dbms_pw'] }}",
        "debug": false,
        "autoMigrate": "{% if not postgres.db_exists '{{ grains['audit_dbms_db'] }}' %}",
        "autoUpdate": "{% if postgres.db_exists '{{ grains['audit_dbms_db'] }}' %}"
    },
}


#### The above throws the following exception when the state is executed. ####

----------
          ID: datasources
    Function: file.managed
        Name: /home/cds/tcmweb/api-server/server/datasources.json
      Result: False
     Comment: Unable to manage file: Jinja syntax error: expected token 'end of statement block', got 'string'; line 24
             
              ---
              [...]
                      "host": "{{ grains['audit_dbms_hostname'] }}",
                      "database": "{{ grains['audit_dbms_db'] }}",
                      "user": "{{ grains['audit_dbms_username'] }}",
                      "password": "{{ grains['audit_dbms_pw'] }}",
                      "debug": false,
                      "autoMigrate": "{% if not postgres.db_exists '{{ grains['audit_dbms_db'] }}' %}",    <======================
                      "autoUpdate": "{% if postgres.db_exists '{{ grains['audit_dbms_db'] }}' %}"
                  },
                  "util": {
                      "connector": "postgresql",
                      "port": "5432",
              [...]
              ---
     Started: 18:59:56.414136
    Duration: 22.641 ms
     Changes:  
----------