Custom Getter

[A-312]

We should allow to set custom getter to add more choice between env, arg and .load(.

Example: Custom Getter for file

const schema = {
  db: {
    name: {
      doc: 'Database name',
      format: String,
      default: 'users',
      getter: 'file',
      filepath: '/mycustompath/togetmy/name'
    }
  }
}

// convict.addGetter(name, priority, getter)
convict.addGetter('file', 70, (name, val, schema) => readFile(schema.filepath))

Custom priority level

And we should allow to set custom priority level : https://github.com/mozilla/node-convict/blob/master/lib/convict.js#L600-L601

Priority level	Getter
0	Default value
20	File or json set in function argument
40	Environment variables (only used when env property is set in schema)
60	Command line arguments (only used when arg property is set in schema)

[A-312]

Instead todo (6 loops) :

(Order : default, value (=.load or .loadFile), env, arg, set (= .set))

// loading schema

1. default loop
2. env loop
3. arg loop

// .load or .loadFile

4. value loop (-> json of .load or .loadFile)
5. env loop
6. arg loop

---

I will do (2 loops) :

// loading schema

1. Check for the value with the most priority --> 1) arg, 2) env, 3) default and get the value. I will write a variable _cvtActualGetter in schema (by the getter name arg/env/default.

// .load or .loadFile

2. value loop (-> json of .load or .loadFile) apply the value depending of the priority (saved in _cvtActualGetter) to run < priority(value) => 'default'.

_cvtActualGetter will be usefull for #260

[A-312]

I referenced some issue to fix it in my PR (to keep them in my head).

[A-312]

The actual prototype is : addGetter(property, getter, useCoerce, usedOnlyOnce, rewrite)

• property : Name & keyname in schema
• getter : function to get the value
• usedOnlyOnce : boolean or function, if true will fire : throw new Error("'" + fullName + "' reuses '" + getterName + "' getter value: " + value + advice); ;
• rewrite : If true you can rewrite a getter with the same name (property).