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]

I think there is two types possible for Getter : Loading only once like (env, arg) or loading for each .load like this :

And priority argument can be number (=> getter is loaded only once) or string ('load' or 'load/set') (=> getter is loaded for each .load (if the value is set)).

const schema = {
  options: {
    format: Array,
    default: [],
    getter: 'array'
  }
}

// convict.addGetter(name, priority, getter)
// priority number or string ('load' | 'load/set')
convict.addGetter('array', 'load/set', (name, val, schema, current) => {
  if (Array.isArray(val))
    return val;
  elseif (typeof val === 'object' && Array.isArray(val.add))
    val.add.forEach((n) => current.push(n))
  else
    throw 'invalid value for Array getter'
})

convict.load({
  options: ['utf8']
})

convict.load({
  options: { add: ['table', 'verbose'] }
})

convict.validate();

// convict.get(options) // ['utf8', 'table', 'verbose']

what do you think ?

EDIT :

I will add two arguments : priority and loadedType -> (run after start (like default) or run after load/loadFile (like env)). EDIT 3 : I find an other/better way.

EDIT 2 :

My example code should be :

const schema = {
  options: {
    format: Array,
    array: [] // array key directly
  }
}

[A-312]

I currently work on. I will change the logic of :

node-convict/lib/convict.js

Lines 329 to 353 in be350a7

	function importEnvironment(o) {
	const env = o.getEnv();
	Object.keys(o._env).forEach(function(envStr) {
	if (env[envStr] !== undefined) {
	let ks = o._env[envStr];
	ks.forEach(function(k) {
	o.set(k, env[envStr]);
	});
	}
	});
	}
	function importArguments(o) {
	const argv = parseArgs(o.getArgs(), {
	configuration: {
	'dot-notation': false
	}
	});
	Object.keys(o._argv).forEach(function(argStr) {
	let k = o._argv[argStr];
	if (argv[argStr] !== undefined) {
	o.set(k, String(argv[argStr]));
	}
	});
	}

node-convict/lib/convict.js

Lines 250 to 264 in be350a7

	if (o.env) {
	if (!env[o.env]) {
	env[o.env] = [];
	}
	env[o.env].push(fullName);
	}
	// associate this property with a command-line argument
	if (o.arg) {
	if (argv[o.arg]) {
	throw new Error("'" + fullName + "' reuses a command-line argument: " +
	o.arg);
	}
	argv[o.arg] = fullName;
	}

[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).