Improve parsing behavior and default property usage

[A-312]

Fix: #337

TODO :

• 1) fix: Add option: Properties with default of undefined [do/do not] behave like properties that have not been specified #355 fix: Providing a default of undefined prevents format from being checked #278 Add schema.required = true to allow optional config property or not

• 2) fix: Improve schema parsing and default property usage #337 Improve schema property parsing with .format: property:

  • format: [ Object ] and default is not defined should be parsing like a config schema property (current behavior) ;
  • format: [ String ] or format: [ typeof this !== 'object' ] should catch like convict property (format of last property) even if default is not set (new behavior).
    .

• 3) fix: Incomprehensible errors when missing default property #88 fix: Validate the schema to require defaults #254 Add strict parameter for schema parsing: convict(schema, { strictParsing: true }) -> default and format are required, magic coerce is disabled. If they are forgotten, throw an error.

• 4) fix: We can not do convict(config.getSchema()) #356 Fix convict(config.getSchema()), .getSchema/getSchemaString() should return a convict schema and .getSchema(debug = true) should return convict data schema (for debug usage only).

• 5) Find a way to be able to use default like config property and not like a convict property. Transform: $~default to default during the schema parsing ? And add opt: convict(schema, { acceptDefaultProperty: 'default' })

• 6) Improve/add doc on parsing behavior:

  • parsing behavior :
    • magic parsing/format; Incomprehensible errors when missing default property #88 (<-- disabled with strictParsing: true P3)
    • behavior when default property is defined or not ; Incomprehensible errors when missing default property #88 (<-- disabled with strictParsing: true P3)
    • new behavior with format ; P2
    • accept default key: $~default. P5
  • required true/false ; P1
  • validate ignore config property when: required:false and default:undefined and value=undefined ; Validate the schema to require defaults #254
  • convict(schema, { strictParsing: true/false }) and parsing behavior. P3
    .

• 7) fix: Improve .defaut() and .reset() errors for users #349 Incomprehensible errors when missing default property #88 Improve error for users : .defaut() and .reset() errors + parents rewrited error.

Breakchange :

• P4 is a breakchange.
• P2 is also a breakchange because it changes the behavior of format: [ typeof this !== 'object' ] during the parsing.

EDIT :

• Add _cvtCoerce, _cvtFormat, and _cvtGetOrigin like reservated word for getter name.
• Add also format and required like reservated word for getter name.

[coveralls]

Coverage remained the same at 100.0% when pulling b0e3710 on A-312:improve-parsing-behavior into 30bcc2e on mozilla:feat-multi-packages-split.

[A-312]

(This PR is based into #353, my first commit of this PR is dbe5f00)

[A-312]

(I will try to finish this one before the end of the month)

[A-312]

I had a doubt to know if I have to fix #355 (P1) or not because I didn't know on what case we have to do this and maybe is not the proper way to set default: undefined and required: true.

After thinking, I find one case: password property, I think nobody will add their password in their schema, default will be undefined. Then we want to catch an error if password stays undefined.

And P1 will be usefull with P2 if default will become less essential to parse convict property.