Merge ENV

An object merging function that has special support for environment variables

Usage

function merge(destination:object, ...sources:object):object

Merge where keys may be in camel-case or as environment variable.

The destination object is mutated and returned.

There is no direct reference to process.env, we simply support the syntax of process.env keys.

Behavior by key

Environment variable

Keys which are uppercase alpha-numeric, with possible underscore, are legal environment variables per IEEE Std 1003.1-2001 Shell and Utilities volume. These keys are assumed to describe camel-case fields where single underscore implies camel-case, and double underscore implies a dot (i.e. nested object). Their value must be some non-object.

For example:

merge({}, {
  FOO_BAR : 1,
  BAR__BAZ: true
});

gives:

{
  fooBar: 1,
  bar: {
    baz: true
  }
}

Note that setting bar.baz was possible even though bar was not present. However if bar is present and a non-object then it will not be assigned. This is undocumented behavior of lodash.set() which is used internally.

Conventional

Other keys describe immediate field names. Object paths in the key are not supported but object values are merged recursively. The value may be any type.

Parsing

In both cases, where an existing value is in the destination object it implies a type. Any values from the source object(s) are parsed to the destination type. Where no such field already exists, parsing is not performed. Only string|number|boolean types may be parsed.