This patch refactors the DNS default resolver code to make it
easier to be included in a snapshot:
- The code specific for the callback-based DNS resolver are not
in a separate module to make the dependency clearer (it's not
actually needed if the user only ever loads `dns/promises`)
- The common part of the callback-based resolver and the promise-
based resolver is now ResolverBase. The other two user-facing
resolvers are now subclasses of ResolverBase. The default
Resolver is constructed with just ResolverBase. This would
be fine as the default resolver is never actually exposed
to the user-land and it has been working using duck-typing anyway.
- Move the construction of Resolver subclasses into a common
method `createResolverClass()` to reduce code duplication.
The two subclasses now also share the same base constructor.
This would make it possible for them to also share code
for snapshot support later.
- `--dns-result-order` is now queried and refreshed during
pre-execution. To avoid loading the cares_wrap binding unnecessarily
the loading of the binding is also made lazy.
PR-URL: https://github.com/nodejs/node/pull/44541
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Zeyu "Alex" Yang <himself65@outlook.com>
Reviewed-By: Minwoo Jung <nodecorelab@gmail.com>
