Don't throw ArgumentTypeException for null values, always

[iconara]

The type checking required by JMESPath is not made for performance. Throwing ArgumentTypeException when a null value is passed to a function that expects a string, for example, is very expensive, when in most cases you expect the result to be null anyway. We implemented this in burtpath our ghetto-fork of jmespath.rb. Could we make something similar for jmespath-java? For example a flag to set to allow functions to be more lenient with null values. The burtpath implementation completely silenced errors when searching (but not when compiling), we might not want to be that extreme, I'm not sure.

[bjorne]

The flag actually made it into JMESPath.rb so I guess using the same semantics (unless considered too Ruby-idiomatic) would be a good idea.

See here for example: https://github.com/jmespath/jmespath.rb/blob/ac6e6ccf2c733ae2ede149c0b78e26b7d46f8d00/lib/jmespath/parser.rb#L32

[iconara]

I can think of two different versions of this:

• A flag that makes any search operation that normally would throw an exception return null. No errors are thrown from Expression#search at all. The search is not aborted though, it carries on so max(foo) | {"max": @} where foo is anything but the expected array of strings or array of numbers would result in {max: null} and not a type error – and max(@, @) | {max: @} would result in {"max": null} and not an arity error.
• A flag that makes functions be more lenient when checking types. When possible they would act reasonably when given null values, but they could still throw type errors when it wouldn't be possible to handle a null value. For example max(foo) where foo was null would behave like when foo was [], i.e. return null. Passing the wrong number of arguments to a function would always be an error.

One motivation for bypassing the strict type checking is that it's a bit arbitrary. It's just functions that are strict, most other operations work fine with null values – foo[] when foo is null works fine, for example.

I'm leaning towards the second option.

[iconara]

This has been released as jmespath-0.3.0-SNAPSHOT