JMESPath evaluation

[robin-aws]

Background

• What do these changes do?
  • Adds the ability to evaluate JmespathExpressions
    • Defines a JmespathRuntime<T> interface to provide the necessary basic operations on JSON values at runtime.
    • The actual Evaluator is largely ported over from smithy-java's JMESPathDocumentQuery, but also taking some inspiration from jmespath-java, which also has a generic interface for adapting any existing JSON value representation.
  • Adds JmespathRuntime<T> implementations for both LiteralExpression and Node.
  • Adds a separate smithy-jmespath-tests module with the compliance tests from https://github.com/jmespath/jmespath.test, and instantiates them for both runtime implementations.
• Why are they important?
  • The existing smithy-java evaluator only works on its own Document type, and evaluating expressions on generated types such as SerializableStruct subtypes currently requires first converting to a Document, which is slow. I've also written up implementations of JmespathRuntime for Document and generated types: see smithy-java link below.
  • JMESPath expressions are very easy to get wrong. The existing type checker/linter helps catch egregious errors but is far from complete. Having an interpreter opens the door to features where models can provide examples/tests of their expressions, possibly using the pending @shapeExamples trait (Add new shapeExamples trait that communicates and enforces allowed and disallowed values #2851)

Testing

• How did you test these changes?
  • Mainly existing regression tests and the new smithy-jmespath-tests module.

Links

• Use Smithy's JMESPath evaluator smithy-java#967

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[github-actions]

This pull request does not contain a staged changelog entry. To create one, use the ./.changes/new-change command. For example:

./.changes/new-change --pull-requests "#2878" --type feature --description "JMESPath evaluation"

Make sure that the description is appropriate for a changelog entry and that the proper feature type is used. See ./.changes/README or run ./.changes/new-change -h for more information.