feat: generate unified error dispatcher

[kuhe]

Currently, output deserializers generate one "Error Dispatcher" per operation output. This may mean hundreds of these dispatcher functions (given that many commands) when the set of modeled errors tends to only be 5 to 10 in number.

This PR merges all error dispatchers into one function per service.

Comparison Metrics:

• Web: bundle size of S3 is ~400 bytes larger when fully gzipped/minified as in a production environment. Total of ~160kb -> ~161kb.

• Node.js: install size of dist-cjs

  • S3, 1020kb -> 976kb
  • Lambda, 784kb -> 700kb
  • EC2, 6.5mb -> 5.8mb
  • SageMaker, 3.1mb -> 2.6mb

• What are the outlier AWS services with the highest count of distinct modeled exceptions? and what is the average count of modeled exceptions per service?

  • cloudtrail, 83

  • codecommit, 188 (600 line de_CommandError fn)

    • regardless of that, codecommit dist-cjs also gets smaller 1.1mb -> 896kb

  • codedeploy, 110

  • config-server, 53

  • a few services have between 20 and 50, (about 20 services)

  • the vast majority have less than 20 distinct exceptions (300+ services)

[kuhe]

it is further possible to convert the syntax of the dispatcher from

switch (code) {
  case 'A':
  case 'B':
      throw await de_ExceptionRes(output, context);
  case 'C':
  case 'D':
      throw await de_Exception2Res(output, context);
  default:
    throwDefaultError(...)
}

to

const exceptions = {
  A: 1, // look up the index of the deser fn
  B: 1,
  C: 2,
  D: 2,
};
const deser = [
  de_ExceptionRes,
  de_Exception2Res
];
if (exceptions[code]) {
  throw await deser[exceptions[code]](output, context);
}
throwDefaultError(...)

But this is a very incremental reduction. Does the Smithy team want to have this part included?

[syall]

LGTM.

Clarifying question: as an edge case, is there a possibility of a tree-shaked artifact to become larger with this change? E.g., only importing 1 command, which pre-PR would only import a smaller command-specific error deserializer, compared to post-PR which will now import a larger unified error deserializer?

[syall]

it is further possible to convert the syntax of the dispatcher from

switch (code) {
  case 'A':
  case 'B':
      throw await de_ExceptionRes(output, context);
  case 'C':
  case 'D':
      throw await de_Exception2Res(output, context);
  default:
    throwDefaultError(...)
}

to

const exceptions = {
  A: 1, // look up the index of the deser fn
  B: 1,
  C: 2,
  D: 2,
};
const deser = [
  de_ExceptionRes,
  de_Exception2Res
];
if (exceptions[code]) {
  throw await deser[exceptions[code]](output, context);
}
throwDefaultError(...)

But this is a very incremental reduction. Does the Smithy team want to have this part included?

I think we can consider further reduction in a separate PR.