Support include-prelude in smithy ast

[mullermp]

Background

• What do these changes do?

It allows you to get prelude shapes when getting the AST.

• Why are they important?

Implementations that do not use Smithy in Java will need a way to get prelude shapes in the JSON model. Otherwise, special casing is necessary to handle prelude shapes.

Testing

clean, build, then smithy-cli:runtime.

smithy-cli/build/image/smithy-cli-darwin-aarch64/bin/smithy ast --include-prelude will include prelude shapes.

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[sugmanue]

It allows you to get prelude shapes when getting the AST.

Can you please elaborate on why is this needed? What use case are you trying to solve that needs the prelude shapes in the serialized model?

[mullermp]

Regardless of other implementations, I think being able to see the prelude shapes in the output of AST is useful, especially if those implementations need to see those definitions, or if you want a complete closure of the model to generate against.

The closure I think is important so that implementations don't need to know about preludes at all. When I'm given a model, I expect that model to be complete. I otherwise need to special case every prelude ID. For example, if a structure targets a string, I can't visit that string, I need to inspect all keys of the structure and ignore prelude keys. If the string prelude is in the model, then I can iterate all members agnostically and check their type field, and visit shapes that way.

[yasmewad]

Can you add unit tests for the flag?

[sugmanue]

Regardless of other implementations, I think being able to see the prelude shapes in the output of AST is useful, especially if those implementations need to see those definitions, or if you want a complete closure of the model to generate against.

I don't feel like this is useful enough to justify this change, in particular because, as discussed offline, the prelude shapes need to be known ahead of time anyway. It's also possible to configure the build to include them without any need for this change, see here.

[mullermp]

How do you use a smithy-build.json with the AST command?

[sugmanue]

How do you use a smithy-build.json with the AST command?

In general you can use -c as in

smithy ast -c smithy-build.json

But it doesn't seem to work as expected, not sure why.

[mullermp]

Yes, I tried that originally. I also don't know why a build config file shouldn't influence the AST command, so I ended up opening this PR. If smithy build can send me a complete model with prelude if configured to do so, AST should as well.