Generate Golang codes for SDK

[duobei]

1. generate Golang code of Record and Ref Type
2. generate Golang code of Enum Type
3. generate file headers
4. generate api messages and errors

[psafont]

Two big issues I've seen:

• I haven't seen any justification for adding the file ocaml/sdk-gen/go/go_file_headers.ml, it looks like it should be instead autogenerated from the datamodel and not committed.

• All the api messages have changed and this causes a lot of churn. I understand you want to have a way to collect all of them and expose them. Don't other language SDKs do this? If not we can look for other ways of doing this (maybe a ppx?) the method should be reused for all other alnguages

[minglumlu]

It seems there are some duplications between ocaml/sdk-gen/go/gen_go_helper.ml and ocaml/idl/json_backend/gen_json.ml. Is it possible to eliminate these duplications? What's more, could the generated JSON be a language-neutral one? So that we only need to focus on the transformations from JSON to go-specific.

Update:
Ah, I see the differences between Yojson and mustache JSON. Could they be converted to each other easily? At least other SDKs are using mustache JSON as well. Could the Yojson be replaced with mustache JSON?

[duobei]

Two big issues I've seen:

• I haven't seen any justification for adding the file ocaml/sdk-gen/go/go_file_headers.ml, it looks like it should be instead autogenerated from the datamodel and not committed.
• All the api messages have changed and this causes a lot of churn. I understand you want to have a way to collect all of them and expose them. Don't other language SDKs do this? If not we can look for other ways of doing this (maybe a ppx?) the method should be reused for all other alnguages

File heders are autogenerated now.
I have split api_errors.ml modifications into its own commit.

[duobei]

It seems there are some duplications between ocaml/sdk-gen/go/gen_go_helper.ml and ocaml/idl/json_backend/gen_json.ml. Is it possible to eliminate these duplications? What's more, could the generated JSON be a language-neutral one? So that we only need to focus on the transformations from JSON to go-specific.

Update: Ah, I see the differences between Yojson and mustache JSON. Could they be converted to each other easily? At least other SDKs are using mustache JSON as well. Could the Yojson be replaced with mustache JSON?

In the beginning, I wanted to reuse gen_json.ml. As development progressed, I abandoned that idea.
Main reasons below:

1. The mustache templates decide the generated JSON. Templates vary widely between different languages.
2. At its core, OCaml and various language data types are converted to each other by some recursion functions.
   Those functions are not shared.

Surprisingly, the transition between Yojson and mustache JSON is simple through pattern matching.

[kc284]

Not a blocker for this PR, it can go in a new one) but it may be a good idea at some point to add a sanity build in .github/workflows/generate-and-build-sdks.yml to ensure that if people make future API changes they won't break the autogenerated Go code (we're in the process of adding them for the other SDKs too, e.g. see PR#5555).

[duobei]

Not a blocker for this PR, it can go in a new one) but it may be a good idea at some point to add a sanity build in .github/workflows/generate-and-build-sdks.yml to ensure that if people make future API changes they won't break the autogenerated Go code (we're in the process of adding them for the other SDKs too, e.g. see PR#5555).

Cool. We will add that in the following PR.

[github-actions]

pytype_reporter extracted 50 problem reports from pytype output

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You can check the results of the job here