[codegen][Go] Fix compilation error of generated go code when schema is free form object

[sebastien-rosset]

codegen:

1. Add helper function isAnyTypeSchema()
2. Add code comments to clearly differentiate between free-form object (which must be a map of string to value) and any type value (which can be array, object, string, integer...).
3. Remove unused min/max fields in CodegenProperty
4. Add code comments in CodegenProperty
5. Fix equals() method in CodegenProperty. The deprecated attribute was a comparison to itself

golang:
When a schema is Free Form object, the go-experimental generator sets the golang dataType to NullableMap[string]interface{}, which is not a valid go type. This causes a compilation failure of the generated code.

This PR is a fix for this problem.

components:
  schema:
        stuff:
            type: object
            nullable: true

Issue: #5387

From this PR, it's clear there is a different interpretation of the OAS spec between the go-experimental generator versus the python-experimental generator. This is a problem that needs to be addressed to get consistency across languages.

• In the generated go client, the only accepted type is a map of string to values
• In the generated python client, any valid JSON document will be accepted.

PR checklist

• Read the contribution guidelines.
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[sebastien-rosset]

@spacether, fyi, there is inconsistent behavior for the validation of the HTTP body between Python and Go.

[spacether]

Does interface allow array and map types?
Those should be allowed per https://swagger.io/docs/specification/data-models/data-types/#any

[sebastien-rosset]

Does interface allow array and map types?

you mean the golang interface{} type? If so yes, but see referenced issue #5387 for details. The way I understand the spec, a "type: object" is only an an unordered set of properties mapping a string to an instance.

[sebastien-rosset]

Does interface allow array and map types?
Those should be allowed per https://swagger.io/docs/specification/data-models/data-types/#any

Good point, thanks for catching that. Based on this, the 'go-experimental' generator is correct to use map[string]interface{}. We have a few use cases:

Case 1: the following schema must validate to a map of string to values (no other type allowed):

components:
  schema:
        stuff:
            type: object

Note that the "python-experimental" generator needs to be fixed. It is currently too lenient.

Case 2: the following schemas must validate to the null value or a map of string to values:

components:
  schema:
        stuff:
            type: object
            nullable: true

Case 3: the following schema can validate to any valid JSON document:

components:
  schema:
        stuff: {}

There should be a follow-up PR to support use case 3 in go-experimental.

[sebastien-rosset]

This was a bug before this PR. There is no markdown file "map[string]interface{}.md"

[sebastien-rosset]

@antihax @bvwells @grokify @kemokemo @bkabrda

[bkabrda]

Hey 👋 could you please check out #5414? I think one of us would need to modify their PR so that they would both work together correctly (also I'd like to hear your thoughts on that PR of mine, since you seem to be a user of go-experimental clients and this does some major changes to fix support for explicit nulls). Thanks!

[sebastien-rosset]

Hey 👋 could you please check out #5414? I think one of us would need to modify their PR so that they would both work together correctly (also I'd like to hear your thoughts on that PR of mine, since you seem to be a user of go-experimental clients and this does some major changes to fix support for explicit nulls). Thanks!

I looked at your PR, and they don't seem to overlap much. Your PR is about nullable objects, my PR is about free-form objects and any type objects. Do you have something specific in mind?

[sebastien-rosset]

@sebastien-rosset can you please resolve the merge conflicts when you've time?

Done.

[sebastien-rosset]

After merge of #5414 , the generated code has compilation errors. TODO, fix.

go-petstore/model_user.go:344:42: o.ArbitraryNullableObject.Get undefined (type map[string]interface {} has no field or method Get)
go-petstore/model_user.go:348:35: o.ArbitraryNullableObject.Get undefined (type map[string]interface {} has no field or method Get)
go-petstore/model_user.go:358:34: o.ArbitraryNullableObject.Get undefined (type map[string]interface {} has no field or method Get)
go-petstore/model_user.go:358:67: o.ArbitraryNullableObject.IsSet undefined (type map[string]interface {} has no field or method IsSet)
go-petstore/model_user.go:363:42: o.ArbitraryNullableObject.IsSet undefined (type map[string]interface {} has no field or method IsSet)
go-petstore/model_user.go:372:27: o.ArbitraryNullableObject.Set undefined (type map[string]interface {} has no field or method Set)
go-petstore/model_user.go:376:27: o.ArbitraryNullableObject.Set undefined (type map[string]interface {} has no field or method Set)
go-petstore/model_user.go:381:27: o.ArbitraryNullableObject.Unset undefined (type map[string]interface {} has no field or method Unset)
go-petstore/model_user.go:418:45: o.ArbitraryNullableTypeValue.Get undefined (type interface {} is interface with no methods)
go-petstore/model_user.go:422:38: o.ArbitraryNullableTypeValue.Get undefined (type interface {} is interface with no methods)
go-petstore/model_user.go:422:38: too many errors

[bkabrda]

@sebastien-rosset sorry for that :/ I might have some spare time by the end of the week, so might be able to help fix your PR if you need.

[sebastien-rosset]

@sebastien-rosset sorry for that :/ I might have some spare time by the end of the week, so might be able to help fix your PR if you need.

I have addressed the issues (I think).