gosnappi - replacement of existing Go SDK

[ashutshkumr]

Currently we generate Go SDK from Open Traffic Generator API using oapi-codegen.

So far multiple problems have been identified with generated code.

• Optional fields are generated as a pointer. This makes constructing config very inconvenient. e.g.

  // Generated struct
  type FlowRate struct {
      // The available types of flow rate.
      Choice *string `json:"choice,omitempty"`
          // .... skipped some fields ...
      // Packets per second.
      Pps *int64 `json:"pps,omitempty"`
  }
  
  // allocate storage
  r := FlowRate{
      Choice: new(string),
      Pps: new(int64),
  }
  // then fill the values in
  *r.Choice = "pps"
  *r.Pps = 1000

• No code is generated for enum types. This results in user providing strings as enum values which isn't type checked at all.
  It is also not very straight-forward to have enums with string values in Go (language limitation).

  // Choice is an enum
  *r.Choice = "pps"
  
  // something like this would've been better
  *r.Choice = r.PPS

• No way to create structs with default fields

  // something like this would've been nice
  r := NewFlowRate()
  fmt.Println(r.Pps) // output: 1000

• Since most nested fields are pointers, logging any struct is not straight-forward at all. Most often you'll see output like this.

  r := FlowRate{
      Choice: new(string),
      Pps: new(int64),
  }
  *r.Choice = "pps"
  *r.Pps = 1000
  fmt.Println(r)  // output: {<nil> 0x4000099050 <nil> <nil> <nil> <nil> 0x40000ba370}

• Types only map to int (and not uint)

• Handling API calls require elaborate steps

  • Setup HTTP client settings (location, certificate, context, etc.)
  • Response needs to be manually unmarshalled into structs - response for every API request needs to be handled by some util func

• No client-side validations - good to have

• No helpers for loading from JSON config (standard support for serdes)

• Generated code is not go getable.

@ajbalogh @ankur-sheth