Add feat codegen for Kotlin using retrofit

[Photon3009]

PR Description

This PR introduces support for generating Kotlin code using Retrofit for API communication. Retrofit is a type-safe HTTP client for Android and Java by Square, Inc., that makes it easy to consume RESTful web services

Related Issues

• Related Issue #247
• Closes #247

Checklist

• [x] I have gone through the contributing guide
• [x] I have run the tests (flutter test) and all tests are passing

Added/updated tests?

We encourage you to add relevant test cases.

• [x] Yes
• [ ] No, and this is why: please replace this line with details on why tests have not been included

[animator]

flutter test is failing for 4 test cases. Recheck.

[Photon3009]

okay

[Photon3009]

@animator please now check, I've updated the pr

[animator]

@Photon3009 Few points:

• Your generated kotlin code has ResponseBody class. What is the structure of this class? how will the user know.

  • You need to write test cases for all the request models as described here. For example, see test file for Python or cURL.

• As the user needs to perform additional tasks to run this generated code, you need to document an example with full steps showing how to do so. So that we can provide a link to the user to learn more. See example for JS (fetch) in this comment

[Photon3009]

hey @animator, please check the example below. If it works, then I will write the remaining tests for this. Otherwise, let me know if we need to add code to print a generic response in the generated code too

Structure of Response Body

The `ResponseBody` class in Retrofit is a generic class that represents the body of an HTTP response. To handle the response properly, you should define a data class that matches the structure of the JSON response you're expecting. For example, if you're fetching user data from an API, your data class might look something like this: ```kotlin data class User( val id: String, val name: String, val email: String ) ```

The actual generated code

```kotlin import retrofit2.Call import retrofit2.http.GET import retrofit2.http.Query interface ApiService { @GET("/api/") fun getUser(@Query("format") format: String): Call } fun main() { val service = Retrofit.Builder() .baseUrl("https://randomuser.me") .addConverterFactory(GsonConverterFactory.create()) .build() .create(ApiService::class.java) // Call your API methods here using service object } ```

Complete Example in Koltin

```kotlin import retrofit2.Call import retrofit2.http.GET import retrofit2.http.Query interface ApiService { @GET("/api/") fun getUser(@Query("format") format: String): Call } fun main() { val service = Retrofit.Builder() .baseUrl("https://randomuser.me") .addConverterFactory(GsonConverterFactory.create()) .build() .create(ApiService::class.java) val call = service.getUser("json") call.enqueue(object : Callback { override fun onResponse(call: Call, response: Response) { if (response.isSuccessful) { val user = response.body() println("User ID: ${user?.id}, Name: ${user?.name}, Email: ${user?.email}") } else { println("Error: ${response.errorBody()}") } } override fun onFailure(call: Call, t: Throwable) { println("Failed to fetch user: ${t.message}") } }) } ```

[animator]

This works

[animator]

Can you add the remaining test cases.

[Photon3009]

sorry for the delay, currently going through my exams, will complete this asap, probably within two days

[animator]

No problem. Good luck for the exams.

[Photon3009]

Thanks @animator I have updated the test cases!

[Photon3009]

@animator did you check this?

[animator]

As announced in the discord server, we are busy with application reviews and all PR reviews are on hold.

[Photon3009]

okay!

[animator]

The generated code for POST with form fields are incorrect. Add complete working examples in comment for the below cases:

• GET 8
• POST 2
• POST 4
• POST 6

[animator]

Please raise a new PR after ironing out everything.