Code Generation

Overview

vel provides an option to generate a client libraries and OpenAPI documentation from your Go handlers. This code-first approach ensures your API documentation and client code are always in sync with your implementation.

Supported Targets

• Go
• TypeScript
• OpenAPI 3.0: API specifications

Client Generation

You have to write simple script in your project to generate a client

package main

import (
    "os"
    "github.com/dennypenta/vel/gen"
)

func main() {
    router := myapp.NewRouter()

    err := gen.GenerateClientToFile(router, gen.ClientGeneratorConfig{
        // generated client class/struct name
        TypeName:    "Client",
        // Package name for Go clients (ignored for TypeScript)
        PackageName: "client",
        // Output directory path
        OutputDir:   "client",
        // "go" or "ts" are supported
        Language:    "go",
        // Post-processing pipe command
        PostProcess: "goimports",
    })
    if err != nil {
        panic(err)
    }
}

Alternatively, you can write a client to a buffer

package main

import (
    "os"
    "bytes"
    "github.com/dennypenta/vel/gen"
)

func main() {
    router := myapp.NewRouter()

    var buf bytes.Buffer{}

    err := gen.GenerateClient(router, &buf, gen.ClientGeneratorConfig{
        // generated client class/struct name
        TypeName:    "Client",
        // Package name for Go clients (ignored for TypeScript)
        PackageName: "client",
        // "go" or "ts" are supported
        Language:    "go",
        // Post-processing pipe command
        PostProcess: "goimports",
    })
    if err != nil {
        panic(err)
    }
    fmt.Println(buf.String())
}

Type Mapping

vel automatically maps Go types to target languages:

Go to TypeScript Mapping:

• string � string
• int, int32, int64, float64 � number
• bool � boolean
• []Type � Type[]
• map[K]V � Record<K, V>
• time.Time � string (ISO format)

Post-processing

Post processing are shell commands that take the generate output and pipe it out. Imagine it as shell code | postProcessingCommand, but technically it is postProcessing < code