Introduction

go-codegen is a library that acts as a wrapper around golang.org/x/tools, providing an API that you can use to parse and generate go code. It's part of my personal stack, and I use it to ease code generation inside another libraries.

This library is something like a compilation of the functions, abstractions, etc, all the code that I usually need when generating code. Feel free to contribute, if you want to.

info

I don't want to use this library to handle the content of the generated files, just to provide tools that ease the process of code generation (code parsing, type inspection, file abstraction, etc).

Don't expect to see code related to template generation, etc. This is intended to be implemented by yourself when generating your code

tip

I strongly recommend that you read this document about GO types, to get a deeper understanding about what we'll talk about in the next chapters. I'll assume will have read.

Getting Started

You will need to install go-codegen before starting. To do it, execute the following command (inside your go module folder):

go get github.com/mathbalduino/go-codegen

As already said, this library acts as a wrapper around golang.org/x/tools, so you will need to create a new GoParser instance (that calls golang.org/x/tools/go/packages.Load) in order to use its utility methods. Example:

package main
import (    "github.com/mathbalduino/go-codegen"    "go/types")
func main() {    config := parser.Config{        // ... your configuration ...        //    }    goParser, e := parser.NewGoParser("<your_pattern>", config)    if e != nil {        panic(e)    }        e = goParser.IterateStructs(func(struct_ *types.TypeName, logger parser.LoggerCLI) error {         // This method will be called once for every struct inside the parsed GO code        // Use the given 'struct_' param to generate your code
        // If you want to stop the iteration, return a non-nil error below        // This error will be forwarded to the caller of 'IterateStructs'        return nil    })    if e != nil {        panic(e)    }}

After you get a working instance of *GoParser, you can call methods that will iterate over the parsed code. With this information, you can generate new code. Currently, you can iterate over structs and interfaces. For more info, see the *GoParser API section.

Don't worry about the configuration, string pattern, etc. All these concepts will be explored in details in the next chapters.

Files abstraction

If you want to generate go or typescript code, the library comes with builtin support for this kind of files, abstracting the file import list, code formatting and persistence (you can use the same API for ts files). Example:

package main
import (    "github.com/mathbalduino/go-codegen/goFile")
func main() {    // ... your goParser instance creation        f := goFile.New("filename", "packageName", "destination/package/import/path")    e := goParser.IterateStructs(func(struct_ *types.TypeName, logger parser.LoggerCLI) error {        generatedCode := generateCodeUsingTemplate(struct_) // or, whatever you want        f.AddCode(generatedCode)        return nil    })    if e != nil {        panic(e)    }        // <title> usually is the name of the library that    // generated the code    // Example: "Code generated by library/import/path v1.2.3"    e = f.Save("<title>", "save/to/folder/x")    if e != nil {        panic(e)    }    // If there's no error, the file has been written to disk}

Focus

The *GoParser, by default, will iterate over the entire parsed code. You can control this behavior by giving a *Focus to the Config, at the *GoParser creation, that tells to the *GoParser to iterate only over some typeName, filePath, etc (for details, see the subsection Focus):

func FocusPackagePath(packagePath string) *Focus { ... }func FocusTypeName(typeName string) *Focus { ... }// ...

Keep reading the docs for details...