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https://github.com/switchupcb/copygen
Go generator to copy values from type to type and fields from struct to struct (copier without reflection). Generate any code based on types.
https://github.com/switchupcb/copygen
code-generation code-generator copy generator go golang
Last synced: 9 days ago
JSON representation
Go generator to copy values from type to type and fields from struct to struct (copier without reflection). Generate any code based on types.
- Host: GitHub
- URL: https://github.com/switchupcb/copygen
- Owner: switchupcb
- License: gpl-3.0
- Created: 2021-09-21T01:51:04.000Z (about 3 years ago)
- Default Branch: main
- Last Pushed: 2024-03-10T21:16:42.000Z (8 months ago)
- Last Synced: 2024-07-31T20:51:43.539Z (3 months ago)
- Topics: code-generation, code-generator, copy, generator, go, golang
- Language: Go
- Homepage: https://switchupcb.com/copygen-license-exception/
- Size: 429 KB
- Stars: 339
- Watchers: 4
- Forks: 22
- Open Issues: 7
-
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
Awesome Lists containing this project
- awesome-go - copygen - Generate type-to-type and type-based code without reflection. (Generators / Search and Analytic Databases)
- awesome-go-extra - copygen - 09-21T01:51:04Z|2022-07-28T12:28:22Z| (Generators / Utility/Miscellaneous)
README
[
](https://github.com/switchupcb/copygen#copygen)
---
[](https://pkg.go.dev/github.com/switchupcb/copygen)
[](https://github.com/switchupcb/copygen/blob/main/LICENSE)
[
](https://github.com/avelino/awesome-go#generators)
Copygen is a command-line **code generator** that generates type-to-type and field-to-field code without adding any reflection or dependencies to your project. Manual-copy code generated by Copygen is [**391x faster**](https://github.com/gotidy/copy#benchmark) than **jinzhu/copier**, and adds no allocation to your program. Copygen is the most customizable type-based generator to-date and features a rich yet simple setup. Copygen supports _**every**_ Go type including `basic`, `array`, `slice`, `map`, `chan`, `interface`, and `func` types.
| Topic | Categories |
| :------------------------------ | :--------------------------------------------------------------------------------- |
| [Usage](#Usage) | [Types](#types), [Setup](#setup), [Command Line](#command-line), [Output](#output) |
| [Customization](#customization) | [Custom Objects](#custom-objects), [Templates](#templates) |
| [Matcher](#matcher) | [Automatch](#automatch), [Manual](#manual), [Depth](#depth) |
| [Usecases](#usecase) | [When to Use](#when-to-use-copygen), [Custom Generation](#custom-generation) |
| [License](#license) | [What can I do?](#what-can-i-do), [License Exception](#license-exception) |
## Usage
Each example has a **README**.
| Example | Description |
| :------------------------------- | :--------------------------------------- |
| main | The default example. |
| [basic](examples/basic/) | Matches a `basic` type to a field. |
| [automatch](examples/automatch/) | Uses the automatch feature with depth. |
| [map](examples/map/) | Uses the manual map feature. |
| [tag](examples/tag/) | Uses the manual tag feature. |
| deepcopy _(Roadmap)_ | Uses the deepcopy option. |
| [error](examples/error/) | Uses `.go` templates to return an error. |
| [tmpl](examples/tmpl/) | Uses `.tmpl` templates. |
| [program](examples/program/) | Uses Copygen programmatically. |
_*[`multi`](examples/_tests/multi/setup/setup.go) tests every type._
This [example](examples/main/) uses three type-structs to generate the `ModelsToDomain()` function using a Command Line Interface.
### Types
The following types are defined in a program.
`./domain/domain.go`
```go
// Package domain contains business logic models.
package domain
// Account represents a user account.
type Account struct {
ID int
UserID string
Name string
Other string // The other field is not used.
}
```
`./models/model.go`
```go
// Package models contains data storage models (i.e database).
package models
// Account represents the data model for account.
type Account struct {
ID int
Name string
Password string
Email string
}
// A User represents the data model for a user.
type User struct {
UserID int
Name string
UserData string
}
```
The `models.Account` and `models.User` fields will be copied to `domain.Account` fields.
### Setup
Setting up Copygen is a 2-step process involving a `YML` and `GO` file.
#### setup.yml
```yml
# Define where the code will be generated.
generated:
setup: ./setup.go
output: ../copygen.go
# Define the optional custom templates used to generate the file (.go, .tmpl supported).
template: ./generate.go
# Define custom options (which are passed to generator options) for customization.
custom:
option: The possibilities are endless.
```
_The main example ignores the template fields._
#### setup.go
Create an interface in the specified setup file with a `type Copygen interface`. In each function, specify _the types you want to copy from_ as parameters, and _the type you want to copy to_ as return values. _This interface is inspired by **goverter**._
```go
/* Specify the name of the generated file's package. */
package copygen
/* Copygen defines the functions that will be generated. */
type Copygen interface {
// custom see table below for options
ModelsToDomain(*models.Account, *models.User) *domain.Account
}
```
_Copygen uses no allocation **with pointers** because Go is pass-by-value. Specifying a pointer results in the object's fields being assigned directly; as opposed to a copy of the object's fields._
#### options
You can specify options for your Copygen functions using comments: Do **NOT** put empty lines between comments that pertain to one function. **Options are evaluated in order of declaration.**
| Option | Use | Description | Example |
| :------------------ | :------------------------------------------------------- | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | :--------------------------------------------------------------------------- |
| `map from to` | Map fields manually. | Copygen uses its [automatcher](#automatch) by default.
Override this to `map` fields to and from each other.
Regex is supported for from-fields. | `map .* package.Type.Field`
`map models.Account.ID domain.Account.ID` |
| `tag field key` | Map fields manually using tags. | Copygen uses its [automatcher](#automatch) by default.
Override this using `tag` with _regex_ and a tag key. | `tag package.Type.Field key`
`tag .* api` _(all fields)_ |
| `depth field level` | Use a specific field depth. | Copygen uses full-field [depth](#depth) by default.
Override this using `depth` with _regex_ and a [depth-level](#depth) integer. | `depth .* 2`
`depth models.Account.* 1` |
| `deepcopy field` | Deepcopy from-fields. | Copygen shallow copies fields by default.
Override this using `deepcopy` with _regex_.
For more info, view [Shallow Copy vs. Deep Copy](#shallow-copy-vs-deep-copy). | `deepcopy package.Type.Field`
`deepcopy .*` _(all fields)_ |
| `automatch field` | Use the automatcher selectively or with `map` and `tag`. | Using `map` or `tag` disables the default automatcher.
Enable it using `automatch` with _regex_.
| `automatch package.Type.Field`
`automatch models.User.*` |
| `custom option` | Specify custom function options. | Use custom options with [templates](#templates).
Returns `map[string][]string` _(trim-spaced)_. | `ignore true`
`swap false` |
_[View a reference on Regex.](https://cheatography.com/davechild/cheat-sheets/regular-expressions/)_
#### Convert
In certain cases, you may want to specify a how a specific type or field is copied with a function. This can be done by defining a function with a `convert` option.
```go
/* Define the function and field this converter is applied to using regex. */
// convert .* models.User.UserID
// Itoa converts an integer to an ascii value.
func Itoa(i int) string {
return c.Itoa(i)
}
```
### Command Line
Install the command line utility: Copygen is an executable and not a dependency, so use `go install`.
```
go install github.com/switchupcb/copygen@latest
```
Install a specific version by specifying a branch.
```
go install github.com/switchupcb/copygen@main
```
Install a specific version by specifying a tag.
```
go install github.com/switchupcb/[email protected]
```
Run the executable with given options.
```bash
# Specify the .yml configuration file.
copygen -yml path/to/yml
```
_The path to the YML file is specified in reference to the current working directory._
### Output
This example outputs a `copygen.go` file with the specified imports and functions.
```go
// Code generated by github.com/switchupcb/copygen
// DO NOT EDIT.
// Package copygen contains the setup information for copygen generated code.
package copygen
import (
c "strconv"
"github.com/switchupcb/copygen/examples/main/domain"
"github.com/switchupcb/copygen/examples/main/models"
)
// Itoa converts an integer to an ascii value.
func Itoa(i int) string {
return c.Itoa(i)
}
// ModelsToDomain copies a *models.Account, *models.User to a *domain.Account.
func ModelsToDomain(tA *domain.Account, fA *models.Account, fU *models.User) {
// *domain.Account fields
tA.ID = fA.ID
tA.UserID = Itoa(fU.UserID)
tA.Name = fA.Name
}
```
## Customization
Copygen's method of input and output allows you to generate code not limited to copying fields.
### Custom Objects
Custom types external to your application can be created for use in the `setup.go` file. When a file is generated, all types _(structs, interfaces, funcs)_ are copied **EXCEPT** the `type Copygen interface`.
```go
type DataTransferObject struct {
// ...
}
type Model interface {
// ...
}
func New() {
// ...
}
```
### Shallow Copy vs. Deep Copy
The library generates a [shallow copy](https://en.m.wikipedia.org/wiki/Object_copying#Shallow_copy) function by default. An easy way to deep-copy fields with the same return type is by using `new()` as or in a converter function **or** by using a custom template.
### Templates
Copygen supports three methods of code generation: `.go`, `.tmpl`, and `programmatic`. View the [models.Generator](cli/models/generator.go) type for context on the parameters passed to each function. Generator options are parsed from the YML configuration file. Function options are parsed from `custom` options. Any other option represents a `FieldOption`.
#### .go
Use `.go` files to customize the code generation algorithm. The `copygen` generator uses the [`package template Generate(*models.Generator) (string, error)`](cli/generator/template/generate.go) to generate code. As a result, **this function is required** for your `.go` templates to work. The [error example](examples/error/) modifies the `.yml` in order to use **custom `.go` template functions** that `return error`. The [`template/generate.go`](/cli//generator/template/generate.go) file provides the default code generation algorithm for generating code.
_Use of non-extracted Go Module Imports in [`generate.go` template files](cli/generator/template/generate.go) are unsupported at the current time._
#### .tmpl
Use `.tmpl` _([`text/templates`](https://pkg.go.dev/text/template))_ to customize the code generation algorithm. The [template example](examples/tmpl/) uses a [`.tmpl`](/examples/tmpl/template/generate.tmpl) file to generate code.
#### programmatic
Use `copygen` as a third-party module in your application. For more information, read the [program example](/examples/program/README.md).
## Matcher
Copygen provides two methods of field-matching: `automatch` and `manual`.
_Disable the matcher from the command-line using `-xm` or programmatically by setting `Enviroment.DisableMatcher` = true._
### Automatch
When fields aren't specified using [options](#options), Copygen will attempt to automatch type-fields by name and definition. Automatch will match one from-field to many to-fields. **Automatch supports field-depth** (where types are located within fields) **and recursive types** (where the same type is in another type). Automatch loads types from Go modules _(in GOPATH)_: Ensure your modules are up to date by using `go get -u `.
### Manual
Using the `map` or `tag` option disables the automatcher, which allows you to manually match fields. In order to re-enable the automatcher, use the `automatch` option. Options are evaluated in order of declaration, so using `automatch .*` **after** declaring `map` and `tag` options provides an easy way to re-enable the _automatcher_ for remaining fields.
#### Depth
The automatcher uses a field-based depth system. A field with a depth-level of 0 will only match itself. Increasing the depth-level allows its sub-fields to be matched. This system allows you to specify the depth-level for whole types **and** specific fields.
```go
// depth-level in relation to the first-level field (0).
type Account
// 1
ID int
Name string
Email string
Basic domain.T // int
User domain.DomainUser
// 2
UserID string
Name string
UserData map[string]interface{}
// 1
Log log.Logger
// 2
mu sync.Mutex
// 3
state int32
sema uint32
// 2
prefix string
flag int
out io.Writer
// 3
Write func(p []byte) (n int, err error)
buf []byte
```
## Usecase
#### When to Use Copygen
Copygen's main purpose is to save you time by generating boilerplate code to map objects together.
#### Why would I do that?
In order to keep a program adaptable _(to new features)_, a program may contain two types of models. The first type of model is the **domain model** which is **used throughout your application** to model its business logic. For example, the [domain models of Copygen](cli/models/) focus on field relations and manipulation. In contrast, the ideal way to store your data _(such as in a database)_ may not match your domain model. In order to amend this problem, you create a **data model**. The [data models of Copygen](cli/config/models.go) are located in its configuration loader. In many cases, you will need a way to map these models together to exchange information from your data-model to your domain _(and vice-versa)_. It's tedious to repeatedly do this in the application _(through assignment or function definitions)_. Copygen solves this problem.
#### Custom Generation
Copygen's customizability with templates allows you to generate any code **based on types** _(and their respective fields, tags, etc)_.
| Example | Description |
| :------ | :-------------------------------------------------------------------------------------- |
| Repogen | Generate a Business-Logic Repository package based on a Data Access Object (DAO) model. |
| Wrapper | Generate functions for requests using an API resource and request object model. |
_Check out more usecases in real-world examples using [Copygen Usecases](https://github.com/switchupcb/copygen/discussions/categories/usecases)._
## License
Copygen uses a [GPLv3 License](https://www.gnu.org/licenses/gpl-3.0.en.html). An exception is provided for template and example files, which are licensed under the [MIT License](cli/generator/template/LICENSE.md).
### What can I do?
**Code generated by Copygen can be used without restriction (including proprietary and commercial usage)** since generated code is not considered a derivative work. In contrast, **modifications** to the _Copygen Software Source Code_ and/or implementing Copygen in a larger work **programmatically** requires you to [adhere to the GPLv3 License](https://www.gnu.org/licenses/gpl-faq.html). These restrictions do **NOT** apply to template or example files, as long as those files don't generate Copygen itself.
### License Exception
A license exception allows you to modify and/or use Copygen programmatically **without restriction**. In order to purchase a license exception, please contact SwitchUpCB using the [Copygen License Exception Inquiry Form](https://switchupcb.com/copygen-license-exception/).
## Contributing
You can contribute to this repository by viewing the [Project Structure, Code Specifications, CI/CD, and Roadmap](CONTRIBUTING.md).