mus-gen: Code Generator for MUS

mus-gen is a Go code generator for the mus and mus-stream serializers.

Capabilities

Generates high-performance serialization code with optional unsafe optimizations.
Supports both in-memory (mus) and streaming (mus-stream) data processing models.
Can generate code for parameterized types, interfaces and types with multiple versions.
Provides multi-package support.
Enables cross-package code generation.
Can be extended to support additional binary serialization formats beyond MUS.

Getting Started Example

Here, we will generate a MUS serializer for the Foo type.

First, download and install Go (version 1.24 or later). Then, create a foo folder with the following structure:

foo/
 |‒‒‒gen/
 |    |‒‒‒main.go
 |‒‒‒foo.g

**foo.go**

```go
//go:generate go run gen/main.go
package foo

type Int int

type Foo[T any] struct {
  s string
  t T
}

gen/main.go

package main

import (
  "os"
  "reflect"

  "example.com/foo"

  musgen "github.com/mus-format/mus-gen-go/mus"
  genopts "github.com/mus-format/mus-gen-go/options/gen"
)

func main() {
  g, err := musgen.NewGenerator(
    genopts.WithPkgPath("example.com/foo"),
    // genopts.WithPackage("bar"), // Can be used to specify the package name for
    // the generated file.
  )
  if err != nil {
    panic(err)
  }
  err = g.AddDefinedType(reflect.TypeFor[foo.Int]())
  if err != nil {
    panic(err)
  }
  err = g.AddStruct(reflect.TypeFor[foo.Foo[foo.Int]]())
  if err != nil {
    panic(err)
  }
  bs, err := g.Generate()
  if err != nil {
    // In case of an error (e.g., if you forget to specify an import path using 
    // genopts.WithImport), the generated code can be inspected for additional 
    // details.
    log.Println(err)
  }
  err = os.WriteFile("./mus.gen.go", bs, 0644)
  if err != nil {
    panic(err)
  }
}

Run from the command line:

cd ~/foo
go mod init example.com/foo
go mod tidy
go generate
go mod tidy

Now you can see mus.gen.go file in the foo folder with IntMUS and FooMUS serializers (see full example).

Generator

The Generator is responsible for generating serialization code.

Configuration

Required Options

There is only one required configuration option:

import (
  musgen "github.com/mus-format/mus-gen-go/mus"
  genopts "github.com/mus-format/mus-gen-go/options/gen"
)

g, err := musgen.NewGenerator(
  genopts.WithPkgPath("pkg path"),  // Sets the package path where the generated 
  // file will be placed. The path must match the standard Go package path 
  // format (e.g., github.com/user/project/pkg) and can be obtained using:
  //
  //   pkgPath := reflect.TypeFor[YourType]().PkgPath()
  //
)

Streaming

To generate streaming code:

import (
  musgen "github.com/mus-format/mus-gen-go/mus"
  genopts "github.com/mus-format/mus-gen-go/options/gen"
)

g := musgen.NewGenerator(
  // ...
  genopts.WithStream(),
)

In this case mus-stream library will be used instead of mus.

Modes

Safe Mode

By default, the generator generates safe code (unsafe package is not used).

Unsafe Mode

To generate unsafe code:

import (
  musgen "github.com/mus-format/mus-gen-go/mus"
  genopts "github.com/mus-format/mus-gen-go/options/gen"
)

g := musgen.NewGenerator(
  // ...
  genopts.WithUnsafe(),
)

Not Unsafe Mode

In this mode, the unsafe package is used for all types except string:

import (
  musgen "github.com/mus-format/mus-gen-go/mus"
  genopts "github.com/mus-format/mus-gen-go/options/gen"
)

g := musgen.NewGenerator(
  // ...  
  genopts.WithNotUnsafe(),
)

It produces the fastest serialization code without unsafe side effects.

Imports

In some cases import statement of the generated file can miss one or more packages. To fix this:

import (
  musgen "github.com/mus-format/mus-gen-go/mus"
  genopts "github.com/mus-format/mus-gen-go/options/gen"
)

g := musgen.NewGenerator(
  // ...
  genopts.WithImport("import path"),
  genopts.WithImportAlias("import path", "alias"),
)

Also, genopts.WithImportAlias helps prevent name conflicts when multiple packages are imported with the same alias.

Serializer Name

Generated serializers follow the following naming convention:

pkg.YourType[T,V] -> YourTypeMUS  // Serialization format is appended to the type name.

To override this behavior, use genopts.WithSerName():

import (
  musgen "github.com/mus-format/mus-gen-go/mus"
  genopts "github.com/mus-format/mus-gen-go/options/gen"
)

g := musgen.NewGenerator(
  // ...
  genopts.WithSerName(reflect.TypeFor[pkg.YourType](), "CustomSerName"),
)

Methods

AddDefinedType()

Supports types defined with the following underlying types:

Number (uint, int, float64, float32, ...)
String
Array
Slice
Map
Pointer

For example:

type Int int
type StringSlice []string
type UintPtr *uint

It can be used as follows:

import tpopts "github.com/mus-format/mus-gen-go/options/type"

type Int int // Where int is the underlying type of Int.

err := g.AddDefinedType(reflect.TypeFor[Int]())

Or with serialization options, for example:

err := g.AddDefinedType(reflect.TypeFor[Int](),
  tpopts.WithNumEncoding(tpopts.NumEncodingRaw), // The raw.Int serializer will be used
  // to serialize the underlying int type.
  tpopts.WithValidator("ValidateInt")) // After unmarshalling, the Int 
  // value will be validated using the ValidateInt function.
  // Validator functions in general should have the following signature:
  //
  //   func(value Type) error
  //
  // where Type denotes the type the validator is applied to.

AddStruct()

Supports types defined with the struct underlying type, such as:

type Struct struct { ... }
type AnotherStruct Struct

It can be used as follows:

import (
  "reflect"
 
  genopts "github.com/mus-format/mus-gen-go/options/gen"
  fldopts "github.com/mus-format/mus-gen-go/options/field"
  stopts "github.com/mus-format/mus-gen-go/options/struct"
  tpopts "github.com/mus-format/mus-gen-go/options/type"
)

type Struct struct {
  Str string
  Ignore int
  Slice []int
  // Interface Interface  // Interface fields are supported as well.
  // Any any              // But not the `any` type.
}

// ...

err := g.AddStruct(reflect.TypeFor[Struct]())

Or with serialization options, for example:

// The number of options should be equal to the number of fields. If you don't
// want to specify options for some field, use stopts.WithField() without
// any parameters.
err := g.AddStruct(reflect.TypeFor[Struct](),
  // No options for the first field.
  stopts.WithField(), 

  // The second field will not be serialized.
  stopts.WithField(fldopts.WithIgnore()), 

  // Options for the third field.
  stopts.WithField( 
    fldopts.WithType(
      // The length of the slice field will be validated using the ValidateLength 
      // function before the rest of the slice is unmarshalled.
      tpopts.WithLenValidator("ValidateLength"), 
      // Each slice element, after unmarshalling, will be validated using the 
      // ValidateSliceElem function.
      tpopts.WithElemValidator("ValidateSliceElem"), 
    ),
  ),
)

A special case for the time.Time underlying type:

type Time time.Time

err = g.AddStruct(reflect.TypeFor[Time](),
  stopts.WithUnderlyingTime(
    // By default TimeUnitSecUTC is used, but you can change it:
    // stopts.WithUnderlyingTimeUnit(tpopts.TimeUnitMilli),
  ),
)

AddTyped()

Supports all types acceptable by the AddDefinedType, AddStruct, and AddInterface methods.

It can be used as follows:

import (
  "reflect"
)

type Int int

t := reflect.TypeFor[Int]()
err := g.AddDefinedType(t)
// ...
err = g.AddTyped(t)

The typed serializer definition will be generated for the specified type.

AddInterface()

Supports types defined with the interface underlying type, such as:

type Interface interface { ... }
type AnyInterface any
type AnotherInterface Interface

It can be used as follows:

import (
  com "github.com/mus-format/common-go"
	intropts "github.com/mus-format/mus-gen-go/options/interface"
)

// 1. Define DTM values for each implementation type.
const (
  Impl1DTM com.DTM = iota + 1
  Impl2DTM
)

type Interface interface {...}
type Impl1 struct {...}
type Impl2 int

var (
  t1 = reflect.TypeFor[Impl1]()
  t2 = reflect.TypeFor[Impl2]()
)

// 2. Add interface implementations.
err := g.AddStruct(t1)
// ...
err = g.AddDefinedType(t2)
// ...

// 3. Add typed serializers for each implementation type.
err = g.AddTyped(t1)
// ...
err = g.AddTyped(t2)
// ...

// 4. Add interface with implementations.
err = g.AddInterface(reflect.TypeFor[Interface](),
  intropts.WithImplType(t1),
  intropts.WithImplType(t2),
  // intropts.WithMarshaller(), // Enables serialization using the 
  // mus.MarshallerTyped interface, that should be satisfied by all 
  // implementation types. Disabled by default.
)

RegisterInterface()

A convenience method that performs the full registration flow for an interface and all of its implementations.

Unlike AddInterface, RegisterInterface does not require you to define DTM values or call AddStruct, AddDefinedType, AddTyped manually:

import (
  "reflect"
	intropts "github.com/mus-format/mus-gen-go/options/interface"
)

type Interface interface { ... }
type Impl1 struct { ... }
type Impl2 int

// ...

err := g.RegisterInterface(reflect.TypeFor[Interface](),
  intropts.WithStructImpl(reflect.TypeFor[Impl1]()),
  intropts.WithDefinedTypeImpl(reflect.TypeFor[Impl2]()),
  // intropts.WithRegisterMarshaller() // optional
)

AddVersioned()

Produce a versioned serializer for the specified type.

import (
  com "github.com/mus-format/common-go"
  veropts "github.com/mus-format/mus-gen-go/options/versioned"
)

// 1. Define DTM values for each type version.
const (
  FooV1DTM com.DTM = iota + 1
  FooV2DTM
)

type Foo FooV2    // target type Foo
type FooV2 string // current version
type FooV1 int    // previous version

var (
  t1 = reflect.TypeFor[FooV1]()
  t2 = reflect.TypeFor[FooV2]()
)

// 2. Add type versions.
err := g.AddDefinedType(t1)
// ...
err = g.AddDefinedType(t2)
// ...

// 3. Add typed serializers for each version.
err = g.AddTyped(t1)
// ...
err = g.AddTyped(t2)
// ...

// 4. Add target type with versions.
err = g.AddVersioned(reflect.TypeFor[Foo](),
  veropts.WithVersion(t1, "MigrateFooV1"),
  veropts.WithCurrentVersion(t2), // No migration function required.
)

The migration function must accept a previous type version and return the target type:

func MigrateFooV1(v FooV1) Foo { ... }

RegisterVersioned()

A convenience method that performs the full registration flow for a specified type and all of its versions.

Unlike AddVersioned, RegisterVersioned does not require you to define DTM values or call AddStruct/AddDefinedType, AddTyped for each type version manually:

import (
  "reflect"
  veropts "github.com/mus-format/mus-gen-go/options/versioned"
)

type Foo FooV2    // target type Foo
type FooV2 string // current version
type FooV1 int    // previous version

err := g.RegisterVersioned(reflect.TypeFor[Foo](),
  veropts.WithVersion(reflect.TypeFor[FooV1](), "MigrateFooV1"),
  veropts.WithCurrentVersion(reflect.TypeFor[FooV2]()),
)

Multi-package support

By default, mus-gen expects a type’s serializer to reside in the same package as the type itself. For example, generating a serializer for the Foo type:

package foo

type Foo struct{
  Bar bar.Bar
}

will result in:

package foo

func (s fooMUS) Marshal(v Foo, bs []byte) (n int) {
  return bar.BarMUS(v.Bar) // mus-gen assumes the Bar serializer is located
  // in the bar package and follows the default naming convention.
}

To reference a Bar serializer defined in a different package or with a non-standard name, use the genopts.WithSerName option:

import (
  musgen "github.com/mus-format/mus-gen-go/mus"
  genopts "github.com/mus-format/mus-gen-go/options/gen"
)

g := musgen.NewGenerator(
  // ...
  genopts.WithSerName(reflect.TypeFor[bar.Bar](), "another.AwesomeBar"),
  // If only the name is non-standard:
  // genopts.WithSerName(reflect.TypeFor[bar.Bar](), "AwesomeBar"),
)

The string another.AwesomeBar will be used as-is, with the serialization format appended:

func (s fooMUS) Marshal(v Foo, bs []byte) (n int) {
  return another.AwesomeBarMUS(v.Bar)
}

Cross-Package Code Generation

mus-gen allows to generate a serializer for a type from an external package, for example, foo.BarMUS for the bar.Bar type.

Serialization Options

Different types support different serialization options. If an unsupported option is specified for a type, it will simply be ignored.

import tpopts "github.com/mus-format/mus-gen-go/options/type"

Numbers

tpopts.WithNumEncoding
tpopts.WithValidator

String

tpopts.WithLenEncoding
tpopts.WithLenValidator
tpopts.WithValidator

Array

tpopts.WithLenEncoding
tpopts.WithElemValidator
tpopts.WithValidator

Slice

tpopts.WithLenEncoding
tpopts.WithLenValidator
tpopts.WithElemValidator
tpopts.WithValidator

Map

tpopts.WithLenEncoding
tpopts.WithLenValidator
tpopts.WithKeyValidator
tpopts.WithElemValidator
tpopts.WithValidator

time.Time

tpopts.WithTimeUnit
tpopts.WithValidator

MUS Format Defaults

Safe Mode

int:        varint
uint:       varint
float:      raw
byte:       raw
bool:       ord
string:     ord
byte_slice: ord
time:       raw
time_ser:   TimeUnixUTC // Default time serializer.

Unsafe Mode

int:        unsafe
uint:       unsafe
float:      unsafe
byte:       unsafe
bool:       unsafe
string:     unsafe
byte_slice: unsafe // ord for mus-stream
time:       unsafe
time_ser:   TimeUnixUTC // Default time serializer.

Not Unsafe Mode

int:        unsafe
uint:       unsafe
float:      unsafe
byte:       unsafe
bool:       unsafe
string:     ord
byte_slice: unsafe // ord for mus-stream
time:       unsafe
time_ser:   TimeUnixUTC // Default time serializer.

Name		Name	Last commit message	Last commit date
.github		.github
classifier		classifier
mus		mus
options		options
scanner		scanner
spec		spec
test		test
typename		typename
LICENSE		LICENSE
README.md		README.md
go.mod		go.mod
go.sum		go.sum

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mus-gen: Code Generator for MUS

Capabilities

Contents

Getting Started Example

Generator

Configuration

Required Options

Streaming

Modes

Safe Mode

Unsafe Mode

Not Unsafe Mode

Imports

Serializer Name

Methods

AddDefinedType()

AddStruct()

AddTyped()

AddInterface()

RegisterInterface()

AddVersioned()

RegisterVersioned()

Multi-package support

Cross-Package Code Generation

Serialization Options

Numbers

String

Array

Slice

Map

time.Time

MUS Format Defaults

Safe Mode

Unsafe Mode

Not Unsafe Mode

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