mid

midlang

What's midlang?

The aim of the first stage is to implement a Data Define Language like protobuf, but have some differences.

1. midlang generated code is highly customizable. Using go template to generates your codes, even documents.
2. midlang was committed to eradicating boring and tedious code which can be generated, not just as a data interchange format.

The compiler midc compile midlang source code to an AST, and then you can visit the AST in template file.

Here is an example template file (package.go.temp):

package {{.Name}}

{{define "T_const"}}
{{.Doc}}const (
	{{range $field := .Consts}}{{$field.Name}} = {{$field.ValueString}}
	{{end}}
)
{{end}}

{{define "T_enum"}}
{{$type := .Name}}
type {{$type}} int

{{.Doc}}const (
	{{range $field := .Fields}}{{$type}}_{{$field.Name}} = {{$field.Value}}{{$field.Comment}}
	{{end}}
)
{{end}}

{{define "T_struct"}}
{{$type := .Name}}
{{.Doc}}type {{$type}} struct {
	{{range $field := .Fields}}{{$field.Name | title}} {{context.BuildType $field.Type}}{{$field.Comment}}
	{{end}}
}
{{end}}

{{define "T_protocol"}}
{{template "T_struct" .}}
{{end}}

{{define "T_service"}}
{{$type := .Name}}
{{.Doc}}type {{$type}} interface {
	{{range $field := .Fields}}{{$field.Name | title}} {{context.BuildType $field.Type}}{{$field.Comment}}
	{{end}}
}
{{end}}

{{.GenerateDeclsBySubTemplates}}

The following will be devoted to writing a document on how to use template in midlang.

Mainly includes the following points:

• template filename form: <kind>[.suffix][.flags].temp

  • kind maybe package,file,const and other bean kinds like struct,protocol,service etc.
  • struct.go.temp -> (struct, go)
  • struct.h.temp -> (struct, h)
  • struct.cpp.temp -> (struct, cpp)
  • struct.cpp.1.temp -> (struct, cpp)

• template kind package: each package as a data be applied to the template file

• template kind file: each source file as a data be applied to the template file

• template kind const: each constant group as a data be applied to the template file

• template kind enum: each enum type as a data be applied to the template file

• template kind struct: each struct as a data be applied to the template file

• template kind protocol: each protocol as a data be applied to the template file

• template kind service: each service as a data be applied to the template file

• template can use some builtin functions, e.g. context,include,include_template,osenv and many utility string functions.(all these functions are defined in mid/src/tools/generator/generator.go)

• The context function returns a object Context which has fields Pkg, Plugin, Config and methods BuildType, Env, FindBean etc.

See builtin templates

Install

install from binary package

• Download binary package from here:

http://midlang.org/dl

• Unpack *.tar.gz, and then cd target directory

$ tar zcf <name>.tar.gz
$ cd <name>

• Install to your local host

1. Copy all files in directory bin to any directory which contained in env PATH
2. Copy file midconfig and directory mid_templates to your home directory or one of these: /etc,/usr/local/etc

install from source

$ go get github.com/midlang/mid
$ cd /path/to/mid # replace `/path/to/mid` with your actual directory
$ ./install.sh

Now, the compiler midc and generators installed to $GOPATH/bin, file midconfig and directory mid_templates copied to $HOME

Getting started

Write a source file demo.mid

/**
 * package declaration must has a `;`
 */
package demo;

// constants
const (
	A = 1;
	B = 2;
)

// doc: status
// Status
enum Status {
	Ok = 0, // ok
	Bad = 1, // bad
}

struct User {
	int64 id;
	string name;
	vector<string> otherNames;
	array<byte,6> code;
}

protocol UserList {
	map<int64,User> users;
}

service UserService {
	sayHello()
	getUsers() UserList
	findUser(int64 uid) User
	delUser(int64) Status
}

struct Info {
	extend User; // extend extends another structure
	string desc;
	map<int64,vector<map<int,array<bool,5>>>> xxx;
}

Compile and generate codes

$ midc -I demo.mid -Ogo=generated/go
# Or
# midc -I demo.mid -Ogo=generated/go -K default

Try midc -h to get help information of compiler midc

Try this:

$ midc -I demo.mid -Ogo=generated/go -K beans

Language plugins

Midlang language plugin used to generate code for the program language

Here are all builtin plugins:

• gengo - golang plugin
• gencpp - c++ plugin

You can write yourself plugin instead of using builtin plugin.

Templates

Templates used to generate codes. You can use option -T<lang>=<template_dir> to specify templates for specified language, also you can use option -K <template_kind> to specify template kind(default template kind is default).

Builtin template kinds: default, beans

Plugin for editor

• vim-mid - https://github.com/midlang/vim-mid

TODO

• Other generators: cpp,java,rust,swift,python,javascript,...
• More builtin templates
• Support extentions while generating codes
• Build website and documents