asty-org / asty

Converts golang AST to JSON and JSON to AST

asty

Not another JSON parser!

AST → JSON | JSON → AST

Marshals golang AST into JSON and unmarshals it back from JSON.

It allows building pattern matching, statistical analysis, language transformation, search/data-mine/anything algorithms for golang with any other language (I like to do it with python. Check out asty-python)

Example

Try it!

Input golang source

package main

import "fmt"

func main() {
    fmt.Println("hello world")
}

Ouput AST in JSON

{
  "NodeType": "File",
  "Name": {
    "NodeType": "Ident",
    "Name": "main"
  },
  "Decls": [
    {
      "NodeType": "GenDecl",
      "Tok": "import",
      "Specs": [
        {
          "NodeType": "ImportSpec",
          "Name": null,
          "Path": {
            "NodeType": "BasicLit",
            "Kind": "STRING",
            "Value": "\"fmt\""
          }
        }
      ]
    },
    {
      "NodeType": "FuncDecl",
      "Recv": null,
      "Name": {
        "NodeType": "Ident",
        "Name": "main"
      },
      "Type": {
        "NodeType": "FuncType",
        "TypeParams": null,
        "Params": {
          "NodeType": "FieldList",
          "List": null
        },
        "Results": null
      },
      "Body": {
        "NodeType": "BlockStmt",
        "List": [
          {
            "NodeType": "ExprStmt",
            "X": {
              "NodeType": "CallExpr",
              "Fun": {
                "NodeType": "SelectorExpr",
                "X": {
                  "NodeType": "Ident",
                  "Name": "fmt"
                },
                "Sel": {
                  "NodeType": "Ident",
                  "Name": "Println"
                }
              },
              "Args": [
                {
                  "NodeType": "BasicLit",
                  "Kind": "STRING",
                  "Value": "\"hello world\""
                }
              ]
            }
          }
        ]
      }
    }
  ]
}

Install

Install asty under $GOPATH/bin

go install github.com/asty-org/asty

asty -h

Building

Just make If you want to do it differently use go build

Usage

Convert AST to JSON

asty go2json -input <input.go> -output <output.json>

Convert JSON to AST

asty json2go -input <input.json> -output <output.go>

Use asty help for more information

Using with docker

docker run astyorg/asty go2json -input <input.go> -output <output.json>

Development principles

• Make json output as close to real golang structures as possible. There is no additional logic introduced. No normalization. No reinterpretation. The only things that were introduced are the names of some enum values.
• Make it very explicit. No reflection. No listing of fields. This is done to facilitate future maintenance. If something will be changed in future versions of golang this code will probably break compile-time.
• Keep polymorphism in JSON structure. If some field references expression then particular type will be discriminated from object type name stored in separate field.

Other solutions

• https://github.com/ReconfigureIO/goblin reinterpret some structures (trying to simplify). Out of maintenance for a long time. Still works in some forks.
• https://github.com/CreativeInquiry/go2json tries to parse golang code with parser written in javascript. Also lacks maintenance. Developed for particular use case of HaXe traspiler.

Article

I wrote an article about this project.