ast_inspect_comments.go

package main

import (
	"fmt"
	"go/ast"
	"go/parser"
	"go/token"
)

func main() {
	//Create a new token set for the file
	fset := token.NewFileSet()
	//Parse the file and create an AST
	file, err := parser.ParseFile(fset, "../nats_publisher/main.go", nil, parser.ParseComments)
	if err != nil {
		panic(err)
	}
	//Create a CommentMap and extract all comments out of the file
	cmap := ast.NewCommentMap(fset, file, file.Comments)
	ast.Inspect(file, func(n ast.Node) bool {
		//Look for all stand-alone expressions
		_, ok := n.(*ast.ExprStmt)
		if ok {
			//Get the statement from the standalone expression (x) and attempt to cast to a function call
			funcCall, ok := n.(*ast.ExprStmt).X.(*ast.CallExpr)
			if ok {
				//Check if it is a selector expression
				mthd, ok := funcCall.Fun.(*ast.SelectorExpr)
				if ok {
					//Retrieve the identifier (the left side of the . in a selector expression)
					_, ok = mthd.X.(*ast.Ident)
					if ok {
						//If method matches and the identifier is "ec" (encoded nats connection), extract values
						if mthd.Sel.Name == "Publish" && mthd.X.(*ast.Ident).Name == "ec" {
							fmt.Printf("Topic: %s \n", funcCall.Args[0].(*ast.BasicLit).Value)
							if _, ok := cmap[n]; ok {
								if len(cmap[n]) > 0 {
									fmt.Println(cmap[n][0].Text())
								}
							}
						}
					}
				}
			}

		}
		return true
	})
}