Source file generation from parsed tree

[NilsBaumgartner1994]

Maybe i oversee something but in some threads its mentioned, that it is super easy to print the parsed CST back to a source file.

My purpose is to parse a source file, manipulate the resulting CST and the convert the CST back to a source file. I am trying to do this for a Java Grammar in JavaScript/TypeScript. Maybe someone has a nice method which i totally missed.

Currently this is my code parsing a simple Java "file":

const input = `
        public class Test {\n
            public static void main(String[] args) {\n
                System.out.println("Hello World!");\n
                int a = 1;\n
                int b = 2;\n
                String c = "Hello";\n
                List<String> list = new ArrayList<>();\n
            }\n
        }
        `
        const chars = new antlr4.InputStream(input)
        const lexer = new JavaLexer(chars);
        const tokens = new antlr4.CommonTokenStream(lexer);
        const parser = new JavaParser(tokens);
        parser.buildParseTrees = true;
        const cst = parser.compilationUnit();
        console.log(cst);
```


What i endet up was that I used the JavaParserListener but witch (in my opinion too much code):
```
class TSListener extends JavaParserListener {
            private indentationLevel: number;
            public output: string;
            constructor() {
                super();
                this.indentationLevel = 0;
                this.output = '';
            }

            enterClassDeclaration(ctx) {
                console.log("enterClassDeclaration")
                console.log(Object.keys(ctx));
                this.output += `class ${ctx.getText()} {\n`;
                console.log(this.output);
                this.indentationLevel++;
            }

            exitClassDeclaration(ctx) {
                this.indentationLevel--;
                this.output += '}\n';
            }

            enterMethodDeclaration(ctx) {
                console.log("enterMethodDeclaration")
                console.log(Object.keys(ctx));
                const methodName = ctx.children[1].getText();
                console.log(methodName)
                const returnType = ctx.children[0].getText();
                console.log(returnType)
                this.output += `${'  '.repeat(this.indentationLevel)}${returnType} ${methodName}(`;
                this.indentationLevel++;
            }

            enterMethodBody(ctx) {
                this.output += `)`;
            }

            enterFormalParameter(ctx) {
                console.log("enterFormalParameter")
                console.log(Object.keys(ctx));
                console.log(ctx.getText())
                this.output += `${ctx.getText()}`;
            }

            enterVariableDeclaratorId(ctx) {
                console.log("enterVariableDeclaratorId")
                console.log(Object.keys(ctx));
                console.log(ctx.getText())
                this.output += ` ${ctx.getText()}`;
            }

            exitMethodDeclaration(ctx) {
                this.indentationLevel--;
                this.output += `${'  '.repeat(this.indentationLevel)}}\n`;
            }

            enterBlock(ctx) {
                this.output += `${'  '.repeat(this.indentationLevel)}{\n`;
                this.indentationLevel++;
            }

            exitBlock(ctx) {
                this.indentationLevel--;
                this.output += `${'  '.repeat(this.indentationLevel)}}\n`;
            }

            enterStatement(ctx) {
                if (ctx.getText().endsWith(';')) {
                    this.output += `${'  '.repeat(this.indentationLevel)}${ctx.getText()}\n`;
                } else {
                    this.output += `${'  '.repeat(this.indentationLevel)}${ctx.getText()} `;
                }
            }
        }

        let listener2 = new TSListener();
        antlr4.tree.ParseTreeWalker.DEFAULT.walk(listener2, cst);
        let output2 = listener2.output;
        console.log(output2);
```