swc/crates/swc_ecma_codegen/examples/gen.rs

/// Use memory allocator
extern crate swc_node_base;

use std::{env, fs, path::Path, time::Instant};

use swc_common::input::SourceFileInput;
use swc_ecma_ast::*;
use swc_ecma_codegen::{text_writer::JsWriter, Emitter};
use swc_ecma_parser::{lexer::Lexer, Parser, Syntax};

fn parse_and_gen(entry: &Path) {
    testing::run_test2(false, |cm, _| {
        let fm = cm.load_file(entry).unwrap();

        let lexer = Lexer::new(
            Syntax::Typescript(Default::default()),
            EsVersion::latest(),
            SourceFileInput::from(&*fm),
            None,
        );
        let mut parser = Parser::new_from(lexer);
        let m = parser
            .parse_module()
            .expect("failed to parse input as a module");

        let code = {
            let mut buf = vec![];

            {
                let mut emitter = Emitter {
                    cfg: Default::default(),
                    cm: cm.clone(),
                    comments: None,
                    wr: JsWriter::new(cm, "\n", &mut buf, None),
                };

                emitter.emit_module(&m).unwrap();
            }

            String::from_utf8_lossy(&buf).to_string()
        };

        fs::write("output.js", code).unwrap();

        Ok(())
    })
    .expect("failed to process a module");
}

/// Usage: ./scripts/instruments path/to/input/file
fn main() {
    let main_file = env::args().nth(1).unwrap();

    let start = Instant::now();
    parse_and_gen(Path::new(&main_file));
    let dur = start.elapsed();
    println!("Took {:?}", dur);
}