swc/crates/swc_ecma_minifier/examples/minifier.rs

extern crate swc_node_base;

use std::{env::args, fs, path::Path};

use swc_common::{input::SourceFileInput, sync::Lrc, Mark, SourceMap};
use swc_ecma_codegen::text_writer::JsWriter;
use swc_ecma_minifier::{
    optimize,
    option::{ExtraOptions, MangleOptions, MinifyOptions},
};
use swc_ecma_parser::{lexer::Lexer, Parser};
use swc_ecma_transforms::{fixer, hygiene, resolver_with_mark};
use swc_ecma_visit::FoldWith;

fn main() {
    let file = args().nth(1).expect("should provide a path to file");

    eprintln!("File: {}", file);

    testing::run_test2(false, |cm, handler| {
        let fm = cm.load_file(Path::new(&file)).expect("failed to load file");

        let top_level_mark = Mark::fresh(Mark::root());

        let lexer = Lexer::new(
            Default::default(),
            Default::default(),
            SourceFileInput::from(&*fm),
            None,
        );

        let mut parser = Parser::new_from(lexer);
        let program = parser
            .parse_module()
            .map_err(|err| {
                err.into_diagnostic(&handler).emit();
            })
            .map(|module| module.fold_with(&mut resolver_with_mark(top_level_mark)))
            .unwrap();

        let output = optimize(
            program,
            cm.clone(),
            None,
            None,
            &MinifyOptions {
                compress: Some(Default::default()),
                mangle: Some(MangleOptions {
                    top_level: true,
                    ..Default::default()
                }),
                ..Default::default()
            },
            &ExtraOptions { top_level_mark },
        );

        let output = output.fold_with(&mut hygiene());
        let output = output.fold_with(&mut fixer(None));

        let code = print(cm, &[output], true);

        fs::write("output.js", code.as_bytes()).expect("failed to write output");

        Ok(())
    })
    .unwrap();
}

fn print<N: swc_ecma_codegen::Node>(cm: Lrc<SourceMap>, nodes: &[N], minify: bool) -> String {
    let mut buf = vec![];

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

        for n in nodes {
            n.emit_with(&mut emitter).unwrap();
        }
    }

    String::from_utf8(buf).unwrap()
}