deno_core 0.398.0

// Copyright 2018-2026 the Deno authors. MIT license.
//! This example shows how to use swc to transpile TypeScript and JSX/TSX
//! modules.
//!
//! It will only transpile, not typecheck (like Deno's `--no-check` flag).

// NB(bartlomieju): this is fine for example code
#![allow(clippy::print_stdout, reason = "example code")]
#![allow(clippy::disallowed_methods, reason = "example code")]

use std::borrow::Cow;
use std::cell::RefCell;
use std::collections::HashMap;
use std::rc::Rc;

use anyhow::Context;
use deno_ast::MediaType;
use deno_ast::ParseParams;
use deno_ast::SourceMapOption;
use deno_core::JsRuntime;
use deno_core::ModuleLoadOptions;
use deno_core::ModuleLoadReferrer;
use deno_core::ModuleLoadResponse;
use deno_core::ModuleLoader;
use deno_core::ModuleSource;
use deno_core::ModuleSourceCode;
use deno_core::ModuleSpecifier;
use deno_core::ModuleType;
use deno_core::ResolutionKind;
use deno_core::RuntimeOptions;
use deno_core::error::ModuleLoaderError;
use deno_core::resolve_import;
use deno_core::resolve_path;
use deno_error::JsErrorBox;

// TODO(bartlomieju): this is duplicated in `testing/checkin`
type SourceMapStore = Rc<RefCell<HashMap<String, Vec<u8>>>>;

// TODO(bartlomieju): this is duplicated in `testing/checkin`
struct TypescriptModuleLoader {
  source_maps: SourceMapStore,
}

// TODO(bartlomieju): this is duplicated in `testing/checkin`
impl ModuleLoader for TypescriptModuleLoader {
  fn resolve(
    &self,
    specifier: &str,
    referrer: &str,
    _kind: ResolutionKind,
  ) -> Result<ModuleSpecifier, ModuleLoaderError> {
    resolve_import(specifier, referrer).map_err(JsErrorBox::from_err)
  }

  fn load(
    &self,
    module_specifier: &ModuleSpecifier,
    _maybe_referrer: Option<&ModuleLoadReferrer>,
    _options: ModuleLoadOptions,
  ) -> ModuleLoadResponse {
    let source_maps = self.source_maps.clone();
    fn load(
      source_maps: SourceMapStore,
      module_specifier: &ModuleSpecifier,
    ) -> Result<ModuleSource, ModuleLoaderError> {
      let path = module_specifier
        .to_file_path()
        .map_err(|_| JsErrorBox::generic("Only file:// URLs are supported."))?;

      let media_type = MediaType::from_path(&path);
      let (module_type, should_transpile) = match MediaType::from_path(&path) {
        MediaType::JavaScript | MediaType::Mjs | MediaType::Cjs => {
          (ModuleType::JavaScript, false)
        }
        MediaType::Jsx => (ModuleType::JavaScript, true),
        MediaType::TypeScript
        | MediaType::Mts
        | MediaType::Cts
        | MediaType::Dts
        | MediaType::Dmts
        | MediaType::Dcts
        | MediaType::Tsx => (ModuleType::JavaScript, true),
        MediaType::Json => (ModuleType::Json, false),
        _ => {
          return Err(JsErrorBox::generic(format!(
            "Unknown extension {:?}",
            path.extension()
          )));
        }
      };

      let code =
        std::fs::read_to_string(&path).map_err(JsErrorBox::from_err)?;
      let code = if should_transpile {
        let parsed = deno_ast::parse_module(ParseParams {
          specifier: module_specifier.clone(),
          text: code.into(),
          media_type,
          capture_tokens: false,
          scope_analysis: false,
          maybe_syntax: None,
        })
        .map_err(JsErrorBox::from_err)?;
        let res = parsed
          .transpile(
            &deno_ast::TranspileOptions {
              imports_not_used_as_values:
                deno_ast::ImportsNotUsedAsValues::Remove,
              decorators: deno_ast::DecoratorsTranspileOption::Ecma,
              ..Default::default()
            },
            &deno_ast::TranspileModuleOptions { module_kind: None },
            &deno_ast::EmitOptions {
              source_map: SourceMapOption::Separate,
              inline_sources: true,
              ..Default::default()
            },
          )
          .map_err(JsErrorBox::from_err)?;
        let res = res.into_source();
        let source_map = res.source_map.unwrap().into_bytes();
        source_maps
          .borrow_mut()
          .insert(module_specifier.to_string(), source_map);
        res.text
      } else {
        code
      };
      Ok(ModuleSource::new(
        module_type,
        ModuleSourceCode::String(code.into()),
        module_specifier,
        None,
      ))
    }

    ModuleLoadResponse::Sync(load(source_maps, module_specifier))
  }

  fn get_source_map(&self, specifier: &str) -> Option<Cow<'_, [u8]>> {
    self
      .source_maps
      .borrow()
      .get(specifier)
      .map(|v| v.clone().into())
  }
}

fn main() -> Result<(), anyhow::Error> {
  let args: Vec<String> = std::env::args().collect();
  if args.len() < 2 {
    println!("Usage: target/examples/debug/ts_module_loader <path_to_module>");
    std::process::exit(1);
  }
  let main_url = &args[1];
  println!("Run {main_url}");

  let source_map_store = Rc::new(RefCell::new(HashMap::new()));

  let mut js_runtime = JsRuntime::new(RuntimeOptions {
    module_loader: Some(Rc::new(TypescriptModuleLoader {
      source_maps: source_map_store,
    })),
    ..Default::default()
  });

  let main_module = resolve_path(
    main_url,
    &std::env::current_dir().context("Unable to get CWD")?,
  )?;

  let future = async move {
    let mod_id = js_runtime.load_main_es_module(&main_module).await?;
    let result = js_runtime.mod_evaluate(mod_id);
    js_runtime.run_event_loop(Default::default()).await?;
    result.await
  };

  tokio::runtime::Builder::new_current_thread()
    .enable_all()
    .build()
    .unwrap()
    .block_on(future)
    .map_err(|e| e.into())
}