feat(cli): add `deno transpile` subcommand by bartlomieju · Pull Request #32691 · denoland/deno

bartlomieju · 2026-03-13T16:03:29Z

Summary

Add a new deno transpile subcommand that transpiles TypeScript/JSX/TSX files to JavaScript using deno_ast, with configurable source map output (--source-map none|inline|separate)
Support --declaration flag to generate .d.ts type declaration files via the TypeScript compiler
Support single file (-o), multi-file (--outdir), and stdout output modes

Changes

cli/args/flags.rs — TranspileFlags, SourceMapMode, clap subcommand definition and parser
cli/tools/transpile.rs — New tool: transpilation via deno_ast, declaration generation via tsc::exec()
cli/tsc/js.rs / cli/tsc/mod.rs / cli/tsc/go.rs — Extend op_emit to capture .d.ts files, add emitted_files to Response
cli/tsc/99_main_compiler.js — Call program.emit() when declaration/emitDeclarationOnly is set
cli/factory.rs / cli/lib.rs / cli/tools/mod.rs — Wiring

Test plan

9 spec tests in tests/specs/transpile/ covering:
- Basic TS→JS transpile to stdout
- Output to file (-o) and directory (--outdir)
- Inline and separate source map modes
- .d.ts declaration generation
- Error handling (multiple files with -o)
- Skipping non-emittable .js files
- TSX transpilation
All pass via ./x test-spec transpile

🤖 Generated with Claude Code

Add a new `deno transpile` subcommand that transpiles TypeScript/JSX/TSX files to JavaScript using deno_ast. Supports single and multiple file transpilation with configurable source map output (none/inline/separate). Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

When `--declaration` is passed, invoke TSC with `emitDeclarationOnly` to generate .d.ts type declaration files alongside the transpiled JS. Changes: - Extend TSC `op_emit` to capture .d.ts files instead of panicking - Add `emitted_files` field to TSC Response to propagate declaration output - Call `program.emit()` in the JS compiler when declaration mode is active - Build module graph and invoke TSC from the transpile tool Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

9 test cases covering: - Basic transpile to stdout - Output to file with -o flag - Multiple files with --outdir - Inline and separate source map modes - .d.ts declaration generation with --declaration - Error on -o with multiple files - Skipping non-emittable .js files - TSX transpilation Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

dsherret · 2026-03-13T16:14:35Z

cli/args/flags.rs

  Ok(())
 }

+fn transpile_parse(


Arg parsing tests?

cli/tools/transpile.rs

dsherret · 2026-03-13T16:24:47Z

cli/tools/transpile.rs

+  // Resolve compiler options, adding declaration-specific settings
+  let compiler_options_resolver = factory.compiler_options_resolver()?;
+  let first_specifier = &root_names[0].0;
+  let base_compiler_options = compiler_options_resolver
+    .for_specifier(first_specifier)
+    .compiler_options_for_lib(cli_options.ts_type_lib_window())?;
+
+  // Merge declaration options into the base compiler options
+  let mut config_value =
+    deno_core::serde_json::to_value(base_compiler_options.as_ref())?;
+  let config_obj = config_value
+    .as_object_mut()
+    .ok_or_else(|| anyhow::anyhow!("Invalid compiler options"))?;
+  config_obj.insert("declaration".into(), json!(true));
+  config_obj.insert("emitDeclarationOnly".into(), json!(true));
+  config_obj.insert("noEmit".into(), json!(false));
+
+  let compiler_options = Arc::new(CompilerOptions::new(config_value));
+
+  let hash_data =
+    deno_lib::util::hash::FastInsecureHasher::new_deno_versioned()
+      .write_hashable(&compiler_options)
+      .finish();
+
+  let jsx_import_source_config_resolver = Arc::new(
+    deno_resolver::deno_json::JsxImportSourceConfigResolver::from_compiler_options_resolver(
+      compiler_options_resolver,
+    )?,
+  );
+
+  // Set up npm state if available
+  let maybe_npm = {
+    let cjs_tracker = Arc::new(tsc::TypeCheckingCjsTracker::new(
+      factory.cjs_tracker()?.clone(),
+      factory.module_info_cache()?.clone(),
+    ));
+    let node_resolver = factory.node_resolver().await?.clone();
+    let npm_resolver = factory.npm_resolver().await?.clone();
+    let package_json_resolver = factory.pkg_json_resolver()?.clone();
+    Some(tsc::RequestNpmState {
+      cjs_tracker,
+      node_resolver,
+      npm_resolver,
+      package_json_resolver,
+    })
+  };
+
+  let response = tsc::exec(
+    tsc::Request {
+      config: compiler_options,
+      debug: cli_options.log_level() == Some(log::Level::Debug),
+      graph: Arc::new(graph),
+      jsx_import_source_config_resolver,
+      hash_data,
+      maybe_npm,
+      maybe_tsbuildinfo: None,
+      root_names,
+      check_mode: TypeCheckMode::All,
+      initial_cwd: cwd.to_path_buf(),
+    },
+    None,
+    None,
+  )?;


This seems like way too much setup code. Can't we use the TypeChecker here instead? tsc::exec( is very low level to be calling here.

I looked into using TypeChecker here but it doesn't currently support returning emitted files — check_diagnostics calls tsc::exec internally but only exposes the diagnostics, not the emitted_files from the Response.

To make this work via TypeChecker, we'd need to add a new method (something like emit_declarations) that wraps the tsc::exec call and returns the emitted .d.ts files. Happy to do that if you think it belongs there — would keep transpile.rs much simpler and make declaration emission reusable.

In the meantime I've simplified the setup by using factory.create_request_npm_state() (new factory method) and getting all other components from the factory directly.

I mean, we should look into adding a method and create_request_npm_state() into the tsc module. We shouldn't be exposing such low level stuff so high up or the code is going to get complex/sloppy.

I can look into refactoring this if you'd like. I think we could move it into TypeChecker.

cli/tools/transpile.rs

- Add arg parsing unit tests for transpile subcommand - Create CliFactory at top of transpile() and use it throughout - Use sys.with_paths_in_errors() for filesystem ops with better error context - Add create_request_npm_state() factory method to reduce duplication - Use deno_path_util::url_to_file_path instead of specifier.to_file_path() - Add error context to all filesystem operations and compute_output_path Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

- Preserve relative directory structure in --outdir instead of flattening - Fix outdir spec test to work on Windows (backslash path separators) - Remove unnecessary canonicalize_path call - Clarify --declaration behavior in help text Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

- Make --output and --outdir mutually exclusive via clap conflicts_with - Error when --declaration used without -o/--outdir - Make type-check errors from --declaration hard errors (exit code 1) - Map .mts->.mjs, .cts->.cjs instead of always .js - Error on --source-map separate when outputting to stdout - Gate .d.ts capture in op_emit_inner behind capture_emitted_files flag - Use BTreeMap for emitted_files for deterministic output order - Error when all input files are skipped (nothing transpiled) - Fix strip_prefix(cwd) producing bad paths for files outside cwd - Add tests for new error cases Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

bartlomieju and others added 3 commits March 13, 2026 16:41

dsherret suggested changes Mar 13, 2026

View reviewed changes

bartlomieju and others added 6 commits March 13, 2026 18:27

fmt

b558df5

refactor: move create_request_npm_state to TypeChecker

d23ce07

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Merge remote-tracking branch 'origin/main' into feature/deno-transpile

bcc7d65

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

feat(cli): add `deno transpile` subcommand#32691

feat(cli): add `deno transpile` subcommand#32691
bartlomieju wants to merge 9 commits intomainfrom
feature/deno-transpile

bartlomieju commented Mar 13, 2026

Uh oh!

dsherret Mar 13, 2026

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

dsherret Mar 13, 2026

Uh oh!

bartlomieju Mar 13, 2026

Uh oh!

dsherret Mar 13, 2026 •

edited

Loading

Uh oh!

dsherret Mar 13, 2026

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Conversation

bartlomieju commented Mar 13, 2026

Summary

Changes

Test plan

Uh oh!

dsherret Mar 13, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Uh oh!

dsherret Mar 13, 2026

Choose a reason for hiding this comment

Uh oh!

bartlomieju Mar 13, 2026

Choose a reason for hiding this comment

Uh oh!

dsherret Mar 13, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Choose a reason for hiding this comment

Uh oh!

dsherret Mar 13, 2026

Choose a reason for hiding this comment

Uh oh!

Uh oh!

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

dsherret Mar 13, 2026 •

edited

Loading