denoland/deno · error

bundling failed

Error message

bundling failed

What it means

Watch-mode bundling: esbuild returned a BuildResponse containing errors. handle_esbuild_errors_and_warnings prints them (with file:line:col) first, then the run bails with this generic message to force a non-zero exit (cli/tools/bundle/mod.rs:366-375) instead of entering the watch loop on a broken graph.

Source

Thrown at cli/tools/bundle/mod.rs:374

      )
      .await?;
  }
  let bundler = bundle_init(flags.clone(), &bundle_flags, None).await?;
  let init_cwd = bundler.cwd.clone();
  let start = std::time::Instant::now();
  let response = bundler.build().await?;
  let end = std::time::Instant::now();
  let duration = end.duration_since(start);

  if bundle_flags.watch {
    if !response.errors.is_empty() || !response.warnings.is_empty() {
      handle_esbuild_errors_and_warnings(
        &response,
        &init_cwd,
        &bundler.plugin_handler.take_deferred_resolve_errors(),
      );
      if !response.errors.is_empty() {
        deno_core::anyhow::bail!("bundling failed");
      }
    }
    return bundle_watch(
      flags,
      bundler,
      bundle_flags.minify,
      bundle_flags.platform,
      bundle_flags.output_dir.as_ref().map(Path::new),
    )
    .await;
  }

  handle_esbuild_errors_and_warnings(
    &response,
    &init_cwd,
    &bundler.plugin_handler.take_deferred_resolve_errors(),
  );

View on GitHub (pinned to 89f33cbef2)

Solutions

1. Read the esbuild diagnostics printed immediately above - they carry the exact file, line, and column of the first error
2. Fix imports first: use explicit extensions (./util.ts not ./util), and run deno install if an npm:/jsr: dependency is missing
3. Verify the project type-checks/compiles once outside watch mode (deno check <entry>, deno bundle <entry>) before restarting watch
4. If errors come from half-written files on save, configure the editor to write atomically or debounce saves

Example fix

// before: extensionless import trips esbuild resolution under watch
import { helper } from './util';
// after
import { helper } from './util.ts';

# Gate the watch session on a clean one-shot bundle first
deno bundle --outdir /tmp/gate src/main.ts || { echo 'fix bundle errors before watching'; exit 1; }
deno bundle --watch --outdir dist src/main.ts

# Wrapper: surface the real esbuild diagnostics when watch aborts
log=$(mktemp)
deno bundle --watch --outdir dist src/main.ts 2>&1 | tee "$log" || {
  echo '--- watch exited; first error: ---'
  grep -m1 -A3 'ERROR' "$log"
}

When it happens

Trigger: deno bundle --watch with a syntax error, an unresolvable import, or a plugin onResolve failure in the entry graph; a file edit that temporarily breaks the graph (half-saved file); missing npm/jsr dependency not yet installed.

Common situations: Editor autosave writing mid-edit buffers during watch; importing a file with a missing ./extension (Deno requires explicit extensions); deleting/renaming a module that the entry imports while watching.

Related errors

• esbuild exited before the rebuild completed
• could not get fetch esbuild binary; download it manually and
• failed to locate output for HTML entry '{}'; {js_entry_name}
• esbuild produced no JavaScript output
• The bench function must have a name

AI-assisted analysis of denoland/deno@89f33cbef2 (2026-08-16). Data as JSON: /api/errors/a20ec3e535f5278d. Report an issue: GitHub.