denoland/deno · info

Exiting due to DENO_INTERNAL_FAST_CHECK_OVERWRITE

Error message

Exiting due to DENO_INTERNAL_FAST_CHECK_OVERWRITE

What it means

With `DENO_INTERNAL_FAST_CHECK_OVERWRITE=1`, publish writes each file module's fast-check (public API) output back to the source files on disk, then deliberately stops with this bail before type checking and publishing continue — nothing is uploaded. It is the internal mode's designed early exit, not a failure of your package.

Source

Thrown at cli/tools/publish/mod.rs:459

        );
      }

      for module in graph.modules() {
        if module.specifier().scheme() != "file" {
          continue;
        }
        let Some(js) = module.js() else {
          continue;
        };
        if let Some(module) = js.fast_check_module() {
          std::fs::write(
            js.specifier.to_file_path().unwrap(),
            module.source.as_ref(),
          )?;
        }
      }

      bail!("Exiting due to DENO_INTERNAL_FAST_CHECK_OVERWRITE")
    } else {
      log::info!("Checking for slow types in the public API...");
      for package in package_configs {
        let export_urls = package.config_file.resolve_export_value_urls()?;
        let diagnostics =
          collect_no_slow_type_diagnostics(&graph, &export_urls);
        if !diagnostics.is_empty() {
          for diagnostic in diagnostics {
            diagnostics_collector
              .push(PublishDiagnostic::FastCheck(diagnostic));
          }
        }
      }

      // skip type checking the slow type graph if there are any errors because
      // errors like remote modules existing will cause type checking to crash
      if diagnostics_collector.has_error() {
        Ok(Arc::new(graph))

View on GitHub (pinned to f7822238ca)

Solutions

1. Treat this exit as success when using the flag — the file rewrite already happened; inspect the result with `git diff`.
2. Unset the env var to run a normal publish: `unset DENO_INTERNAL_FAST_CHECK_OVERWRITE`.

Example fix

# before: unexpected non-zero exit breaks scripts
DENO_INTERNAL_FAST_CHECK_OVERWRITE=1 deno publish --dry-run
# after: the rewrite is the goal, so accept the designed stop
DENO_INTERNAL_FAST_CHECK_OVERWRITE=1 deno publish --dry-run || true
git diff --stat

#!/usr/bin/env bash
if [ "${DENO_INTERNAL_FAST_CHECK_OVERWRITE:-}" = "1" ]; then
  deno publish --dry-run || true   # designed stop after the source rewrite
  git diff --stat                  # inspect the rewritten output
else
  deno publish
fi

# the bail is the internal mode's success path — branch on the env var, not the exit code
if DENO_INTERNAL_FAST_CHECK_OVERWRITE=1 deno publish --dry-run; then
  : # unexpected: mode should stop with the bail
else
  rc=$?
  [ "$rc" -ne 0 ] && echo "fast-check rewrite finished (exit $rc is expected)"
fi

When it happens

Trigger: Running `deno publish` with `DENO_INTERNAL_FAST_CHECK_OVERWRITE=1` and a clean repo: after overwriting the module sources, execution always terminates here.

Common situations: Deno internal development workflows that regenerate fast-check output and diff it (e.g. `git diff` afterwards) in CI.

Related errors

• When using DENO_INTERNAL_FAST_CHECK_OVERWRITE, the git repo
• Failed ensuring public API type output is valid. {:#} You
• ${name} is already registered
• JS PANIC: {}
• displaying graphs that have multiple roots is not supported.

AI-assisted analysis of denoland/deno@f7822238ca (2026-08-20). Data as JSON: /api/errors/111bcf997c92493b. Report an issue: GitHub.