denoland/deno · error

{entry_text} is missing a prefix. Did you mean `{}`?

Error message

{entry_text} is missing a prefix. Did you mean `{}`?

What it means

When `AddRmPackageReq::parse` cannot resolve a registry prefix for a bare specifier, the code checks whether the name exists on JSR or npm and, if so, tells you the exact prefixed command to run. Per the in-code comment this branch is currently unreachable through the CLI (default_registry always defaults to Npm) and acts as a safety net for API callers passing no default registry.

Source

Thrown at cli/tools/pm/mod.rs:658

                add_req.package_name()
              )),
            );
          }
        }
        package_reqs.push(add_req)
      }
      // Currently unreachable: default_registry is always Some (defaults to Npm),
      // so parse() always resolves a prefix. Kept as a safety fallback in case
      // the API is called with None from elsewhere.
      Err(package_req) => {
        if jsr_resolver
          .req_to_nv(&package_req)
          .await
          .ok()
          .flatten()
          .is_some()
        {
          bail!(
            "{entry_text} is missing a prefix. Did you mean `{}`?",
            crate::colors::yellow(format!("deno {cmd_name} jsr:{package_req}"))
          )
        } else if npm_resolver
          .req_to_nv(&package_req)
          .await
          .ok()
          .flatten()
          .is_some()
        {
          bail!(
            "{entry_text} is missing a prefix. Did you mean `{}`?",
            crate::colors::yellow(format!("deno {cmd_name} npm:{package_req}"))
          )
        } else {
          bail!(
            "{} was not found in either jsr or npm.",
            crate::colors::red(entry_text)

View on GitHub (pinned to 9ad36f7a2c)

Solutions

1. Prefix the specifier explicitly: `deno add jsr:oak` or `deno add npm:chalk`, matching the suggestion in the message.
2. If scripting around the CLI, don't strip registry prefixes from user input.
3. On the CLI today, bare names resolve to npm by default — pass a default registry if you call the API directly.

Example fix

# before
deno add oak
# after
deno add jsr:oak

const spec = process.argv[2] ?? "";
if (!spec.includes(":")) {
  console.error(`bare specifier "${spec}"; be explicit: jsr:${spec} or npm:${spec}`);
  process.exit(1);
}

const hasRegistryPrefix = (spec: string): boolean =>
  /^(npm|jsr|http|https|file|data|node):/.test(spec);

When it happens

Trigger: Calling the add flow programmatically with no default registry and a bare name like `deno add oak` where `oak` resolves on JSR (suggests `jsr:oak`) or npm (suggests `npm:oak`). Bare names in the shipped CLI are auto-treated as npm and do not hit this.

Common situations: Embedders/tests invoking the internal add API with default_registry: None; older Deno versions where bare jsr packages were ambiguous; spec strings missing their `jsr:`/`npm:` prefix after tooling mangles input.

Related errors

• Only npm packages are supported: {}
• Unexpected package json dependency string: "{string_value}"
• unable to find npm package in workspace
• missing version in package.json of npm package
• Either `node` or `range` must be provided when reporting an

AI-assisted analysis of denoland/deno@9ad36f7a2c (2026-08-20). Data as JSON: /api/errors/011776c5f58b96c5. Report an issue: GitHub.