windmill-labs/windmill · error · UnsupportedLocalPathScriptPreviewError

Local PathScript ${filePath} requires codebase assets, which

Error message

Local PathScript ${filePath} requires codebase assets, which flow preview/dev cannot inline yet

What it means

Also in bundleSingleFileCodebaseScript (cli/src/utils/local_path_scripts.ts): if the SyncCodebase declares assets (codebase.assets is a non-empty array), the bundled script cannot be inlined into flow preview/dev, which only supports single-file payloads, so UnsupportedLocalPathScriptPreviewError is thrown. Like the multi-file case, this is a declared preview limitation — deploy via sync works fine with assets.

Source

Thrown at cli/src/utils/local_path_scripts.ts:75

    define: codebase.define,
    loader: codebase.loader ?? { ".node": "file" },
    outdir: "/",
    platform: "node",
    packages: "bundle",
    target: "esnext",
    banner: codebase.banner,
  });

  if (out.outputFiles.length === 0) {
    throw new Error(`No output files found for ${filePath}`);
  }
  if (out.outputFiles.length > 1) {
    throw new UnsupportedLocalPathScriptPreviewError(
      `Local PathScript ${filePath} requires a multi-file bundle, which flow preview/dev cannot inline yet`
    );
  }
  if (Array.isArray(codebase.assets) && codebase.assets.length > 0) {
    throw new UnsupportedLocalPathScriptPreviewError(
      `Local PathScript ${filePath} requires codebase assets, which flow preview/dev cannot inline yet`
    );
  }

  return out.outputFiles[0].text;
}

export function createPreviewLocalScriptReader(opts: {
  exts: string[];
  defaultTs?: "bun" | "deno";
  codebases: SyncCodebase[];
}): (scriptPath: string) => Promise<LocalScriptInfo | undefined> {
  return async (scriptPath) => {
    const localScript = await resolvePreviewLocalScriptState(scriptPath, opts);
    if (!localScript) {
      return undefined;
    }

View on GitHub (pinned to e474e8803c)

Solutions

1. Deploy via `wmill sync push` instead of flow preview/dev when the codebase has assets — assets are fully supported there
2. Remove the assets from the codebase if they are not needed for the previewed flow step
3. Split the asset-dependent script out of the flow into a separately deployed script and call it by path
4. Inline the asset content directly into the script source if it is small, eliminating the assets declaration

Example fix

// before: flow dev on a step whose codebase declares assets
codebase: { assets: ["data.csv"] }
wmill flow dev flow.yaml // UnsupportedLocalPathScriptPreviewError

// after: deploy the codebase script and reference it in the flow instead of inlining
wmill sync push // script with assets deployed
// flow step: path: f/scripts/asset_script instead of a local inline file

if (Array.isArray(codebase.assets) && codebase.assets.length > 0 && isFlowPreviewPath(scriptPath)) {
  throw new Error(`${scriptPath}'s codebase declares ${codebase.assets.length} asset(s); flow preview/dev cannot inline them — deploy via 'wmill sync push'`);
}

function isUnsupportedPreviewError(err: unknown): err is import("./local_path_scripts.ts").UnsupportedLocalPathScriptPreviewError {
  return err instanceof Error && err.name === "UnsupportedLocalPathScriptPreviewError";
}

import { UnsupportedLocalPathScriptPreviewError } from "./utils/local_path_scripts.ts";
try {
  const inlined = await inlineLocalScript(scriptPath);
} catch (e) {
  if (e instanceof UnsupportedLocalPathScriptPreviewError && /codebase assets/.test(e.message)) {
    console.error(`${scriptPath} needs codebase assets; deploy with 'wmill sync push' and reference it by path in the flow`);
  } else throw e;
}

When it happens

Trigger: bundleSingleFileCodebaseScript is invoked during flow preview/dev for a bun PathScript whose matching codebase (found via findCodebase) has Array.isArray(codebase.assets) && codebase.assets.length > 0, regardless of the esbuild output itself.

Common situations: A codebase.yaml/folder declaring asset files (data files, native libs) alongside the script; sharing one codebase between a deployable script and a step inlined in flow preview; forgetting that preview/dev supports only inline single-file scripts; assets added recently to an existing codebase that previously previewed fine.

Related errors

• Local PathScript ${filePath} requires a multi-file bundle, w
• No output files found for ${filePath}
• native esbuild is not usable; falling back to esbuild-wasm (
• result.substring(__ERR_PREFIX.length)
• App ${appPath} not found

AI-assisted analysis of windmill-labs/windmill@e474e8803c (2026-09-03). Data as JSON: /api/errors/28333181dbaa79d7. Report an issue: GitHub.