evanw/esbuild · error · Error

Invalid banner file type: ${type}

Error message

Invalid banner file type: ${type}

What it means

Error "Invalid banner file type: ${type}" thrown in evanw/esbuild.

Source

Thrown at lib/shared/common.ts:320

  if (tsconfig) flags.push(`--tsconfig=${tsconfig}`)
  if (packages) flags.push(`--packages=${packages}`)
  if (resolveExtensions) flags.push(`--resolve-extensions=${validateAndJoinStringArray(resolveExtensions, 'resolve extension')}`)
  if (publicPath) flags.push(`--public-path=${publicPath}`)
  if (entryNames) flags.push(`--entry-names=${entryNames}`)
  if (chunkNames) flags.push(`--chunk-names=${chunkNames}`)
  if (assetNames) flags.push(`--asset-names=${assetNames}`)
  if (mainFields) flags.push(`--main-fields=${validateAndJoinStringArray(mainFields, 'main field')}`)
  if (conditions) flags.push(`--conditions=${validateAndJoinStringArray(conditions, 'condition')}`)
  if (external) for (let name of external) flags.push(`--external:${validateStringValue(name, 'external')}`)
  if (alias) {
    for (let old in alias) {
      if (old.indexOf('=') >= 0) throw new Error(`Invalid package name in alias: ${old}`)
      flags.push(`--alias:${old}=${validateStringValue(alias[old], 'alias', old)}`)
    }
  }
  if (banner) {
    for (let type in banner) {
      if (type.indexOf('=') >= 0) throw new Error(`Invalid banner file type: ${type}`)
      flags.push(`--banner:${type}=${validateStringValue(banner[type], 'banner', type)}`)
    }
  }
  if (footer) {
    for (let type in footer) {
      if (type.indexOf('=') >= 0) throw new Error(`Invalid footer file type: ${type}`)
      flags.push(`--footer:${type}=${validateStringValue(footer[type], 'footer', type)}`)
    }
  }
  if (inject) for (let path of inject) flags.push(`--inject:${validateStringValue(path, 'inject')}`)
  if (loader) {
    for (let ext in loader) {
      if (ext.indexOf('=') >= 0) throw new Error(`Invalid loader extension: ${ext}`)
      flags.push(`--loader:${ext}=${validateStringValue(loader[ext], 'loader', ext)}`)
    }
  }
  if (outExtension) {
    for (let ext in outExtension) {

View on GitHub (pinned to 6ff1d8b0d8)

Solutions

1. Use only "js" or "css" as banner file types
2. Remove banner entries whose keys are not "js" or "css"

Example fix

esbuild.buildSync({ banner: { js: '/* license */', css: '/* license */' } });

When it happens

Trigger: Thrown at lib/shared/common.ts:320 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of evanw/esbuild@6ff1d8b0d8 (2026-08-03). Data as JSON: /data/errors/5ab229b3b6e437d8.json. Report an issue: GitHub.