evanw/esbuild · error · Error

Expected value for supported ${quote(key)} to be a boolean,

Error message

Expected value for supported ${quote(key)} to be a boolean, got ${typeof value} instead

What it means

Error "Expected value for supported ${quote(key)} to be a boolean, got ${typeof value} instead" thrown in evanw/esbuild.

Source

Thrown at lib/shared/common.ts:227

  if (jsxSideEffects) flags.push(`--jsx-side-effects`)

  if (define) {
    for (let key in define) {
      if (key.indexOf('=') >= 0) throw new Error(`Invalid define: ${key}`)
      flags.push(`--define:${key}=${validateStringValue(define[key], 'define', key)}`)
    }
  }
  if (logOverride) {
    for (let key in logOverride) {
      if (key.indexOf('=') >= 0) throw new Error(`Invalid log override: ${key}`)
      flags.push(`--log-override:${key}=${validateStringValue(logOverride[key], 'log override', key)}`)
    }
  }
  if (supported) {
    for (let key in supported) {
      if (key.indexOf('=') >= 0) throw new Error(`Invalid supported: ${key}`)
      const value = supported[key]
      if (typeof value !== 'boolean') throw new Error(`Expected value for supported ${quote(key)} to be a boolean, got ${typeof value} instead`)
      flags.push(`--supported:${key}=${value}`)
    }
  }
  if (pure) for (let fn of pure) flags.push(`--pure:${validateStringValue(fn, 'pure')}`)
  if (keepNames) flags.push(`--keep-names`)
}

function flagsForBuildOptions(
  callName: string,
  options: types.BuildOptions,
  isTTY: boolean,
  logLevelDefault: types.LogLevel,
  writeDefault: boolean,
): {
  entries: [string, string][],
  flags: string[],
  write: boolean,
  stdinContents: Uint8Array | null,

View on GitHub (pinned to 6ff1d8b0d8)

Solutions

1. Pass a boolean (true/false) for the supported feature flag instead of the reported type
2. Remove or correct non-boolean entries in the "supported" map

Example fix

esbuild.buildSync({ supported: { 'async-await': true } });

When it happens

Trigger: Thrown at lib/shared/common.ts:227 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/9ca0fc84e0e871cd.json. Report an issue: GitHub.