{"id":"40fdcfa32bd57559","repo":"evanw/esbuild","slug":"invalid-out-extension-ext","errorCode":null,"errorMessage":"Invalid out extension: ${ext}","messagePattern":"Invalid out extension: (.+?)","errorType":"validation","errorClass":"Error","httpStatus":null,"severity":"error","filePath":"lib/shared/common.ts","lineNumber":339,"sourceCode":"      flags.push(`--banner:${type}=${validateStringValue(banner[type], 'banner', type)}`)\n    }\n  }\n  if (footer) {\n    for (let type in footer) {\n      if (type.indexOf('=') >= 0) throw new Error(`Invalid footer file type: ${type}`)\n      flags.push(`--footer:${type}=${validateStringValue(footer[type], 'footer', type)}`)\n    }\n  }\n  if (inject) for (let path of inject) flags.push(`--inject:${validateStringValue(path, 'inject')}`)\n  if (loader) {\n    for (let ext in loader) {\n      if (ext.indexOf('=') >= 0) throw new Error(`Invalid loader extension: ${ext}`)\n      flags.push(`--loader:${ext}=${validateStringValue(loader[ext], 'loader', ext)}`)\n    }\n  }\n  if (outExtension) {\n    for (let ext in outExtension) {\n      if (ext.indexOf('=') >= 0) throw new Error(`Invalid out extension: ${ext}`)\n      flags.push(`--out-extension:${ext}=${validateStringValue(outExtension[ext], 'out extension', ext)}`)\n    }\n  }\n\n  if (entryPoints) {\n    if (Array.isArray(entryPoints)) {\n      for (let i = 0, n = entryPoints.length; i < n; i++) {\n        let entryPoint = entryPoints[i]\n        if (typeof entryPoint === 'object' && entryPoint !== null) {\n          let entryPointKeys: OptionKeys = Object.create(null)\n          let input = getFlag(entryPoint, entryPointKeys, 'in', mustBeString)\n          let output = getFlag(entryPoint, entryPointKeys, 'out', mustBeString)\n          checkForInvalidFlags(entryPoint, entryPointKeys, 'in entry point at index ' + i)\n          if (input === undefined) throw new Error('Missing property \"in\" for entry point at index ' + i)\n          if (output === undefined) throw new Error('Missing property \"out\" for entry point at index ' + i)\n          entries.push([output, input])\n        } else {\n          entries.push(['', validateStringValue(entryPoint, 'entry point at index ' + i)])","sourceCodeStart":321,"sourceCodeEnd":357,"githubUrl":"https://github.com/evanw/esbuild/blob/6ff1d8b0d8c134e867a397eef39702a223ebef9e/lib/shared/common.ts#L321-L357","documentation":"Error \"Invalid out extension: ${ext}\" thrown in evanw/esbuild.","triggerScenarios":"Thrown at lib/shared/common.ts:339 when the library encounters an invalid state.","commonSituations":"See trigger scenarios.","solutions":["Ensure out extension keys are valid file extensions beginning with a dot (e.g. \".js\", \".css\")","Fix or remove the malformed extension in the outExtension map"],"exampleFix":"esbuild.buildSync({ outExtension: { '.js': '.mjs' } });","handlingStrategy":null,"validationCode":null,"typeGuard":null,"tryCatchPattern":null,"preventionTips":[],"tags":[],"analyzedSha":"6ff1d8b0d8c134e867a397eef39702a223ebef9e","analyzedAt":"2026-08-03T19:42:38.433Z","schemaVersion":2}