{"record":{"id":"c6377292edacc871","repo":"cypress-io/cypress","slug":"failed-to-update-config-file-file-with-string","errorCode":null,"errorMessage":"Failed to update config file ${file} with ${stringify(obj)}: ${e.message}","messagePattern":"Failed to update config file (.+?) with (.+?): (.+?)","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"packages/data-context/src/util/config-file-updater.ts","lineNumber":23,"sourceCode":"import type { namedTypes } from 'ast-types'\nimport Debug from 'debug'\nimport fs from 'fs-extra'\nimport stringify from 'stringify-object'\n\nconst debug = Debug('cypress:data-context:config-file-updater')\n\ninterface ErrorObj {\n  get(type: string, ...args: any[]): Error\n}\n\nexport async function insertValuesInConfigFile (file: string, obj: {}, errors: ErrorObj) {\n  const fileContents = await fs.readFile(file, { encoding: 'utf8' })\n\n  const transformedFileContents = await insertValueInJSString(fileContents, obj, errors)\n\n  debug('transformedFileContents %s', transformedFileContents)\n  await fs.writeFile(file, transformedFileContents).catch((e) => {\n    throw new Error(`Failed to update config file ${file} with ${stringify(obj)}: ${e.message}`)\n  })\n}\n\nexport async function insertValueInJSString (fileContents: string, obj: Record<string, any>, errors: ErrorObj): Promise<string> {\n  const ast = parse(fileContents, { plugins: ['typescript'], sourceType: 'module' })\n\n  let objectLiteralNode: namedTypes.ObjectExpression | undefined\n\n  function handleExport (nodePath: NodePath<namedTypes.CallExpression, any> | NodePath<namedTypes.ObjectExpression, any>): void {\n    if (nodePath.node.type === 'CallExpression'\n        && nodePath.node.callee.type === 'Identifier') {\n      const functionName = nodePath.node.callee.name\n\n      if (isDefineConfigFunction(ast as File, functionName)) {\n        return handleExport(nodePath.get('arguments', 0))\n      }\n    }\n","sourceCodeStart":5,"sourceCodeEnd":41,"githubUrl":"https://github.com/cypress-io/cypress/blob/0d85fdc91230885bca0a91df278312800a48b727/packages/data-context/src/util/config-file-updater.ts#L5-L41","documentation":"Thrown by insertValuesInConfigFile (config-file-updater.ts:22-24) when fs.writeFile of the AST-transformed cypress.config file rejects. The catch wraps the underlying error message with the target file path and the stringified values object (via stringify-object) for debuggability. This is purely a WRITE failure; structural/parse problems with the config throw a separate COULD_NOT_UPDATE_CONFIG_FILE error earlier (via errors.get in insertValueInJSString). So hitting this message specifically means the file was parsed and transformed successfully but could not be saved.","triggerScenarios":"fs.writeFile(file, transformedFileContents) rejects — EACCES (no write permission), EISDIR (path is a directory), ENOSPC (disk full), EBUSY/EPERM (file locked on Windows by an editor or watcher), or the directory was removed between read and write.","commonSituations":"cypress.config.js is read-only or owned by another user; an editor or file watcher holds an exclusive lock on the file (Windows); disk/full partition; the project root is on a read-only mount; a security/antivirus tool blocks writes; the file path became invalid after a rename.","solutions":["Check write permissions on the config file and its directory (chmod/chown) and remove any read-only flag.","Close editors or tools that may be locking the file (especially on Windows) and retry.","Free disk space if ENOSPC, and confirm the project directory still exists and is writable.","Read the underlying e.message in the thrown error — it carries the exact errno (EACCES/EBUSY/ENOSPC) that points to the fix."],"exampleFix":"// before\nawait insertValuesInConfigFile(file, obj, errors) // opaque write failure\n\n// after\nimport fs from 'fs-extra'\ntry {\n  await fs.access(file, fs.constants.W_OK)\n} catch {\n  throw new Error(`Config file ${file} is not writable; check permissions/locks`)\n}\nawait insertValuesInConfigFile(file, obj, errors)","handlingStrategy":"try-catch","validationCode":"// Verify the config file is writable before attempting the update\nimport fs from 'fs-extra'\n\nasync function isConfigWritable(file: string): Promise<boolean> {\n  try {\n    await fs.access(file, fs.constants.W_OK)\n    return true\n  } catch {\n    return false\n  }\n}\n\nif (!(await isConfigWritable(file))) {\n  throw new Error(`Cannot write config file ${file}; check permissions/locks`)\n}\nawait insertValuesInConfigFile(file, obj, errors)","typeGuard":null,"tryCatchPattern":"try {\n  await insertValuesInConfigFile(file, obj, errors)\n} catch (e) {\n  // e.message already includes file path, stringified obj, and underlying errno.\n  // Parse the tail (EACCES/EBUSY/ENOSPC) to pick the right remediation.\n  const errno = /EACCES|EBUSY|ENOSPC|EISDIR|EPERM/.exec(e.message)?.[0]\n  reportToUser(`Could not save cypress.config: ${errno ?? 'write error'}`, e.message)\n}","preventionTips":["Keep cypress.config.{js,ts} writable by the user running Cypress; avoid checking it in read-only or with restrictive perms.","On Windows, ensure no editor or file watcher holds an exclusive lock before Cypress tries to update the config.","Free disk space and confirm the project directory is on a writable mount.","Read the underlying errno embedded in the message — it pinpoints permissions vs lock vs space vs path problems."],"tags":["config-file","filesystem","write-failure","permissions","ast-transform"],"backgroundTag":null,"analyzedSha":"0d85fdc91230885bca0a91df278312800a48b727","analyzedAt":"2026-08-12T16:24:28.056Z","schemaVersion":2},"datasetVersion":"2026-08-12T18:17:37.767Z"}