angular/angular-cli · error · Error

Failed to parse "${path}" as JSON AST Object. ${printParseEr

Error message

Failed to parse "${path}" as JSON AST Object. ${printParseErrorCode(error)} at location: ${offset}.

What it means

`formatError` in the CLI's JSON-file utility converts the first `ParseError` reported by the `jsonc-parser` tokenizer into a descriptive `Error`, including the file path, the parser error code text (`printParseErrorCode`), and the byte offset where parsing failed. It is thrown whenever a JSON file the CLI reads (workspace config, etc.) is not syntactically valid JSON.

Source

Thrown at packages/angular/cli/src/utilities/json-file.ts:213

 */
export function readAndParseJson<T extends JsonValue>(path: string): T {
  const errors: ParseError[] = [];
  const content = parse(readFileSync(path, 'utf-8'), errors, { allowTrailingComma: true }) as T;
  if (errors.length) {
    formatError(path, errors);
  }

  return content;
}

/**
 * Formats a JSON parsing error and throws an exception.
 * @param path The path to the file that failed to parse.
 * @param errors The list of parsing errors.
 */
function formatError(path: string, errors: ParseError[]): never {
  const { error, offset } = errors[0];
  throw new Error(
    `Failed to parse "${path}" as JSON AST Object. ${printParseErrorCode(
      error,
    )} at location: ${offset}.`,
  );
}

/**
 * Parses a JSON string, supporting comments and trailing commas.
 * @param content The JSON string to parse.
 * @returns The parsed JSON object.
 */
export function parseJson<T extends JsonValue>(content: string): T {
  return parse(content, undefined, { allowTrailingComma: true }) as T;
}

View on GitHub (pinned to bb72145f9a)

Solutions

1. Open the file and fix the syntax at the reported offset (the message gives the location).
2. Run a validator: `jq . <file>` or `npx jsonlint <file>` to pinpoint the problem.
3. Restore from version control: `git checkout -- angular.json`.
4. If you edit configs programmatically, validate JSON before saving (e.g. `JSON.parse` round-trip in a pre-commit hook).

Example fix

// before
{ "version": 1, "projects": { } // missing closing brace
// after
{ "version": 1, "projects": { } }

import { readFile } from 'node:fs/promises';
const text = await readFile(path, 'utf8');
try { JSON.parse(text); } catch (e) {
  throw new Error(`${path} is not valid JSON; fix syntax before the CLI reads it.`, { cause: e });
}

function parsesAsJson(text: string): boolean {
  try { JSON.parse(text); return true; } catch { return false; }
}

try {
  await runNgCommand();
} catch (e) {
  if (e instanceof Error && e.message.includes('Failed to parse') && e.message.includes('as JSON AST Object')) {
    // message contains file, error code, and offset — fix the syntax there
  } else { throw e; }
}

When it happens

Trigger: Reading a JSON file through the CLI's JSON utilities (e.g. `readAndParseJson`, `JsonAst`) when `jsonc-parser`'s `parse`/`parseTree` reports errors — invalid syntax, unexpected characters, truncated file.

Common situations: Hand-edited `angular.json` with typos or trailing commas; merge-conflict markers (`<<<<<<<`) left in the config; a tool writing partial/truncated JSON; HTML error pages saved where a JSON file was expected.

Understand the failure class

Background: JSON parse error: "Unexpected token" / "not valid JSON" / "failed to parse" — what JSON parsers are really complaining about — this error's family across 45 libraries.

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Invalid config found at ${workspace.filePath}. CLI should be
• Workspace config file cannot be loaded: ${configPath}
• ${message}
• Failed to parse "${path}" as JSON. ${printParseErrorCode(err
• Could not find ${level} workspace.

AI-assisted analysis of angular/angular-cli@bb72145f9a (2026-08-30). Data as JSON: /api/errors/927973a50065ce0e. Report an issue: GitHub.