Failed to parse fixture ${p}: ${err instanceof Error ? err.m

Error message

Failed to parse fixture ${p}: ${err instanceof Error ? err.message : String(err)}

What it means

loadFixture reads a fixture JSON file for a site/command pair and parses it. If the file exists but is unreadable or is not valid JSON, the low-level error is wrapped in a descriptive Error naming the fixture path and the parse failure, so callers know exactly which fixture is corrupt.

Source

Thrown at src/browser/verify-fixture.ts:122

  /^hn_id$/i,
  /^username$/i,
  /^handle$/i,
  /^uri$/i,
];

export function fixturePath(site: string, command: string): string {
  return path.join(os.homedir(), '.opencli', 'sites', site, 'verify', `${command}.json`);
}

export function loadFixture(site: string, command: string): Fixture | null {
  const p = fixturePath(site, command);
  if (!fs.existsSync(p)) return null;
  try {
    const raw = fs.readFileSync(p, 'utf-8');
    const parsed = JSON.parse(raw) as Fixture;
    return parsed;
  } catch (err) {
    throw new Error(`Failed to parse fixture ${p}: ${err instanceof Error ? err.message : String(err)}`);
  }
}

export function writeFixture(site: string, command: string, fixture: Fixture): string {
  const p = fixturePath(site, command);
  fs.mkdirSync(path.dirname(p), { recursive: true });
  fs.writeFileSync(p, `${JSON.stringify(fixture, null, 2)}\n`, 'utf-8');
  return p;
}

/**
 * Derive a reasonable fixture from sample output. Used by `--write-fixture`
 * to seed a first draft the author can hand-tune.
 *
 * Heuristics:
 * - rowCount.min = 1 if rows non-empty, else 0
 * - columns = keys from the first row
 * - types = typeof of the first row's values, with "number|string" for mixed

View on GitHub (pinned to 49907e53dc)

Solutions

Open the path from the error message and fix the JSON syntax (validate with jq or a JSON linter).
Delete the corrupt fixture and regenerate it with writeFixture by re-running the command that produces it.
Check file permissions/readability if the wrapped message is a read error rather than a parse error.
Verify the file has no BOM, comments, or trailing commas.

Example fix

// before (fixtures/foo.json)
{ "steps": [1, 2,] }
// after
{ "steps": [1, 2] }

Defensive patterns

Strategy: fallback

Validate before calling

import { readFileSync, existsSync } from 'fs';
function fixtureLooksValid(p) {
  if (!existsSync(p)) return true;
  try { JSON.parse(readFileSync(p, 'utf-8')); return true; } catch { return false; }
}

Type guard

function isFixture(v: unknown): v is Fixture {
  return typeof v === 'object' && v !== null && !Array.isArray(v);
}

Try / catch

try {
  const fixture = loadFixture(site, command);
} catch (err) {
  console.error(err.message);
  // regenerate the corrupt fixture
  writeFixture(site, command, defaultFixture);
  fixture = defaultFixture;
}

Prevention

Validate fixture JSON with jq after hand edits.
Always let writeFixture serialize fixtures instead of editing them manually.
Treat fixture files as generated artifacts; regenerate rather than repair.
Watch for concurrent runs writing the same fixture path.

When it happens

Trigger: The fixture file at fixturePath(site, command) exists but contains malformed JSON (trailing commas, truncated writes, hand-edited syntax errors) or cannot be read (permissions, encoding).

Common situations: Manually editing a fixture and breaking JSON; a crashed run leaving a half-written fixture via writeFixture; fixtures committed with BOM or comments; concurrent runs corrupting the file.

Understand the failure class

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

Related errors

AI-assisted analysis of jackwener/OpenCLI@49907e53dc (2026-08-29). Data as JSON: /api/errors/f7ab1ed97beef9d3. Report an issue: GitHub.