logto/packages/app-insights/src/normalize-error.ts

import { trySafe } from '@silverhand/essentials';

const transformedKey = Symbol('Indicates an object is transformed from an `Error` instance');

// eslint-disable-next-line @typescript-eslint/ban-types
const isObject = (value: unknown): value is object => typeof value === 'object' && value !== null;

// Edited from https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Errors/Cyclic_object_value#circular_references
function getCircularReplacer() {
  const ancestors: unknown[] = [];
  const transformedMap = new WeakMap<Error, unknown>();

  const transformErrorValue = (value: unknown) => {
    // Special handling for `Error` instances since they have non-enumerable properties
    if (value instanceof Error) {
      if (!transformedMap.has(value)) {
        const transformed: Record<string | symbol, unknown> = {};

        for (const key of Object.getOwnPropertyNames(value)) {
          // @ts-expect-error getOwnPropertyNames() returns the valid keys
          // eslint-disable-next-line @silverhand/fp/no-mutation
          transformed[key] = value[key];
        }

        // eslint-disable-next-line @silverhand/fp/no-mutation
        transformed[transformedKey] = true;

        transformedMap.set(value, transformed);
      }

      return transformedMap.get(value);
    }

    return value;
  };

  return function (this: unknown, key: string, value: unknown) {
    // Ignore `stack` property since ApplicationInsights will show it
    if (
      isObject(this) &&
      Object.prototype.hasOwnProperty.call(this, transformedKey) &&
      key === 'stack'
    ) {
      return;
    }

    if (!isObject(value)) {
      return value;
    }

    // `this` is the object that value is contained in,
    // i.e., its direct parent.
    while (ancestors.length > 0 && ancestors.at(-1) !== this) {
      // eslint-disable-next-line @silverhand/fp/no-mutating-methods
      ancestors.pop();
    }

    const transformed = transformErrorValue(value);

    if (ancestors.includes(transformed)) {
      return '[Circular ~]';
    }

    // eslint-disable-next-line @silverhand/fp/no-mutating-methods
    ancestors.push(transformed);
    return transformed;
  };
}

/**
 * Clone and stringify error object for ApplicationInsights. The stringified result
 * will be used as the error message. This is necessary because ApplicationInsights
 * only shows limited error properties.
 */
export const normalizeError = (error: unknown) => {
  /**
   * - Ensure the message if not empty otherwise Application Insights will respond 400
   *   and the error will not be recorded.
   * - We stringify error object here since other error properties won't show on the
   *   ApplicationInsights details page.
   */
  const message = trySafe(() => JSON.stringify(error, getCircularReplacer())) ?? 'Unknown error';

  // Ensure we don't mutate the original error
  const normalized = new Error(message);

  if (error instanceof Error) {
    // Manually clone key fields of the error for AppInsights display
    /* eslint-disable @silverhand/fp/no-mutation */
    normalized.name = error.name;
    normalized.stack = error.stack;
    normalized.cause = error.cause;
    /* eslint-enable @silverhand/fp/no-mutation */
  }

  return normalized;
};