playwright-bdd/src/playwright/fixtureParameterNames.ts

BDD Testing with Playwright runner

/**
 * Extracted from playwright.
 * https://github.com/microsoft/playwright/blob/main/packages/playwright-test/src/common/fixtures.ts#L226
 */

/* eslint-disable @typescript-eslint/no-explicit-any, @typescript-eslint/no-unsafe-function-type */
/* eslint-disable max-statements, visual/complexity, max-len, max-depth */

const signatureSymbol = Symbol('signature');

export function fixtureParameterNames(fn: Function | any): string[] {
  if (typeof fn !== 'function') return [];
  if (!fn[signatureSymbol]) fn[signatureSymbol] = innerFixtureParameterNames(fn);
  return fn[signatureSymbol];
}

function innerFixtureParameterNames(fn: Function): string[] {
  const text = filterOutComments(fn.toString());
  const match = text.match(/(?:async)?(?:\s+function)?[^(]*\(([^)]*)/);
  if (!match) return [];
  const trimmedParams = match[1].trim();
  if (!trimmedParams) return [];
  const [firstParam] = splitByComma(trimmedParams);
  if (firstParam[0] !== '{' || firstParam[firstParam.length - 1] !== '}') {
    throw new Error(
      'First argument must use the object destructuring pattern: ' +
        firstParam +
        ' ' +
        fn.toString(),
    );
  }
  const props = splitByComma(firstParam.substring(1, firstParam.length - 1)).map((prop) => {
    const colon = prop.indexOf(':');
    return colon === -1 ? prop.trim() : prop.substring(0, colon).trim();
  });
  const restProperty = props.find((prop) => prop.startsWith('...'));
  if (restProperty) {
    throw new Error(
      `Rest property "${restProperty}" is not supported. List all used fixtures explicitly, separated by comma. ${fn.toString()}`,
    );
  }
  return props;
}

function filterOutComments(s: string): string {
  const result: string[] = [];
  let commentState: 'none' | 'singleline' | 'multiline' = 'none';
  for (let i = 0; i < s.length; ++i) {
    if (commentState === 'singleline') {
      if (s[i] === '\n') commentState = 'none';
    } else if (commentState === 'multiline') {
      if (s[i - 1] === '*' && s[i] === '/') commentState = 'none';
    } else if (commentState === 'none') {
      if (s[i] === '/' && s[i + 1] === '/') {
        commentState = 'singleline';
      } else if (s[i] === '/' && s[i + 1] === '*') {
        commentState = 'multiline';
        i += 2;
      } else {
        result.push(s[i]);
      }
    }
  }
  return result.join('');
}

function splitByComma(s: string) {
  const result: string[] = [];
  const stack: string[] = [];
  let start = 0;
  for (let i = 0; i < s.length; i++) {
    if (s[i] === '{' || s[i] === '[') {
      stack.push(s[i] === '{' ? '}' : ']');
    } else if (s[i] === stack[stack.length - 1]) {
      stack.pop();
    } else if (!stack.length && s[i] === ',') {
      const token = s.substring(start, i).trim();
      if (token) result.push(token);
      start = i + 1;
    }
  }
  const lastToken = s.substring(start).trim();
  if (lastToken) result.push(lastToken);
  return result;
}