scripts/eslint_rules/lib/trace-engine-test-timeouts.ts

// Copyright 2023 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

import type {TSESTree} from '@typescript-eslint/utils';

import {createRule} from './utils/ruleCreator.ts';

type Node = TSESTree.Node;
type CallExpression = TSESTree.CallExpression;
type CallExpressionArgument = TSESTree.CallExpressionArgument;

const MOCHA_CALLS_TO_CHECK = new Set<string>([
  'it',
  'before',
  'beforeEach',
  'after',
  'afterEach',
]);

export default createRule({
  name: 'trace-engine-test-timeouts',
  meta: {
    type: 'problem',
    docs: {
      description: 'Ensure trace engine tests are defined as functions for test timeouts.',
      category: 'Possible Errors',
    },
    fixable: 'code',
    messages: {
      needsFunction: 'Test should use a function keyword, not an arrow function.',
    },
    schema: [],  // no options
  },
  defaultOptions: [],
  create: function(context) {
    function walkUpTreeToFindMochaFunctionCall(
        node: Node|null,
        ): CallExpression|null {
      if (!node) {
        return null;
      }

      if (node.type === 'CallExpression' && node.callee.type === 'Identifier' &&
          MOCHA_CALLS_TO_CHECK.has(node.callee.name)) {
        return node;
      }

      // Access parent safely
      const parent = node.parent;
      if (!parent) {
        return null;
      }
      return walkUpTreeToFindMochaFunctionCall(parent);
    }

    return {
      MemberExpression(node) {
        const objectIsTraceLoader = node.object.type === 'Identifier' && node.object.name === 'TraceLoader';
        if (!objectIsTraceLoader) {
          return;
        }
        // Find out if this is an await call (which needs the additional test timeout).
        const callExpression = node.parent;
        // Ensure parent is a CallExpression before checking its parent
        if (callExpression.type !== 'CallExpression') {
          return;
        }

        const isAwait = callExpression.parent && callExpression.parent.type === 'AwaitExpression';
        if (!isAwait) {
          return;
        }
        // We now know that we have await TraceLoader.[something]();
        // Now we need to walk up the tree to find the it() call. If we do,
        // we can then check that its function is defined via a function
        // and not as an arrow function.
        const mochaFunctionCall = walkUpTreeToFindMochaFunctionCall(node);
        if (!mochaFunctionCall) {
          return;
        }
        // This code is within a mocha call. If the call is an `it`, we need
        // the second argument, otherwise we use the first argument (Mocha
        // functions like `beforeEach` take only a function as the argument.)
        const functionArg: CallExpressionArgument|undefined =
            mochaFunctionCall.callee.type === 'Identifier' && mochaFunctionCall.callee.name === 'it' ?
            mochaFunctionCall.arguments[1] :
            mochaFunctionCall.arguments[0];

        if (!functionArg) {
          // The node unexpectedly does not have a function passed. The
          // developer is probably in the middle of writing it, so we should
          // just stop and leave them to it.
          return;
        }

        if (functionArg.type === 'ArrowFunctionExpression') {
          context.report({
            node: functionArg,
            messageId: 'needsFunction',
            fix(fixer) {
              // Ensure range exists before using it
              if (!functionArg.range) {
                return null;
              }

              const rangeToReplace: [number, number] = [
                // We want to replace `async () =>` [11 characters] with
                // `async function()`. So we replace the first 11 characters of
                // the function.
                // We check if the function is async first.
                functionArg.range[0],
                functionArg.range[0] + (functionArg.async ? 11 : 5),  // 11 for "async () =>", 5 for "() =>"
              ];

              const replacementText = functionArg.async ? 'async function()' : 'function()';

              return fixer.replaceTextRange(rangeToReplace, replacementText);
            },
          });
        }
      },
    };
  },
});