valid-expect.ts

/*
 * This implementation is ported from from eslint-plugin-jasmine.
 * MIT license, Tom Vincent.
 */

import {
  AST_NODE_TYPES,
  TSESTree,
} from '@typescript-eslint/experimental-utils';
import {
  ModifierName,
  createRule,
  getAccessorValue,
  isExpectCall,
  isExpectMember,
  isSupportedAccessor,
  parseExpectCall,
} from './utils';

/**
 * Async assertions might be called in Promise
 * methods like `Promise.x(expect1)` or `Promise.x([expect1, expect2])`.
 * If that's the case, Promise node have to be awaited or returned.
 *
 * @Returns CallExpressionNode
 */
const getPromiseCallExpressionNode = (node: TSESTree.Node) => {
  if (
    node &&
    node.type === AST_NODE_TYPES.ArrayExpression &&
    node.parent &&
    node.parent.type === AST_NODE_TYPES.CallExpression
  ) {
    node = node.parent;
  }

  if (
    node.type === AST_NODE_TYPES.CallExpression &&
    node.callee &&
    node.callee.type === AST_NODE_TYPES.MemberExpression &&
    isSupportedAccessor(node.callee.object) &&
    getAccessorValue(node.callee.object) === 'Promise' &&
    node.parent
  ) {
    return node;
  }

  return null;
};

const findPromiseCallExpressionNode = (node: TSESTree.Node) =>
  node.parent &&
  node.parent.parent &&
  [AST_NODE_TYPES.CallExpression, AST_NODE_TYPES.ArrayExpression].includes(
    node.parent.type,
  )
    ? getPromiseCallExpressionNode(node.parent)
    : null;

const getParentIfThenified = (node: TSESTree.Node): TSESTree.Node => {
  const grandParentNode = node.parent && node.parent.parent;

  if (
    grandParentNode &&
    grandParentNode.type === AST_NODE_TYPES.CallExpression &&
    grandParentNode.callee &&
    isExpectMember(grandParentNode.callee) &&
    ['then', 'catch'].includes(
      getAccessorValue(grandParentNode.callee.property),
    ) &&
    grandParentNode.parent
  ) {
    // Just in case `then`s are chained look one above.
    return getParentIfThenified(grandParentNode);
  }

  return node;
};

const isAcceptableReturnNode = (
  node: TSESTree.Node,
  allowReturn: boolean,
): node is
  | TSESTree.ArrowFunctionExpression
  | TSESTree.AwaitExpression
  | TSESTree.ReturnStatement =>
  (allowReturn && node.type === AST_NODE_TYPES.ReturnStatement) ||
  [
    AST_NODE_TYPES.ArrowFunctionExpression,
    AST_NODE_TYPES.AwaitExpression,
  ].includes(node.type);

const promiseArrayExceptionKey = ({ start, end }: TSESTree.SourceLocation) =>
  `${start.line}:${start.column}-${end.line}:${end.column}`;

type MessageIds =
  | 'multipleArgs'
  | 'noArgs'
  | 'noAssertions'
  | 'invalidProperty'
  | 'propertyWithoutMatcher'
  | 'matcherOnPropertyNotCalled'
  | 'asyncMustBeAwaited'
  | 'promisesWithAsyncAssertionsMustBeAwaited';

export default createRule<[{ alwaysAwait?: boolean }], MessageIds>({
  name: __filename,
  meta: {
    docs: {
      category: 'Best Practices',
      description: 'Enforce valid `expect()` usage',
      recommended: 'error',
    },
    messages: {
      multipleArgs: 'More than one argument was passed to expect().',
      noArgs: 'No arguments were passed to expect().',
      noAssertions: 'No assertion was called on expect().',
      invalidProperty:
        '"{{ propertyName }}" is not a valid property of expect.',
      propertyWithoutMatcher: '"{{ propertyName }}" needs to call a matcher.',
      matcherOnPropertyNotCalled: '"{{ propertyName }}" was not called.',
      asyncMustBeAwaited: 'Async assertions must be awaited{{ orReturned }}.',
      promisesWithAsyncAssertionsMustBeAwaited:
        'Promises which return async assertions must be awaited{{ orReturned }}.',
    },
    type: 'suggestion',
    schema: [
      {
        type: 'object',
        properties: {
          alwaysAwait: {
            type: 'boolean',
            default: false,
          },
        },
        additionalProperties: false,
      },
    ],
  },
  defaultOptions: [{ alwaysAwait: false }],
  create(context, [{ alwaysAwait }]) {
    // Context state
    const arrayExceptions = new Set<string>();

    const pushPromiseArrayException = (loc: TSESTree.SourceLocation) =>
      arrayExceptions.add(promiseArrayExceptionKey(loc));

    /**
     * Promise method that accepts an array of promises,
     * (eg. Promise.all), will throw warnings for the each
     * unawaited or non-returned promise. To avoid throwing
     * multiple warnings, we check if there is a warning in
     * the given location.
     */
    const promiseArrayExceptionExists = (loc: TSESTree.SourceLocation) =>
      arrayExceptions.has(promiseArrayExceptionKey(loc));

    return {
      CallExpression(node) {
        if (!isExpectCall(node)) {
          return;
        }

        const { expect, modifier, matcher } = parseExpectCall(node);

        if (expect.arguments.length > 1) {
          const secondArgumentLocStart = expect.arguments[1].loc.start;
          const lastArgumentLocEnd =
            expect.arguments[node.arguments.length - 1].loc.end;

          context.report({
            loc: {
              end: {
                column: lastArgumentLocEnd.column - 1,
                line: lastArgumentLocEnd.line,
              },
              start: secondArgumentLocStart,
            },
            messageId: 'multipleArgs',
            node,
          });
        } else if (expect.arguments.length === 0) {
          const expectLength = getAccessorValue(expect.callee).length;
          context.report({
            loc: {
              end: {
                column: node.loc.start.column + expectLength + 1,
                line: node.loc.start.line,
              },
              start: {
                column: node.loc.start.column + expectLength,
                line: node.loc.start.line,
              },
            },
            messageId: 'noArgs',
            node,
          });
        }

        // something was called on `expect()`
        if (!matcher) {
          if (modifier) {
            context.report({
              data: { propertyName: modifier.name }, // todo: rename to 'modifierName'
              messageId: 'propertyWithoutMatcher', // todo: rename to 'modifierWithoutMatcher'
              node: modifier.node.property,
            });
          }

          return;
        }

        if (matcher.node.parent && isExpectMember(matcher.node.parent)) {
          context.report({
            messageId: 'invalidProperty', // todo: rename to 'invalidModifier'
            data: { propertyName: matcher.name }, // todo: rename to 'matcherName' (or modifierName?)
            node: matcher.node.property,
          });

          return;
        }

        if (!matcher.arguments) {
          context.report({
            data: { propertyName: matcher.name }, // todo: rename to 'matcherName'
            messageId: 'matcherOnPropertyNotCalled', // todo: rename to 'matcherNotCalled'
            node: matcher.node.property,
          });
        }

        const parentNode = matcher.node.parent;

        if (
          !modifier ||
          !parentNode ||
          !parentNode.parent ||
          modifier.name === ModifierName.not
        ) {
          return;
        }
        /**
         * If parent node is an array expression, we'll report the warning,
         * for the array object, not for each individual assertion.
         */
        const isParentArrayExpression =
          parentNode.parent.type === AST_NODE_TYPES.ArrayExpression;
        const orReturned = alwaysAwait ? '' : ' or returned';
        /**
         * An async assertion can be chained with `then` or `catch` statements.
         * In that case our target CallExpression node is the one with
         * the last `then` or `catch` statement.
         */
        const targetNode = getParentIfThenified(parentNode);
        const finalNode =
          findPromiseCallExpressionNode(targetNode) || targetNode;
        if (
          finalNode.parent &&
          // If node is not awaited or returned
          !isAcceptableReturnNode(finalNode.parent, !alwaysAwait) &&
          // if we didn't warn user already
          !promiseArrayExceptionExists(finalNode.loc)
        ) {
          context.report({
            loc: finalNode.loc,
            data: {
              orReturned,
            },
            messageId:
              finalNode === targetNode
                ? 'asyncMustBeAwaited'
                : 'promisesWithAsyncAssertionsMustBeAwaited',
            node,
          });

          if (isParentArrayExpression) {
            pushPromiseArrayException(finalNode.loc);
          }
        }
      },

      // nothing called on "expect()"
      'CallExpression:exit'(node: TSESTree.CallExpression) {
        if (
          isExpectCall(node) &&
          node.parent.type === AST_NODE_TYPES.ExpressionStatement
        ) {
          context.report({ messageId: 'noAssertions', node });
        }
      },
    };
  },
});