eslint-plugin-ember/lib/utils/computed-properties.js

ESLint plugin for Ember.js apps

const types = require('./types');
const assert = require('assert');

module.exports = {
  isComputedPropertyBodyArg,
  getComputedPropertyFunctionBody,
};

/**
 * Checks whether a computed property argument is the type of node that could contain the
 * function body of the computed property (which would be passed as the last arg).
 *
 * Handles:
 * * computed('prop1', 'prop2', function() { ... })
 * * computed('prop1', 'prop2', () => { ... })
 * * computed('prop1', 'prop2', { get() { ... } })
 *
 * @param {ASTNode} node - computed property argument to check
 * @returns {boolean} whether the node could be the function body argument of a computed property
 */
function isComputedPropertyBodyArg(node) {
  return (
    types.isFunctionExpression(node) ||
    types.isArrowFunctionExpression(node) ||
    types.isObjectExpression(node)
  );
}

/**
 * Gets the function body of the computed property.
 *
 * Handles:
 * * computed('prop1', 'prop2', function() { ... })
 * * computed('prop1', 'prop2', () => { ... })
 * * computed('prop1', 'prop2', { get() { ... } })
 * * @computed('prop1', 'prop2') get fullName() { ... }
 * * @computed get fullName() { ... }
 *
 * @param {ASTNode} node - computed property CallExpression node
 * @returns {ASTNode} function body of computed property
 */
function getComputedPropertyFunctionBody(node) {
  assert(
    types.isCallExpression(node) || types.isIdentifier(node),
    'Should only call this function on a CallExpression or Identifier'
  );

  if (types.isCallExpression(node)) {
    const lastArg = node.arguments.at(-1);

    if (types.isArrowFunctionExpression(lastArg) || types.isFunctionExpression(lastArg)) {
      // Example: computed('prop1', 'prop2', function() { ... })
      // Example: computed('prop1', 'prop2', () => { ... })
      return lastArg.body;
    } else if (types.isObjectExpression(lastArg)) {
      // Example: computed('prop1', 'prop2', { get() { ... } })
      const getFunction = lastArg.properties.find(
        (property) =>
          property.method && types.isIdentifier(property.key) && property.key.name === 'get'
      );
      if (getFunction) {
        return getFunction.value.body;
      }
    }
  }

  if (
    types.isDecorator(node.parent) &&
    types.isMethodDefinition(node.parent.parent) &&
    node.parent.parent.kind === 'get'
  ) {
    // Example: @computed('first', 'last') get fullName() {}
    // Example: @computed get fullName() {}
    return node.parent.parent.value.body;
  }

  return undefined;
}