feat(prefer-await-to-then): ignore constructor scope unless with strict option (#496)

Fixes #436

**What is the purpose of this pull request?**

- [x] Changes an existing rule

**What changes did you make? (Give an overview)**

Ignores constructor scope in `prefer-await-to-then` when reporting on
use of `then` (unless the `strict` option is enabled).

Co-authored-by: Yosuke Ota <otameshiyo23@gmail.com>

Author: brettz9

__tests__/prefer-await-to-then.js

@@ -34,6 +34,11 @@ ruleTester.run('prefer-await-to-then', rule, {
     `function isThenable(obj) {
       return obj && typeof obj.then === 'function';
     }`,
+    `class Foo {
+      constructor () {
+        doSomething.then(abc);
+      }
+    }`,
   ],
 
   invalid: [
@@ -70,6 +75,19 @@ ruleTester.run('prefer-await-to-then', rule, {
         },
       ],
     },
+    {
+      code: `class Foo {
+        constructor () {
+          doSomething.then(abc);
+        }
+      }`,
+      errors: [{ message }],
+      options: [
+        {
+          strict: true,
+        },
+      ],
+    },
     {
       code: 'async function hi() { await thing().catch() }',
       errors: [{ message }],

rules/lib/is-inside-callback.js

@@ -3,7 +3,7 @@
 const isInsidePromise = require('./is-inside-promise')
 
 function isInsideCallback(node) {
-  const isCallExpression =
+  const isFunction =
     node.type === 'FunctionExpression' ||
     node.type === 'ArrowFunctionExpression' ||
     node.type === 'FunctionDeclaration' // this may be controversial
@@ -13,7 +13,7 @@ function isInsideCallback(node) {
 
   const name = node.params && node.params[0] && node.params[0].name
   const firstArgIsError = name === 'err' || name === 'error'
-  const isInACallback = isCallExpression && firstArgIsError
+  const isInACallback = isFunction && firstArgIsError
   return isInACallback
 }
 

rules/prefer-await-to-then.js

@@ -41,6 +41,15 @@ module.exports = {
       })
     }
 
+    /** Returns true if node is inside a constructor */
+    function isInsideConstructor(node) {
+      return getAncestors(context, node).some((parent) => {
+        return (
+          parent.type === 'MethodDefinition' && parent.kind === 'constructor'
+        )
+      })
+    }
+
     /**
      * Returns true if node is created at the top-level scope.
      * Await statements are not allowed at the top level,
@@ -57,6 +66,7 @@ module.exports = {
         if (
           isTopLevelScoped(node) ||
           (!strict && isInsideYieldOrAwait(node)) ||
+          (!strict && isInsideConstructor(node)) ||
           isMemberCallWithObjectName('cy', node.parent)
         ) {
           return