From 5e149f07a9e56bc528da6609c8dfdd2a408d392d Mon Sep 17 00:00:00 2001
From: Peter Wagenet <peter.wagenet@gmail.com>
Date: Thu, 3 Sep 2020 15:23:17 -0700
Subject: [PATCH] =?UTF-8?q?=F0=9F=A4=96=20Merge=20PR=20#47212=20[ember-dat?=
 =?UTF-8?q?a]=20Adapter=20headers=20should=20be=20overwriteable=20with=20a?=
 =?UTF-8?q?=20getter=20by=20@wagenet?=
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Instead of being declared as a property we now declare it in an
interface. This works around the issue noted here with TypeScript 4:
https://github.com/microsoft/TypeScript/issues/40220
---
 types/ember-data/index.d.ts      | 22 ++++++++++++++--------
 types/ember-data/test/adapter.ts |  9 +++++++++
 types/ember-data/tsconfig.json   |  1 +
 3 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/types/ember-data/index.d.ts b/types/ember-data/index.d.ts
index 0062108fd7a2738..9f4853657dade99 100644
--- a/types/ember-data/index.d.ts
+++ b/types/ember-data/index.d.ts
@@ -1258,14 +1258,6 @@ export namespace DS {
          * An adapter can target other hosts by setting the `host` property.
          */
         host: string;
-        /**
-         * Some APIs require HTTP headers, e.g. to provide an API
-         * key. Arbitrary headers can be set as key/value pairs on the
-         * `RESTAdapter`'s `headers` object and Ember Data will send them
-         * along with each ajax request. For dynamic headers see [headers
-         * customization](/api/data/classes/DS.RESTAdapter.html#toc_headers-customization).
-         */
-        headers: {};
         /**
          * Called by the store in order to fetch the JSON for a given
          * type and ID.
@@ -1496,6 +1488,20 @@ export namespace DS {
          */
         pathForType<K extends keyof ModelRegistry>(modelName: K): string;
     }
+
+    // Instead of declaring `headers as a property we now declare it in an
+    // interface. This works around the issue noted here with TypeScript 4:
+    // https://github.com/microsoft/TypeScript/issues/40220
+    interface RESTAdapter {
+        /**
+         * Some APIs require HTTP headers, e.g. to provide an API
+         * key. Arbitrary headers can be set as key/value pairs on the
+         * `RESTAdapter`'s `headers` object and Ember Data will send them
+         * along with each ajax request. For dynamic headers see [headers
+         * customization](/api/data/classes/DS.RESTAdapter.html#toc_headers-customization).
+         */
+        headers: {};
+    }
     /**
      * ## Using Embedded Records
      */
diff --git a/types/ember-data/test/adapter.ts b/types/ember-data/test/adapter.ts
index 647d1623684402f..3b29f52cb50a982 100644
--- a/types/ember-data/test/adapter.ts
+++ b/types/ember-data/test/adapter.ts
@@ -29,6 +29,15 @@ const AuthTokenHeader = DS.JSONAPIAdapter.extend({
     })
 });
 
+// Ensure that we are allowed to overwrite headers with a getter
+class GetterHeader extends DS.JSONAPIAdapter {
+    get headers() {
+        return {
+            'CUSTOM_HEADER': 'Some header value'
+        };
+    }
+}
+
 const UseAjax = DS.JSONAPIAdapter.extend({
     query(store: DS.Store, type: string, query: object) {
         const url = 'https://api.example.com/my-api';
diff --git a/types/ember-data/tsconfig.json b/types/ember-data/tsconfig.json
index 14228f8cd7e20ed..57761c3070b7eba 100644
--- a/types/ember-data/tsconfig.json
+++ b/types/ember-data/tsconfig.json
@@ -5,6 +5,7 @@
             "es6",
             "dom"
         ],
+        "target": "es5",
         "noImplicitAny": true,
         "noImplicitThis": true,
         "strictNullChecks": true,