Make the context option mergeable (#1459)

Author: ghermeto

Diff for: readme.md

@@ -251,9 +251,7 @@ JSON body. If the `Content-Type` header is not set, it will be set to `applicati
 
 Type: `object`
 
-User data. In contrast to other options, `context` is not enumerable.
-
-**Note:** The object is never merged, it's just passed through. Got will not modify the object in any way.
+User data. `context` is shallow merged and enumerable. If it contains non-enumerable properties they will NOT be merged.
 
 It's very useful for storing auth tokens:
 

Diff for: source/core/index.ts

@@ -515,10 +515,7 @@ interface PlainOptions extends URLOptions {
 	dnsCache?: CacheableLookup | boolean;
 
 	/**
-	User data. In contrast to other options, `context` is not enumerable.
-
-	__Note__: The object is never merged, it's just passed through.
-	Got will not modify the object in any way.
+	User data. `context` is shallow merged and enumerable. If it contains non-enumerable properties they will NOT be merged.
 
 	@example
 	```
@@ -1139,9 +1136,8 @@ const waitForOpenFile = async (file: ReadStream): Promise<void> => new Promise((
 
 const redirectCodes: ReadonlySet<number> = new Set([300, 301, 302, 303, 304, 307, 308]);
 
-type NonEnumerableProperty = 'context' | 'body' | 'json' | 'form';
+type NonEnumerableProperty = 'body' | 'json' | 'form';
 const nonEnumerableProperties: NonEnumerableProperty[] = [
-	'context',
 	'body',
 	'json',
 	'form'
@@ -1780,9 +1776,7 @@ export default class Request extends Duplex implements RequestEvents<Request> {
 		}
 
 		// `options.context`
-		if (!options.context) {
-			options.context = {};
-		}
+		options.context = {...defaults?.context, ...options.context};
 
 		// `options.hooks`
 		const areHooksDefault = options.hooks === defaults?.hooks;

Diff for: source/types.ts

@@ -371,7 +371,7 @@ export interface Got extends Record<HTTPAlias, GotRequestFunction>, GotRequestFu
 		- If the parent property is a plain `object` too, both values are merged recursively into a new `object`.
 		- Otherwise, only the new value is deeply cloned.
 	- If the new property is an `Array`, it overwrites the old one with a deep clone of the new property.
-	- Properties that are not enumerable, such as `context`, `body`, `json`, and `form`, will not be merged.
+	- Properties that are not enumerable, such as `body`, `json`, and `form`, will not be merged.
 	- Otherwise, the new value is assigned to the key.
 
 	**Note:** Only Got options are merged! Custom user options should be defined via [`options.context`](#context).

Diff for: test/arguments.ts

@@ -328,7 +328,7 @@ test('throws if the `searchParams` value is invalid', async t => {
 	});
 });
 
-test('`context` option is not enumerable', withServer, async (t, server, got) => {
+test('`context` option is enumerable', withServer, async (t, server, got) => {
 	server.get('/', echoUrl);
 
 	const context = {
@@ -340,8 +340,8 @@ test('`context` option is not enumerable', withServer, async (t, server, got) =>
 		hooks: {
 			beforeRequest: [
 				options => {
-					t.is(options.context, context);
-					t.false({}.propertyIsEnumerable.call(options, 'context'));
+					t.deepEqual(options.context, context);
+					t.true({}.propertyIsEnumerable.call(options, 'context'));
 				}
 			]
 		}
@@ -360,8 +360,8 @@ test('`context` option is accessible when using hooks', withServer, async (t, se
 		hooks: {
 			beforeRequest: [
 				options => {
-					t.is(options.context, context);
-					t.false({}.propertyIsEnumerable.call(options, 'context'));
+					t.deepEqual(options.context, context);
+					t.true({}.propertyIsEnumerable.call(options, 'context'));
 				}
 			]
 		}
@@ -375,8 +375,27 @@ test('`context` option is accessible when extending instances', t => {
 
 	const instance = got.extend({context});
 
-	t.is(instance.defaults.options.context, context);
-	t.false({}.propertyIsEnumerable.call(instance.defaults.options, 'context'));
+	t.deepEqual(instance.defaults.options.context, context);
+	t.true({}.propertyIsEnumerable.call(instance.defaults.options, 'context'));
+});
+
+test('`context` option is shallow merged', t => {
+	const context = {
+		foo: 'bar'
+	};
+
+	const context2 = {
+		bar: 'baz'
+	};
+
+	const instance1 = got.extend({context});
+
+	t.deepEqual(instance1.defaults.options.context, context);
+	t.true({}.propertyIsEnumerable.call(instance1.defaults.options, 'context'));
+
+	const instance2 = instance1.extend({context: context2});
+
+	t.deepEqual(instance2.defaults.options.context, {...context, ...context2});
 });
 
 test('throws if `options.encoding` is `null`', async t => {

Diff for: test/hooks.ts

@@ -426,7 +426,7 @@ test('beforeRetry is called with options', withServer, async (t, server, got) =>
 			beforeRetry: [
 				(options, error, retryCount) => {
 					t.is(options.url.hostname, 'localhost');
-					t.is(options.context, context);
+					t.deepEqual(options.context, context);
 					t.truthy(error);
 					t.true(retryCount! >= 1);
 				}