Fix Link caching stale resource after a mutating request

CHANGELOG.md

@@ -7,6 +7,7 @@
 * [#319](https://github.com/codegram/hyperclient/pull/319): Fixed `Resource#to_h` returning `nil` instead of the same result as `#to_hash` - [@dblock](https://github.com/dblock).
 * [#320](https://github.com/codegram/hyperclient/pull/320): Documented how to handle non-`hal+json` responses via the Faraday response middleware's `content_type` matcher - [@dblock](https://github.com/dblock).
 * [#321](https://github.com/codegram/hyperclient/pull/321): Added Ruby 4.0 to the CI test matrix - [@dblock](https://github.com/dblock).
+* [#322](https://github.com/codegram/hyperclient/pull/322): Fixed `Link` caching a mutating request's (`_post`/`_put`/`_patch`/`_delete`) response as its resource, causing subsequent reads (e.g. `#each`, `method_missing`) to return stale data instead of a fresh `_get` - [@dblock](https://github.com/dblock).
 * Your contribution here.
 
 ### 2.0.0 (2024/02/01)

lib/hyperclient/link.rb

@@ -190,10 +190,19 @@ def _uri_template
     end
 
     def http_method(method, body = nil)
-      @resource = begin
-        response = @entry_point.connection.run_request(method, _url, body, nil)
-        Resource.new(response.body, @entry_point, response)
-      end
+      response = @entry_point.connection.run_request(method, _url, body, nil)
+      resource = Resource.new(response.body, @entry_point, response)
+
+      # Only cache GET responses. Caching the response of a mutating
+      # request (POST/PUT/PATCH/DELETE) as `@resource` would make
+      # subsequent delegated calls (e.g. `#each`, `method_missing`) see
+      # the stale mutation response instead of fetching a fresh
+      # resource, requiring users to create a new client between a
+      # `_post` and a `_get`. See #107.
+      @resource = resource if method == :get
+      @delegate = nil
+
+      resource
     end
   end
 end

test/hyperclient/link_test.rb

@@ -151,6 +151,19 @@ module Hyperclient
 
         link._resource
       end
+
+      it 'fetches a fresh resource after a mutating request instead of returning the cached response (#107)' do
+        link = Link.new('key', { 'href' => '/productions/1' }, entry_point)
+
+        stub_request(entry_point.connection) do |stub|
+          stub.post('http://api.example.org/productions/1') { [201, {}, { 'status' => 'created' }] }
+          stub.get('http://api.example.org/productions/1') { [200, {}, { 'status' => 'fetched' }] }
+        end
+
+        link._post('foo' => 'bar')
+
+        _(link._resource.status).must_equal 'fetched'
+      end
     end
 
     describe 'get' do