Add JSON format for compatibility of a gem

Gemfile

@@ -23,6 +23,7 @@ gem "kredis",                                   "~> 1.2"
 gem "net-pop",                                  github: "ruby/net-pop"
 gem "octokit",                                  "~> 9.1"
 gem "octopoller",                               "~> 0.3"
+gem "ostruct"
 gem "propshaft",                                "~> 0.8"
 gem "pry-rails",                                "~> 0.3"
 gem "puma",                                     "~> 6.4"

Gemfile.lock

@@ -281,6 +281,7 @@ GEM
       faraday (>= 1, < 3)
       sawyer (~> 0.9)
     octopoller (0.3.1)
+    ostruct (0.6.3)
     pg (1.5.6)
     popper_js (2.11.8)
     pp (0.6.3)
@@ -471,6 +472,7 @@ GEM
 PLATFORMS
   arm64-darwin-23
   arm64-darwin-24
+  arm64-darwin-25
   x86_64-linux
 
 DEPENDENCIES
@@ -501,6 +503,7 @@ DEPENDENCIES
   net-pop!
   octokit (~> 9.1)
   octopoller (~> 0.3)
+  ostruct
   pg
   propshaft (~> 0.8)
   pry-rails (~> 0.3)

app/controllers/gemmies_controller.rb

@@ -24,7 +24,19 @@ def index
   end
 
   def show
-    @gemmy = Gemmy.find_by_name!(params[:id])
+    @gemmy = Gemmy.find_by_name(params[:id])
+
+    if @gemmy
+      respond_to do |format|
+        format.html
+        format.json { render json: gemmy_compatibility_json(@gemmy) }
+      end
+    else
+      respond_to do |format|
+        format.html { head :not_found }
+        format.json { render json: { error: "Gem not found" }, status: :not_found }
+      end
+    end
   end
 
   def compat_table
@@ -37,6 +49,31 @@ def compat_table
 
   private
 
+    def gemmy_compatibility_json(gemmy)
+      rails_releases = RailsRelease.all.sort_by { |release| Gem::Version.new(release.version.to_s) }
+
+      {
+        name: gemmy.name,
+        compatibility: rails_releases.map { |rails_release|
+          compats = gemmy.compats_for_rails_release(rails_release)
+          status = helpers.compats_status(gemmy, compats)
+
+          {
+            rails_version: rails_release.version.to_s,
+            status: status.to_s,
+            compats: compats.map { |compat|
+              {
+                id: compat.id,
+                status: compat.status,
+                dependencies: compat.dependencies,
+                checked_at: compat.checked_at
+              }
+            }
+          }
+        }
+      }
+    end
+
     def gemmy_params
       params.require(:gemmy).permit(:name)
     end

spec/controllers/email_notifications_controller_spec.rb

@@ -51,7 +51,7 @@
         it "renders the form partial with unprocessable entity status" do
           post :create, params: invalid_params
           expect(response).to render_template(partial: "email_notifications/_form")
-          expect(response).to have_http_status(:unprocessable_entity)
+          expect(response).to have_http_status(:unprocessable_content)
         end
       end
 

spec/requests/api/compats_spec.rb

@@ -0,0 +1,97 @@
+require "rails_helper"
+
+RSpec.describe "Gemmies JSON API", type: :request do
+  include FactoryBot::Syntax::Methods
+
+  describe "GET /gems/:id.json" do
+    context "when the gem exists with compats" do
+      let(:rails_71) { create(:rails_release, version: "7.1") }
+      let(:rails_72) { create(:rails_release, version: "7.2") }
+      let(:gemmy) { create(:gemmy, name: "devise") }
+      let!(:compatible_compat) do
+        create(:compat,
+          rails_release: rails_71,
+          dependencies: { "devise" => "~> 4.9" },
+          status: :compatible,
+          checked_at: Time.current,
+          status_determined_by: "bundler"
+        )
+      end
+      let!(:incompatible_compat) do
+        create(:compat,
+          rails_release: rails_72,
+          dependencies: { "devise" => "~> 3.0" },
+          status: :incompatible,
+          checked_at: Time.current,
+          status_determined_by: "bundler"
+        )
+      end
+
+      before do
+        gemmy.update!(compat_ids: [compatible_compat.id, incompatible_compat.id])
+      end
+
+      it "returns gem name and compatibility per Rails version" do
+        get "/gems/devise.json"
+
+        expect(response).to have_http_status(:ok)
+        expect(response.content_type).to include("application/json")
+
+        json = JSON.parse(response.body)
+        expect(json["name"]).to eq("devise")
+        expect(json["compatibility"]).to be_an(Array)
+        expect(json["compatibility"].size).to eq(2)
+
+        compat_71 = json["compatibility"].find { |c| c["rails_version"] == "7.1" }
+        expect(compat_71["status"]).to eq("compatible")
+        expect(compat_71["compats"]).to be_an(Array)
+        expect(compat_71["compats"].first["dependencies"]).to eq({ "devise" => "~> 4.9" })
+
+        compat_72 = json["compatibility"].find { |c| c["rails_version"] == "7.2" }
+        expect(compat_72["status"]).to eq("incompatible")
+      end
+    end
+
+    context "when the gem has pending compats" do
+      let(:rails_release) { create(:rails_release, version: "7.1") }
+      let(:gemmy) { create(:gemmy, name: "sidekiq") }
+      let!(:pending_compat) do
+        create(:compat,
+          rails_release: rails_release,
+          dependencies: { "sidekiq" => "~> 7.0" },
+          status: :pending
+        )
+      end
+
+      before do
+        gemmy.update!(compat_ids: [pending_compat.id])
+      end
+
+      it "returns checking status" do
+        get "/gems/sidekiq.json"
+
+        expect(response).to have_http_status(:ok)
+
+        json = JSON.parse(response.body)
+        compat = json["compatibility"].first
+        expect(compat["status"]).to eq("checking")
+      end
+    end
+
+    context "when the gem has no compats for a Rails version" do
+      let!(:rails_release) { create(:rails_release, version: "7.1") }
+      let!(:gemmy) { create(:gemmy, name: "tiny_gem", compat_ids: []) }
+
+      it "returns checking status for that version" do
+        get "/gems/tiny_gem.json"
+
+        expect(response).to have_http_status(:ok)
+
+        json = JSON.parse(response.body)
+        compat = json["compatibility"].first
+        expect(compat["rails_version"]).to eq("7.1")
+        expect(compat["status"]).to eq("checking")
+      end
+    end
+  end
+end