Return errors for malformed manifests in manifest_diff

- also fixes bug in apply_manifest with an improper 400

[finishes #173688915]
[finsihes #173818750]

Co-authored-by: James Palmer <jpalmer@pivotal.io>
Co-authored-by: Merric de Launey <mdelauney@pivotal.io>

Author: jpalmerpivotal

app/controllers/v3/space_manifests_controller.rb

@@ -120,7 +120,7 @@ def check_version_is_supported!
   def parsed_app_manifests
     check_version_is_supported!
     parsed_applications = params[:body]['applications']
-    raise invalid_request!('Invalid app manifest') unless parsed_applications.present?
+    raise unprocessable!("Cannot parse manifest with no 'applications' field.") unless parsed_applications.present?
 
     parsed_applications.map(&:to_unsafe_h)
   end

docs/v3/source/includes/resources/manifests/_create_diff.md

@@ -43,6 +43,8 @@ Content-Type: application/json
 
 Create a manifest diff for apps in the provided manifest and their underlying processes. Currently manifest_diff only supports version 1 manifests.
 
+Manifests require the `applications` field.
+
 #### Definition
 `GET /v3/spaces/:guid/manifest_diff`
 

spec/request/space_manifests_spec.rb

@@ -573,53 +573,67 @@
       end
       it_behaves_like 'permissions for single object endpoint', ALL_PERMISSIONS
     end
-    context 'the manifest is unparseable' do
-      let(:yml_manifest) do
-        {
-          89 => [
-            {
-              'name' => 'new-app',
-            },
-          ]
-        }.to_yaml
-      end
-
+    context 'when the request is invalid' do
       before do
         space.organization.add_user(user)
         space.add_developer(user)
       end
 
-      it 'returns an appropriate error' do
-        post "/v3/spaces/#{space.guid}/manifest_diff", yml_manifest, yml_headers(user_header)
-        parsed_response = MultiJson.load(last_response.body)
+      context 'when there is a manifest without \'applications\'' do
+        let(:yml_manifest) do
+          {
+            'not-applications' => [
+              {
+                'name' => 'new-app',
+              },
+            ]
+          }.to_yaml
+        end
 
-        expect(last_response).to have_status_code(400)
-        expect(parsed_response['errors'].first['detail']).to eq('The request is invalid')
-      end
-    end
-    context 'the manifest is a not supported version' do
-      let(:yml_manifest) do
-        {
-          'version' => 1234567,
-          'applications' => [
-            {
-              'name' => 'new-app',
-            },
-          ]
-        }.to_yaml
+        it 'returns an appropriate error' do
+          post "/v3/spaces/#{space.guid}/manifest_diff", yml_manifest, yml_headers(user_header)
+          parsed_response = MultiJson.load(last_response.body)
+
+          expect(last_response).to have_status_code(422)
+          expect(parsed_response['errors'].first['detail']).to eq("Cannot parse manifest with no 'applications' field.")
+        end
       end
 
-      before do
-        space.organization.add_user(user)
-        space.add_developer(user)
+      context 'the manifest is unparseable' do
+        let(:yml_manifest) do
+          {
+            'key' => 'this is json, not yaml'
+          }
+        end
+
+        it 'returns an appropriate error' do
+          post "/v3/spaces/#{space.guid}/manifest_diff", yml_manifest, yml_headers(user_header)
+          parsed_response = MultiJson.load(last_response.body)
+
+          expect(last_response).to have_status_code(400)
+          expect(parsed_response['errors'].first['detail']).to eq('Request invalid due to parse error: invalid request body')
+        end
       end
 
-      it 'returns an appropriate error' do
-        post "/v3/spaces/#{space.guid}/manifest_diff", yml_manifest, yml_headers(user_header)
-        parsed_response = MultiJson.load(last_response.body)
+      context 'the manifest is a not supported version' do
+        let(:yml_manifest) do
+          {
+            'version' => 1234567,
+            'applications' => [
+              {
+                'name' => 'new-app',
+              },
+            ]
+          }.to_yaml
+        end
 
-        expect(last_response).to have_status_code(422)
-        expect(parsed_response['errors'].first['detail']).to eq('Unsupported manifest schema version. Currently supported versions: [1].')
+        it 'returns an appropriate error' do
+          post "/v3/spaces/#{space.guid}/manifest_diff", yml_manifest, yml_headers(user_header)
+          parsed_response = MultiJson.load(last_response.body)
+
+          expect(last_response).to have_status_code(422)
+          expect(parsed_response['errors'].first['detail']).to eq('Unsupported manifest schema version. Currently supported versions: [1].')
+        end
       end
     end
     context 'the space does not exist' do

spec/unit/controllers/v3/space_manifests_controller_spec.rb

@@ -115,18 +115,18 @@
       context 'when the yaml is missing an applications array' do
         let(:request_body) { { 'name' => 'blah', 'instances' => 4 } }
 
-        it 'returns a 400' do
+        it 'returns a 422' do
           post :apply_manifest, params: { guid: space.guid }.merge(request_body), as: :yaml
-          expect(response.status).to eq(400)
+          expect(response.status).to eq(422)
         end
       end
 
       context 'when the requested applications array is empty' do
         let(:request_body) { { 'applications' => [] } }
 
-        it 'returns a 400' do
+        it 'returns a 422' do
           post :apply_manifest, params: { guid: space.guid }.merge(request_body), as: :yaml
-          expect(response.status).to eq(400)
+          expect(response.status).to eq(422)
         end
       end