Fix app env vars when updating an existing Image

* In the original PR (cloudfoundry#1600), we only applied environment variables when
creating the first "Image" resource

[#172301179]

Authored-by: Aakash Shah <ashah@pivotal.io>

Author: Aakash Shah

lib/cloud_controller/kpack/stager.rb

@@ -46,6 +46,7 @@ def mark_build_as_failed(build, message)
     def update_image_resource(image, staging_details)
       image.metadata.labels[BUILD_GUID_LABEL_KEY.to_sym] = staging_details.staging_guid
       image.spec.source.blob.url = blobstore_url_generator.package_download_url(staging_details.package)
+      image.spec.build.env = get_environment_variables(staging_details)
 
       image
     end
@@ -77,14 +78,18 @@ def image_resource(staging_details)
             }
           },
           build: {
-            env: staging_details.environment_variables.to_a.
-                  delete_if { |key, value| key == 'VCAP_SERVICES' }.
-                  map { |key, value| { name: key, value: value.to_s } }
+            env: get_environment_variables(staging_details),
           }
         }
       })
     end
 
+    def get_environment_variables(staging_details)
+      staging_details.environment_variables.
+        except('VCAP_SERVICES').
+        map { |key, value| { name: key, value: value.to_s } }
+    end
+
     def logger
       @logger ||= Steno.logger('cc.stager')
     end

spec/unit/lib/cloud_controller/kpack/stager_spec.rb

@@ -79,7 +79,10 @@ module Kpack
               }
             },
             build: {
-              env: [{ name: 'BP_JAVA_VERSION', value: '8.*' }, { name: 'BPL_HEAD_ROOM', value: '0' }]
+              env: [
+                { name: 'BP_JAVA_VERSION', value: '8.*' },
+                { name: 'BPL_HEAD_ROOM', value: '0' },
+              ]
             }
           }
         }))
@@ -135,11 +138,18 @@ module Kpack
                 blob: {
                   url: 'old-package-url',
                 }
+              },
+              build: {
+                env: [],
               }
             }
           })
         end
 
+        let(:environment_variables) do
+          { 'VCAP_SERVICES' => 'ignored', 'FOO' => 'BAR' }
+        end
+
         before do
           allow(client).to receive(:get_image).with(package.app.guid, 'namespace').and_return(existing_image)
         end
@@ -148,6 +158,9 @@ module Kpack
           updated_image = Kubeclient::Resource.new(existing_image.to_hash)
           updated_image.metadata.labels[Kpack::Stager::BUILD_GUID_LABEL_KEY.to_sym] = build.guid
           updated_image.spec.source.blob.url = 'package-download-url'
+          updated_image.spec.build.env = [
+            { name: 'FOO', value: 'BAR' }
+          ]
 
           expect(client).to_not receive(:create_image)
           expect(client).to receive(:update_image).with(updated_image)