Fix bug: diff being detected for source_repo_repository even when the…

…re are no changes (#3786)

This patch fixes a bug in source_repo_repository where a diff was always
being generated for the TypeSet field `pubsub_configs` since its Set
hashing function was not accounting for the fact that
`pubsub_configs[].topic` can contain either a topic's name or relative
path.

products/sourcerepo/terraform.yaml

@@ -49,9 +49,11 @@ overrides: !ruby/object:Overrides::ResourceOverrides
           A Cloud Pub/Sub topic in this repo's project. Values are of the form
           `projects/<project>/topics/<topic>` or `<topic>` (where the topic will
           be inferred).
+        set_hash_func: 'resourceSourceRepoRepositoryPubSubConfigsHash'
       pubsubConfigs.serviceAccountEmail: !ruby/object:Overrides::Terraform::PropertyOverride
         default_from_api: true
     custom_code: !ruby/object:Provider::Terraform::CustomCode
+      constants: templates/terraform/constants/source_repo_repository.go.erb
       update_encoder: templates/terraform/update_encoder/source_repo_repository.erb
       post_create: templates/terraform/post_create/source_repo_repository_update.go.erb
 # This is for copying files over

templates/terraform/constants/source_repo_repository.go.erb

@@ -0,0 +1,30 @@
+<%- # the license inside this block applies to this file
+        # Copyright 2019 Google Inc.
+        # Licensed under the Apache License, Version 2.0 (the "License");
+        # you may not use this file except in compliance with the License.
+        # You may obtain a copy of the License at
+        #
+        #     http://www.apache.org/licenses/LICENSE-2.0
+        #
+        # Unless required by applicable law or agreed to in writing, software
+        # distributed under the License is distributed on an "AS IS" BASIS,
+        # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+        # See the License for the specific language governing permissions and
+        # limitations under the License.
+-%>
+func resourceSourceRepoRepositoryPubSubConfigsHash(v interface{}) int {
+        if v == nil {
+                return 0
+        }
+
+        var buf bytes.Buffer
+        m := v.(map[string]interface{})
+
+        buf.WriteString(fmt.Sprintf("%s-", GetResourceNameFromSelfLink(m["topic"].(string))))
+        buf.WriteString(fmt.Sprintf("%s-", m["message_format"].(string)))
+        if v, ok := m["service_account_email"]; ok {
+                buf.WriteString(fmt.Sprintf("%s-", v.(string)))
+        }
+
+        return hashcode.String(buf.String())
+}