Merge pull request #90 from zadowsmash/add-no-fail-on-change-set-option

add the ability to not fail on empty change set

CHANGES.md

@@ -1,5 +1,9 @@
 # CHANGES
 
+## 1.7.0 (2020-11-25)
+
+* Feature: --no-fail-on-empty-change-set
+
 ## 1.6.0 (2020-11-19)
 
 * Feature: Support --service-role-arn on "change-set create"

README.md

@@ -218,6 +218,8 @@ The change-set name defaults to "pending", but can be overridden using `--name`.
 
 The `change-set create` subcommand, like the `up` command, supports `--service-role-arn` to specify a service role.
 
+It is impossible to create a change set with no changes. By default, stackup will only return successfully if a change set was actually created, and will otherwise fail. If the `--no-fail-on-empty-change-set` option is provided, stackup will return successfully if a change set was created _or_ if no change set was created because no changes were needed.
+
 ## Programmatic usage
 
 Get a handle to a `Stack` object as follows:

lib/stackup/change_set.rb

@@ -56,6 +56,7 @@ def create(options = {})
       options[:change_set_name] = name
       options[:change_set_type] = stack.exists? ? "UPDATE" : "CREATE"
       force = options.delete(:force)
+      allow_empty_change_set = options.delete(:allow_empty_change_set)
       options[:template_body] = MultiJson.dump(options.delete(:template)) if options[:template]
       # optionally override template_body with the original template to preserve formatting (& comments in YAML)
       template_orig = options.delete(:template_orig)
@@ -73,8 +74,12 @@ def create(options = {})
           when /COMPLETE/
             return current.status
           when "FAILED"
-            logger.error(current.status_reason)
-            raise StackUpdateError, "change-set creation failed" if status == "FAILED"
+            if allow_empty_change_set and current.status_reason == "The submitted information didn't contain changes. Submit different information to create a change set."
+              return current.status_reason
+            else
+              logger.error(current.status_reason)
+              raise StackUpdateError, "change-set creation failed" if status == "FAILED"
+            end
           end
           sleep(wait_poll_interval)
         end

lib/stackup/main_command.rb

@@ -280,6 +280,9 @@ def pad(s, width)
         option ["--force"], :flag,
                "replace existing change-set of the same name"
 
+        option ["--no-fail-on-empty-change-set"], :flag, "don't fail on empty change-set",
+               :attribute_name => :allow_empty_change_set
+
         include HasParameters
 
         option "--tags", "FILE", "stack tags file",
@@ -314,6 +317,7 @@ def execute
           options[:role_arn] = service_role_arn if service_role_arn
           options[:use_previous_template] = use_previous_template?
           options[:force] = force?
+          options[:allow_empty_change_set] = allow_empty_change_set?
           options[:capabilities] = capability_list
           options[:preserve] = preserve_template_formatting?
           report_change do

lib/stackup/version.rb

@@ -1,5 +1,5 @@
 module Stackup
 
-  VERSION = "1.6.0".freeze
+  VERSION = "1.7.0".freeze
 
 end

spec/stackup/main_command_spec.rb

@@ -1,15 +1,19 @@
 require "stackup/main_command"
 
 describe Stackup::MainCommand do
-  context "change-set create --service-role-arn"
-    it "invokes stack.change_set.create with role arn passed through" do
-      mock_stackup = double()
-      mock_stack = double()
-      mock_change_set = double()
-      allow_any_instance_of(Stackup::MainCommand).to receive(:Stackup).and_return(mock_stackup)
-      allow(mock_stackup).to receive(:stack).and_return(mock_stack)
-      allow(mock_stack).to receive(:change_set).and_return(mock_change_set)
 
+  let(:mock_change_set) { double() }
+
+  before(:example) do
+    mock_stackup = double()
+    mock_stack = double()
+    allow_any_instance_of(Stackup::MainCommand).to receive(:Stackup).and_return(mock_stackup)
+    allow(mock_stackup).to receive(:stack).and_return(mock_stack)
+    allow(mock_stack).to receive(:change_set).and_return(mock_change_set)
+  end
+
+  context "change-set create --service-role-arn" do
+    it "invokes stack.change_set.create with role arn passed through" do
       expected_args = {
         role_arn: "arn:aws:iam::000000000000:role/example"
       }
@@ -20,4 +24,33 @@
         "--template", "examples/template.yml",
         "--service-role-arn", "arn:aws:iam::000000000000:role/example"])
     end
+  end
+
+  context "change-set create" do
+    it "invokes stack.change_set.create with allow_empty_change_set nil" do
+      expected_args = {
+        allow_empty_change_set: nil
+      }
+      expect(mock_change_set).to receive(:create).with(hash_including(expected_args))
+
+      Stackup::MainCommand.run("stackup", [
+        "STACK-NAME", "change-set", "create",
+        "--template", "examples/template.yml"])
+    end
+  end
+
+  context "change-set create --no-fail-on-empty-change-set" do
+    it "invokes stack.change_set.create with allow_empty_change_set true" do
+      expected_args = {
+        allow_empty_change_set: true
+      }
+      expect(mock_change_set).to receive(:create).with(hash_including(expected_args))
+
+      Stackup::MainCommand.run("stackup", [
+        "STACK-NAME", "change-set", "create",
+        "--template", "examples/template.yml",
+        "--no-fail-on-empty-change-set"])
+    end
+  end
+
 end

spec/stackup/stack_spec.rb

@@ -429,6 +429,38 @@ def create_change_set
 
       end
 
+      context "when allow_empty_change_set is nil and there are no changes" do
+        it "raises an exception" do
+          cf_client.stub_responses(:describe_change_set, [{
+            status: "FAILED",
+            status_reason: "The submitted information didn't contain changes. Submit different information to create a change set."
+          }])
+          expect { create_change_set }.to raise_error(Stackup::StackUpdateError)
+        end
+      end
+
+      context "when allow_empty_change_set is true and there are no changes" do
+        it "does not raise an exception" do
+          cf_client.stub_responses(:describe_change_set, [{
+            status: "FAILED",
+            status_reason: "The submitted information didn't contain changes. Submit different information to create a change set."
+          }])
+          options[:allow_empty_change_set] = true
+          expect { create_change_set }.not_to raise_error
+        end
+      end
+
+      context "when allow_empty_change_set is true and there is some other failure" do
+        it "raises an exception" do
+          cf_client.stub_responses(:describe_change_set, [{
+            status: "FAILED",
+            status_reason: "some other failure message"
+          }])
+          options[:allow_empty_change_set] = true
+          expect { create_change_set }.to raise_error(Stackup::StackUpdateError)
+        end
+      end
+
     end
 
     describe "#change_set#execute" do