fix: handle empty tag values

Closes #301

Author: theburningmonk

lib/deploy/stepFunctions/compileStateMachines.js

@@ -22,7 +22,9 @@ function toTags(obj) {
     return tags;
   }
 
-  _.forEach(obj, (Value, Key) => tags.push({ Key, Value: Value.toString() }));
+  _.forEach(obj, (Value, Key) => {
+    tags.push({ Key, Value: (Value || '').toString() });
+  });
 
   return tags;
 }

lib/deploy/stepFunctions/compileStateMachines.test.js

@@ -630,6 +630,45 @@ describe('#compileStateMachines', () => {
     expect(() => serverlessStepFunctions.compileStateMachines()).to.throw(Error);
   });
 
+  it('should leave empty tag values as empty string', () => {
+    serverless.service.provider.tags = {
+      team: undefined,
+    };
+
+    serverless.service.stepFunctions = {
+      stateMachines: {
+        myStateMachine1: {
+          definition: 'definition1',
+          name: 'stateMachineBeta1',
+          tags: {
+            score: undefined,
+          },
+        },
+        myStateMachine2: {
+          definition: 'definition2',
+          name: 'stateMachineBeta2',
+          tags: {
+            score: undefined,
+          },
+        },
+      },
+    };
+
+    serverlessStepFunctions.compileStateMachines();
+    const stateMachineBeta1 = serverlessStepFunctions.serverless.service
+      .provider.compiledCloudFormationTemplate.Resources
+      .StateMachineBeta1;
+    const stateMachineBeta2 = serverlessStepFunctions.serverless.service
+      .provider.compiledCloudFormationTemplate.Resources
+      .StateMachineBeta2;
+    expect(stateMachineBeta1.Properties.Tags).to.have.lengthOf(2);
+    expect(stateMachineBeta2.Properties.Tags).to.have.lengthOf(2);
+    expect(stateMachineBeta1.Properties.Tags)
+      .to.deep.eq([{ Key: 'team', Value: '' }, { Key: 'score', Value: '' }]);
+    expect(stateMachineBeta2.Properties.Tags)
+      .to.deep.eq([{ Key: 'team', Value: '' }, { Key: 'score', Value: '' }]);
+  });
+
   it('should respect CloudFormation intrinsic functions', () => {
     serverless.service.stepFunctions = {
       stateMachines: {