fix(ssm): Generate correct SSM Parameter ARN (#1726)

The SSM parameter name (`resourceName` portion of it's ARN) is required
to start with a `/`, which caused the presence of a doubled `//` in the generated
ARN caused by the fact `sep` defaults to `/`.

This change allows `sep` to be set to an empty string, allowing SSM rendering
of correct SSM parameter ARNs.

packages/@aws-cdk/aws-ssm/lib/parameter.ts

@@ -119,6 +119,7 @@ export abstract class ParameterBase extends cdk.Construct implements IParameter
  return cdk.Stack.find(this).formatArn({
  service: 'ssm',
  resource: 'parameter',
+ sep: '', // Sep is empty because this.parameterName starts with a / already!
  resourceName: this.parameterName,
  });
  }

packages/@aws-cdk/aws-ssm/test/integ.parameter.lit.expected.json

@@ -60,7 +60,7 @@
  {
  "Ref": "AWS::AccountId"
  },
- ":parameter/",
+ ":parameter",
  {
  "Ref": "StringParameter472EED0E"
  }

packages/@aws-cdk/aws-ssm/test/test.parameter.ts

@@ -100,4 +100,25 @@ export = {
  }));
  test.done();
  },
+
+ 'parameterArn is crafted correctly'(test: Test) {
+ // GIVEN
+ const stack = new cdk.Stack();
+ const param = new ssm.StringParameter(stack, 'Parameter', { value: 'Foo' });
+
+ // THEN
+ test.deepEqual(param.node.resolve(param.parameterArn), {
+ 'Fn::Join': ['', [
+ 'arn:',
+ { Ref: 'AWS::Partition' },
+ ':ssm:',
+ { Ref: 'AWS::Region' },
+ ':',
+ { Ref: 'AWS::AccountId' },
+ ':parameter',
+ { Ref: 'Parameter9E1B4FBA' }
+ ]]
+ });
+ test.done();
+ }
 };

packages/@aws-cdk/cdk/lib/cloudformation/arn.ts

@@ -13,7 +13,7 @@ import { Stack } from './stack';
  *
  * The ARN will be formatted as follows:
  *
- * arn:{partition}:{service}:{region}:{account}:{resource}{sep}}{resource-name}
+ * arn:{partition}:{service}:{region}:{account}:{resource}{sep}{resource-name}
  *
  * The required ARN pieces that are omitted will be taken from the stack that
  * the 'scope' is attached to. If all ARN pieces are supplied, the supplied scope
@@ -23,12 +23,12 @@ export function arnFromComponents(components: ArnComponents, stack: Stack): stri
  const partition = components.partition !== undefined ? components.partition : stack.partition;
  const region = components.region !== undefined ? components.region : stack.region;
  const account = components.account !== undefined ? components.account : stack.accountId;
+ const sep = components.sep !== undefined ? components.sep : '/';
 
  const values = [ 'arn', ':', partition, ':', components.service, ':', region, ':', account, ':', components.resource ];
 
- const sep = components.sep || '/';
- if (sep !== '/' && sep !== ':') {
- throw new Error('resourcePathSep may only be ":" or "/"');
+ if (sep !== '/' && sep !== ':' && sep !== '') {
+ throw new Error('resourcePathSep may only be ":", "/" or an empty string');
  }
 
  if (components.resourceName != null) {
@@ -257,7 +257,7 @@ export interface ArnComponents {
  /**
  * Separator between resource type and the resource.
  *
- * Can be either '/' or ':'. Will only be used if path is defined.
+ * Can be either '/', ':' or an empty string. Will only be used if resourceName is defined.
  * @default '/'
  */
  sep?: string;

packages/@aws-cdk/cdk/test/cloudformation/test.arn.ts

@@ -68,6 +68,23 @@ export = {
  test.done();
  },
 
+ 'resourcePathSep can be set to "" instead of the default "/"'(test: Test) {
+ const stack = new Stack();
+
+ const arn = stack.formatArn({
+ service: 'ssm',
+ resource: 'parameter',
+ sep: '',
+ resourceName: '/parameter-name'
+ });
+
+ const pseudo = new Aws(stack);
+
+ test.deepEqual(stack.node.resolve(arn),
+ stack.node.resolve(`arn:${pseudo.partition}:ssm:${pseudo.region}:${pseudo.accountId}:parameter/parameter-name`));
+ test.done();
+ },
+
  'fails if resourcePathSep is neither ":" nor "/"'(test: Test) {
  const stack = new Stack();