Combine string literals while resolving fragments, so we never have n…

…on-intrinsics

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

@@ -1,4 +1,4 @@
-import { DEFAULT_ENGINE_NAME, ProvisioningEngine, StringFragment } from "../core/engine-strings";
+import { ProvisioningEngine, StringFragment } from "../core/engine-strings";
 import { IntrinsicToken  } from "../core/tokens";
 
 /**
@@ -24,5 +24,4 @@ const cloudFormationEngine = {
     }
 };
 
-ProvisioningEngine.register(CLOUDFORMATION_ENGINE, cloudFormationEngine);
-ProvisioningEngine.register(DEFAULT_ENGINE_NAME, cloudFormationEngine);
+ProvisioningEngine.register(CLOUDFORMATION_ENGINE, cloudFormationEngine);

packages/@aws-cdk/cdk/lib/core/engine-strings.ts

@@ -17,15 +17,20 @@ export class ProvisioningEngine {
      * Resolves the result.
      */
     public static combineStringFragments(fragments: StringFragment[]): any {
+        simplifyFragments(fragments);
+
         if (fragments.length === 0) { return ''; }
         if (fragments.length === 1) { return fragments[0].value; }
 
         const engines = Array.from(new Set<string>(fragments.filter(f => f.intrinsicEngine !== undefined).map(f => f.intrinsicEngine!)));
+        if (engines.length === 0) {
+            throw new Error('Should not happen; no intrinsics found in StringFragment list.');
+        }
         if (engines.length > 1) {
             throw new Error(`Combining different engines in one string fragment: ${engines.join(', ')}`);
         }
 
-        const engine = engines.length > 0 ? engines[0] : DEFAULT_ENGINE_NAME;
+        const engine = engines[0];
         if (!(engine in HANDLERS)) {
             throw new Error(`No Token handler registered for engine: ${engine}`);
         }
@@ -63,7 +68,7 @@ export interface StringFragment {
  */
 export enum FragmentSource {
     Literal = 'Literal',
-    Token = 'Token'
+    Intrinsic = 'Intrinsic'
 }
 
 /**
@@ -77,11 +82,23 @@ export interface IProvisioningEngine {
 }
 
 /**
- * The engine that will be used if no Tokens are found
+ * Global handler map
  */
-export const DEFAULT_ENGINE_NAME = 'default';
+const HANDLERS: {[engine: string]: IProvisioningEngine} = {};
 
 /**
- * Global handler map
+ * Combine adjacent string literals in the fragment list
+ *
+ * List is modified in-place.
  */
-const HANDLERS: {[engine: string]: IProvisioningEngine} = {};
+function simplifyFragments(fragments: StringFragment[]) {
+    let i = 0;
+    while (i < fragments.length - 1) {
+        if (fragments[i].source === FragmentSource.Literal && fragments[i + 1].source === FragmentSource.Literal) {
+            fragments[i].value += fragments[i + 1].value;
+            fragments.splice(i + 1, 1);
+        } else {
+            i++;
+        }
+    }
+}

packages/@aws-cdk/cdk/lib/core/util.ts

@@ -1,4 +1,4 @@
-import { intrinsicEngine } from './engine-intrinsics';
+import { intrinsicEngine, isIntrinsic } from './engine-intrinsics';
 import { FragmentSource, StringFragment } from './engine-strings';
 import { resolve } from './tokens';
 
@@ -101,7 +101,11 @@ export function resolveMarkerSpans(spans: MarkerSpan[], lookup: (id: string) =>
                 return { source: FragmentSource.Literal, value: span.value };
             case 'marker':
                 const value = lookup(span.id);
-                return { source: FragmentSource.Token, value, intrinsicEngine: intrinsicEngine(value) };
+                if (isIntrinsic(value)) {
+                    return { source: FragmentSource.Intrinsic, value, intrinsicEngine: intrinsicEngine(value) };
+                } else {
+                    return { source: FragmentSource.Literal, value: `${value}` };
+                }
         }
     });
 }

packages/@aws-cdk/cdk/test/core/test.tokens.ts

@@ -153,7 +153,7 @@ export = {
         const resolved = resolve(stringified);
 
         // THEN
-        test.deepEqual(resolved, {'Fn::Join': ['', ['The dog says: ', 'woof woof']]});
+        test.deepEqual(evaluateCFN(resolved), 'The dog says: woof woof');
         test.done();
     },