workaround CloudFormation bug re non-octal strings with leading 0s

src/preprocess/index.ts

@@ -1147,11 +1147,23 @@ const visitArray = (node: AnyButUndefined[], path: string, env: Env): AnyButUnde
   _.map(node, (v, i) => visitNode(v, appendPath(path, i.toString()), env));
 
 export function visitString(node: string, path: string, env: Env): string {
+  let res: string;
   if (node.search(HANDLEBARS_RE) > -1) {
-    return interpolateHandlebarsString(node, env.$envValues, path);
+    res = interpolateHandlebarsString(node, env.$envValues, path);
   } else {
-    return node;
+    res = node;
+  }
+  if (res.match(/^(0\d+)$/)) {
+    // this encoding works around non-octal numbers with leading 0s
+    // not being quoted by jsyaml.dump which then causes issues with
+    // CloudFormation mis-parsing those as octal numbers. The encoding
+    // is removed in ../yaml.ts:dump
+
+    // js-yaml devs don't want to change the behaviour so we need this
+    // workaround https://github.com/nodeca/js-yaml/issues/394
+    res = `$0string ${res}`;
   }
+  return res;
 }
 
 ////////////////////////////////////////////////////////////////////////////////

src/yaml.ts

@@ -196,4 +196,6 @@ export const loadString = (content: string | Buffer, filename: string): any =>
 export const dump = (doc: object): string =>
   jsyaml.safeDump(doc, {schema: schema, lineWidth: 999})
     .replace(/!<!([^>]+?)>/g, '!$1')
-    .replace(/ !\$include /g, ' !$ ');
+    .replace(/ !\$include /g, ' !$ ')
+    .replace(/\$0string \s*(0\d+)/g, "'$1'");
+// $0string ^ is an encoding added in preprocess/index.ts:visitString