fix: Emit valid YAML-1.1 (#876)

`yamljs` would emit YAML version 1.2, but CloudFormation expects YAML version 1.1. The differences
between versions include some surrogate representations of booleans (`ON`, `OFF`, `YES`, ...) that are
no longer supported in 1.2. This changes implementation to `js-yaml`, which makes extra effort in
emitting YAML that is compatible with previous versions of the standard.

Fixes #875

packages/aws-cdk/bin/cdk.ts

@@ -5,11 +5,11 @@ import cxapi = require('@aws-cdk/cx-api');
 import childProcess = require('child_process');
 import colors = require('colors/safe');
 import fs = require('fs-extra');
+import YAML = require('js-yaml');
 import minimatch = require('minimatch');
 import os = require('os');
 import path = require('path');
 import util = require('util');
-import YAML = require('yamljs');
 import yargs = require('yargs');
 import cdkUtil = require('../lib/util');
 
@@ -676,7 +676,7 @@ async function initCommandLine() {
     /* Attempt to parse YAML, fall back to JSON. */
     function parseTemplate(text: string): any {
       try {
-        return YAML.parse(text);
+        return YAML.safeLoad(text);
       } catch (e) {
         return JSON.parse(text);
       }
@@ -785,7 +785,7 @@ async function initCommandLine() {
     } else {
       const inlineJsonAfterDepth = 16;
       const indentWidth = 4;
-      return YAML.stringify(object, inlineJsonAfterDepth, indentWidth);
+      return YAML.safeDump(object, { indent: indentWidth, flowLevel: inlineJsonAfterDepth });
     }
   }
 }

packages/aws-cdk/lib/api/deploy-stack.ts

@@ -1,8 +1,8 @@
 import cxapi = require('@aws-cdk/cx-api');
 import aws = require('aws-sdk');
 import colors = require('colors/safe');
+import YAML = require('js-yaml');
 import uuid = require('uuid');
-import YAML = require('yamljs');
 import { prepareAssets } from '../assets';
 import { debug, error } from '../logging';
 import { Mode } from './aws-auth/credentials';
@@ -94,7 +94,7 @@ async function getStackOutputs(cfn: aws.CloudFormation, stackName: string): Prom
  * @param toolkitInfo information about the toolkit stack
  */
 async function makeBodyParameter(stack: cxapi.SynthesizedStack, toolkitInfo?: ToolkitInfo): Promise<TemplateBodyParameter> {
-  const templateJson = YAML.stringify(stack.template, 16, 4);
+  const templateJson = YAML.safeDump(stack.template, { indent: 4, flowLevel: 16 });
   if (toolkitInfo) {
     const s3KeyPrefix = `cdk/${stack.name}/`;
     const s3KeySuffix = '.yml';

packages/aws-cdk/package.json

@@ -37,7 +37,7 @@
     "@types/mockery": "^1.4.29",
     "@types/request": "^2.47.1",
     "@types/uuid": "^3.4.3",
-    "@types/yamljs": "^0.2.0",
+    "@types/js-yaml": "^3.11.2",
     "@types/yargs": "^8.0.3",
     "cdk-build-tools": "^0.10.0",
     "mockery": "^2.1.0",
@@ -58,7 +58,7 @@
     "proxy-agent": "^3.0.1",
     "request": "^2.83.0",
     "source-map-support": "^0.5.6",
-    "yamljs": "^0.2.0",
+    "js-yaml": "^3.12.0",
     "yargs": "^9.0.1"
   },
   "repository": {