fix: Lazy require 'typescript' module. (#72)

* [fix] Lazy require 'typescript' module.

* [refactor] Be slightly less lazy when requiring 'typescript'

* [fix] Pretend like I know what I am doing in TypeScript.

* chore: clean up imports

package.json

@@ -17,7 +17,7 @@
     "@types/indent-string": "^3.2.0",
     "@types/lodash": "^4.14.120",
     "@types/mocha": "^5.2.5",
-    "@types/node": "^10.12.19",
+    "@types/node": "^10.12.20",
     "@types/proxyquire": "^1.3.28",
     "@types/wrap-ansi": "^3.0.0",
     "chai": "^4.2.0",

src/ts-node.ts

@@ -1,16 +1,21 @@
 import * as fs from 'fs'
 import * as path from 'path'
 import * as TSNode from 'ts-node'
-import {parseConfigFileTextToJson} from 'typescript'
 
 import Debug from './debug'
+const debug = Debug()
+
+let typescript: typeof import('typescript')
+try {
+  typescript = require('typescript')
+} catch (ex) {
+  debug('Cannot find typescript', ex)
+}
 
 const tsconfigs: {[root: string]: TSConfig} = {}
 const rootDirs: string[] = []
 const typeRoots = [`${__dirname}/../node_modules/@types`]
 
-const debug = Debug()
-
 export interface TSConfig {
   compilerOptions: {
     rootDir?: string
@@ -60,8 +65,8 @@ function registerTSNode(root: string) {
 
 function loadTSConfig(root: string): TSConfig | undefined {
   const tsconfigPath = path.join(root, 'tsconfig.json')
-  if (fs.existsSync(tsconfigPath)) {
-    const tsconfig = parseConfigFileTextToJson(
+  if (fs.existsSync(tsconfigPath) && typescript) {
+    const tsconfig = typescript.parseConfigFileTextToJson(
       tsconfigPath,
       fs.readFileSync(tsconfigPath, 'utf8')
     ).config

yarn.lock

@@ -121,10 +121,10 @@
   dependencies:
     "@types/node" "*"
 
-"@types/node@*", "@types/node@^10.12.19":
-  version "10.12.19"
-  resolved "https://registry.yarnpkg.com/@types/node/-/node-10.12.19.tgz#ca1018c26be01f07e66ac7fefbeb6407e4490c61"
-  integrity sha512-2NVovndCjJQj6fUUn9jCgpP4WSqr+u1SoUZMZyJkhGeBFsm6dE46l31S7lPUYt9uQ28XI+ibrJA1f5XyH5HNtA==
+"@types/node@*", "@types/node@^10.12.20":
+  version "10.12.20"
+  resolved "https://registry.yarnpkg.com/@types/node/-/node-10.12.20.tgz#f79f959acd3422d0889bd1ead1664bd2d17cd367"
+  integrity sha512-9spv6SklidqxevvZyOUGjZVz4QRXGu2dNaLyXIFzFYZW0AGDykzPRIUFJXTlQXyfzAucddwTcGtJNim8zqSOPA==
 
 "@types/proxyquire@^1.3.28":
   version "1.3.28"