Prepare for rollup-1.0 (#124)

* Check for existence of tsconfig before trying to load it

* Add node 7 tests to CI

* Test tslib can be overridden

* Update readme

* Make tests run with rollup 1.0

* Support dynamic imports, remove tslib from source-maps

* Remove unused externals

* Test that module type is checked, test that module type is case insensitive

* Clarify how to pass options in readme

* Allow specifying tsconfig path

* Make it possible to transpile CommonJS imports

Author: lukastaegert

.gitignore

@@ -1,3 +1,4 @@
 /node_modules
+!test/sample/dts/node_modules
 dist
 test/**/*.out

.travis.yml

@@ -2,4 +2,5 @@ language: node_js
 node_js:
   - "10"
   - "8"
+  - "7"
 

README.md

@@ -12,9 +12,11 @@ See [rollup-plugin-babel](https://github.com/rollup/rollup-plugin-babel).
 ## Installation
 
 ```bash
-npm install --save-dev rollup-plugin-typescript
+npm install --save-dev rollup-plugin-typescript typescript tslib
 ```
 
+Note that both `typescript` and `tslib` are peer dependencies of this plugin that need to be installed separately.
+
 ## Usage
 
 ```js
@@ -23,31 +25,67 @@ import typescript from 'rollup-plugin-typescript';
 
 export default {
   input: './main.ts',
-
   plugins: [
     typescript()
   ]
 }
 ```
 
-The plugin loads any [`compilerOptions`](http://www.typescriptlang.org/docs/handbook/compiler-options.html) from the `tsconfig.json` file by default. Passing options to the plugin directly overrides those options.
+The plugin loads any [`compilerOptions`](http://www.typescriptlang.org/docs/handbook/compiler-options.html) from the `tsconfig.json` file by default. Passing options to the plugin directly overrides those options:
+
+```js
+...
+export default {
+  input: './main.ts',
+  plugins: [
+      typescript({lib: ["es5", "es6", "dom"], target: "es5"})
+  ]
+}
+```
 
 The following options are unique to `rollup-plugin-typescript`:
 
 * `options.include` and `options.exclude` (each a minimatch pattern, or array of minimatch patterns), which determine which files are transpiled by Typescript (all `.ts` and `.tsx` files by default).
 
-* `tsconfig` when set to false, ignores any options specified in the config file
+* `tsconfig` when set to false, ignores any options specified in the config file. If set to a string that corresponds to a file path, the specified file will be used as config file.
+
+* `typescript` overrides TypeScript used for transpilation:
+  ```js
+  typescript({
+    typescript: require('some-fork-of-typescript')
+  })
+  ```
 
-* `typescript` overrides TypeScript used for transpilation
+* `tslib` overrides the injected TypeScript helpers with a custom version
+  ```js
+  typescript({
+    tslib: require('some-fork-of-tslib')
+  })
+  ```
 
 ### TypeScript version
-[TypeScript 2.6.2](https://github.com/Microsoft/TypeScript/wiki/Roadmap#26-october-2017) is used by default. Should your project require it, you can override the TypeScript version used for _transpiling the sources_.
+Due to the use of `tslib` to inject helpers, this plugin requires at least [TypeScript 2.1](https://github.com/Microsoft/TypeScript/wiki/Roadmap#21-december-2016). See also [here](https://blog.mariusschulz.com/2016/12/16/typescript-2-1-external-helpers-library#the-importhelpers-flag-and-tslib).
+
+### Importing CommonJS
+Though it is not recommended, it is possible to configure this plugin to handle imports of CommonJS files from TypeScript. For this, you need to specify `CommonJS` as the module format and add `rollup-plugin-commonjs` to transpile the CommonJS output generated by TypeScript to ES Modules so that rollup can process it.
 
 ```js
-typescript({
-  typescript: require('some-fork-of-typescript')
-})
+// rollup.config.js
+import typescript from 'rollup-plugin-typescript';
+import commonjs from 'rollup-plugin-commonjs';
+
+export default {
+  input: './main.ts',
+  plugins: [
+    typescript({module: 'CommonJS'}),
+    commonjs({extensions: ['.js', '.ts']}) // the ".ts" extension is required
+  ]
+}
 ```
 
+Note that this will often result in less optimal output.
+
 ## Issues
-Emit-less types, see [#28](https://github.com/rollup/rollup-plugin-typescript/issues/28).
+This plugin will currently **not warn for any type violations**. This plugin relies on TypeScript's [transpileModule](https://github.com/Microsoft/TypeScript/wiki/Using-the-Compiler-API#a-simple-transform-function) function which basically transpiles TypeScript to JavaScript by stripping any type information on a per-file basis. While this is faster than using the language service, no cross-file type checks are possible with this approach.
+
+This also causes issues with emit-less types, see [#28](https://github.com/rollup/rollup-plugin-typescript/issues/28).