(fix): parse tsconfig extends, trailing commas, and comments

- use ts.readConfigFile to properly parse a tsconfig instead of just
  trying to readJSON
- add tests for all of the above use cases

NOTE: this is only necessary for internal, TSDX-specific parsing of
tsconfig.json. rollup-plugin-typescript2 already handles these options,
but internal options like esModuleInterop etc are also used & parsed
independently of rpts2

src/createRollupConfig.ts

@@ -10,10 +10,11 @@ import replace from '@rollup/plugin-replace';
 import resolve from '@rollup/plugin-node-resolve';
 import sourceMaps from 'rollup-plugin-sourcemaps';
 import typescript from 'rollup-plugin-typescript2';
+import ts from 'typescript';
+
 import { extractErrors } from './errors/extractErrors';
 import { babelPluginTsdx } from './babelPluginTsdx';
 import { TsdxOptions } from './types';
-import * as fs from 'fs-extra';
 
 const errorCodeOpts = {
   errorMapFilePath: paths.appErrorsJson,
@@ -43,10 +44,9 @@ export async function createRollupConfig(
     .filter(Boolean)
     .join('.');
 
-  let tsconfigJSON;
-  try {
-    tsconfigJSON = await fs.readJSON(opts.tsconfig || paths.tsconfigJson);
-  } catch (e) {}
+  const tsconfigPath = opts.tsconfig || paths.tsconfigJson;
+  // borrowed from https://github.com/facebook/create-react-app/pull/7248
+  const tsconfigJSON = ts.readConfigFile(tsconfigPath, ts.sys.readFile).config;
 
   return {
     // Tell Rollup the entry point to the package
@@ -136,7 +136,7 @@ export async function createRollupConfig(
         },
       },
       typescript({
-        typescript: require('typescript'),
+        typescript: ts,
         cacheRoot: `./node_modules/.cache/tsdx/${opts.format}/`,
         tsconfig: opts.tsconfig,
         tsconfigDefaults: {

test/fixtures/build-default/tsconfig.base.json

@@ -0,0 +1,28 @@
+{
+  "compilerOptions": {
+    "module": "ESNext",
+    "lib": ["dom", "esnext"],
+    "declaration": true,
+    "sourceMap": true,
+    "rootDir": "./",
+    "strict": true,
+    "noImplicitAny": true,
+    "strictNullChecks": true,
+    "strictFunctionTypes": true,
+    "strictPropertyInitialization": true,
+    "noImplicitThis": true,
+    "alwaysStrict": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "moduleResolution": "node",
+    "baseUrl": "./",
+    "paths": {
+      "*": ["src/*", "node_modules/*"]
+    },
+    "jsx": "react",
+    "esModuleInterop": true
+  },
+  "include": ["src", "types"], // test parsing of trailing comma & comment
+}

test/fixtures/build-default/tsconfig.json

@@ -1,29 +1,4 @@
 {
-  "compilerOptions": {
-    "target": "es5",
-    "module": "ESNext",
-    "lib": ["dom", "esnext"],
-    "declaration": true,
-    "sourceMap": true,
-    "rootDir": "./",
-    "strict": true,
-    "noImplicitAny": true,
-    "strictNullChecks": true,
-    "strictFunctionTypes": true,
-    "strictPropertyInitialization": true,
-    "noImplicitThis": true,
-    "alwaysStrict": true,
-    "noUnusedLocals": true,
-    "noUnusedParameters": true,
-    "noImplicitReturns": true,
-    "noFallthroughCasesInSwitch": true,
-    "moduleResolution": "node",
-    "baseUrl": "./",
-    "paths": {
-      "*": ["src/*", "node_modules/*"]
-    },
-    "jsx": "react",
-    "esModuleInterop": true
-  },
-  "include": ["src", "types"]
+  // ensure that extends works
+  "extends": "./tsconfig.base.json",
 }