feat: accept babelConfig option making ts possible

closes #1

src/index.ts

@@ -1,6 +1,6 @@
 import type { Plugin, ServerHook, TransformResult } from 'vite';
-import type { TransformHook, TransformPluginContext } from 'rollup';
-import { transformSync } from '@babel/core';
+import type { SourceMap, TransformHook, TransformPluginContext } from 'rollup';
+import { transformAsync, TransformOptions } from '@babel/core';
 import BabelPluginIstanbul from 'babel-plugin-istanbul';
 import * as TestExclude from 'test-exclude';
 
@@ -10,6 +10,7 @@ interface IstanbulPluginOptions {
   extension?: string|string[];
   requireEnv?: boolean;
   cypress?: boolean;
+  babelConfig?: TransformOptions;
 }
 
 declare global {
@@ -42,31 +43,40 @@ function createConfigureServer(): ServerHook {
   };
 }
 
-function transformCode(this: TransformPluginContext, srcCode: string, id: string, opts: IstanbulPluginOptions): TransformResult {
-  const plugins = [[ BabelPluginIstanbul, opts ]];
-  const cwd = process.cwd();
+async function instrumentCode(this: TransformPluginContext, srcCode: string, id: string, opts: IstanbulPluginOptions): Promise<TransformResult> {
+  opts.babelConfig = opts.babelConfig || {}
+  opts.babelConfig.plugins = opts.babelConfig.plugins || []
+  opts.babelConfig.parserOpts = opts.babelConfig.parserOpts || {}
 
-  const { code, map } = transformSync(srcCode, {
-    plugins, cwd,
+  const cwd = process.cwd();
+  const babelConfig: TransformOptions = {
+    ...opts.babelConfig,
+    plugins: [...opts.babelConfig.plugins, [ BabelPluginIstanbul, opts ]], 
+    cwd,
     filename: id,
     ast: false,
     sourceMaps: true,
     comments: true,
-    compact: true,
+    compact: false,
     babelrc: false,
     configFile: false,
     parserOpts: {
+      ...opts.babelConfig.parserOpts,
       allowReturnOutsideFunction: true,
       sourceType: 'module',
     },
     // Only keep primitive properties
-    inputSourceMap: JSON.parse(JSON.stringify(this.getCombinedSourcemap())),
-  });
+    inputSourceMap: this.getCombinedSourcemap(),
+  }
+
+  const { code, map } = await transformAsync(srcCode, babelConfig);
 
   // Required to cast to correct mapping value
-  return { code, map: JSON.parse(JSON.stringify(map)) };
+  return { code, map: map as SourceMap };
 }
 
+const scriptRE = /<script([^>]*)>/g
+
 function createTransform(opts: IstanbulPluginOptions = {}): TransformHook {
   const exclude = new TestExclude({
     cwd: process.cwd(),
@@ -76,37 +86,48 @@ function createTransform(opts: IstanbulPluginOptions = {}): TransformHook {
     excludeNodeModules: true,
   });
 
-  return function (srcCode: string, id: string) {
+  return async function (this: TransformPluginContext, srcCode: string, id: string): Promise<{code:string, map: string}> {
     if (process.env.NODE_ENV == 'production' || id.startsWith('/@modules/')) {
       // do not transform if this is a dep
       // do not transform for production builds
       return;
     }
 
     if (exclude.shouldInstrument(id)) {
-      if (!id.endsWith('.vue')) {
-        return transformCode.call(this, srcCode, id, opts);
+      // is the vue component has already been transformed, 
+      // it can only be sliced
+      if (!id.endsWith('.vue') || srcCode.trim().slice(0, 1) !== "<") {
+        return instrumentCode.call(this, srcCode, id, opts);
       }
 
       // Vue files are special, it requires a hack to fix the source mappings
       // We take the source code from within the <script> tag and instrument this
       // Then we pad the lines to get the correct line numbers for the mappings
-      let startIndex = srcCode.indexOf('<script>');
+      const openScriptTagObject = scriptRE.exec(srcCode) || { index: -1};
       const endIndex = srcCode.indexOf('</script>');
-
-      if (startIndex == -1 || endIndex == -1) {
+      
+      if (!openScriptTagObject || endIndex == -1) {
         // ignore this vue file, doesn't contain any javascript
         return;
       }
+
+      const startIndex = openScriptTagObject.index
+      const openScriptTag = openScriptTagObject[0]
 
-      const lines = srcCode.slice(0, endIndex).match(/\n/g)?.length ?? 0;
-      const startOffset = '<script>'.length;
+      const numberOfLinesBeforeScript = srcCode.slice(0, endIndex).match(/\n/g)?.length ?? 0;
+      const startOffset = openScriptTag.length;
+
+      const scriptCode = '\n'.repeat(numberOfLinesBeforeScript) + srcCode.slice(startIndex + startOffset, endIndex);
 
-      srcCode = '\n'.repeat(lines) + srcCode.slice(startIndex + startOffset, endIndex);
+      const res = await instrumentCode.call(this, scriptCode, id, opts);
 
-      const res = transformCode.call(this, srcCode, id, opts);
+      // if </script> is anywhere in the script block, even in a string, 
+      // the parser errors
+      const resCodeSanatized = res.code.replace(/<\/script>/g, "<\\/script>")
 
-      res.code = `${srcCode.slice(0, startIndex + startOffset)}\n${res.code}\n${srcCode.slice(endIndex)}`;
+      console.log(resCodeSanatized)
+
+      res.code = `${srcCode.slice(0, startIndex + startOffset)}\n${resCodeSanatized}\n${srcCode.slice(endIndex)}`;
       return res;
     }
   };