feat: adds maxBuffer option that sets buffer limit for preprocess

fixes #20

Author: ilyavf

README.md

@@ -158,14 +158,17 @@ The default mode is to load `svelte.config.js` from the current project root to
 
 When `upward` is set it will stop at the first config file it finds above the file being transformed, but will walk up the directory structure all the way to the filesystem root if it cannot find any config file. This means that if there is no `svelte.config.js` file in the project above the file being transformed, it is always possible that someone will have a forgotten `svelte.config.js` in their home directory which could cause unexpected errors in your builds.
 
+`maxBuffer` (default: 10485760): Sets limit for buffer when `preprocess` is true. It defines the largest amount of data in bytes allowed on stdout or stderr for [child_process.spawnSync](https://nodejs.org/api/child_process.html#child_process_child_process_spawnsync_command_args_options). If exceeded, the child process is terminated and any output is truncated. The default value of 10Mb overrides Node's default value of 1Mb.
+
 ```json
 "transform": {
   "^.+\\.js$": "babel-jest",
   "^.+\\.svelte$": ["svelte-jester", { 
     "preprocess": false,
     "debug": false,
     "compilerOptions": {},
-    "rootMode": ""
+    "rootMode": "",
+    "maxBuffer": 15000000
   }]
 }
 ```

src/__tests__/transformer.test.js

@@ -44,4 +44,11 @@ describe('transformer', () => {
     const esInterop = 'Object.defineProperty(exports, "__esModule", { value: true });'
     expect(global.window.console.log).toHaveBeenCalledWith(code.replace(esInterop, ''))
   })
+
+  it('should accept maxBuffer option for preprocess buffer limit', () => {
+    expect(
+      () => runTransformer('SassComp', { preprocess: true, maxBuffer: 1 })
+    ).toThrow('spawnSync /bin/sh ENOBUFS');
+    runTransformer('SassComp', { preprocess: true, maxBuffer: 5 * 1024 * 1024 })
+  })
 })

src/transformer.js

@@ -5,15 +5,16 @@ const svelte = require('svelte/compiler')
 const { getSvelteConfig } = require('./svelteconfig.js')
 
 const transformer = (options = {}) => (source, filename) => {
-  const { debug, compilerOptions, preprocess, rootMode } = options
+  const { debug, compilerOptions, preprocess, rootMode, maxBuffer } = options
 
   let processed = source
 
   if (preprocess) {
     const svelteConfig = getSvelteConfig(rootMode, filename)
     const preprocessor = require.resolve('./preprocess.js')
     processed = execSync(`node --unhandled-rejections=strict --abort-on-uncaught-exception "${preprocessor}"`, {
-      env: { PATH: process.env.PATH, source, filename, svelteConfig }
+      env: { PATH: process.env.PATH, source, filename, svelteConfig },
+      maxBuffer: maxBuffer || 10 * 1024 * 1024
     }).toString()
   }