chore: get ready for Svelte 4

Author: dummdidumm

CHANGELOG.md

@@ -1,5 +1,9 @@
 # svelte-loader changelog
 
+## 3.1.8
+
+* Get ready for Svelte 4
+
 ## 3.1.7
 
 * More robust `conditionNames: ['svelte']` detection ([#226](https://github.com/sveltejs/svelte-loader/pull/226))

index.js

@@ -2,7 +2,7 @@ const path = require('path');
 const fs = require('fs');
 const { getOptions } = require('loader-utils');
 const { buildMakeHot } = require('./lib/make-hot.js');
-const { compile, preprocess } = require('svelte/compiler');
+const { compile, preprocess, VERSION } = require('svelte/compiler');
 
 function posixify(file) {
 	return file.replace(/[/\\]/g, '/');
@@ -53,6 +53,8 @@ try {
 	// do nothing and hope for the best
 }
 
+let warned = false;
+
 module.exports = function(source, map) {
 	this.cacheable();
 
@@ -72,9 +74,17 @@ module.exports = function(source, map) {
 	const compileOptions = {
 		filename: this.resourcePath,
 		css: !options.emitCss,
-		...options.compilerOptions,
-		format: (options.compilerOptions && options.compilerOptions.format) || 'esm'
+		...options.compilerOptions
 	};
+	if (VERSION[0] === '3') {
+		compileOptions.format = (options.compilerOptions && options.compilerOptions.format) || 'esm'
+	} else {
+		if (options.compilerOptions && options.compilerOptions.format && !warned) {
+			warned = true;
+			console.warn(`[svelte-loader] Svelte's "format" compiler option was removed in version 4, the output is always ESM now.` +
+				` Remove the format option from your webpack config to remove this warning.`);
+		}
+	}
 
 	const handleWarning = warning => this.emitWarning(new Error(warning));
 

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "svelte-loader",
-  "version": "3.1.7",
+  "version": "3.1.8",
   "author": "Nico Rehwaldt <git_nikku@nixis.de>",
   "description": "A webpack loader for svelte",
   "license": "MIT",
@@ -29,7 +29,7 @@
     "svelte": "^3.0.0"
   },
   "peerDependencies": {
-    "svelte": "^3.0.0 || ^4.0.0"
+    "svelte": "^3.0.0 || 4.0.0-next.0 || 4.0.0-next.1 || ^4.0.0"
   },
   "repository": {
     "type": "git",