fix: make errors serializable (#516)

lint-staged.config.js

@@ -1,4 +1,4 @@
 module.exports = {
-  "*": ["prettier --write --ignore-unknown", "cspell"],
+  "*": ["prettier --write --ignore-unknown", "cspell --no-must-find-files"],
   "*.{js}": ["eslint --cache --fix"],
 };

src/index.js

@@ -6,8 +6,8 @@ import {
   isUnsupportedUrl,
   normalizeSourceMap,
   getLessImplementation,
+  errorFactory,
 } from "./utils";
-import LessError from "./LessError";
 
 async function lessLoader(source) {
   const options = this.getOptions(schema);
@@ -78,7 +78,7 @@ async function lessLoader(source) {
       this.addDependency(path.normalize(error.filename));
     }
 
-    callback(new LessError(error));
+    callback(errorFactory(error));
 
     return;
   } finally {

src/utils.js

@@ -240,9 +240,46 @@ function getLessImplementation(loaderContext, implementation) {
   return resolvedImplementation;
 }
 
+function getFileExcerptIfPossible(error) {
+  if (typeof error.extract === "undefined") {
+    return [];
+  }
+
+  const excerpt = error.extract.slice(0, 2);
+  const column = Math.max(error.column - 1, 0);
+
+  if (typeof excerpt[0] === "undefined") {
+    excerpt.shift();
+  }
+
+  excerpt.push(`${new Array(column).join(" ")}^`);
+
+  return excerpt;
+}
+
+function errorFactory(error) {
+  const message = [
+    "\n",
+    ...getFileExcerptIfPossible(error),
+    error.message.charAt(0).toUpperCase() + error.message.slice(1),
+    error.filename
+      ? `      Error in ${path.normalize(error.filename)} (line ${
+          error.line
+        }, column ${error.column})`
+      : "",
+  ].join("\n");
+
+  const obj = new Error(message, { cause: error });
+
+  obj.stack = null;
+
+  return obj;
+}
+
 export {
   getLessOptions,
   isUnsupportedUrl,
   normalizeSourceMap,
   getLessImplementation,
+  errorFactory,
 };

test/__snapshots__/loader.test.js.snap

@@ -431,6 +431,15 @@ exports[`loader should resolve unresolved url with alias: errors 1`] = `[]`;
 
 exports[`loader should resolve unresolved url with alias: warnings 1`] = `[]`;
 
+exports[`loader should throw an error: errors 1`] = `
+[
+  "ModuleBuildError: Module build failed (from \`replaced original path\`):
+",
+]
+`;
+
+exports[`loader should throw an error: warnings 1`] = `[]`;
+
 exports[`loader should transform urls: css 1`] = `
 ".img4 {
   background: url(folder/img.jpg);

test/fixtures/broken.less

@@ -0,0 +1 @@
+broken;

test/loader.test.js

@@ -991,4 +991,13 @@ describe("loader", () => {
     expect(getWarnings(stats)).toMatchSnapshot("warnings");
     expect(getErrors(stats)).toMatchSnapshot("errors");
   });
+
+  it("should throw an error", async () => {
+    const testId = "./broken.less";
+    const compiler = getCompiler(testId);
+    const stats = await compile(compiler);
+
+    expect(getWarnings(stats)).toMatchSnapshot("warnings");
+    expect(getErrors(stats)).toMatchSnapshot("errors");
+  });
 });