fix: handle empty files

src/index.js

@@ -622,7 +622,7 @@ class CssMinimizerPlugin {
                 innerSourceMap,
                 true,
               );
-            } else if (item.code) {
+            } else if (typeof item.code !== "undefined" && item.code !== null) {
               output.source = new RawSource(item.code);
             }
           }

src/utils.js

@@ -20,21 +20,6 @@ const notSettled = Symbol("not-settled");
  * @returns {Promise<T[]>} A promise that fulfills to an array of the results
  */
 function throttleAll(limit, tasks) {
-  if (!Number.isInteger(limit) || limit < 1) {
-    throw new TypeError(
-      `Expected \`limit\` to be a finite number > 0, got \`${limit}\` (${typeof limit})`,
-    );
-  }
-
-  if (
-    !Array.isArray(tasks) ||
-    !tasks.every((task) => typeof task === "function")
-  ) {
-    throw new TypeError(
-      "Expected `tasks` to be a list of functions returning a promise",
-    );
-  }
-
   return new Promise((resolve, reject) => {
     const result = Array.from({ length: tasks.length }).fill(notSettled);
     const entries = tasks.entries();

test/CssMinimizerPlugin.test.js

@@ -239,6 +239,34 @@ describe("CssMinimizerPlugin", () => {
     ).toMatchSnapshot();
   });
 
+  it("should work", async () => {
+    const compiler = getCompiler({
+      entry: path.join(__dirname, "fixtures", "entry.js"),
+    });
+
+    new CssMinimizerPlugin().apply(compiler);
+
+    const stats = await compile(compiler);
+
+    expect(readAssets(compiler, stats, /\.css$/)).toMatchSnapshot("assets");
+    expect(getErrors(stats)).toMatchSnapshot("errors");
+    expect(getWarnings(stats)).toMatchSnapshot("warnings");
+  });
+
+  it("should work with empty files", async () => {
+    const compiler = getCompiler({
+      entry: path.join(__dirname, "fixtures", "empty.js"),
+    });
+
+    new CssMinimizerPlugin().apply(compiler);
+
+    const stats = await compile(compiler);
+
+    expect(readAssets(compiler, stats, /\.css$/)).toMatchSnapshot("assets");
+    expect(getErrors(stats)).toMatchSnapshot("errors");
+    expect(getWarnings(stats)).toMatchSnapshot("warnings");
+  });
+
   it("should build error", () => {
     const compiler = getCompiler({
       entry: {

test/__snapshots__/CssMinimizerPlugin.test.js.snap

@@ -232,6 +232,16 @@ exports[`CssMinimizerPlugin should work with child compilation: errors 1`] = `[]
 
 exports[`CssMinimizerPlugin should work with child compilation: warnings 1`] = `[]`;
 
+exports[`CssMinimizerPlugin should work with empty files: assets 1`] = `
+{
+  "main.css": "",
+}
+`;
+
+exports[`CssMinimizerPlugin should work with empty files: errors 1`] = `[]`;
+
+exports[`CssMinimizerPlugin should work with empty files: warnings 1`] = `[]`;
+
 exports[`CssMinimizerPlugin should work with source map and use memory cache when the "cache" option is "true" and the asset has been changed: assets 1`] = `
 {
   "foo.css": "body{color:red}a{color:blue}
@@ -396,6 +406,16 @@ exports[`CssMinimizerPlugin should work with warnings and use memory cache when
 ]
 `;
 
+exports[`CssMinimizerPlugin should work: assets 1`] = `
+{
+  "main.css": "body{color:red}a{color:blue}",
+}
+`;
+
+exports[`CssMinimizerPlugin should work: errors 1`] = `[]`;
+
+exports[`CssMinimizerPlugin should work: warnings 1`] = `[]`;
+
 exports[`CssMinimizerPlugin should write stdout and stderr of workers to stdout and stderr of main process in parallel mode: assets 1`] = `
 {
   "one.css": ".minify {};",

test/__snapshots__/minify-option.test.js.snap

@@ -510,15 +510,7 @@ exports[`"minify" option should work with "csso" minifier: warning 1`] = `[]`;
 
 exports[`"minify" option should work with empty code: assets 1`] = `
 {
-  "foo.css": "body {
-  color: red;
-}
-a {
-  color: blue;
-}
-
-/*# sourceMappingURL=foo.css.map*/",
-  "foo.css.map": "{"version":3,"file":"foo.css","mappings":"AAAA;EACE,UAAU;AACZ;AACA;EACE,WAAW;AACb,C","sources":["webpack:///./foo.css"],"sourcesContent":["body {\\n  color: red;\\n}\\na {\\n  color: blue;\\n}"],"names":[],"sourceRoot":""}",
+  "foo.css": "",
 }
 `;
 

test/fixtures/empty.css

@@ -0,0 +1 @@
+/* comment */

test/fixtures/empty.js

@@ -0,0 +1 @@
+import "./empty.css";

test/helpers/getCompiler.js

@@ -8,7 +8,7 @@ import webpack from "webpack";
  * @param {import("webpack").Configuration} config Webpack configuration
  * @returns {import("webpack").Compiler} Webpack compiler
  */
-export default function getCompiler(config) {
+export default function getCompiler(config = {}) {
   const compiler = webpack({
     mode: "development",
     devtool: config.devtool || false,