feat: added the lessLogAsWarnOrErr option

README.md

@@ -66,6 +66,7 @@ And run `webpack` via your preferred method.
 - **[`sourceMap`](#sourcemap)**
 - **[`webpackImporter`](#webpackimporter)**
 - **[`implementation`](#implementation)**
+- **[`lessLogAsWarnAndErr`](#lesslogaswarnanderr)**
 
 ### `lessOptions`
 
@@ -411,6 +412,52 @@ module.exports = {
 };
 ```
 
+### `lessLogAsWarnOrErr`
+
+Type:
+
+```ts
+type lessLogAsWarnOrErr = boolean;
+```
+
+Default: `false`
+
+`Less` warnings and errors will be webpack warnings and errors, not just logs.
+
+**warning.less**
+
+```less
+div {
+  &:extend(.body1);
+}
+```
+
+If `lessLogAsWarnOrErr` is set to `false` it will be just a log and webpack will compile successfully, but if you set this option to `true` webpack will compile fail with a warning.
+
+**webpack.config.js**
+
+```js
+module.exports = {
+  module: {
+    rules: [
+      {
+        test: /\.less$/i,
+        use: [
+          "style-loader",
+          "css-loader",
+          {
+            loader: "less-loader",
+            options: {
+              lessLogAsWarnOrErr: true,
+            },
+          },
+        ],
+      },
+    ],
+  },
+};
+```
+
 ## Examples
 
 ### Normal usage

src/index.js

@@ -52,12 +52,23 @@ async function lessLoader(source) {
   }
 
   const logger = this.getLogger("less-loader");
+  const loaderContext = this;
   const loggerListener = {
     error(message) {
-      logger.error(message);
+      // TODO enable by default in the next major release
+      if (options.lessLogAsWarnOrErr) {
+        loaderContext.emitError(new Error(message));
+      } else {
+        logger.error(message);
+      }
     },
     warn(message) {
-      logger.warn(message);
+      // TODO enable by default in the next major release
+      if (options.lessLogAsWarnOrErr) {
+        loaderContext.emitWarning(new Error(message));
+      } else {
+        logger.warn(message);
+      }
     },
     info(message) {
       logger.log(message);

src/options.json

@@ -48,6 +48,11 @@
           "type": "object"
         }
       ]
+    },
+    "lessLogAsWarnOrErr": {
+      "description": "Less warnings and errors will be webpack warnings or errors.",
+      "link": "https://github.com/webpack-contrib/less-loader#lesslogaswarnorerr",
+      "type": "boolean"
     }
   },
   "additionalProperties": false

test/__snapshots__/loader.test.js.snap

@@ -84,6 +84,17 @@ exports[`loader should emit an error: errors 1`] = `
 
 exports[`loader should emit an error: warnings 1`] = `[]`;
 
+exports[`loader should emit less warning as webpack warning: css 1`] = `""`;
+
+exports[`loader should emit less warning as webpack warning: errors 1`] = `[]`;
+
+exports[`loader should emit less warning as webpack warning: warnings 1`] = `
+[
+  "ModuleWarning: Module Warning (from \`replaced original path\`):
+extend ' .body1' has no matches",
+]
+`;
+
 exports[`loader should get absolute path relative rootContext: css 1`] = `
 ".box {
   color: #fe33ac;

test/__snapshots__/validate-options.test.js.snap

@@ -114,6 +114,13 @@ exports[`validate options should throw an error on the "implementation" option w
       object { … }"
 `;
 
+exports[`validate options should throw an error on the "lessLogAsWarnOrErr" option with "string" value 1`] = `
+"Invalid options object. Less Loader has been initialized using an options object that does not match the API schema.
+ - options.lessLogAsWarnOrErr should be a boolean.
+   -> Less warnings and errors will be webpack warnings or errors.
+   -> Read more at https://github.com/webpack-contrib/less-loader#lesslogaswarnorerr"
+`;
+
 exports[`validate options should throw an error on the "lessOptions" option with "[]" value 1`] = `
 "Invalid options object. Less Loader has been initialized using an options object that does not match the API schema.
  - options.lessOptions should be one of these:
@@ -184,49 +191,49 @@ exports[`validate options should throw an error on the "sourceMap" option with "
 exports[`validate options should throw an error on the "unknown" option with "/test/" value 1`] = `
 "Invalid options object. Less Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation? }"
+   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation?, lessLogAsWarnOrErr? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "[]" value 1`] = `
 "Invalid options object. Less Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation? }"
+   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation?, lessLogAsWarnOrErr? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "{"foo":"bar"}" value 1`] = `
 "Invalid options object. Less Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation? }"
+   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation?, lessLogAsWarnOrErr? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "{}" value 1`] = `
 "Invalid options object. Less Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation? }"
+   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation?, lessLogAsWarnOrErr? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "1" value 1`] = `
 "Invalid options object. Less Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation? }"
+   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation?, lessLogAsWarnOrErr? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "false" value 1`] = `
 "Invalid options object. Less Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation? }"
+   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation?, lessLogAsWarnOrErr? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "test" value 1`] = `
 "Invalid options object. Less Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation? }"
+   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation?, lessLogAsWarnOrErr? }"
 `;
 
 exports[`validate options should throw an error on the "unknown" option with "true" value 1`] = `
 "Invalid options object. Less Loader has been initialized using an options object that does not match the API schema.
  - options has an unknown property 'unknown'. These properties are valid:
-   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation? }"
+   object { lessOptions?, additionalData?, sourceMap?, webpackImporter?, implementation?, lessLogAsWarnOrErr? }"
 `;
 
 exports[`validate options should throw an error on the "webpackImporter" option with "string" value 1`] = `

test/fixtures/err.less

@@ -0,0 +1,6 @@
+div {
+  .m(@x) when (default())    {}
+  .m(@x) when not(default()) {}
+
+  .m(1); // Error
+}

test/fixtures/warn.less

@@ -0,0 +1,3 @@
+div {
+  &:extend(.body1);
+}

test/loader.test.js

@@ -1047,4 +1047,17 @@ describe("loader", () => {
     expect(getWarnings(stats)).toMatchSnapshot("warnings");
     expect(getErrors(stats)).toMatchSnapshot("errors");
   });
+
+  it("should emit less warning as webpack warning", async () => {
+    const testId = "./warn.less";
+    const compiler = getCompiler(testId, {
+      lessLogAsWarnOrErr: true,
+    });
+    const stats = await compile(compiler);
+    const codeFromBundle = getCodeFromBundle(stats, compiler);
+
+    expect(codeFromBundle.css).toMatchSnapshot("css");
+    expect(getWarnings(stats)).toMatchSnapshot("warnings");
+    expect(getErrors(stats)).toMatchSnapshot("errors");
+  });
 });

test/validate-options.test.js

@@ -30,6 +30,10 @@ describe("validate options", () => {
       success: [require("less"), "less"],
       failure: [true, false, () => {}, []],
     },
+    lessLogAsWarnOrErr: {
+      success: [true, false],
+      failure: ["string"],
+    },
     unknown: {
       success: [],
       failure: [1, true, false, "test", /test/, [], {}, { foo: "bar" }],