Less Modules in react-scripts test (#83)

We need to modify the jest config so that the Less Modules can be tested properly.

https://jestjs.io/docs/webpack#mocking-css-modules

```diff
 const jestConfig = {
   moduleNameMapper: {
-    "^.+\\.module\\.(css|sass|scss)$": "identity-obj-proxy",
+    "^.+\\.module\\.(css|less|sass|scss)$": "identity-obj-proxy",
   },
   transformIgnorePatterns: [
-    "^.+\\.module\\.(css|sass|scss)$",
+    "^.+\\.module\\.(css|less|sass|scss)$",
   ],
 };
```

Co-authored-by: Kamron Batman <3953314+kamronbatman@users.noreply.github.com>

Author: fanck0605

.npmignore

@@ -9,6 +9,7 @@ yarn-error.log
 .vscode
 coverage
 lib/*.test.js
+lib/test-utils.js
 yarn.lock
 craco-less-*.tgz
 .github/

README.md

@@ -63,7 +63,7 @@ you should use the [`craco-antd`](https://github.com/DocSpring/craco-antd) plugi
 
 ## Installation
 
-First, follow the [`craco` Installation Instructions](https://github.com/sharegate/craco/blob/master/packages/craco/README.md##installation) to install the `craco` package, create a `craco.config.js` file, and modify the scripts in your `package.json`.
+First, follow the [`craco` Installation Instructions](https://github.com/gsoft-inc/craco/blob/master/packages/craco/README.md#installation) to install the `craco` package, create a `craco.config.js` file, and modify the scripts in your `package.json`.
 
 Then install `craco-less`:
 

lib/craco-less.js

@@ -1,23 +1,21 @@
 const path = require("path");
 const { deepClone, styleRuleByName } = require("./utils");
+const { loaderByName, throwUnexpectedConfigError } = require("@craco/craco");
 
 const lessRegex = /\.less$/;
 const lessModuleRegex = /\.module\.less$/;
 
-const overrideWebpackConfig = ({ context, webpackConfig, pluginOptions }) => {
-  const { loaderByName, throwUnexpectedConfigError } = require("@craco/craco");
+const throwError = (message, githubIssueQuery) =>
+  throwUnexpectedConfigError({
+    packageName: "craco-less",
+    githubRepo: "DocSpring/craco-less",
+    message,
+    githubIssueQuery,
+  });
 
+const overrideWebpackConfig = ({ context, webpackConfig, pluginOptions }) => {
   // This is mocked in Windows tests
   const pathSep = module.exports.pathSep;
-
-  const throwError = (message, githubIssueQuery) =>
-    throwUnexpectedConfigError({
-      packageName: "craco-less",
-      githubRepo: "DocSpring/craco-less",
-      message,
-      githubIssueQuery,
-    });
-
   pluginOptions = pluginOptions || {};
 
   const createLessRule = ({ baseRule, overrideRule }) => {
@@ -174,8 +172,44 @@ const overrideWebpackConfig = ({ context, webpackConfig, pluginOptions }) => {
   return webpackConfig;
 };
 
+const overrideJestConfig = ({ context, jestConfig }) => {
+  const moduleNameMapper = jestConfig.moduleNameMapper;
+  const cssModulesPattern = Object.keys(moduleNameMapper).find((p) =>
+    p.match(/\\\.module\\\.\(.*?css.*?\)/)
+  );
+
+  if (!cssModulesPattern) {
+    throwError(
+      `Can't find CSS Modules pattern under moduleNameMapper in the ${context.env} jest config!`,
+      "jest+moduleNameMapper+css"
+    );
+  }
+
+  moduleNameMapper[cssModulesPattern.replace("css", "css|less")] =
+    moduleNameMapper[cssModulesPattern];
+  delete moduleNameMapper[cssModulesPattern];
+
+  const transformIgnorePatterns = jestConfig.transformIgnorePatterns;
+  const cssModulesPatternIndex = transformIgnorePatterns.findIndex((p) =>
+    p.match(/\\\.module\\\.\(.*?css.*?\)/)
+  );
+  if (cssModulesPatternIndex === -1) {
+    throwError(
+      `Can't find CSS Modules pattern under transformIgnorePatterns in the ${context.env} jest config!`,
+      "jest+transformIgnorePatterns+css"
+    );
+  }
+
+  transformIgnorePatterns[cssModulesPatternIndex] = transformIgnorePatterns[
+    cssModulesPatternIndex
+  ].replace("css", "css|less");
+
+  return jestConfig;
+};
+
 // pathSep is mocked in Windows tests
 module.exports = {
   overrideWebpackConfig,
+  overrideJestConfig,
   pathSep: path.sep,
 };

lib/craco-less.test.test.js

@@ -0,0 +1,86 @@
+const { createJestConfig } = require("@craco/craco");
+const { processCracoConfig } = require("@craco/craco/lib/config");
+const { applyJestConfigPlugins } = require("@craco/craco/lib/features/plugins");
+const clone = require("clone");
+const CracoLessPlugin = require("./craco-less");
+const { getCracoContext } = require("./test-utils");
+
+process.env.NODE_ENV = "test";
+
+const baseCracoConfig = {};
+const cracoContext = getCracoContext(baseCracoConfig);
+const originalJestConfig = createJestConfig(baseCracoConfig);
+
+const overrideJestConfig = (callerCracoConfig, jestConfig) => {
+  return applyJestConfigPlugins(
+    processCracoConfig({
+      ...baseCracoConfig,
+      ...callerCracoConfig,
+    }),
+    jestConfig,
+    cracoContext
+  );
+};
+
+let jestConfig;
+beforeEach(() => {
+  // deep clone the object before each test.
+  jestConfig = clone(originalJestConfig);
+});
+
+test("the jest config is modified correctly", () => {
+  jestConfig = overrideJestConfig(
+    {
+      plugins: [{ plugin: CracoLessPlugin }],
+    },
+    jestConfig
+  );
+
+  const moduleNameMapper = jestConfig.moduleNameMapper;
+  expect(moduleNameMapper["^.+\\.module\\.(css|sass|scss)$"]).toBeUndefined();
+  expect(moduleNameMapper["^.+\\.module\\.(css|less|sass|scss)$"]).toEqual(
+    "identity-obj-proxy"
+  );
+
+  const transformIgnorePatterns = jestConfig.transformIgnorePatterns;
+  expect(transformIgnorePatterns[1]).toEqual(
+    "^.+\\.module\\.(css|less|sass|scss)$"
+  );
+});
+
+test("throws an error when we can't find CSS Modules pattern under moduleNameMapper in the jest config", () => {
+  delete jestConfig.moduleNameMapper["^.+\\.module\\.(css|sass|scss)$"];
+
+  const runTest = () => {
+    overrideJestConfig(
+      {
+        plugins: [{ plugin: CracoLessPlugin }],
+      },
+      jestConfig
+    );
+  };
+
+  expect(runTest).toThrowError(
+    /^Can't find CSS Modules pattern under moduleNameMapper in the test jest config!/
+  );
+});
+
+test("throws an error when we can't find CSS Modules pattern under transformIgnorePatterns in the jest config", () => {
+  jestConfig.transformIgnorePatterns =
+    jestConfig.transformIgnorePatterns.filter(
+      (e) => e !== "^.+\\.module\\.(css|sass|scss)$"
+    );
+
+  const runTest = () => {
+    overrideJestConfig(
+      {
+        plugins: [{ plugin: CracoLessPlugin }],
+      },
+      jestConfig
+    );
+  };
+
+  expect(runTest).toThrowError(
+    /^Can't find CSS Modules pattern under transformIgnorePatterns in the test jest config!/
+  );
+});

lib/test-utils.js

@@ -0,0 +1,13 @@
+const { processCracoConfig } = require("@craco/craco/lib/config");
+const { getCraPaths } = require("@craco/craco/lib/cra");
+
+const getCracoContext = (callerCracoConfig, env = process.env.NODE_ENV) => {
+  const context = { env };
+  const cracoConfig = processCracoConfig(callerCracoConfig, { env });
+  context.paths = getCraPaths(cracoConfig);
+  return context;
+};
+
+module.exports = {
+  getCracoContext,
+};