Handle node module duplicate filename import resolution

index.ts

@@ -135,10 +135,47 @@ export default function scss(options: CSSPluginOptions = {}): Plugin {
                  * The paths property tells `require.resolve()` where to begin
                  * resolution (i.e. who is requesting the file). */
                 try {
-                  const resolved = require.resolve(cleanUrl, {
+                  let resolved = require.resolve(cleanUrl, {
                     paths: [prefix + scss]
                   })
 
+                  const allowedExtensions: string[] = ['.css', '.scss', '.sass'];
+
+                  const resolvedHasAllowedExtension = allowedExtensions.some((allowedExtension: string) => {
+                    return resolved.endsWith(allowedExtension)
+                  });
+
+                  /* It is possible that the `resolved` value is unintentionally
+                   * a path to an unintended file which shares the same name
+                   * but has a different file extension. */
+                  if (!resolvedHasAllowedExtension) {
+                    for (const [index, allowedExtension] of allowedExtensions.entries()) {
+                      try {
+                        /* Make an additional attempt to resolve the path by
+                         * specifying the file extension. */
+                        resolved = require.resolve(cleanUrl + allowedExtension, {
+                          paths: [prefix + scss]
+                        })
+
+                        /* For the first file extension that allows the path to
+                         * be reolved, break out of the loop. */
+                        break
+                      /* If not the path could not be resolved with the
+                       * file extension. */
+                      } catch (e) {
+                        if (index < allowedExtensions.length - 1) {
+                          /* If not the final iteration then proceed
+                           *  to the next. */
+                          continue
+                        } else {
+                          /* If the final iteration then re-throw the error
+                           *  onto the next catch. */
+                          throw e
+                        }
+                      }
+                    }
+                  }
+
                   /* Since `require.resolve()` will throw an error if a file
                    * doesn't exist. It's safe to assume the file exists and
                    * pass it off to the sass compiler. */

package.json

@@ -16,7 +16,8 @@
     "test:postcss": "cd test/postcss && rm -f output.* && rollup -c && cmp output.js ../expected.js && cmp output.css expected.css && cd ../..",
     "test:processor": "cd test/processor && rm -f output.* && rollup -c && cmp output.js ../expected.js && cmp output.css expected.css && cd ../..",
     "test:sourcemap": "cd test/sourcemap && rm -f output.* && rollup -c && cmp output.js ../expected.js && cmp nested/output.css expected.css && cmp nested/output.css.map expected.css.map && cd ../..",
-    "test": "npm run test:node-sass && npm run test:sass && npm run test:processor && npm run test:postcss && npm run test:sourcemap && npm run test:insert",
+    "test:import-resolution": "cd test/import-resolution && node setup.js && rm -f output.* && rollup -c && node teardown.js && cmp output.js expected.js && cmp output.css expected.css && cd ../..",
+    "test": "npm run test:node-sass && npm run test:sass && npm run test:processor && npm run test:postcss && npm run test:sourcemap && npm run test:insert && npm run test:import-resolution",
     "testw": "cd test/node-sass && rm -f output.* && rollup -cw; cd ..",
     "prepare": "rollup -c"
   },

test/import-resolution/expected.css

@@ -0,0 +1,8 @@
+.importable {
+  color: red;
+}
+
+.rollup .plugin .scss {
+  color: green;
+  user-select: none;
+}

test/import-resolution/expected.js

@@ -0,0 +1 @@
+console.log('scss imported from native files and node_modules');

test/import-resolution/input.js

@@ -0,0 +1,3 @@
+import './input.scss'
+
+console.log('scss imported from native files and node_modules')

test/import-resolution/input.scss

@@ -0,0 +1,10 @@
+@import 'import-resolution-test/main';
+
+.rollup {
+  .plugin {
+    .scss {
+      color: green;
+      user-select: none;
+    }
+  }
+}

test/import-resolution/main.js

@@ -0,0 +1 @@
+// A .js file with the same name as the intended .scss file to be imported.

test/import-resolution/main.scss

@@ -0,0 +1,3 @@
+.importable {
+  color: red;
+}

test/import-resolution/rollup.config.js

@@ -0,0 +1,10 @@
+import scss from '../../index.es.js'
+
+export default {
+  input: './input.js',
+  output: {
+    file: 'output.js',
+    format: 'esm'
+  },
+  plugins: [scss({ fileName: 'output.css' })]
+}

test/import-resolution/setup.js

@@ -0,0 +1,39 @@
+const fs = require('node:fs');
+const path = require('node:path');
+
+const NODE_MODULES_MOCK_PACKAGE_PATH = path.join(__dirname, '../../node_modules/import-resolution-test');
+const CURRENT_DIRECTORY_PATH = path.join(__dirname, '.');
+
+const IMPORTABLE_FILE_NAME = 'main';
+const IMPORTABLE_JS_FILE_NAME = `${IMPORTABLE_FILE_NAME}.js`;
+const IMPORTABLE_SCSS_FILE_NAME = `${IMPORTABLE_FILE_NAME}.scss`;
+
+/* If one does not already exist,
+ * create a path to the node_modules mock package. */
+if (!fs.existsSync(NODE_MODULES_MOCK_PACKAGE_PATH)) {
+  fs.mkdirSync(NODE_MODULES_MOCK_PACKAGE_PATH);
+}
+
+/* Copy the specified file with the .js extension
+ * to the node_modules mock package. */
+fs.copyFile(
+  `${CURRENT_DIRECTORY_PATH}/${IMPORTABLE_JS_FILE_NAME}`,
+  `${NODE_MODULES_MOCK_PACKAGE_PATH}/${IMPORTABLE_JS_FILE_NAME}`,
+  error => {
+    if (error) {
+      console.log(error);
+    }
+  }
+)
+
+/* Copy the specified file with the .scss extension
+ * to the node_modules mock package. */
+fs.copyFile(
+  `${CURRENT_DIRECTORY_PATH}/${IMPORTABLE_SCSS_FILE_NAME}`,
+  `${NODE_MODULES_MOCK_PACKAGE_PATH}/${IMPORTABLE_SCSS_FILE_NAME}`,
+  error => {
+    if (error) {
+      console.log(error);
+    }
+  }
+)

test/import-resolution/teardown.js

@@ -0,0 +1,16 @@
+const fs = require('node:fs');
+const path = require('node:path');
+
+const NODE_MODULES_MOCK_PACKAGE_PATH = path.join(__dirname, '../../node_modules/import-resolution-test');
+
+/* Now that it has served its purpose,
+ * remove the node_modules mock package. */
+fs.rm(
+  NODE_MODULES_MOCK_PACKAGE_PATH,
+  { recursive: true, force: true },
+  error => {
+    if (error) {
+      throw error;
+    }
+  }
+);