Pass sass options to plugin

plugins/plugin-sass/README.md

@@ -30,6 +30,23 @@ module.exports = {
 
 ## Plugin Options
 
-| Name     |   Type    | Description                                                                                                                                                                                                                                                                            |
-| :------- | :-------: | :------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
-| `native` | `boolean` | If true, the plugin will ignore the npm version of sass installed locally for the native Sass CLI [installed separately](https://sass-lang.com/install). This involves extra set up, but the result can be [up to 9x faster.](https://stackoverflow.com/a/56422541) Defaults to false. |
+| Name                |   Type    | Description                                                                                                                                                                                                                                                                              |
+| :------------------ | :-------: | :--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `native`            | `boolean` | If `true`, the plugin will ignore the npm version of sass installed locally for the native Sass CLI [installed separately](https://sass-lang.com/install). This involves extra setup, but the result can be [up to 9× faster.](https://stackoverflow.com/a/56422541) (default: `false`). |
+| `compilerOptions.*` | `object`  | Pass [Sass options][sass-options] directly to the Sass compiler (see `compilerOptions`).                                                                                                                                                                                                 |
+
+### `compilerOptions`
+
+These options are camelCased equivalents of the [Sass CLI Options][sass-options]. The options listed here are safe for use. The other flags not listed here may cause issues or conflicts with Snowpack and/or other plugins; use at your discretion.
+
+| Name             |              Type              | Description                                                                                             |
+| :--------------- | :----------------------------: | :------------------------------------------------------------------------------------------------------ |
+| `style`          | `'expanded'` \| `'compressed'` | The output style. Specify `'compressed'` to enable Sass’ built-in minification (default: `'expanded'`). |
+| `sourceMap`      |           `boolean`            | Enable / disable source maps (default: `true`).                                                         |
+| `sourceMapUrls`  |  `'relative'` \| `'absolute'`  | How to link from source maps to source files (default: `'relative'`).                                   |
+| `embedSources`   |           `boolean`            | Embed source file contents in source maps (default: `false`).                                           |
+| `embedSourceMap` |           `boolean`            | Embed source map contents in CSS (default: `false`).                                                    |
+| `charset`        |           `boolean`            | Emit a `@charset` or BOM for CSS with non-ASCII characters. (default: `true`).                          |
+| `update`         |           `boolean`            | Only compile out-of-date stylesheets (default: `false`).                                                |
+
+[sass-options]: https://sass-lang.com/documentation/cli/dart-sass#options

plugins/plugin-sass/plugin.js

@@ -27,7 +27,7 @@ function scanSassImports(fileContents, filePath, fileExt) {
     });
 }
 
-module.exports = function postcssPlugin(_, {native}) {
+module.exports = function sassPlugin(_, {native, compilerOptions = {}} = {}) {
   /** A map of partially resolved imports to the files that imported them. */
   const importedByMap = new Map();
 
@@ -89,11 +89,29 @@ module.exports = function postcssPlugin(_, {native}) {
         const sassImports = scanSassImports(contents, filePath, fileExt);
         sassImports.forEach((imp) => addImportsToMap(filePath, imp));
       }
+
       // If file is `.sass`, use YAML-style. Otherwise, use default.
       const args = ['--stdin', '--load-path', path.dirname(filePath)];
       if (fileExt === '.sass') {
         args.push('--indented');
       }
+
+      // Pass in user-defined options
+      Object.entries(compilerOptions).forEach(([flag, value]) => {
+        let flagName = flag.replace(/[A-Z]/g, (c) => `-${c.toLowerCase()}`); // convert camelCase to kebab-case
+        switch (typeof value) {
+          case 'boolean': {
+            args.push(`--${value === false ? 'no-' : ''}${flagName}`);
+            break;
+          }
+          case 'string':
+          case 'number': {
+            args.push(`--${flagName}=${value}`);
+            break;
+          }
+        }
+      });
+
       // Build the file.
       const {stdout, stderr} = await execa('sass', args, {
         input: contents,

plugins/plugin-sass/test/plugin-mocked.test.js

@@ -0,0 +1,47 @@
+/**
+ * This test requires mocks which could disrupt other tests
+ */
+const path = require('path');
+const mockExeca = jest.fn().mockImplementation(() => Promise.resolve({stdout: '', stderr: ''}));
+jest.mock('execa', () => (cmd, args) => mockExeca(cmd, args));
+const plugin = require('../plugin');
+
+const MOCK_CONFIG = null;
+const MOCK_LOAD = {filePath: path.join(__dirname, 'fixtures', 'scss', 'App.scss'), isDev: false};
+
+const tests = [
+  {name: 'no options', given: {}, expect: []},
+  {
+    name: 'string option',
+    given: {compilerOptions: {style: 'compressed'}},
+    expect: [`--style=compressed`],
+  },
+  {
+    name: 'boolean option',
+    given: {compilerOptions: {sourceMaps: false}},
+    expect: [`--no-source-maps`],
+  },
+  {
+    name: 'combination',
+    given: {compilerOptions: {style: 'compressed', sourceMaps: true}},
+    expect: [`--style=compressed`, `--source-maps`],
+  },
+];
+
+describe('plugin-sass', () => {
+  afterEach(() => {
+    mockExeca.mockClear(); // clear calls between each test
+  });
+
+  tests.forEach((t) => {
+    it(t.name, async () => {
+      const {load} = plugin(MOCK_CONFIG, t.given);
+      await load(MOCK_LOAD);
+      // Note: this test assumes execa is only used once in the entire plugin.
+      // If execa needs to be used for another purpose, you can filter calls by 'sass' 1st param here
+      t.expect.forEach((arg) => {
+        expect(mockExeca.mock.calls[0][1]).toContain(arg);
+      });
+    });
+  });
+});