#98 - Updated plugins 'custom' sass file importer to enforce load order.

- Updated 'SassImporterResult' type to match Sass's 'LegacyImporterResult' - We had defined our type because the version of sass the library using, and sass versions users might be using, did not/may not contain this type (so basically our type was that type but slightly imprecise (we had both 'file?:...', and 'content?:...'  as part of the same interface, but actually they need to be separate ones (:-))).

dist/types.d.ts

@@ -16,10 +16,11 @@ export interface RollupPluginSassOptions {
     output?: boolean | string | RollupPluginSassOutputFn;
     runtime?: any;
 }
-export declare type SassImporterResult = null | {
-    file?: string;
-    contents?: string;
-} | Error;
+export declare type SassImporterResult = {
+    file: string;
+} | {
+    contents: string;
+} | Error | null;
 export declare type SassDoneFn<T extends SassImporterResult = SassImporterResult> = (result: T) => void | T;
 export declare type SassImporter<T extends SassImporterResult = SassImporterResult> = (url: string, prev: string, done: SassDoneFn<T>) => void | T;
 export interface SassFunctionsObject {

package.json

@@ -1,6 +1,6 @@
 {
   "name": "rollup-plugin-sass",
-  "version": "1.2.13",
+  "version": "1.2.13-alpha.1",
   "description": "Rollup Sass files.",
   "main": "dist/index.js",
   "typings": "dist/index.d.ts",

src/index.ts

@@ -6,6 +6,7 @@ import * as fs from 'fs';
 import {createFilter} from '@rollup/pluginutils';
 import {insertStyle} from './style';
 import {
+  SassImporterResult,
   RollupAssetInfo,
   RollupChunkInfo,
   RollupPluginSassOptions,
@@ -29,33 +30,42 @@ const MATCH_SASS_FILENAME_RE = /\.sass$/,
    * @see https://sass-lang.com/documentation/js-api#importer
    */
   getImporterList = (sassOptions: SassOptions) => {
-    const importer1 = (url, importer, done) => {
+    // `Promise` to chain all `importer1` calls to;  E.g.,  subsequent `importer1` calls won't call `done` until previous `importer1` calls have called `done` (import order enforcement) - Required since importer below is actually 'async'.
+    let lastResult = Promise.resolve();
+
+    /**
+     * Legacy Sass (*.scss/*.sass) file importer (works in new, and older, versions of `sass` module).
+     * @see https://sass-lang.com/documentation/js-api/modules#LegacyAsyncImporter
+     * @param {string} url - Url found in `@import`/`@use`, found in parent sass file, exactly as it appears in sass file.
+     * @param {string} prevUrl - Url of file that contains '@import' rule for `url`.
+     * @param {(result: LegacyImporterResult | SassImporterResult) => void} done - Signals import completion.  Note: `LegacyImporterResult`, and `SassImporterResult`, are the same here - We've defined the type for out plugin, since older versions of sass don't have the type defined amongst their types.
+     * @returns {void}
+     */
+    const importer1 = (url: string, prevUrl: string, done: (rslt: SassImporterResult) => void): void => {
       if (!MATCH_NODE_MODULE_RE.test(url)) {
         return null;
       }
 
       const moduleUrl = url.slice(1);
       const resolveOptions = {
-        basedir: dirname(importer),
+        basedir: dirname(prevUrl),
         extensions: ['.scss', '.sass'],
       };
 
-      let file: string;
-
       try {
-        file = resolve.sync(moduleUrl, resolveOptions);
-        done({file});
+        const file = resolve.sync(moduleUrl, resolveOptions);
+        lastResult = lastResult.then(() => done({file}));
       } catch (err) {
         warn('[rollup-plugin-sass]: Recovered from error: ', err);
         // If importer has sibling importers then exit and allow one of the other
         //  importers to attempt file path resolution.
         if (sassOptions.importer && sassOptions.importer.length > 1) {
-          done(null);
+          lastResult = lastResult.then(() => done(null));
           return;
         }
-        done({
+        lastResult = lastResult.then(() => done({
           file: url,
-        });
+        }));
       }
     }
     return [importer1].concat(sassOptions.importer || [])

src/types.ts

@@ -53,10 +53,7 @@ export interface RollupPluginSassOptions {
   runtime?: any,
 }
 
-export type SassImporterResult = null | {
-  file?: string,
-  contents?: string
-} | Error;
+export type SassImporterResult = { file: string } | { contents: string } | Error | null;
 
 export type SassDoneFn<T extends SassImporterResult = SassImporterResult> =
   (result: T) => void | T;