feat(styling): Allow loading .css files as a fallback if no .scss file is found(#954)

Author: vakrilov

Diff for: nativescript-angular/resource-loader.ts

@@ -1,25 +1,51 @@
-import { path, knownFolders, File } from "tns-core-modules/file-system";
 import { ResourceLoader } from "@angular/compiler";
+import { File, knownFolders, path } from "tns-core-modules/file-system";
+
+const extensionsFallbacks = [
+    [".scss", ".css"],
+    [".sass", ".css"],
+    [".less", ".css"]
+];
 
 export class FileSystemResourceLoader extends ResourceLoader {
-    resolve(url: string, baseUrl: string): string {
-        // Angular assembles absolute URL's and prefixes them with //
+    get(url: string): Promise<string> {
+        const resolvedPath = this.resolve(url);
+
+        const templateFile = File.fromPath(resolvedPath);
+
+        return templateFile.readText();
+    }
+
+    private handleAbsoluteUrls(url: string): string {
+        // Angular assembles absolute URLs and prefixes them with //
         if (url.indexOf("/") !== 0) {
-            // Resolve relative URL's based on the app root.
-            return path.join(baseUrl, url);
+            // Resolve relative URLs based on the app root.
+            return path.join(knownFolders.currentApp().path, url);
         } else {
             return url;
         }
     }
 
-    get(url: string): Promise<string> {
-        const appDir = knownFolders.currentApp().path;
-        const templatePath = this.resolve(url, appDir);
+    private resolve(url: string) {
+        const normalizedUrl = this.handleAbsoluteUrls(url);
 
-        if (!File.exists(templatePath)) {
-            throw new Error(`File ${templatePath} does not exist. Resolved from: ${url}.`);
+        if (File.exists(normalizedUrl)) {
+            return normalizedUrl;
         }
-        let templateFile = File.fromPath(templatePath);
-        return templateFile.readText();
+
+        const fallbackCandidates = [];
+        extensionsFallbacks.forEach(([extension, fallback]) => {
+            if (normalizedUrl.endsWith(extension)) {
+                fallbackCandidates.push(normalizedUrl.substr(0, normalizedUrl.length - extension.length) + fallback);
+            }
+        });
+
+        for (let i = 0; i < fallbackCandidates.length; i++) {
+            if (File.exists(fallbackCandidates[i])) {
+                return fallbackCandidates[i];
+            }
+        }
+
+        throw new Error(`Could not resolve ${url}. Looked for: ${normalizedUrl}, ${fallbackCandidates}`);
     }
 }