refactor: resource loader (#968)

* chore(lint): use 4 spaces instead of 2 in ns-file-system

* refactor: resource loader

* test(xhr-paths): assert resource loader throws when resolving non-existing files

Author: sis0k0

Diff for: nativescript-angular/file-system/ns-file-system.ts

@@ -6,15 +6,15 @@ import { knownFolders, Folder, File } from "tns-core-modules/file-system";
 
 @Injectable()
 export class NSFileSystem {
-  public currentApp(): Folder {
-    return knownFolders.currentApp();
-  }
+    public currentApp(): Folder {
+        return knownFolders.currentApp();
+    }
 
-  public fileFromPath(path: string): File {
-    return File.fromPath(path);
-  }
+    public fileFromPath(path: string): File {
+        return File.fromPath(path);
+    }
 
-  public fileExists(path: string): boolean {
-    return File.exists(path);
-  }
+    public fileExists(path: string): boolean {
+        return File.exists(path);
+    }
 }

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

@@ -24,7 +24,24 @@ export class FileSystemResourceLoader extends ResourceLoader {
         return templateFile.readText();
     }
 
-    resolveRelativeUrls(url: string): string {
+    resolve(url: string): string {
+        const normalizedUrl = this.resolveRelativeUrls(url);
+
+        if (this.fs.fileExists(normalizedUrl)) {
+            return normalizedUrl;
+        }
+
+        const { candidates: fallbackCandidates, resource: fallbackResource } =
+            this.fallbackResolve(normalizedUrl);
+
+        if (fallbackResource) {
+            return fallbackResource;
+        }
+
+        throw new Error(`Could not resolve ${url}. Looked for: ${normalizedUrl}, ${fallbackCandidates}`);
+    }
+
+    private resolveRelativeUrls(url: string): string {
         // Angular assembles absolute URLs and prefixes them with //
         if (url.indexOf("/") !== 0) {
             // Resolve relative URLs based on the app root.
@@ -34,26 +51,22 @@ export class FileSystemResourceLoader extends ResourceLoader {
         }
     }
 
-    resolve(url: string) {
-        const normalizedUrl = this.resolveRelativeUrls(url);
+    private fallbackResolve(url: string):
+        ({ resource: string, candidates: string[] }) {
 
-        if (this.fs.fileExists(normalizedUrl)) {
-            return normalizedUrl;
-        }
+        const candidates = extensionsFallbacks
+            .filter(([extension]) => url.endsWith(extension))
+            .map(([extension, fallback]) =>
+                 this.replaceExtension(url, extension, fallback));
 
-        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 (this.fs.fileExists(fallbackCandidates[i])) {
-                return fallbackCandidates[i];
-            }
-        }
+        const resource = candidates.find(candidate => this.fs.fileExists(candidate));
 
-        throw new Error(`Could not resolve ${url}. Looked for: ${normalizedUrl}, ${fallbackCandidates}`);
+        return { candidates, resource };
+    }
+
+    private replaceExtension(fileName: string, oldExtension: string, newExtension: string): string {
+        const baseName = fileName.substr(0, fileName.length - oldExtension.length);
+        return baseName + newExtension;
     }
 }
+

Diff for: tests/app/tests/xhr-paths.ts

@@ -15,7 +15,7 @@ class NSFileSystemMock {
     }
 
     public fileExists(path: string): boolean {
-        // mycomponent.html aways exists
+        // mycomponent.html always exists
         // mycomponent.css is the other file
         return path.indexOf("mycomponent.html") >= 0 || path === "/app/dir/mycomponent.css";
     }
@@ -65,4 +65,8 @@ describe("XHR name resolution", () => {
             "/app/dir/mycomponent.css",
             resourceLoader.resolve("mycomponent.less"));
     });
+
+    it("throws for non-existing file that has no fallbacks", () => {
+        assert.throws(() => resourceLoader.resolve("does-not-exist.css"));
+    });
 });