fix(cli): implement missing response override referrer behavior (#543)

The documentation calls out user-defined redirect behavior using the
.referrer parameter in the response override configuration. This PR
enables the SWA CLI emulator to support that functionality.

Fixes #542

Author: thsackos

src/msha/routes-engine/rules/response-overrides.spec.ts

@@ -56,6 +56,32 @@ describe("responseOverrides()", () => {
     expect(req.url).toBe(`${CUSTOM_URL_SCHEME}foo`);
   });
 
+  it("should override redirect rule with .referrer replacement and query string", () => {
+    req.url = "/foo";
+    res.statusCode = 404;
+    userConfig = {
+      "404": {
+        redirect: "/.auth/login/aad/post_login_redirect_uri=.referrer",
+      },
+    };
+    responseOverrides(req, res, userConfig);
+
+    expect(res.setHeader).toHaveBeenCalledWith("Location", "/.auth/login/aad/post_login_redirect_uri=%2Ffoo");
+  });
+
+  it("should override redirect rule with .referrer replacement", () => {
+    req.url = "/foo?with=query&params=1-1";
+    res.statusCode = 404;
+    userConfig = {
+      "404": {
+        redirect: "/.auth/login/aad/post_login_redirect_uri=.referrer",
+      },
+    };
+    responseOverrides(req, res, userConfig);
+
+    expect(res.setHeader).toHaveBeenCalledWith("Location", "/.auth/login/aad/post_login_redirect_uri=%2Ffoo%3Fwith%3Dquery%26params%3D1-1");
+  });
+
   it("should override redirect rule", () => {
     res.statusCode = 404;
     userConfig = {

src/msha/routes-engine/rules/response-overrides.ts

@@ -27,7 +27,16 @@ export function responseOverrides(req: http.IncomingMessage, res: http.ServerRes
       if (rule.redirect) {
         const statusCodeToServe = parseInt(`${rule?.statusCode}`, 10) === 301 ? 301 : 302;
         res.statusCode = statusCodeToServe;
-        res.setHeader("Location", rule.redirect);
+
+        if (rule.redirect.indexOf(".referrer") !== -1) {
+          // The Production SWA service supports replacing `.referrer` with the current route, so that the user can redirected to a deep link after the authentication flow.
+          // Since the route can contain a path with a query we will want to encode it and the `auth.html` page will need to decode it before changing the page.
+          const redirectWithReferrerReplaced = rule.redirect.replace(".referrer", encodeURIComponent(req.url || ""));
+          res.setHeader("Location", redirectWithReferrerReplaced);
+        } else {
+          // No `.referrer` param is used, just use user-provided rule redirect as-is
+          res.setHeader("Location", rule.redirect);
+        }
 
         logger.silly(` - redirect: ${chalk.yellow(rule.redirect)}`);
       }

src/public/auth.html

@@ -202,7 +202,8 @@ <h1 class="pb-4">Azure Static Web Apps Auth</h1>
           const urlSearch = (metaSearch || location.search).replace("?", "");
           const urlQuery = urlSearch && Object.fromEntries(new Map(urlSearch.split("&").map((query) => query.split("="))));
           const postLoginRedirectUri = urlQuery ? urlQuery["post_login_redirect_uri"] : redirectPath;
-          window.location.href = postLoginRedirectUri || defaultRedirectPath;
+
+          window.location.href = decodeURIComponent(postLoginRedirectUri) || defaultRedirectPath;
         } catch (error) {
           console.warn(error);
           window.location.href = defaultRedirectPath;