chore(svelte): prepare v0 docs hostname routing

packages/stacks-svelte/netlify.toml

@@ -17,3 +17,19 @@
   to = "https://svelte.stackoverflow.design/:splat"
   status = 301
   force = true
+
+# Add v0 as a production domain alias only after these rules are deployed.
+# Upgrade explicitly: Netlify's automatic HTTPS redirect may not apply to proxies.
+[[redirects]]
+  from = "http://v0.svelte.stackoverflow.design/*"
+  to = "https://v0.svelte.stackoverflow.design/:splat"
+  status = 301
+  force = true
+
+# Keep the v2 branch deploy enabled: it remains the legacy content source.
+# Use its Netlify hostname, not a custom domain that may redirect back to v0.
+[[redirects]]
+  from = "https://v0.svelte.stackoverflow.design/*"
+  to = "https://v2--stacks-svelte.netlify.app/:splat"
+  status = 200
+  force = true

packages/stacks-svelte/tools/netlify-config.test.js

@@ -9,12 +9,54 @@ const netlifyConfig = readFileSync(
     join(toolsDirectory, "..", "netlify.toml"),
     "utf8"
 );
+const redirects = netlifyConfig
+    .split(/^\s*\[\[redirects\]\]\s*$/m)
+    .slice(1)
+    .map((block) => block.split("\n").map((line) => line.trim()));
+
+const expectedRules = [
+    {
+        name: "redirects the beta hostname to the current documentation",
+        from: "https://beta.svelte.stackoverflow.design/*",
+        to: "https://svelte.stackoverflow.design/:splat",
+        status: 301,
+    },
+    {
+        name: "upgrades the v0 hostname to HTTPS before proxying",
+        from: "http://v0.svelte.stackoverflow.design/*",
+        to: "https://v0.svelte.stackoverflow.design/:splat",
+        status: 301,
+    },
+    {
+        name: "serves the existing v2 branch deploy behind the HTTPS v0 hostname",
+        from: "https://v0.svelte.stackoverflow.design/*",
+        to: "https://v2--stacks-svelte.netlify.app/:splat",
+        status: 200,
+    },
+];
 
 describe("Netlify configuration", () => {
-    test("redirects the beta hostname to the current documentation", () => {
-        assert.match(
-            netlifyConfig,
-            /\[\[redirects\]\][\s\S]*from = "https:\/\/beta\.svelte\.stackoverflow\.design\/\*"[\s\S]*to = "https:\/\/svelte\.stackoverflow\.design\/:splat"[\s\S]*status = 301[\s\S]*force = true/
+    test("limits routing rules to the beta and v0 hostnames", () => {
+        assert.deepStrictEqual(
+            redirects.map((rule) =>
+                rule.find((line) => line.startsWith("from = "))
+            ),
+            expectedRules.map(({ from }) => `from = "${from}"`)
         );
     });
+
+    for (const { name, from, to, status } of expectedRules) {
+        test(name, () => {
+            const rule = redirects.find((lines) =>
+                lines.includes(`from = "${from}"`)
+            );
+
+            assert.ok(rule, `Missing routing rule for ${from}`);
+            // Check each block independently so another rule cannot satisfy it.
+            // No target query string means Netlify passes query parameters through.
+            assert.ok(rule.includes(`to = "${to}"`));
+            assert.ok(rule.includes(`status = ${status}`));
+            assert.ok(rule.includes("force = true"));
+        });
+    }
 });