[labs/ssr-client] Provide better error message on hydration value mis…

…match (#4481)
lit · Jan 9, 2024 · 1a1f3f0 · 1a1f3f0
1 parent fa73bbb
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diff --git a/.changeset/few-garlics-dress.md b/.changeset/few-garlics-dress.md
@@ -0,0 +1,5 @@
+---
+'@lit-labs/ssr-client': patch
+---
+
+Provide better error message in `createAttributeParts()` when an error occurs due to hydration value mismatch.
diff --git a/packages/labs/ssr-client/src/lib/hydrate-lit-html.ts b/packages/labs/ssr-client/src/lib/hydrate-lit-html.ts
@@ -437,7 +437,13 @@ const createAttributeParts = (
       state.templatePartIndex++;
     }
   } else {
-    throw new Error('internal error');
+    // TODO(augustjk): This message may need to be updated based on
+    // hydration strategy. See https://github.com/lit/lit/issues/1434
+    throw new Error(
+      `Hydration value mismatch: Primitive found where TemplateResult expected.` +
+        ` This usually occurs due to conditional rendering that resulted in a ` +
+        `different value or template being rendered between the server and client.`
+    );
   }
 };