From b1cf815e3590696b29bb383a747355b481b1cc94 Mon Sep 17 00:00:00 2001
From: Dobes Vandermeer <dobesv@gmail.com>
Date: Mon, 20 May 2019 13:53:55 -0700
Subject: [PATCH] Clarify that the result of `readQuery` should not be modified
 (#4815)

The `readQuery` call may return an object that is shared with the current contents of cache, which can cause some weird behavior if you mutate the `readQuery` result.

See also:
https://github.com/apollographql/apollo-client/pull/4514
https://github.com/apollographql/apollo-client/pull/4543
---
 docs/source/advanced/caching.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/docs/source/advanced/caching.md b/docs/source/advanced/caching.md
index 09ea8a9aca5..e00f9299c8b 100644
--- a/docs/source/advanced/caching.md
+++ b/docs/source/advanced/caching.md
@@ -147,6 +147,8 @@ const { todo } = client.readQuery({
 });
 ```
 
+Note that you should not modify the return value of `readQuery` because the same object may be reused between components.  If you want to update the data in the cache, create a new replacement object and pass it to `writeQuery`.
+
 <h3 id="readfragment">readFragment</h3>
 
 This method allows you great flexibility around the data in your cache. Whereas `readQuery` only allowed you to read data from your root query type, `readFragment` allows you to read data from _any node you have queried_. This is incredibly powerful. You use this method as follows: