From 4e0879c4863c0319ac388dc09c344701818a50df Mon Sep 17 00:00:00 2001
From: Pam Selle <204372+pselle@users.noreply.github.com>
Date: Thu, 30 Jan 2020 17:18:16 -0500
Subject: [PATCH] Document for_each key requirements

---
 website/docs/configuration/resources.html.md | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/website/docs/configuration/resources.html.md b/website/docs/configuration/resources.html.md
index b6d208a960..e8c22fde8b 100644
--- a/website/docs/configuration/resources.html.md
+++ b/website/docs/configuration/resources.html.md
@@ -340,6 +340,12 @@ infrastructure object associated with it (as described above in
 [Resource Behavior](#resource-behavior)), and each is separately created,
 updated, or destroyed when the configuration is applied.
 
+-> **Note:** The keys of the map (or all the values in the case of a set of strings) must
+be _known values_, or you will get an error message that `for_each` has dependencies
+that cannot be determined before apply, and a `-target` may be needed. `for_each` keys
+cannot be the result (or rely on the result of) of impure functions, including `uuid`, `bcrypt`,
+or `timestamp`, as their evaluation is deferred resource during evaluation.
+
 ```hcl
 resource "azurerm_resource_group" "rg" {
   for_each = {