From ee49be73be94d947bd75d668080111c8cdbabec1 Mon Sep 17 00:00:00 2001
From: Martin Atkins <mart@degeneration.co.uk>
Date: Thu, 6 Sep 2018 16:53:46 -0700
Subject: [PATCH] core: Don't panic if ApplyResourceChange returns invalid new
 value

The provider is allowed to return a partial result if it also includes
error diagnostics. Real providers still return at least a null value in
that case due to the RPC format, but test mocks are often more sloppy.
---
 terraform/eval_apply.go | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/terraform/eval_apply.go b/terraform/eval_apply.go
index 02cff0d5c..16369745e 100644
--- a/terraform/eval_apply.go
+++ b/terraform/eval_apply.go
@@ -76,6 +76,13 @@ func (n *EvalApply) Eval(ctx EvalContext) (interface{}, error) {
 	// incomplete.
 	newVal := resp.NewState
 
+	// newVal should never be cty.NilVal in a real case, but it can happen
+	// sometimes in sloppy mocks in tests where error diagnostics are returned
+	// and the mock implementation doesn't populate the value at all.
+	if newVal == cty.NilVal {
+		newVal = cty.NullVal(schema.ImpliedType())
+	}
+
 	for _, err := range newVal.Type().TestConformance(schema.ImpliedType()) {
 		diags = diags.Append(tfdiags.Sourceless(
 			tfdiags.Error,