From 8db60c0c359ccaa77b5b13f23b0dbf15aff0de9a Mon Sep 17 00:00:00 2001
From: Martin Atkins <mart@degeneration.co.uk>
Date: Tue, 18 Sep 2018 13:53:25 -0700
Subject: [PATCH] core: testDiffFn must properly populate "Old" in computed
 attr diff

When applying a diff to a value we verify that the "old" value in diff is
consistent with the given prior value, as a safety check.

The mock must comply with this or else any tests that produce diffs with
computed new values will not pass the safety check.

This change is verified by the now-passing TestContext2Apply_taintDep .
---
 terraform/context_test.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/terraform/context_test.go b/terraform/context_test.go
index a81f8ff2a..32b2e5068 100644
--- a/terraform/context_test.go
+++ b/terraform/context_test.go
@@ -296,8 +296,12 @@ func testDiffFn(
 		if k == "id" {
 			continue
 		}
+		old := ""
+		if s != nil {
+			old = s.Attributes[k]
+		}
 		diff.Attributes[k] = &ResourceAttrDiff{
-			Old:         "",
+			Old:         old,
 			NewComputed: true,
 		}
 	}