From e59eb00ce1f671e1137c44f21eecc973e9b6a9d0 Mon Sep 17 00:00:00 2001
From: Violet Hynes <violet.hynes@hashicorp.com>
Date: Thu, 10 Jul 2025 17:19:01 -0400
Subject: [PATCH] Fix issue with merging observations config (#31248)

---
 command/server/config.go      |  4 ++--
 command/server/config_test.go | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/command/server/config.go b/command/server/config.go
index eff210ab30..12f09df0dd 100644
--- a/command/server/config.go
+++ b/command/server/config.go
@@ -447,8 +447,8 @@ func (c *Config) Merge(c2 *Config) *Config {
 		if c2.Observations.LedgerPath != "" {
 			result.Observations.LedgerPath = c2.Observations.LedgerPath
 		}
-		result.Observations.TypePrefixDenylist = append(c.Observations.TypePrefixDenylist, c2.Observations.TypePrefixDenylist...)
-		result.Observations.TypePrefixAllowlist = append(c.Observations.TypePrefixAllowlist, c2.Observations.TypePrefixAllowlist...)
+		result.Observations.TypePrefixDenylist = append(result.Observations.TypePrefixDenylist, c2.Observations.TypePrefixDenylist...)
+		result.Observations.TypePrefixAllowlist = append(result.Observations.TypePrefixAllowlist, c2.Observations.TypePrefixAllowlist...)
 		if c2.Observations.FileMode != "" {
 			result.Observations.FileMode = c2.Observations.FileMode
 		}
diff --git a/command/server/config_test.go b/command/server/config_test.go
index a3d7205b31..7f12def700 100644
--- a/command/server/config_test.go
+++ b/command/server/config_test.go
@@ -139,6 +139,27 @@ func Test_ObservationSystemConfigMerge(t *testing.T) {
 	require.Equal(t, "0777", merged.Observations.FileMode)
 }
 
+// Test_ObservationSystemConfigMergeFromNoObservations checks merge for observation system config from a config
+// without an observation system defined
+func Test_ObservationSystemConfigMergeFromNoObservations(t *testing.T) {
+	config, err := LoadConfigFile("./test-fixtures/config.hcl")
+	require.NoError(t, err)
+	require.NotNil(t, config)
+
+	config2, err := LoadConfigFile("./test-fixtures/observations_allow_deny.hcl")
+	require.NoError(t, err)
+	require.NotNil(t, config2)
+
+	merged := config.Merge(config2)
+	require.NotNil(t, merged)
+	require.NotNil(t, merged.Observations)
+	require.Equal(t, "/var/ledger.log", merged.Observations.LedgerPath)
+	require.Equal(t, []string{"deny1", "deny2"}, merged.Observations.TypePrefixDenylist)
+	require.Equal(t, []string{"allow1", "allow2", "allow3"}, merged.Observations.TypePrefixAllowlist)
+	require.Equal(t, "0777", merged.Observations.FileMode)
+	require.Equal(t, true, merged.EnableUI)
+}
+
 // TestDuplicateKeyValidationHcl checks that the server command displays a warning when the HCL config file contains duplicate keys.
 func TestDuplicateKeyValidationHcl(t *testing.T) {
 	testDuplicateKeyValidationHcl(t)