From f4998bcecf656f482a6003e016ff595f0c8b859c Mon Sep 17 00:00:00 2001
From: Brian Brazil <brian.brazil@robustperception.io>
Date: Tue, 25 Sep 2018 14:42:09 +0100
Subject: [PATCH] Allow keeping of old labels from lookups.

Signed-off-by: Brian Brazil <brian.brazil@robustperception.io>
---
 generator/README.md    |  3 ++-
 generator/config.go    |  1 +
 generator/tree.go      |  6 ++++--
 generator/tree_test.go | 48 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 55 insertions(+), 3 deletions(-)

diff --git a/generator/README.md b/generator/README.md
index c37ae581..2394af6d 100644
--- a/generator/README.md
+++ b/generator/README.md
@@ -82,7 +82,7 @@ modules:
                             # Required if context is configured on the device.
 
     lookups:  # Optional list of lookups to perform.
-              # This must only be used when the new index is unique.
+              # If keep_old is the default of false, this must only be used when the new index is unique.
 
       # If the index of a table is bsnDot11EssIndex, usually that'd be the label
       # on the resulting metrics from that table. Instead, use the index to
@@ -90,6 +90,7 @@ modules:
       # with that value.
       - old_indexes: [bsnDot11EssIndex]
         new_index: bsnDot11EssSsid
+        keep_old: false  # If true, don't delete old index label for this lookup.
 
      overrides: # Allows for per-module overrides of bits of MIBs
        metricName:
diff --git a/generator/config.go b/generator/config.go
index 109a7415..d0dabb14 100644
--- a/generator/config.go
+++ b/generator/config.go
@@ -55,4 +55,5 @@ type ModuleConfig struct {
 type Lookup struct {
 	OldIndexes []string `yaml:"old_indexes"`
 	NewIndex   string   `yaml:"new_index"`
+	KeepOld    bool     `yaml:"keep_old,omitempty"`
 }
diff --git a/generator/tree.go b/generator/tree.go
index 8a968be9..31a23b84 100644
--- a/generator/tree.go
+++ b/generator/tree.go
@@ -407,8 +407,10 @@ func generateConfigModule(cfg *ModuleConfig, node *Node, nameToNode map[string]*
 				} else {
 					needToWalk[indexNode.Oid] = struct{}{}
 				}
-				// Avoid leaving the old labelname around.
-				toDelete = append(toDelete, lookup.OldIndexes...)
+				if !lookup.KeepOld {
+					// Avoid leaving the old labelname around.
+					toDelete = append(toDelete, lookup.OldIndexes...)
+				}
 			}
 		}
 		for _, l := range toDelete {
diff --git a/generator/tree_test.go b/generator/tree_test.go
index a91a9e6e..8f6e5ab3 100644
--- a/generator/tree_test.go
+++ b/generator/tree_test.go
@@ -940,6 +940,54 @@ func TestGenerateConfigModule(t *testing.T) {
 				},
 			},
 		},
+		// One table lookup, lookup not walked, labels kept.
+		{
+			node: &Node{Oid: "1", Label: "root",
+				Children: []*Node{
+					{Oid: "1.1", Label: "octet",
+						Children: []*Node{
+							{Oid: "1.1.1", Label: "octetEntry", Indexes: []string{"octetIndex"},
+								Children: []*Node{
+									{Oid: "1.1.1.1", Access: "ACCESS_READONLY", Label: "octetIndex", Type: "INTEGER"},
+									{Oid: "1.1.1.2", Access: "ACCESS_READONLY", Label: "octetDesc", Type: "OCTETSTR"},
+									{Oid: "1.1.1.3", Access: "ACCESS_READONLY", Label: "octetFoo", Type: "INTEGER"}}}}}}},
+			cfg: &ModuleConfig{
+				Walk: []string{"octetFoo"},
+				Lookups: []*Lookup{
+					{
+						OldIndexes: []string{"octetIndex"},
+						NewIndex:   "octetDesc",
+						KeepOld:    true,
+					},
+				},
+			},
+			out: &config.Module{
+				// Walk is expanded to include the lookup OID.
+				Walk: []string{"1.1.1.2", "1.1.1.3"},
+				Metrics: []*config.Metric{
+					{
+						Name: "octetFoo",
+						Oid:  "1.1.1.3",
+						Help: " - 1.1.1.3",
+						Type: "gauge",
+						Indexes: []*config.Index{
+							{
+								Labelname: "octetIndex",
+								Type:      "gauge",
+							},
+						},
+						Lookups: []*config.Lookup{
+							{
+								Labels:    []string{"octetIndex"},
+								Labelname: "octetDesc",
+								Type:      "OctetString",
+								Oid:       "1.1.1.2",
+							},
+						},
+					},
+				},
+			},
+		},
 		// One table lookup, lookup not walked.
 		{
 			node: &Node{Oid: "1", Label: "root",