From 6c2157ac35440bf78f8ab78691bb171cde21fa61 Mon Sep 17 00:00:00 2001
From: Wayne Starr <Racer159@users.noreply.github.com>
Date: Sat, 4 Nov 2023 16:00:54 -0600
Subject: [PATCH] fix: properly handle variable and constant merging (#2129)

## Description

This fixes variable and constant merging within component composability.

## Related Issue

Fixes #2125

## Type of change

- [X] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Other (security config, docs update, etc)

## Checklist before merging

- [X] Test, docs, adr added or updated as needed
- [X] [Contributor Guide
Steps](https://github.com/defenseunicorns/zarf/blob/main/CONTRIBUTING.md#developer-workflow)
followed
---
 src/pkg/packager/composer/list.go      |  14 +-
 src/pkg/packager/composer/list_test.go | 180 +++++++++++++++++++++++++
 2 files changed, 188 insertions(+), 6 deletions(-)

diff --git a/src/pkg/packager/composer/list.go b/src/pkg/packager/composer/list.go
index 8354bb958f..89da2380c0 100644
--- a/src/pkg/packager/composer/list.go
+++ b/src/pkg/packager/composer/list.go
@@ -256,13 +256,14 @@ func (ic *ImportChain) MergeVariables(existing []types.ZarfPackageVariable) (mer
 		return v1.Name == v2.Name
 	}
 
-	merged = helpers.MergeSlices(existing, merged, exists)
-	node := ic.head
+	node := ic.tail
 	for node != nil {
 		// merge the vars
 		merged = helpers.MergeSlices(node.vars, merged, exists)
-		node = node.next
+		node = node.prev
 	}
+	merged = helpers.MergeSlices(existing, merged, exists)
+
 	return merged
 }
 
@@ -272,13 +273,14 @@ func (ic *ImportChain) MergeConstants(existing []types.ZarfPackageConstant) (mer
 		return c1.Name == c2.Name
 	}
 
-	merged = helpers.MergeSlices(existing, merged, exists)
-	node := ic.head
+	node := ic.tail
 	for node != nil {
 		// merge the consts
 		merged = helpers.MergeSlices(node.consts, merged, exists)
-		node = node.next
+		node = node.prev
 	}
+	merged = helpers.MergeSlices(existing, merged, exists)
+
 	return merged
 }
 
diff --git a/src/pkg/packager/composer/list_test.go b/src/pkg/packager/composer/list_test.go
index abcce2b8df..bca4cd2fd5 100644
--- a/src/pkg/packager/composer/list_test.go
+++ b/src/pkg/packager/composer/list_test.go
@@ -259,6 +259,186 @@ func TestCompose(t *testing.T) {
 	}
 }
 
+func TestMerging(t *testing.T) {
+	t.Parallel()
+
+	type testCase struct {
+		name           string
+		ic             *ImportChain
+		existingVars   []types.ZarfPackageVariable
+		existingConsts []types.ZarfPackageConstant
+		expectedVars   []types.ZarfPackageVariable
+		expectedConsts []types.ZarfPackageConstant
+	}
+
+	head := Node{
+		vars: []types.ZarfPackageVariable{
+			{
+				Name:    "TEST",
+				Default: "head",
+			},
+			{
+				Name: "HEAD",
+			},
+		},
+		consts: []types.ZarfPackageConstant{
+			{
+				Name:  "TEST",
+				Value: "head",
+			},
+			{
+				Name: "HEAD",
+			},
+		},
+	}
+	tail := Node{
+		vars: []types.ZarfPackageVariable{
+			{
+				Name:    "TEST",
+				Default: "tail",
+			},
+			{
+				Name: "TAIL",
+			},
+		},
+		consts: []types.ZarfPackageConstant{
+			{
+				Name:  "TEST",
+				Value: "tail",
+			},
+			{
+				Name: "TAIL",
+			},
+		},
+	}
+	head.next = &tail
+	tail.prev = &head
+	testIC := &ImportChain{head: &head, tail: &tail}
+
+	testCases := []testCase{
+		{
+			name: "empty-ic",
+			ic:   &ImportChain{},
+			existingVars: []types.ZarfPackageVariable{
+				{
+					Name: "TEST",
+				},
+			},
+			existingConsts: []types.ZarfPackageConstant{
+				{
+					Name: "TEST",
+				},
+			},
+			expectedVars: []types.ZarfPackageVariable{
+				{
+					Name: "TEST",
+				},
+			},
+			expectedConsts: []types.ZarfPackageConstant{
+				{
+					Name: "TEST",
+				},
+			},
+		},
+		{
+			name:           "no-existing",
+			ic:             testIC,
+			existingVars:   []types.ZarfPackageVariable{},
+			existingConsts: []types.ZarfPackageConstant{},
+			expectedVars: []types.ZarfPackageVariable{
+				{
+					Name:    "TEST",
+					Default: "head",
+				},
+				{
+					Name: "HEAD",
+				},
+				{
+					Name: "TAIL",
+				},
+			},
+			expectedConsts: []types.ZarfPackageConstant{
+				{
+					Name:  "TEST",
+					Value: "head",
+				},
+				{
+					Name: "HEAD",
+				},
+				{
+					Name: "TAIL",
+				},
+			},
+		},
+		{
+			name: "with-existing",
+			ic:   testIC,
+			existingVars: []types.ZarfPackageVariable{
+				{
+					Name:    "TEST",
+					Default: "existing",
+				},
+				{
+					Name: "EXISTING",
+				},
+			},
+			existingConsts: []types.ZarfPackageConstant{
+				{
+					Name:  "TEST",
+					Value: "existing",
+				},
+				{
+					Name: "EXISTING",
+				},
+			},
+			expectedVars: []types.ZarfPackageVariable{
+				{
+					Name:    "TEST",
+					Default: "existing",
+				},
+				{
+					Name: "EXISTING",
+				},
+				{
+					Name: "HEAD",
+				},
+				{
+					Name: "TAIL",
+				},
+			},
+			expectedConsts: []types.ZarfPackageConstant{
+				{
+					Name:  "TEST",
+					Value: "existing",
+				},
+				{
+					Name: "EXISTING",
+				},
+				{
+					Name: "HEAD",
+				},
+				{
+					Name: "TAIL",
+				},
+			},
+		},
+	}
+
+	for _, testCase := range testCases {
+		testCase := testCase
+
+		t.Run(testCase.name, func(t *testing.T) {
+			t.Parallel()
+
+			mergedVars := testCase.ic.MergeVariables(testCase.existingVars)
+			require.EqualValues(t, testCase.expectedVars, mergedVars)
+
+			mergedConsts := testCase.ic.MergeConstants(testCase.existingConsts)
+			require.EqualValues(t, testCase.expectedConsts, mergedConsts)
+		})
+	}
+}
+
 func createChainFromSlice(components []types.ZarfComponent) (ic *ImportChain) {
 	ic = &ImportChain{}