compare: treat an empty value and an absent key as equal

feature/github-repo-importer/pkg/compare/compare.go

@@ -102,6 +102,7 @@ func hashNormalizedYamlFile(path string) (string, error) {
 		removeKey(root, "id")
 		removeKey(root, "branch_policy_ids")
 		removeKey(root, "tag_policy_ids")
+		removeEmptyValues(root)
 		sortMappingNode(root)
 	}
 
@@ -136,6 +137,34 @@ func removeKey(node *yaml.Node, target string) {
 	}
 }
 
+func removeEmptyValues(node *yaml.Node) {
+	switch node.Kind {
+	case yaml.MappingNode:
+		newContent := make([]*yaml.Node, 0, len(node.Content))
+		for i := 0; i < len(node.Content); i += 2 {
+			k := node.Content[i]
+			v := node.Content[i+1]
+			if isEmptyScalar(v) {
+				continue
+			}
+			removeEmptyValues(v)
+			newContent = append(newContent, k, v)
+		}
+		node.Content = newContent
+	case yaml.SequenceNode:
+		for _, elem := range node.Content {
+			removeEmptyValues(elem)
+		}
+	}
+}
+
+func isEmptyScalar(node *yaml.Node) bool {
+	if node.Kind != yaml.ScalarNode {
+		return false
+	}
+	return node.Tag == "!!null" || (node.Tag == "!!str" && node.Value == "")
+}
+
 func sortMappingNode(node *yaml.Node) {
 	if node.Kind != yaml.MappingNode {
 		return

feature/github-repo-importer/pkg/compare/compare_test.go

@@ -37,6 +37,24 @@ func TestHashingYamlFiles(t *testing.T) {
 			pathOfFresh:    "testdata/existing/existing4.yaml",
 			wantEqual:      true,
 		},
+		{
+			name:           "empty and null values are equivalent to the key being absent",
+			pathOfImported: "testdata/imported/imported5.yaml",
+			pathOfFresh:    "testdata/existing/existing5.yaml",
+			wantEqual:      true,
+		},
+		{
+			name:           "a real difference is still detected alongside an empty value",
+			pathOfImported: "testdata/imported/imported6.yaml",
+			pathOfFresh:    "testdata/existing/existing6.yaml",
+			wantEqual:      false,
+		},
+		{
+			name:           "a false value on one side only is a difference, not an empty value",
+			pathOfImported: "testdata/imported/imported7.yaml",
+			pathOfFresh:    "testdata/existing/existing7.yaml",
+			wantEqual:      false,
+		},
 	}
 
 	for _, tt := range tests {

feature/github-repo-importer/pkg/compare/testdata/existing/existing5.yaml

@@ -0,0 +1,21 @@
+description: ""
+homepage_url: ""
+visibility: public
+default_branch: main
+has_issues: true
+has_downloads: false
+allow_auto_merge: false
+archived: false
+license_template:
+rulesets:
+  - enforcement: active
+    name: test
+    rules:
+      deletion: true
+      non_fast_forward: true
+    target: branch
+    conditions:
+      ref_name:
+        include:
+          - ~DEFAULT_BRANCH
+vulnerability_alerts_enabled: true

feature/github-repo-importer/pkg/compare/testdata/existing/existing6.yaml

@@ -0,0 +1,8 @@
+description: Managed by Terraform
+homepage_url: ""
+visibility: public
+default_branch: main
+has_issues: true
+has_downloads: false
+archived: false
+vulnerability_alerts_enabled: true

feature/github-repo-importer/pkg/compare/testdata/existing/existing7.yaml

@@ -0,0 +1,6 @@
+visibility: public
+default_branch: main
+has_issues: true
+has_downloads: false
+archived: false
+vulnerability_alerts_enabled: true

feature/github-repo-importer/pkg/compare/testdata/imported/imported5.yaml

@@ -0,0 +1,18 @@
+visibility: public
+default_branch: main
+has_issues: true
+has_downloads: false
+allow_auto_merge: false
+archived: false
+rulesets:
+  - enforcement: active
+    name: test
+    rules:
+      deletion: true
+      non_fast_forward: true
+    target: branch
+    conditions:
+      ref_name:
+        include:
+          - ~DEFAULT_BRANCH
+vulnerability_alerts_enabled: true

feature/github-repo-importer/pkg/compare/testdata/imported/imported6.yaml

@@ -0,0 +1,7 @@
+description: Edited by hand outside the tool
+visibility: public
+default_branch: main
+has_issues: true
+has_downloads: false
+archived: false
+vulnerability_alerts_enabled: true

feature/github-repo-importer/pkg/compare/testdata/imported/imported7.yaml

@@ -0,0 +1,5 @@
+visibility: public
+default_branch: main
+has_issues: true
+archived: false
+vulnerability_alerts_enabled: true