From 7ff0acae94a4074454495020ba90dd0c69b2ca87 Mon Sep 17 00:00:00 2001
From: Tom Payne <twpayne@gmail.com>
Date: Tue, 7 Feb 2023 23:42:44 +0100
Subject: [PATCH] feat: Add pruneEmptyDicts template function

---
 .../templates/functions/pruneEmptyDicts.md    | 11 +++++++
 assets/chezmoi.io/mkdocs.yml                  |  1 +
 pkg/cmd/config.go                             |  1 +
 pkg/cmd/templatefuncs.go                      | 20 +++++++++++
 pkg/cmd/templatefuncs_test.go                 | 33 +++++++++++++++++++
 pkg/cmd/testdata/scripts/templatefuncs.txtar  |  7 ++++
 6 files changed, 73 insertions(+)
 create mode 100644 assets/chezmoi.io/docs/reference/templates/functions/pruneEmptyDicts.md

diff --git a/assets/chezmoi.io/docs/reference/templates/functions/pruneEmptyDicts.md b/assets/chezmoi.io/docs/reference/templates/functions/pruneEmptyDicts.md
new file mode 100644
index 00000000000..e1ebbbb005a
--- /dev/null
+++ b/assets/chezmoi.io/docs/reference/templates/functions/pruneEmptyDicts.md
@@ -0,0 +1,11 @@
+# `pruneEmptyDicts` *dict*
+
+`pruneEmptyDicts` modifies *dict* to remove nested empty dicts. Properties are
+pruned from the bottom up, so any nested dicts that themselves only contain
+empty dicts are pruned.
+
+!!! example
+
+    ```
+    {{ dict "key" "value" inner (dict) | pruneEmptyDicts | toJson }}
+    ```
diff --git a/assets/chezmoi.io/mkdocs.yml b/assets/chezmoi.io/mkdocs.yml
index bf9d816bcf4..2c9da43f4d9 100644
--- a/assets/chezmoi.io/mkdocs.yml
+++ b/assets/chezmoi.io/mkdocs.yml
@@ -193,6 +193,7 @@ nav:
       - lstat: reference/templates/functions/lstat.md
       - mozillaInstallHash: reference/templates/functions/mozillaInstallHash.md
       - output: reference/templates/functions/output.md
+      - pruneEmptyDicts: reference/templates/functions/pruneEmptyDicts.md
       - quoteList: reference/templates/functions/quoteList.md
       - replaceAllRegex: reference/templates/functions/replaceAllRegex.md
       - setValueAtPath: reference/templates/functions/setValueAtPath.md
diff --git a/pkg/cmd/config.go b/pkg/cmd/config.go
index cbd9a7f534e..4b82584581c 100644
--- a/pkg/cmd/config.go
+++ b/pkg/cmd/config.go
@@ -396,6 +396,7 @@ func newConfig(options ...configOption) (*Config, error) {
 		"passFields":               c.passFieldsTemplateFunc,
 		"passRaw":                  c.passRawTemplateFunc,
 		"passhole":                 c.passholeTemplateFunc,
+		"pruneEmptyDicts":          c.pruneEmptyDictsTemplateFunc,
 		"quoteList":                c.quoteListTemplateFunc,
 		"replaceAllRegex":          c.replaceAllRegexTemplateFunc,
 		"secret":                   c.secretTemplateFunc,
diff --git a/pkg/cmd/templatefuncs.go b/pkg/cmd/templatefuncs.go
index d07afc7eb1c..b5e14978ac2 100644
--- a/pkg/cmd/templatefuncs.go
+++ b/pkg/cmd/templatefuncs.go
@@ -312,6 +312,11 @@ func (c *Config) outputTemplateFunc(name string, args ...string) string {
 	return string(output)
 }
 
+func (c *Config) pruneEmptyDictsTemplateFunc(dict map[string]any) map[string]any {
+	pruneEmptyMaps(dict)
+	return dict
+}
+
 func (c *Config) quoteListTemplateFunc(list []any) []string {
 	result := make([]string, 0, len(list))
 	for _, elem := range list {
@@ -587,6 +592,21 @@ func needsQuote(s string) bool {
 	return false
 }
 
+// pruneEmptyMaps prunes all empty maps from m and returns if m is now empty
+// itself.
+func pruneEmptyMaps(m map[string]any) bool {
+	for key, value := range m {
+		nestedMap, ok := value.(map[string]any)
+		if !ok {
+			continue
+		}
+		if pruneEmptyMaps(nestedMap) {
+			delete(m, key)
+		}
+	}
+	return len(m) == 0
+}
+
 func sortedKeys[K constraints.Ordered, V any](m map[K]V) []K {
 	keys := maps.Keys(m)
 	slices.Sort(keys)
diff --git a/pkg/cmd/templatefuncs_test.go b/pkg/cmd/templatefuncs_test.go
index ca1aa7dd1da..f18887ece40 100644
--- a/pkg/cmd/templatefuncs_test.go
+++ b/pkg/cmd/templatefuncs_test.go
@@ -160,6 +160,39 @@ func TestDeleteValueAtPathTemplateFunc(t *testing.T) {
 	}
 }
 
+func TestPruneEmptyDicts(t *testing.T) {
+	for _, tc := range []struct {
+		name     string
+		dict     map[string]any
+		expected map[string]any
+	}{
+		{
+			name:     "nil",
+			dict:     nil,
+			expected: nil,
+		},
+		{
+			name:     "empty",
+			dict:     map[string]any{},
+			expected: map[string]any{},
+		},
+		{
+			name: "nested_empty",
+			dict: map[string]any{
+				"key1": map[string]any{},
+				"key2": 0,
+			},
+			expected: map[string]any{
+				"key2": 0,
+			},
+		},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			assert.Equal(t, tc.expected, (&Config{}).pruneEmptyDictsTemplateFunc(tc.dict))
+		})
+	}
+}
+
 func TestSetValueAtPathTemplateFunc(t *testing.T) {
 	for _, tc := range []struct {
 		name        string
diff --git a/pkg/cmd/testdata/scripts/templatefuncs.txtar b/pkg/cmd/testdata/scripts/templatefuncs.txtar
index 22f5d1672dd..5fb0dc5d56d 100644
--- a/pkg/cmd/testdata/scripts/templatefuncs.txtar
+++ b/pkg/cmd/testdata/scripts/templatefuncs.txtar
@@ -84,6 +84,11 @@ stdout 2656FF1E876E9973
 [!(windows||illumos)] stderr 'error calling output: .*/false: exit status 1'
 [illumos] stderr 'error calling output: .*/false: exit status 255'
 
+# test pruneEmptyDicts template function
+exec chezmoi execute-template '{{ dict "key1" "value1" "key2" (dict) | pruneEmptyDicts | toJson }}'
+rmfinalnewline golden/pruneEmptyDicts
+cmp stdout golden/pruneEmptyDicts
+
 # test replaceAllRegex template function
 exec chezmoi execute-template '{{ "foo bar baz" | replaceAllRegex "ba" "BA" }}'
 stdout 'foo BAr BAz'
@@ -191,6 +196,8 @@ file2.txt
 # contents of .include
 -- golden/include-relpath --
 # contents of .local/share/chezmoi/.include
+-- golden/pruneEmptyDicts --
+{"key1":"value1"}
 -- golden/setValueAtPath --
 {"key1":{"key2":"value2"}}
 -- golden/toIni --