sort_by works on maps

examples/data1.yaml

@@ -1,11 +1,3 @@
-# block comments come through
-person: # neither do comments on maps
-    name: Mike Wazowski # comments on values appear
-    pets: 
-    - cat # comments on array values appear
-    - dog # comments on array values appear
-    - things:
-        - frog
-    food: [pizza] # comments on arrays do not
-emptyArray: []
-emptyMap: []
+Foo: 3
+apple: 1
+bar: 2

go.mod

@@ -29,6 +29,4 @@ require (
 	golang.org/x/sys v0.28.0 // indirect
 )
 
-go 1.21.0
-
-toolchain go1.22.5
+go 1.23.0

pkg/yqlib/candidate_node.go

@@ -198,6 +198,29 @@ func (n *CandidateNode) SetParent(parent *CandidateNode) {
 	n.Parent = parent
 }
 
+type ValueVisitor func(*CandidateNode) error
+
+func (n *CandidateNode) VisitValues(visitor ValueVisitor) error {
+	if n.Kind == MappingNode {
+		for i := 1; i < len(n.Content); i = i + 2 {
+			if err := visitor(n.Content[i]); err != nil {
+				return err
+			}
+		}
+	} else if n.Kind == SequenceNode {
+		for i := 0; i < len(n.Content); i = i + 1 {
+			if err := visitor(n.Content[i]); err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}
+
+func (n *CandidateNode) CanVisitValues() bool {
+	return n.Kind == MappingNode || n.Kind == SequenceNode
+}
+
 func (n *CandidateNode) AddKeyValueChild(rawKey *CandidateNode, rawValue *CandidateNode) (*CandidateNode, *CandidateNode) {
 	key := rawKey.Copy()
 	key.SetParent(n)

pkg/yqlib/doc/operators/headers/sort-keys.md

@@ -12,5 +12,5 @@ diff file1.yml file2.yml
 
 Note that `yq` does not yet consider anchors when sorting by keys - this may result in invalid yaml documents if you are using merge anchors.
 
-For more advanced sorting, using `to_entries` to convert the map to an array, then sort/process the array as you like (e.g. using `sort_by`) and convert back to a map using `from_entries`.
-See [here](https://mikefarah.gitbook.io/yq/operators/entries#custom-sort-map-keys) for an example. 
+For more advanced sorting, you can use the [sort_by](https://mikefarah.gitbook.io/yq/operators/sort) function on a map, and give it a custom function like `sort_by(key | downcase)`.
+

pkg/yqlib/doc/operators/sort-keys.md

@@ -12,8 +12,8 @@ diff file1.yml file2.yml
 
 Note that `yq` does not yet consider anchors when sorting by keys - this may result in invalid yaml documents if you are using merge anchors.
 
-For more advanced sorting, using `to_entries` to convert the map to an array, then sort/process the array as you like (e.g. using `sort_by`) and convert back to a map using `from_entries`.
-See [here](https://mikefarah.gitbook.io/yq/operators/entries#custom-sort-map-keys) for an example. 
+For more advanced sorting, you can use the [sort_by](https://mikefarah.gitbook.io/yq/operators/sort) function on a map, and give it a custom function like `sort_by(key | downcase)`.
+
 
 ## Sort keys of map
 Given a sample.yml file of:

pkg/yqlib/doc/operators/sort.md

@@ -109,6 +109,46 @@ cool:
   - c: banana
 ```
 
+## Sort a map
+Sorting a map, by default, will sort by the values
+
+Given a sample.yml file of:
+```yaml
+y: b
+z: a
+x: c
+```
+then
+```bash
+yq 'sort' sample.yml
+```
+will output
+```yaml
+z: a
+y: b
+x: c
+```
+
+## Sort a map by keys
+Use sort_by to sort a map using a custom function
+
+Given a sample.yml file of:
+```yaml
+Y: b
+z: a
+x: c
+```
+then
+```bash
+yq 'sort_by(key | downcase)' sample.yml
+```
+will output
+```yaml
+x: c
+Y: b
+z: a
+```
+
 ## Sort is stable
 Note the order of the elements in unchanged when equal in sorting.
 

pkg/yqlib/operator_sort.go

@@ -24,30 +24,40 @@ func sortByOperator(d *dataTreeNavigator, context Context, expressionNode *Expre
 	for el := context.MatchingNodes.Front(); el != nil; el = el.Next() {
 		candidate := el.Value.(*CandidateNode)
 
-		if candidate.Kind != SequenceNode {
-			return context, fmt.Errorf("node at path [%v] is not an array (it's a %v)", candidate.GetNicePath(), candidate.Tag)
-		}
-
-		sortableArray := make(sortableNodeArray, len(candidate.Content))
-
-		for i, originalNode := range candidate.Content {
-
-			compareContext, err := d.GetMatchingNodes(context.SingleReadonlyChildContext(originalNode), expressionNode.RHS)
-			if err != nil {
-				return Context{}, err
+		var sortableArray sortableNodeArray
+
+		if candidate.CanVisitValues() {
+			sortableArray = make(sortableNodeArray, 0)
+			visitor := func(valueNode *CandidateNode) error {
+				compareContext, err := d.GetMatchingNodes(context.SingleReadonlyChildContext(valueNode), expressionNode.RHS)
+				if err != nil {
+					return err
+				}
+				sortableNode := sortableNode{Node: valueNode, CompareContext: compareContext, dateTimeLayout: context.GetDateTimeLayout()}
+				sortableArray = append(sortableArray, sortableNode)
+				return nil
 			}
-
-			sortableArray[i] = sortableNode{Node: originalNode, CompareContext: compareContext, dateTimeLayout: context.GetDateTimeLayout()}
-
+			if err := candidate.VisitValues(visitor); err != nil {
+				return context, err
+			}
+		} else {
+			return context, fmt.Errorf("node at path [%v] is not an array or map (it's a %v)", candidate.GetNicePath(), candidate.Tag)
 		}
 
 		sort.Stable(sortableArray)
 
-		sortedList := candidate.CreateReplacementWithComments(SequenceNode, "!!seq", candidate.Style)
-
-		for _, sortedNode := range sortableArray {
-			sortedList.AddChild(sortedNode.Node)
+		sortedList := candidate.CopyWithoutContent()
+		if candidate.Kind == MappingNode {
+			for _, sortedNode := range sortableArray {
+				sortedList.AddKeyValueChild(sortedNode.Node.Key, sortedNode.Node)
+			}
+		} else if candidate.Kind == SequenceNode {
+			for _, sortedNode := range sortableArray {
+				sortedList.AddChild(sortedNode.Node)
+			}
 		}
+
+		// convert array of value nodes back to map
 		results.PushBack(sortedList)
 	}
 	return context.ChildContext(results), nil

pkg/yqlib/operator_sort_test.go

@@ -84,6 +84,24 @@ var sortByOperatorScenarios = []expressionScenario{
 			"D0, P[], (!!map)::cool: [{a: banana}, {b: banana}, {c: banana}]\n",
 		},
 	},
+	{
+		description:    "Sort a map",
+		subdescription: "Sorting a map, by default this will sort by the values",
+		document:       "y: b\nz: a\nx: c\n",
+		expression:     `sort`,
+		expected: []string{
+			"D0, P[], (!!map)::z: a\ny: b\nx: c\n",
+		},
+	},
+	{
+		description:    "Sort a map by keys",
+		subdescription: "Use sort_by to sort a map using a custom function",
+		document:       "Y: b\nz: a\nx: c\n",
+		expression:     `sort_by(key | downcase)`,
+		expected: []string{
+			"D0, P[], (!!map)::x: c\nY: b\nz: a\n",
+		},
+	},
 	{
 		description:    "Sort is stable",
 		subdescription: "Note the order of the elements in unchanged when equal in sorting.",