Assignment op no longer clobbers anchor (#1029)

pkg/yqlib/candidate_node.go

@@ -104,14 +104,14 @@ func (n *CandidateNode) Copy() (*CandidateNode, error) {
 }
 
 // updates this candidate from the given candidate node
-func (n *CandidateNode) UpdateFrom(other *CandidateNode) {
+func (n *CandidateNode) UpdateFrom(other *CandidateNode, prefs assignPreferences) {
 
-	n.UpdateAttributesFrom(other)
+	n.UpdateAttributesFrom(other, prefs)
 	n.Node.Content = other.Node.Content
 	n.Node.Value = other.Node.Value
 }
 
-func (n *CandidateNode) UpdateAttributesFrom(other *CandidateNode) {
+func (n *CandidateNode) UpdateAttributesFrom(other *CandidateNode, prefs assignPreferences) {
 	log.Debug("UpdateAttributesFrom: n: %v other: %v", n.GetKey(), other.GetKey())
 	if n.Node.Kind != other.Node.Kind {
 		// clear out the contents when switching to a different type
@@ -122,7 +122,10 @@ func (n *CandidateNode) UpdateAttributesFrom(other *CandidateNode) {
 	n.Node.Kind = other.Node.Kind
 	n.Node.Tag = other.Node.Tag
 	n.Node.Alias = other.Node.Alias
+
+	if !prefs.DontOverWriteAnchor {
 		n.Node.Anchor = other.Node.Anchor
+	}
 
 	// merge will pickup the style of the new thing
 	// when autocreating nodes

pkg/yqlib/doc/assign-update.md

@@ -196,6 +196,22 @@ will output
 {a: {b: bogs}}
 ```
 
+## Update node value that has an anchor
+Anchor will remaple
+
+Given a sample.yml file of:
+```yaml
+a: &cool cat
+```
+then
+```bash
+yq eval '.a = "dog"' sample.yml
+```
+will output
+```yaml
+a: &cool dog
+```
+
 ## Update empty object and array
 Given a sample.yml file of:
 ```yaml

pkg/yqlib/expression_tokeniser.go

@@ -94,7 +94,8 @@ func assignOpToken(updateAssign bool) lex.Action {
 	return func(s *lex.Scanner, m *machines.Match) (interface{}, error) {
 		log.Debug("assignOpToken %v", string(m.Bytes))
 		value := string(m.Bytes)
-		op := &Operation{OperationType: assignOpType, Value: assignOpType.Type, StringValue: value, UpdateAssign: updateAssign}
+		prefs := assignPreferences{DontOverWriteAnchor: true}
+		op := &Operation{OperationType: assignOpType, Value: assignOpType.Type, StringValue: value, UpdateAssign: updateAssign, Preferences: prefs}
 		return &token{TokenType: operationToken, Operation: op}, nil
 	}
 }

pkg/yqlib/operator_assign.go

@@ -1,9 +1,16 @@
 package yqlib
 
-func assignUpdateFunc(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
+type assignPreferences struct {
+	DontOverWriteAnchor bool
+}
+
+func assignUpdateFunc(prefs assignPreferences) crossFunctionCalculation {
+	return func(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
 		rhs.Node = unwrapDoc(rhs.Node)
-	lhs.UpdateFrom(rhs)
+
+		lhs.UpdateFrom(rhs, prefs)
 		return lhs, nil
+	}
 }
 
 func assignUpdateOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
@@ -12,9 +19,14 @@ func assignUpdateOperator(d *dataTreeNavigator, context Context, expressionNode
 		return Context{}, err
 	}
 
+	prefs := assignPreferences{}
+	if expressionNode.Operation.Preferences != nil {
+		prefs = expressionNode.Operation.Preferences.(assignPreferences)
+	}
+
 	if !expressionNode.Operation.UpdateAssign {
 		// this works because we already ran against LHS with an editable context.
-		_, err := crossFunction(d, context.ReadOnlyClone(), expressionNode, assignUpdateFunc, false)
+		_, err := crossFunction(d, context.ReadOnlyClone(), expressionNode, assignUpdateFunc(prefs), false)
 		return context, err
 	}
 
@@ -33,7 +45,7 @@ func assignUpdateOperator(d *dataTreeNavigator, context Context, expressionNode
 		if first != nil {
 			rhsCandidate := first.Value.(*CandidateNode)
 			rhsCandidate.Node = unwrapDoc(rhsCandidate.Node)
-			candidate.UpdateFrom(rhsCandidate)
+			candidate.UpdateFrom(rhsCandidate, prefs)
 		}
 	}
 
@@ -60,7 +72,11 @@ func assignAttributesOperator(d *dataTreeNavigator, context Context, expressionN
 		first := rhs.MatchingNodes.Front()
 
 		if first != nil {
-			candidate.UpdateAttributesFrom(first.Value.(*CandidateNode))
+			prefs := assignPreferences{}
+			if expressionNode.Operation.Preferences != nil {
+				prefs = expressionNode.Operation.Preferences.(assignPreferences)
+			}
+			candidate.UpdateAttributesFrom(first.Value.(*CandidateNode), prefs)
 		}
 	}
 	return context, nil

pkg/yqlib/operator_assign_test.go

@@ -145,6 +145,16 @@ var assignOperatorScenarios = []expressionScenario{
 			"D0, P[], (doc)::{a: {b: bogs}}\n",
 		},
 	},
+	{
+		description:           "Update node value that has an anchor",
+		subdescription:        "Anchor will remaple",
+		dontFormatInputForDoc: true,
+		document:              `a: &cool cat`,
+		expression:            `.a = "dog"`,
+		expected: []string{
+			"D0, P[], (doc)::a: &cool dog\n",
+		},
+	},
 	{
 		description:           "Update empty object and array",
 		dontFormatInputForDoc: true,