From 88bfbec97b77703efc8a1151789131075d5dfc62 Mon Sep 17 00:00:00 2001
From: Mike Farah <mikefarah@gmail.com>
Date: Thu, 12 Jun 2025 14:25:05 +1000
Subject: [PATCH] Fix add op when there are not matches piped in, #2383, #2384

---
 pkg/yqlib/expression_parser.go |  6 +++++
 pkg/yqlib/operator_add.go      |  5 +++-
 pkg/yqlib/operator_add_test.go | 45 ++++++++++++++++++++++++++++++++++
 3 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/pkg/yqlib/expression_parser.go b/pkg/yqlib/expression_parser.go
index 622fb416..399ef9c7 100644
--- a/pkg/yqlib/expression_parser.go
+++ b/pkg/yqlib/expression_parser.go
@@ -9,6 +9,7 @@ type ExpressionNode struct {
 	Operation *Operation
 	LHS       *ExpressionNode
 	RHS       *ExpressionNode
+	Parent    *ExpressionNode
 }
 
 type ExpressionParserInterface interface {
@@ -57,6 +58,7 @@ func (p *expressionParserImpl) createExpressionTree(postFixPath []*Operation) (*
 				}
 				remaining, rhs := stack[:len(stack)-1], stack[len(stack)-1]
 				newNode.RHS = rhs
+				rhs.Parent = &newNode
 				stack = remaining
 			case 2:
 				if len(stack) < 2 {
@@ -64,7 +66,11 @@ func (p *expressionParserImpl) createExpressionTree(postFixPath []*Operation) (*
 				}
 				remaining, lhs, rhs := stack[:len(stack)-2], stack[len(stack)-2], stack[len(stack)-1]
 				newNode.LHS = lhs
+				lhs.Parent = &newNode
+
 				newNode.RHS = rhs
+				rhs.Parent = &newNode
+
 				stack = remaining
 			}
 		}
diff --git a/pkg/yqlib/operator_add.go b/pkg/yqlib/operator_add.go
index 044fe4a0..37be8f81 100644
--- a/pkg/yqlib/operator_add.go
+++ b/pkg/yqlib/operator_add.go
@@ -38,8 +38,11 @@ func toNodes(candidate *CandidateNode, lhs *CandidateNode) []*CandidateNode {
 
 func addOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
 	log.Debugf("Add operator")
+	// if we don't have any matching nodes, but we were piped into (have a parent exp?) then we
+	// shouldn't calcWhenEmpt
+	calcWhenEmpty := expressionNode.Parent == nil
 
-	return crossFunction(d, context.ReadOnlyClone(), expressionNode, add, true)
+	return crossFunction(d, context.ReadOnlyClone(), expressionNode, add, calcWhenEmpty)
 }
 
 func add(_ *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
diff --git a/pkg/yqlib/operator_add_test.go b/pkg/yqlib/operator_add_test.go
index 5b1b773d..92ed3d96 100644
--- a/pkg/yqlib/operator_add_test.go
+++ b/pkg/yqlib/operator_add_test.go
@@ -5,6 +5,51 @@ import (
 )
 
 var addOperatorScenarios = []expressionScenario{
+	{
+		skipDoc:    true,
+		expression: `"foo" + "bar"`,
+		expected: []string{
+			"D0, P[], (!!str)::foobar\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		expression: `[] | .[] | "foo" + .`,
+		expected:   []string{},
+	},
+	{
+		skipDoc:    true,
+		expression: `[] | .[] | . + "foo"`,
+		expected:   []string{},
+	},
+	{
+		skipDoc:    true,
+		expression: `select(.) | "foo" + "bar"`,
+		expected: []string{
+			"D0, P[], (!!str)::foobar\n", // jq does not do this :/ - but yq has for quite some time.
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   "apples: 3",
+		expression: `.apples + 3`,
+		expected: []string{
+			"D0, P[apples], (!!int)::6\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   "apples: 3",
+		expression: `.bobo + 3`,
+		expected: []string{
+			"D0, P[], (!!int)::3\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		expression: `select(.) | "cat" + .`,
+		expected:   []string{},
+	},
 	{
 		skipDoc:    true,
 		document:   `[{a: foo, b: bar}, {a: 1, b: 2}]`,