Length compares to null instead of 0 issue #1427

pkg/yqlib/compare_operators.go

@@ -16,7 +16,7 @@ type compareTypePref struct {
 func compareOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
 	log.Debugf("-- compareOperator")
 	prefs := expressionNode.Operation.Preferences.(compareTypePref)
-	return crossFunction(d, context.ReadOnlyClone(), expressionNode, compare(prefs), true)
+	return crossFunction(d, context, expressionNode, compare(prefs), true)
 }
 
 func compare(prefs compareTypePref) func(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
@@ -127,6 +127,10 @@ func compareScalars(context Context, prefs compareTypePref, lhs *yaml.Node, rhs
 			return lhs.Value > rhs.Value, nil
 		}
 		return lhs.Value < rhs.Value, nil
+	} else if lhsTag == "!!null" && rhsTag == "!!null" && prefs.OrEqual {
+		return true, nil
+	} else if lhsTag == "!!null" || rhsTag == "!!null" {
+		return false, nil
 	}
 
 	return false, fmt.Errorf("%v not yet supported for comparison", lhs.Tag)

pkg/yqlib/compare_operators_test.go

@@ -14,6 +14,13 @@ var compareOperatorScenarios = []expressionScenario{
 			"D0, P[a], (!!bool)::true\n",
 		},
 	},
+	{
+		skipDoc:    true,
+		expression: "(.k | length) >= 0",
+		expected: []string{
+			"D0, P[k], (!!bool)::true\n",
+		},
+	},
 	{
 		skipDoc:    true,
 		document:   "a: 5\nb: 4",
@@ -285,28 +292,28 @@ var compareOperatorScenarios = []expressionScenario{
 		description: "Both sides are null: > is false",
 		expression:  ".a > .b",
 		expected: []string{
-			"D0, P[], (!!bool)::false\n",
+			"D0, P[a], (!!bool)::false\n",
 		},
 	},
 	{
 		skipDoc:    true,
 		expression: ".a < .b",
 		expected: []string{
-			"D0, P[], (!!bool)::false\n",
+			"D0, P[a], (!!bool)::false\n",
 		},
 	},
 	{
 		description: "Both sides are null: >= is true",
 		expression:  ".a >= .b",
 		expected: []string{
-			"D0, P[], (!!bool)::true\n",
+			"D0, P[a], (!!bool)::true\n",
 		},
 	},
 	{
 		skipDoc:    true,
 		expression: ".a <= .b",
 		expected: []string{
-			"D0, P[], (!!bool)::true\n",
+			"D0, P[a], (!!bool)::true\n",
 		},
 	},
 
@@ -350,7 +357,7 @@ var compareOperatorScenarios = []expressionScenario{
 		document:   `a: 5`,
 		expression: ".b <= .a",
 		expected: []string{
-			"D0, P[a], (!!bool)::false\n",
+			"D0, P[b], (!!bool)::false\n",
 		},
 	},
 	{
@@ -358,7 +365,7 @@ var compareOperatorScenarios = []expressionScenario{
 		document:   `a: 5`,
 		expression: ".b < .a",
 		expected: []string{
-			"D0, P[a], (!!bool)::false\n",
+			"D0, P[b], (!!bool)::false\n",
 		},
 	},
 }

pkg/yqlib/operator_equals.go

@@ -4,7 +4,7 @@ import "gopkg.in/yaml.v3"
 
 func equalsOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
 	log.Debugf("-- equalsOperation")
-	return crossFunction(d, context.ReadOnlyClone(), expressionNode, isEquals(false), true)
+	return crossFunction(d, context, expressionNode, isEquals(false), true)
 }
 
 func isEquals(flip bool) func(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {

pkg/yqlib/operator_equals_test.go

@@ -9,7 +9,14 @@ var equalsOperatorScenarios = []expressionScenario{
 		skipDoc:    true,
 		expression: ".a == .b",
 		expected: []string{
-			"D0, P[], (!!bool)::true\n",
+			"D0, P[a], (!!bool)::true\n",
+		},
+	},
+	{
+		expression: `(.k | length) == 0`,
+		skipDoc:    true,
+		expected: []string{
+			"D0, P[k], (!!bool)::true\n",
 		},
 	},
 	{
@@ -25,7 +32,7 @@ var equalsOperatorScenarios = []expressionScenario{
 		document:   `a: cat`,
 		expression: ".b == .a",
 		expected: []string{
-			"D0, P[a], (!!bool)::false\n",
+			"D0, P[b], (!!bool)::false\n",
 		},
 	},
 	{
@@ -50,7 +57,7 @@ var equalsOperatorScenarios = []expressionScenario{
 		document:   "{}",
 		expression: ".a == .b",
 		expected: []string{
-			"D0, P[], (!!bool)::true\n",
+			"D0, P[a], (!!bool)::true\n",
 		},
 	},
 	{

pkg/yqlib/operator_select_test.go

@@ -76,9 +76,10 @@ var selectOperatorScenarios = []expressionScenario{
 		},
 	},
 	{
-		skipDoc:    true,
+		description: "select does not update the map",
-		document:   `[{animal: cat, legs: {cool: true}}, {animal: fish}]`,
+		skipDoc:     true,
-		expression: `(.[] | select(.legs.cool == true).canWalk) = true | (.[] | .alive.things) = "yes"`,
+		document:    `[{animal: cat, legs: {cool: true}}, {animal: fish}]`,
+		expression:  `(.[] | select(.legs.cool == true).canWalk) = true | (.[] | .alive.things) = "yes"`,
 		expected: []string{
 			"D0, P[], (doc)::[{animal: cat, legs: {cool: true}, canWalk: true, alive: {things: yes}}, {animal: fish, alive: {things: yes}}]\n",
 		},

pkg/yqlib/operator_traverse_path.go

@@ -39,7 +39,7 @@ func traverse(context Context, matchingNode *CandidateNode, operation *Operation
 	log.Debug("Traversing %v", NodeToString(matchingNode))
 	value := matchingNode.Node
 
-	if value.Tag == "!!null" && operation.Value != "[]" {
+	if value.Tag == "!!null" && operation.Value != "[]" && !context.DontAutoCreate {
 		log.Debugf("Guessing kind")
 		// we must have added this automatically, lets guess what it should be now
 		switch operation.Value.(type) {