From c0fd3fe38b756eef3745db4019fce23a119bd6dc Mon Sep 17 00:00:00 2001
From: TJ Miller <millert@us.ibm.com>
Date: Thu, 9 Mar 2023 15:59:12 -0800
Subject: [PATCH] Handle int modulo by 0 and add tests

---
 pkg/yqlib/doc/operators/modulo.md | 35 +++++++++++++++++++++++++++++++
 pkg/yqlib/operator_modulo.go      |  3 +++
 pkg/yqlib/operator_modulo_test.go | 16 ++++++++++++++
 3 files changed, 54 insertions(+)

diff --git a/pkg/yqlib/doc/operators/modulo.md b/pkg/yqlib/doc/operators/modulo.md
index b26a39b2..b7ecd7e0 100644
--- a/pkg/yqlib/doc/operators/modulo.md
+++ b/pkg/yqlib/doc/operators/modulo.md
@@ -35,3 +35,38 @@ a: !!float 2
 b: 2.5
 ```
 
+## Number modulo - int by zero
+If the lhs is an int and rhs is a 0 the result is an error.
+
+Given a sample.yml file of:
+```yaml
+a: 1
+b: 0
+```
+then
+```bash
+yq '.a = .a % .b' sample.yml
+```
+will output
+```bash
+Error: cannot modulo by 0
+```
+
+## Number modulo - float by zero
+If the lhs is a float and rhs is a 0 the result is NaN.
+
+Given a sample.yml file of:
+```yaml
+a: 1.1
+b: 0
+```
+then
+```bash
+yq '.a = .a % .b' sample.yml
+```
+will output
+```yaml
+a: !!float NaN
+b: 0
+```
+
diff --git a/pkg/yqlib/operator_modulo.go b/pkg/yqlib/operator_modulo.go
index 116f614b..cc4e6860 100644
--- a/pkg/yqlib/operator_modulo.go
+++ b/pkg/yqlib/operator_modulo.go
@@ -68,6 +68,9 @@ func moduloScalars(context Context, target *CandidateNode, lhs *yaml.Node, rhs *
 		if err != nil {
 			return err
 		}
+		if rhsNum == 0 {
+			return fmt.Errorf("cannot modulo by 0")
+		}
 		remainder := lhsNum % rhsNum
 
 		target.Node.Tag = lhs.Tag
diff --git a/pkg/yqlib/operator_modulo_test.go b/pkg/yqlib/operator_modulo_test.go
index ae94ed91..ee1c9101 100644
--- a/pkg/yqlib/operator_modulo_test.go
+++ b/pkg/yqlib/operator_modulo_test.go
@@ -40,6 +40,22 @@ var moduloOperatorScenarios = []expressionScenario{
 			"D0, P[], (doc)::{a: !!float 2, b: 2.5}\n",
 		},
 	},
+	{
+		description:    "Number modulo - int by zero",
+		subdescription: "If the lhs is an int and rhs is a 0 the result is an error.",
+		document:       `{a: 1, b: 0}`,
+		expression:     `.a = .a % .b`,
+		expectedError:  "cannot modulo by 0",
+	},
+	{
+		description:    "Number modulo - float by zero",
+		subdescription: "If the lhs is a float and rhs is a 0 the result is NaN.",
+		document:       `{a: 1.1, b: 0}`,
+		expression:     `.a = .a % .b`,
+		expected: []string{
+			"D0, P[], (doc)::{a: !!float NaN, b: 0}\n",
+		},
+	},
 	{
 		skipDoc:     true,
 		description: "Custom types: that are really numbers",