Added modulo operator

pkg/yqlib/doc/operators/modulo.md

@@ -0,0 +1,37 @@
+
+## Number modulo - int
+If the lhs and rhs are ints then the expression will be calculated with ints.
+
+Given a sample.yml file of:
+```yaml
+a: 13
+b: 2
+```
+then
+```bash
+yq '.a = .a % .b' sample.yml
+```
+will output
+```yaml
+a: 1
+b: 2
+```
+
+## Number modulo - float
+If the lhs or rhs are floats then the expression will be calculated with floats.
+
+Given a sample.yml file of:
+```yaml
+a: 12
+b: 2.5
+```
+then
+```bash
+yq '.a = .a % .b' sample.yml
+```
+will output
+```yaml
+a: !!float 2
+b: 2.5
+```
+

pkg/yqlib/lexer_participle.go

@@ -212,6 +212,8 @@ var participleYqRules = []*participleYqRule{
 
 	{"Divide", `\/`, opToken(divideOpType), 0},
 
+	{"Modulo", `%`, opToken(moduloOpType), 0},
+
 	{"AddAssign", `\+=`, opToken(addAssignOpType), 0},
 	{"Add", `\+`, opToken(addOpType), 0},
 

pkg/yqlib/lib.go

@@ -64,6 +64,8 @@ var multiplyAssignOpType = &operationType{Type: "MULTIPLY_ASSIGN", NumArgs: 2, P
 
 var divideOpType = &operationType{Type: "DIVIDE", NumArgs: 2, Precedence: 42, Handler: divideOperator}
 
+var moduloOpType = &operationType{Type: "MODULO", NumArgs: 2, Precedence: 42, Handler: moduloOperator}
+
 var addOpType = &operationType{Type: "ADD", NumArgs: 2, Precedence: 42, Handler: addOperator}
 var subtractOpType = &operationType{Type: "SUBTRACT", NumArgs: 2, Precedence: 42, Handler: subtractOperator}
 var alternativeOpType = &operationType{Type: "ALTERNATIVE", NumArgs: 2, Precedence: 42, Handler: alternativeOperator}

pkg/yqlib/operator_modulo.go

@@ -0,0 +1,98 @@
+package yqlib
+
+import (
+	"fmt"
+	"math"
+	"strconv"
+	"strings"
+
+	yaml "gopkg.in/yaml.v3"
+)
+
+func createModuloOp(lhs *ExpressionNode, rhs *ExpressionNode) *ExpressionNode {
+	return &ExpressionNode{Operation: &Operation{OperationType: moduloOpType},
+		LHS: lhs,
+		RHS: rhs}
+}
+
+func moduloOperator(d *dataTreeNavigator, context Context, expressionNode *ExpressionNode) (Context, error) {
+	log.Debugf("Modulo operator")
+
+	return crossFunction(d, context.ReadOnlyClone(), expressionNode, modulo, false)
+}
+
+func modulo(d *dataTreeNavigator, context Context, lhs *CandidateNode, rhs *CandidateNode) (*CandidateNode, error) {
+	lhs.Node = unwrapDoc(lhs.Node)
+	rhs.Node = unwrapDoc(rhs.Node)
+
+	lhsNode := lhs.Node
+
+	if lhsNode.Tag == "!!null" {
+		return nil, fmt.Errorf("%v (%v) cannot modulo by %v (%v)", lhsNode.Tag, lhs.GetNicePath(), rhs.Node.Tag, rhs.GetNicePath())
+	}
+
+	target := lhs.CreateReplacement(&yaml.Node{
+		Anchor: lhs.Node.Anchor,
+	})
+
+	if lhsNode.Kind == yaml.ScalarNode && rhs.Node.Kind == yaml.ScalarNode {
+		if err := moduloScalars(context, target, lhsNode, rhs.Node); err != nil {
+			return nil, err
+		}
+	} else {
+		return nil, fmt.Errorf("%v (%v) cannot modulo by %v (%v)", lhsNode.Tag, lhs.GetNicePath(), rhs.Node.Tag, rhs.GetNicePath())
+	}
+
+	return target, nil
+}
+
+func moduloScalars(context Context, target *CandidateNode, lhs *yaml.Node, rhs *yaml.Node) error {
+	lhsTag := lhs.Tag
+	rhsTag := guessTagFromCustomType(rhs)
+	lhsIsCustom := false
+	if !strings.HasPrefix(lhsTag, "!!") {
+		// custom tag - we have to have a guess
+		lhsTag = guessTagFromCustomType(lhs)
+		lhsIsCustom = true
+	}
+
+	if lhsTag == "!!int" && rhsTag == "!!int" {
+		target.Node.Kind = yaml.ScalarNode
+		target.Node.Style = lhs.Style
+
+		format, lhsNum, err := parseInt64(lhs.Value)
+		if err != nil {
+			return err
+		}
+		_, rhsNum, err := parseInt64(rhs.Value)
+		if err != nil {
+			return err
+		}
+		remainder := lhsNum % rhsNum
+
+		target.Node.Tag = lhs.Tag
+		target.Node.Value = fmt.Sprintf(format, remainder)
+	} else if (lhsTag == "!!int" || lhsTag == "!!float") && (rhsTag == "!!int" || rhsTag == "!!float") {
+		target.Node.Kind = yaml.ScalarNode
+		target.Node.Style = lhs.Style
+
+		lhsNum, err := strconv.ParseFloat(lhs.Value, 64)
+		if err != nil {
+			return err
+		}
+		rhsNum, err := strconv.ParseFloat(rhs.Value, 64)
+		if err != nil {
+			return err
+		}
+		remainder := math.Mod(lhsNum, rhsNum)
+		if lhsIsCustom {
+			target.Node.Tag = lhs.Tag
+		} else {
+			target.Node.Tag = "!!float"
+		}
+		target.Node.Value = fmt.Sprintf("%v", remainder)
+	} else {
+		return fmt.Errorf("%v cannot modulo by %v", lhsTag, rhsTag)
+	}
+	return nil
+}

pkg/yqlib/operator_modulo_test.go

@@ -0,0 +1,104 @@
+package yqlib
+
+import (
+	"testing"
+)
+
+var moduloOperatorScenarios = []expressionScenario{
+	{
+		skipDoc:    true,
+		document:   `[{a: 2.5, b: 2}, {a: 2, b: 0.75}]`,
+		expression: ".[] | .a % .b",
+		expected: []string{
+			"D0, P[0 a], (!!float)::0.5\n",
+			"D0, P[1 a], (!!float)::0.5\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   `{}`,
+		expression: "(.a / .b) as $x | .",
+		expected: []string{
+			"D0, P[], (doc)::{}\n",
+		},
+	},
+	{
+		description:    "Number modulo - int",
+		subdescription: "If the lhs and rhs are ints then the expression will be calculated with ints.",
+		document:       `{a: 13, b: 2}`,
+		expression:     `.a = .a % .b`,
+		expected: []string{
+			"D0, P[], (doc)::{a: 1, b: 2}\n",
+		},
+	},
+	{
+		description:    "Number modulo - float",
+		subdescription: "If the lhs or rhs are floats then the expression will be calculated with floats.",
+		document:       `{a: 12, b: 2.5}`,
+		expression:     `.a = .a % .b`,
+		expected: []string{
+			"D0, P[], (doc)::{a: !!float 2, b: 2.5}\n",
+		},
+	},
+	{
+		skipDoc:     true,
+		description: "Custom types: that are really numbers",
+		document:    "a: !horse 333.975\nb: !goat 299.2",
+		expression:  `.a = .a % .b`,
+		expected: []string{
+			"D0, P[], (doc)::a: !horse 34.775000000000034\nb: !goat 299.2\n",
+		},
+	},
+	{
+		skipDoc:    true,
+		document:   "a: 2\nb: !goat 2.3",
+		expression: `.a = .a % .b`,
+		expected: []string{
+			"D0, P[], (doc)::a: !!float 2\nb: !goat 2.3\n",
+		},
+	},
+	{
+		skipDoc:     true,
+		description: "Keep anchors",
+		document:    "a: &horse [1]",
+		expression:  `.a[1] = .a[0] % 2`,
+		expected: []string{
+			"D0, P[], (doc)::a: &horse [1, 1]\n",
+		},
+	},
+	{
+		skipDoc:       true,
+		description:   "Modulo int by string",
+		document:      "a: 123\nb: '2'",
+		expression:    `.a % .b`,
+		expectedError: "!!int cannot modulo by !!str",
+	},
+	{
+		skipDoc:       true,
+		description:   "Modulo string by int",
+		document:      "a: 2\nb: '123'",
+		expression:    `.b % .a`,
+		expectedError: "!!str cannot modulo by !!int",
+	},
+	{
+		skipDoc:       true,
+		description:   "Modulo map by int",
+		document:      "a: {\"a\":1}\nb: 2",
+		expression:    `.a % .b`,
+		expectedError: "!!map (a) cannot modulo by !!int (b)",
+	},
+	{
+		skipDoc:       true,
+		description:   "Modulo array by str",
+		document:      "a: [1,2]\nb: '2'",
+		expression:    `.a % .b`,
+		expectedError: "!!seq (a) cannot modulo by !!str (b)",
+	},
+}
+
+func TestModuloOperatorScenarios(t *testing.T) {
+	for _, tt := range moduloOperatorScenarios {
+		testScenario(t, &tt)
+	}
+	documentOperatorScenarios(t, "modulo", moduloOperatorScenarios)
+}