[ottl/pkg] Remove the ottlarg struct tag for the arguments and rely o…

…n field ordering (#25705)

Remove the ottlarg struct tag and rely on field ordering
**Link to tracking Issue:**
#24874

pkg/ottl/expression.go

@@ -280,15 +280,7 @@ func (g StandardFunctionGetter[K]) Get(args Arguments) (Expr[K], error) {
 	}
 	for i := 0; i < fArgsVal.NumField(); i++ {
 		field := argsVal.Field(i)
-		argIndex, err := getArgumentIndex(i, argsVal)
-		if err != nil {
-			return Expr[K]{}, err
-		}
-		fArgIndex, err := getArgumentIndex(argIndex, fArgsVal)
-		if err != nil {
-			return Expr[K]{}, err
-		}
-		fArgsVal.Field(fArgIndex).Set(field)
+		fArgsVal.Field(i).Set(field)
 	}
 	fn, err := g.fact.CreateFunction(g.fCtx, fArgs)
 	if err != nil {

pkg/ottl/expression_test.go

@@ -690,11 +690,6 @@ func Test_FunctionGetter(t *testing.T) {
 			&multipleArgsArguments{},
 			functionWithStringGetter,
 		),
-		createFactory[any](
-			"no_struct_tag",
-			&noStructTagFunctionArguments{},
-			functionWithStringGetter,
-		),
 		NewFactory(
 			"cannot_create_function",
 			&stringGetterArguments{},
@@ -753,18 +748,6 @@ func Test_FunctionGetter(t *testing.T) {
 			valid:            false,
 			expectedErrorMsg: "incorrect number of arguments. Expected: 4 Received: 1",
 		},
-		{
-			name: "Invalid Arguments struct tag",
-			getter: StandardStringGetter[interface{}]{
-				Getter: func(ctx context.Context, tCtx interface{}) (interface{}, error) {
-					return nil, nil
-				},
-			},
-			function:         StandardFunctionGetter[any]{fCtx: FunctionContext{Set: componenttest.NewNopTelemetrySettings()}, fact: functions["no_struct_tag"]},
-			want:             "anything",
-			valid:            false,
-			expectedErrorMsg: "no `ottlarg` struct tag on Arguments field \"StringArg\"",
-		},
 		{
 			name: "Cannot create function",
 			getter: StandardStringGetter[interface{}]{

pkg/ottl/functions.go

@@ -7,7 +7,6 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
-	"strconv"
 	"strings"
 )
 
@@ -47,22 +46,6 @@ func (p *Parser[K]) newFunctionCall(ed editor) (Expr[K], error) {
 	return Expr[K]{exprFunc: fn}, err
 }
 
-func getArgumentIndex(index int, args reflect.Value) (int, error) {
-	argsType := args.Type()
-	fieldTag, ok := argsType.Field(index).Tag.Lookup("ottlarg")
-	if !ok {
-		return 0, fmt.Errorf("no `ottlarg` struct tag on Arguments field %q", argsType.Field(index).Name)
-	}
-	argNum, err := strconv.Atoi(fieldTag)
-	if err != nil {
-		return 0, fmt.Errorf("ottlarg struct tag on field %q is not a valid integer: %w", argsType.Field(index).Name, err)
-	}
-	if argNum < 0 || argNum >= args.NumField() {
-		return 0, fmt.Errorf("ottlarg struct tag on field %q has value %d, but must be between 0 and %d", argsType.Field(index).Name, argNum, args.NumField())
-	}
-	return argNum, nil
-}
-
 func (p *Parser[K]) buildArgs(ed editor, argsVal reflect.Value) error {
 	if len(ed.Arguments) != argsVal.NumField() {
 		return fmt.Errorf("incorrect number of arguments. Expected: %d Received: %d", argsVal.NumField(), len(ed.Arguments))
@@ -71,12 +54,9 @@ func (p *Parser[K]) buildArgs(ed editor, argsVal reflect.Value) error {
 	for i := 0; i < argsVal.NumField(); i++ {
 		field := argsVal.Field(i)
 		fieldType := field.Type()
-		argNum, err := getArgumentIndex(i, argsVal)
-		if err != nil {
-			return err
-		}
-		argVal := ed.Arguments[argNum]
+		argVal := ed.Arguments[i]
 		var val any
+		var err error
 		switch {
 		case strings.HasPrefix(fieldType.Name(), "FunctionGetter"):
 			var name string

pkg/ottl/functions_test.go

@@ -63,31 +63,6 @@ func Test_NewFunctionCall_invalid(t *testing.T) {
 			errorFunctionArguments{},
 			functionThatHasAnError,
 		),
-		createFactory(
-			"no_struct_tag",
-			&noStructTagFunctionArguments{},
-			functionThatHasAnError,
-		),
-		createFactory(
-			"wrong_struct_tag",
-			&wrongTagFunctionArguments{},
-			functionThatHasAnError,
-		),
-		createFactory(
-			"bad_struct_tag",
-			&badStructTagFunctionArguments{},
-			functionThatHasAnError,
-		),
-		createFactory(
-			"negative_struct_tag",
-			&negativeStructTagFunctionArguments{},
-			functionThatHasAnError,
-		),
-		createFactory(
-			"out_of_bounds_struct_tag",
-			&outOfBoundsStructTagFunctionArguments{},
-			functionThatHasAnError,
-		),
 		createFactory(
 			"testing_unknown_function",
 			&functionGetterArguments{},
@@ -349,61 +324,6 @@ func Test_NewFunctionCall_invalid(t *testing.T) {
 				Function: "non_pointer",
 			},
 		},
-		{
-			name: "no struct tags",
-			inv: editor{
-				Function: "no_struct_tag",
-				Arguments: []value{
-					{
-						String: ottltest.Strp("str"),
-					},
-				},
-			},
-		},
-		{
-			name: "using the wrong struct tag",
-			inv: editor{
-				Function: "wrong_struct_tag",
-				Arguments: []value{
-					{
-						String: ottltest.Strp("str"),
-					},
-				},
-			},
-		},
-		{
-			name: "non-integer struct tags",
-			inv: editor{
-				Function: "bad_struct_tag",
-				Arguments: []value{
-					{
-						String: ottltest.Strp("str"),
-					},
-				},
-			},
-		},
-		{
-			name: "struct tag index too low",
-			inv: editor{
-				Function: "negative_struct_tag",
-				Arguments: []value{
-					{
-						String: ottltest.Strp("str"),
-					},
-				},
-			},
-		},
-		{
-			name: "struct tag index too high",
-			inv: editor{
-				Function: "out_of_bounds_struct_tag",
-				Arguments: []value{
-					{
-						String: ottltest.Strp("str"),
-					},
-				},
-			},
-		},
 	}
 
 	for _, tt := range tests {
@@ -1612,26 +1532,6 @@ func functionWithEnum(Enum) (ExprFunc[interface{}], error) {
 	}, nil
 }
 
-type noStructTagFunctionArguments struct {
-	StringArg string
-}
-
-type badStructTagFunctionArguments struct {
-	StringArg string `ottlarg:"a"`
-}
-
-type negativeStructTagFunctionArguments struct {
-	StringArg string `ottlarg:"-1"`
-}
-
-type outOfBoundsStructTagFunctionArguments struct {
-	StringArg string `ottlarg:"1"`
-}
-
-type wrongTagFunctionArguments struct {
-	StringArg string `argument:"1"`
-}
-
 func createFactory[A any](name string, args A, fn any) Factory[any] {
 	createFunction := func(fCtx FunctionContext, oArgs Arguments) (ExprFunc[any], error) {
 		fArgs, ok := oArgs.(A)

pkg/ottl/ottlfuncs/func_concat.go

@@ -12,8 +12,8 @@ import (
 )
 
 type ConcatArguments[K any] struct {
-	Vals      []ottl.StringLikeGetter[K] `ottlarg:"0"`
-	Delimiter string                     `ottlarg:"1"`
+	Vals      []ottl.StringLikeGetter[K]
+	Delimiter string
 }
 
 func NewConcatFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_convert_case.go

@@ -14,8 +14,8 @@ import (
 )
 
 type ConvertCaseArguments[K any] struct {
-	Target ottl.StringGetter[K] `ottlarg:"0"`
-	ToCase string               `ottlarg:"1"`
+	Target ottl.StringGetter[K]
+	ToCase string
 }
 
 func NewConvertCaseFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_delete_key.go

@@ -11,8 +11,8 @@ import (
 )
 
 type DeleteKeyArguments[K any] struct {
-	Target ottl.PMapGetter[K] `ottlarg:"0"`
-	Key    string             `ottlarg:"1"`
+	Target ottl.PMapGetter[K]
+	Key    string
 }
 
 func NewDeleteKeyFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_delete_matching_keys.go

@@ -14,8 +14,8 @@ import (
 )
 
 type DeleteMatchingKeysArguments[K any] struct {
-	Target  ottl.PMapGetter[K] `ottlarg:"0"`
-	Pattern string             `ottlarg:"1"`
+	Target  ottl.PMapGetter[K]
+	Pattern string
 }
 
 func NewDeleteMatchingKeysFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_duration.go

@@ -12,7 +12,7 @@ import (
 )
 
 type DurationArguments[K any] struct {
-	Duration ottl.StringGetter[K] `ottlarg:"0"`
+	Duration ottl.StringGetter[K]
 }
 
 func NewDurationFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_fnv.go

@@ -12,7 +12,7 @@ import (
 )
 
 type FnvArguments[K any] struct {
-	Target ottl.StringGetter[K] `ottlarg:"0"`
+	Target ottl.StringGetter[K]
 }
 
 func NewFnvFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_int.go

@@ -11,7 +11,7 @@ import (
 )
 
 type IntArguments[K any] struct {
-	Target ottl.IntLikeGetter[K] `ottlarg:"0"`
+	Target ottl.IntLikeGetter[K]
 }
 
 func NewIntFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_is_map.go

@@ -11,7 +11,7 @@ import (
 )
 
 type IsMapArguments[K any] struct {
-	Target ottl.PMapGetter[K] `ottlarg:"0"`
+	Target ottl.PMapGetter[K]
 }
 
 func NewIsMapFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_is_match.go

@@ -12,8 +12,8 @@ import (
 )
 
 type IsMatchArguments[K any] struct {
-	Target  ottl.StringLikeGetter[K] `ottlarg:"0"`
-	Pattern string                   `ottlarg:"1"`
+	Target  ottl.StringLikeGetter[K]
+	Pattern string
 }
 
 func NewIsMatchFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_is_string.go

@@ -11,7 +11,7 @@ import (
 )
 
 type IsStringArguments[K any] struct {
-	Target ottl.StringGetter[K] `ottlarg:"0"`
+	Target ottl.StringGetter[K]
 }
 
 func NewIsStringFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_keep_keys.go

@@ -13,8 +13,8 @@ import (
 )
 
 type KeepKeysArguments[K any] struct {
-	Target ottl.PMapGetter[K] `ottlarg:"0"`
-	Keys   []string           `ottlarg:"1"`
+	Target ottl.PMapGetter[K]
+	Keys   []string
 }
 
 func NewKeepKeysFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_len.go

@@ -21,7 +21,7 @@ const (
 )
 
 type LenArguments[K any] struct {
-	Target ottl.Getter[K] `ottlarg:"0"`
+	Target ottl.Getter[K]
 }
 
 func NewLenFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_limit.go

@@ -13,9 +13,9 @@ import (
 )
 
 type LimitArguments[K any] struct {
-	Target       ottl.PMapGetter[K] `ottlarg:"0"`
-	Limit        int64              `ottlarg:"1"`
-	PriorityKeys []string           `ottlarg:"2"`
+	Target       ottl.PMapGetter[K]
+	Limit        int64
+	PriorityKeys []string
 }
 
 func NewLimitFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_log.go

@@ -12,7 +12,7 @@ import (
 )
 
 type LogArguments[K any] struct {
-	Target ottl.FloatLikeGetter[K] `ottlarg:"0"`
+	Target ottl.FloatLikeGetter[K]
 }
 
 func NewLogFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_merge_maps.go

@@ -19,9 +19,9 @@ const (
 )
 
 type MergeMapsArguments[K any] struct {
-	Target   ottl.PMapGetter[K] `ottlarg:"0"`
-	Source   ottl.PMapGetter[K] `ottlarg:"1"`
-	Strategy string             `ottlarg:"2"`
+	Target   ottl.PMapGetter[K]
+	Source   ottl.PMapGetter[K]
+	Strategy string
 }
 
 func NewMergeMapsFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_parse_json.go

@@ -14,7 +14,7 @@ import (
 )
 
 type ParseJSONArguments[K any] struct {
-	Target ottl.StringGetter[K] `ottlarg:"0"`
+	Target ottl.StringGetter[K]
 }
 
 func NewParseJSONFactory[K any]() ottl.Factory[K] {

pkg/ottl/ottlfuncs/func_replace_all_matches.go

@@ -14,9 +14,9 @@ import (
 )
 
 type ReplaceAllMatchesArguments[K any] struct {
-	Target      ottl.PMapGetter[K]   `ottlarg:"0"`
-	Pattern     string               `ottlarg:"1"`
-	Replacement ottl.StringGetter[K] `ottlarg:"2"`
+	Target      ottl.PMapGetter[K]
+	Pattern     string
+	Replacement ottl.StringGetter[K]
 }
 
 func NewReplaceAllMatchesFactory[K any]() ottl.Factory[K] {