feat: add IsDouble function (#29076)

**Description:** Adds new a new `IsDouble` function to facilitate type
checking. Most useful when checking the type of a body to determine if
it needs to be parsed or not.

**Link to tracking Issue:**
#27895

**Testing:** Added unit test

**Documentation:** Updated the func readme.

Co-authored-by: Tyler Helmuth <12352919+TylerHelmuth@users.noreply.github.com>

.chloggen/etiennep.issue-27895-IsDouble-converter.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: pkg/ottl
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add new IsDouble function to facilitate type checking.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [27895]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

pkg/ottl/ottlfuncs/README.md

@@ -298,6 +298,7 @@ Available Converters:
 - [Duration](#duration)
 - [Int](#int)
 - [IsBool](#isbool)
+- [IsDouble](#isdouble)
 - [IsMap](#ismap)
 - [IsMatch](#ismatch)
 - [IsString](#isstring)
@@ -507,6 +508,22 @@ Examples:
 
 - `IsBool(attributes["any key"])`
 
+### IsDouble
+
+`IsDouble(value)`
+
+The `IsDouble` Converter returns true if the given value is a double.
+
+The `value` is either a path expression to a telemetry field to retrieve, or a literal.
+
+If `value` is a `float64` or a `pcommon.ValueTypeDouble` then returns `true`, otherwise returns `false`.
+
+Examples:
+
+- `IsDouble(body)`
+
+- `IsDouble(attributes["maybe a double"])`
+
 ### IsMap
 
 `IsMap(value)`

pkg/ottl/ottlfuncs/func_is_double.go

@@ -0,0 +1,45 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package ottlfuncs // import "github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl/ottlfuncs"
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
+)
+
+type IsDoubleArguments[K any] struct {
+	Target ottl.FloatGetter[K]
+}
+
+func NewIsDoubleFactory[K any]() ottl.Factory[K] {
+	return ottl.NewFactory("IsDouble", &IsDoubleArguments[K]{}, createIsDoubleFunction[K])
+}
+
+func createIsDoubleFunction[K any](_ ottl.FunctionContext, oArgs ottl.Arguments) (ottl.ExprFunc[K], error) {
+	args, ok := oArgs.(*IsDoubleArguments[K])
+
+	if !ok {
+		return nil, fmt.Errorf("IsDoubleFactory args must be of type *IsDoubleArguments[K]")
+	}
+
+	return isDouble(args.Target), nil
+}
+
+// nolint:errorlint
+func isDouble[K any](target ottl.FloatGetter[K]) ottl.ExprFunc[K] {
+	return func(ctx context.Context, tCtx K) (any, error) {
+		_, err := target.Get(ctx, tCtx)
+		// Use type assertion because we don't want to check wrapped errors
+		switch err.(type) {
+		case ottl.TypeError:
+			return false, nil
+		case nil:
+			return true, nil
+		default:
+			return false, err
+		}
+	}
+}

pkg/ottl/ottlfuncs/func_is_double_test.go

@@ -0,0 +1,84 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package ottlfuncs
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"go.opentelemetry.io/collector/pdata/pcommon"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
+)
+
+func Test_IsDouble(t *testing.T) {
+	tests := []struct {
+		name     string
+		value    any
+		expected bool
+	}{
+		{
+			name:     "float64",
+			value:    float64(2.7),
+			expected: true,
+		},
+		{
+			name:     "float64 without decimal",
+			value:    float64(55),
+			expected: true,
+		},
+		{
+			name:     "an integer",
+			value:    int64(333),
+			expected: false,
+		},
+		{
+			name:     "ValueTypeDouble",
+			value:    pcommon.NewValueDouble(5.5),
+			expected: true,
+		},
+		{
+			name:     "not a number",
+			value:    "string",
+			expected: false,
+		},
+		{
+			name:     "ValueTypeSlice",
+			value:    pcommon.NewValueSlice(),
+			expected: false,
+		},
+		{
+			name:     "nil",
+			value:    nil,
+			expected: false,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			exprFunc := isDouble[any](&ottl.StandardFloatGetter[any]{
+				Getter: func(context.Context, any) (any, error) {
+					return tt.value, nil
+				},
+			})
+			result, err := exprFunc(context.Background(), nil)
+			assert.NoError(t, err)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}
+
+// nolint:errorlint
+func Test_IsDouble_Error(t *testing.T) {
+	exprFunc := isString[any](&ottl.StandardStringGetter[any]{
+		Getter: func(context.Context, any) (any, error) {
+			return nil, ottl.TypeError("")
+		},
+	})
+	result, err := exprFunc(context.Background(), nil)
+	assert.Equal(t, false, result)
+	assert.Error(t, err)
+	_, ok := err.(ottl.TypeError)
+	assert.False(t, ok)
+}

pkg/ottl/ottlfuncs/functions.go

@@ -43,6 +43,7 @@ func converters[K any]() []ottl.Factory[K] {
 		NewHoursFactory[K](),
 		NewIntFactory[K](),
 		NewIsBoolFactory[K](),
+		NewIsDoubleFactory[K](),
 		NewIsMapFactory[K](),
 		NewIsMatchFactory[K](),
 		NewIsStringFactory[K](),