[pkg/ottl] Add Double converter (#27457)

**Description:** Adding a Double converter to pkg/ottl

**Link to tracking Issue:** closes #22056

.chloggen/double-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: doubleconverter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: "Adding a double converter into pkg/ottl"
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [22056]
+
+# (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

@@ -294,6 +294,7 @@ Available Converters:
 - [ExtractPatterns](#extractpatterns)
 - [FNV](#fnv)
 - [Hours](#hours)
+- [Double](#double)
 - [Duration](#duration)
 - [Int](#int)
 - [IsMap](#ismap)
@@ -365,6 +366,29 @@ Examples:
 
 - `ConvertCase(metric.name, "snake")`
 
+### Double
+
+The `Double` Converter converts an inputted `value` into a double.
+
+The returned type is float64.
+
+The input `value` types:
+* float64. returns the `value` without changes.
+* string. Tries to parse a double from string. If it fails then nil will be returned.
+* bool. If `value` is true, then the function will return 1 otherwise 0.
+* int64. The function converts the integer to a double.
+
+If `value` is another type or parsing failed nil is always returned.
+
+The `value` is either a path expression to a telemetry field to retrieve or a literal.
+
+Examples:
+
+- `Double(attributes["http.status_code"])`
+
+
+- `Double("2.0")`
+
 ### Duration
 
 `Duration(duration)`

pkg/ottl/ottlfuncs/func_double.go

@@ -0,0 +1,42 @@
+// 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 DoubleArguments[K any] struct {
+	Target ottl.FloatLikeGetter[K]
+}
+
+func NewDoubleFactory[K any]() ottl.Factory[K] {
+	return ottl.NewFactory("Double", &DoubleArguments[K]{}, createDoubleFunction[K])
+}
+
+func createDoubleFunction[K any](_ ottl.FunctionContext, oArgs ottl.Arguments) (ottl.ExprFunc[K], error) {
+	args, ok := oArgs.(*DoubleArguments[K])
+
+	if !ok {
+		return nil, fmt.Errorf("DoubleFactory args must be of type *DoubleArguments[K]")
+	}
+
+	return doubleFunc(args.Target), nil
+}
+
+func doubleFunc[K any](target ottl.FloatLikeGetter[K]) ottl.ExprFunc[K] {
+	return func(ctx context.Context, tCtx K) (interface{}, error) {
+		value, err := target.Get(ctx, tCtx)
+		if err != nil {
+			return nil, err
+		}
+		if value == nil {
+			return nil, nil
+		}
+		return *value, nil
+	}
+}

pkg/ottl/ottlfuncs/func_double_test.go

@@ -0,0 +1,93 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package ottlfuncs
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
+)
+
+func Test_Double(t *testing.T) {
+	tests := []struct {
+		name     string
+		value    interface{}
+		expected interface{}
+		err      bool
+	}{
+		{
+			name:     "string",
+			value:    "50",
+			expected: float64(50),
+		},
+		{
+			name:     "empty string",
+			value:    "",
+			expected: nil,
+			err:      true,
+		},
+		{
+			name:     "not a number string",
+			value:    "test",
+			expected: nil,
+			err:      true,
+		},
+		{
+			name:     "int64",
+			value:    int64(333),
+			expected: float64(333),
+		},
+		{
+			name:     "float64",
+			value:    float64(2.7),
+			expected: float64(2.7),
+		},
+		{
+			name:     "float64 without decimal",
+			value:    float64(55),
+			expected: float64(55),
+		},
+		{
+			name:     "true",
+			value:    true,
+			expected: float64(1),
+		},
+		{
+			name:     "false",
+			value:    false,
+			expected: float64(0),
+		},
+		{
+			name:     "nil",
+			value:    nil,
+			expected: nil,
+		},
+		{
+			name:     "some struct",
+			value:    struct{}{},
+			expected: nil,
+			err:      true,
+		},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			exprFunc := doubleFunc[interface{}](&ottl.StandardFloatLikeGetter[interface{}]{
+
+				Getter: func(context.Context, interface{}) (interface{}, error) {
+					return test.value, nil
+				},
+			})
+			result, err := exprFunc(nil, nil)
+			if test.err {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+			}
+			assert.Equal(t, test.expected, result)
+		})
+	}
+}

pkg/ottl/ottlfuncs/functions.go

@@ -36,6 +36,7 @@ func converters[K any]() []ottl.Factory[K] {
 		// Converters
 		NewConcatFactory[K](),
 		NewConvertCaseFactory[K](),
+		NewDoubleFactory[K](),
 		NewDurationFactory[K](),
 		NewExtractPatternsFactory[K](),
 		NewFnvFactory[K](),