Add ottl truncate editor

.chloggen/add-ottl-truncate-editor.yaml

@@ -0,0 +1,20 @@
+# Use this changelog template to create an entry for release notes.
+# If your change doesn't affect end users, such as a test fix or a tooling change,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+
+# 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 truncate editor
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [23847]
+
+# (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:

pkg/ottl/ottlfuncs/README.md

@@ -41,6 +41,7 @@ Available Editors:
 - [replace_match](#replace_match)
 - [replace_pattern](#replace_pattern)
 - [set](#set)
+- [truncate](#truncate)
 - [truncate_all](#truncate_all)
 
 ### delete_key
@@ -252,6 +253,20 @@ Examples:
 
 - `set(attributes["source"], trace_state["source"])`
 
+### truncate
+
+`truncate(target, limit)`
+
+The `truncate` function truncates the string value such that the result is no longer than the limit.
+
+`target` is a path expression to a telemetry field. `pattern` is a string following [filepath.Match syntax](https://pkg.go.dev/path/filepath#Match).
+
+The `target` will be mutated such that the number of characters in it is less than or equal to the limit. Non-string values are ignored.
+
+Examples:
+
+- `truncate(body, 100)`
+
 ### truncate_all
 
 `truncate_all(target, limit)`

pkg/ottl/ottlfuncs/func_truncate.go

@@ -0,0 +1,48 @@
+// 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 TruncateArguments[K any] struct {
+	Target ottl.GetSetter[K] `ottlarg:"0"`
+	Limit  int64             `ottlarg:"1"`
+}
+
+func NewTruncateFactory[K any]() ottl.Factory[K] {
+	return ottl.NewFactory("truncate", &TruncateArguments[K]{}, createTruncateFunction[K])
+}
+
+func createTruncateFunction[K any](_ ottl.FunctionContext, oArgs ottl.Arguments) (ottl.ExprFunc[K], error) {
+	args, ok := oArgs.(*TruncateArguments[K])
+
+	if !ok {
+		return nil, fmt.Errorf("TruncateFactory args must be of type *TruncateArguments[K]")
+	}
+
+	return truncate(args.Target, args.Limit)
+}
+
+func truncate[K any](target ottl.GetSetter[K], limit int64) (ottl.ExprFunc[K], error) {
+	if limit < 0 {
+		return nil, fmt.Errorf("invalid limit for truncate function, %d cannot be negative", limit)
+	}
+	return func(ctx context.Context, tCtx K) (interface{}, error) {
+		val, err := target.Get(ctx, tCtx)
+		if err != nil {
+			return nil, err
+		}
+		if valStr, ok := val.(string); ok {
+			if int64(len(valStr)) > limit {
+				return nil, target.Set(ctx, tCtx, valStr[:limit])
+			}
+		}
+		return nil, nil
+	}, nil
+}

pkg/ottl/ottlfuncs/func_truncate_all.go

@@ -36,10 +36,6 @@ func TruncateAll[K any](target ottl.PMapGetter[K], limit int64) (ottl.ExprFunc[K
 		return nil, fmt.Errorf("invalid limit for truncate_all function, %d cannot be negative", limit)
 	}
 	return func(ctx context.Context, tCtx K) (interface{}, error) {
-		if limit < 0 {
-			return nil, nil
-		}
-
 		val, err := target.Get(ctx, tCtx)
 		if err != nil {
 			return nil, err

pkg/ottl/ottlfuncs/func_truncate_test.go

@@ -0,0 +1,134 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package ottlfuncs
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.opentelemetry.io/collector/pdata/pcommon"
+
+	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
+)
+
+func Test_truncate(t *testing.T) {
+	input := pcommon.NewValueStr("hello world")
+
+	target := &ottl.StandardGetSetter[pcommon.Value]{
+		Getter: func(ctx context.Context, tCtx pcommon.Value) (interface{}, error) {
+			return tCtx.Str(), nil
+		},
+		Setter: func(ctx context.Context, tCtx pcommon.Value, val interface{}) error {
+			tCtx.SetStr(val.(string))
+			return nil
+		},
+	}
+
+	tests := []struct {
+		name   string
+		target ottl.GetSetter[pcommon.Value]
+		limit  int64
+		want   func(value pcommon.Value)
+	}{
+		{
+			name:   "below limit",
+			target: target,
+			limit:  20,
+			want: func(expectedValue pcommon.Value) {
+				expectedValue.SetStr("hello world")
+			},
+		},
+		{
+			name:   "above limit",
+			target: target,
+			limit:  10,
+			want: func(expectedValue pcommon.Value) {
+				expectedValue.SetStr("hello worl")
+			},
+		},
+		{
+			name:   "at limit",
+			target: target,
+			limit:  11,
+			want: func(expectedValue pcommon.Value) {
+				expectedValue.SetStr("hello world")
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			scenarioValue := pcommon.NewValueStr(input.Str())
+
+			exprFunc, err := truncate(tt.target, tt.limit)
+			assert.NoError(t, err)
+			result, err := exprFunc(nil, scenarioValue)
+			assert.NoError(t, err)
+			assert.Nil(t, result)
+
+			expected := pcommon.NewValueStr("")
+			tt.want(expected)
+
+			assert.Equal(t, expected, scenarioValue)
+		})
+	}
+}
+
+func Test_truncate_bad_input(t *testing.T) {
+	input := pcommon.NewValueInt(1)
+	target := &ottl.StandardGetSetter[interface{}]{
+		Getter: func(ctx context.Context, tCtx interface{}) (interface{}, error) {
+			return tCtx, nil
+		},
+		Setter: func(ctx context.Context, tCtx interface{}, val interface{}) error {
+			t.Errorf("nothing should be set in this scenario")
+			return nil
+		},
+	}
+
+	exprFunc, err := truncate[interface{}](target, 10)
+	assert.NoError(t, err)
+
+	result, err := exprFunc(nil, input)
+	assert.NoError(t, err)
+	assert.Nil(t, result)
+
+	assert.Equal(t, pcommon.NewValueInt(1), input)
+}
+
+func Test_truncate_get_nil(t *testing.T) {
+	target := &ottl.StandardGetSetter[interface{}]{
+		Getter: func(ctx context.Context, tCtx interface{}) (interface{}, error) {
+			return tCtx, nil
+		},
+		Setter: func(ctx context.Context, tCtx interface{}, val interface{}) error {
+			t.Errorf("nothing should be set in this scenario")
+			return nil
+		},
+	}
+
+	exprFunc, err := truncate[interface{}](target, 10)
+	assert.NoError(t, err)
+
+	result, err := exprFunc(nil, nil)
+	assert.NoError(t, err)
+	assert.Nil(t, result)
+}
+
+func Test_truncate_validation(t *testing.T) {
+	target := &ottl.StandardGetSetter[interface{}]{
+		Getter: func(ctx context.Context, tCtx interface{}) (interface{}, error) {
+			return tCtx, nil
+		},
+		Setter: func(ctx context.Context, tCtx interface{}, val interface{}) error {
+			t.Errorf("nothing should be set in this scenario")
+			return nil
+		},
+	}
+
+	_, err := truncate[interface{}](target, -1)
+	require.Error(t, err)
+	assert.ErrorContains(t, err, "invalid limit for truncate function, -1 cannot be negative")
+}

pkg/ottl/ottlfuncs/functions.go

@@ -20,6 +20,7 @@ func StandardFuncs[K any]() map[string]ottl.Factory[K] {
 		NewReplaceMatchFactory[K](),
 		NewReplacePatternFactory[K](),
 		NewSetFactory[K](),
+		NewTruncateFactory[K](),
 		NewTruncateAllFactory[K](),
 	}
 	f = append(f, converters[K]()...)