[pkg/ottl] Conflict resolution strategy for set function

.chloggen/set-conflicts.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: Added a conflict resolution strategy argument for `set` function
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [31808]
+
+# (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

@@ -332,14 +332,23 @@ If using OTTL outside of collector configuration, `$` should not be escaped and
 
 ### set
 
-`set(target, value)`
+`set(target, value, Optional[conflict_resolution_strategy])`
 
 The `set` function allows users to set a telemetry field using a value.
 
 `target` is a path expression to a telemetry field. `value` is any value type. If `value` resolves to `nil`, e.g. it references an unset map value, there will be no action.
 
 How the underlying telemetry field is updated is decided by the path expression implementation provided by the user to the `ottl.ParseStatements`.
 
+`conflict_resolution_strategy` specifies behavior in case of conflict and can fall into following cases:
+
+- **upsert**: Is the default behavior. This setting results in creating field in case it's missing or updating existing value.
+- **update**: This setting updates only existing value. In case value is missing no action is taken.
+- **insert**: Creates a new field in case it's not present. In case field is already present no action is taken.
+- **fail**: Similar to `insert` creates a field in case it's missing but returns an error otherwise.
+
+> In case field is preset but contains a zero value (e.g empty string, 0 for int64) it is considered missing.
+
 Examples:
 
 - `set(attributes["http.path"], "/foo")`

pkg/ottl/ottlfuncs/func_set.go

@@ -5,14 +5,28 @@ package ottlfuncs // import "github.com/open-telemetry/opentelemetry-collector-c
 
 import (
 	"context"
+	"errors"
 	"fmt"
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl"
+	"go.opentelemetry.io/collector/pdata/pcommon"
+)
+
+var (
+	ErrValueAlreadyPresent = errors.New("value already present")
+)
+
+const (
+	setConflictUpsert = "upsert"
+	setConflictFail   = "fail"
+	setConflictInsert = "insert"
+	setConflictUpdate = "update"
 )
 
 type SetArguments[K any] struct {
-	Target ottl.Setter[K]
-	Value  ottl.Getter[K]
+	Target           ottl.GetSetter[K]
+	Value            ottl.Getter[K]
+	ConflictStrategy ottl.Optional[string]
 }
 
 func NewSetFactory[K any]() ottl.Factory[K] {
@@ -26,10 +40,22 @@ func createSetFunction[K any](_ ottl.FunctionContext, oArgs ottl.Arguments) (ott
 		return nil, fmt.Errorf("SetFactory args must be of type *SetArguments[K]")
 	}
 
-	return set(args.Target, args.Value), nil
+	return set(args.Target, args.Value, args.ConflictStrategy)
 }
 
-func set[K any](target ottl.Setter[K], value ottl.Getter[K]) ottl.ExprFunc[K] {
+func set[K any](target ottl.GetSetter[K], value ottl.Getter[K], strategy ottl.Optional[string]) (ottl.ExprFunc[K], error) {
+	conflictStrategy := setConflictUpsert
+	if !strategy.IsEmpty() {
+		conflictStrategy = strategy.Get()
+	}
+
+	if conflictStrategy != setConflictUpsert &&
+		conflictStrategy != setConflictUpdate &&
+		conflictStrategy != setConflictFail &&
+		conflictStrategy != setConflictInsert {
+		return nil, fmt.Errorf("invalid value for conflict strategy, %v, must be %q, %q, %q or %q", conflictStrategy, setConflictUpsert, setConflictUpdate, setConflictFail, setConflictUpsert)
+	}
+
 	return func(ctx context.Context, tCtx K) (any, error) {
 		val, err := value.Get(ctx, tCtx)
 		if err != nil {
@@ -38,11 +64,99 @@ func set[K any](target ottl.Setter[K], value ottl.Getter[K]) ottl.ExprFunc[K] {
 
 		// No fields currently support `null` as a valid type.
 		if val != nil {
+			oldVal, err := target.Get(ctx, tCtx)
+			if err != nil {
+				return nil, err
+			}
+
+			valueMissing := oldVal == nil || isDefaultValue(oldVal)
+			switch conflictStrategy {
+			case setConflictUpsert:
+				// overwrites if present or create when missing
+			case setConflictUpdate:
+				// update existing field with a new value. If the field does not exist, then no action will be taken
+				if valueMissing {
+					return nil, nil
+				}
+			case setConflictFail:
+				// fail if target field present
+				if !valueMissing {
+					return nil, ErrValueAlreadyPresent
+				}
+			case setConflictInsert:
+				// noop if target field present
+				if !valueMissing {
+					return nil, nil
+				}
+			}
+
 			err = target.Set(ctx, tCtx, val)
 			if err != nil {
 				return nil, err
 			}
 		}
 		return nil, nil
+	}, nil
+}
+
+func isDefaultValue(val any) bool {
+	switch v := val.(type) {
+	case string:
+		return len(v) == 0
+	case bool:
+		return !v
+	case float64:
+		return v == 0
+	case int64:
+		return v == 0
+
+	case []byte:
+		return len(v) == 0
+	case []string:
+		return len(v) == 0
+	case []int64:
+		return len(v) == 0
+	case []float64:
+		return len(v) == 0
+	case [][]byte:
+		return len(v) == 0
+	case []any:
+		return len(v) == 0
+
+	case pcommon.ByteSlice:
+		return v.Len() == 0
+	case pcommon.Float64Slice:
+		return v.Len() == 0
+	case pcommon.UInt64Slice:
+		return v.Len() == 0
+	case pcommon.Slice:
+		return v.Len() == 0
+
+	case pcommon.Value:
+		if v.Type() == pcommon.ValueTypeStr ||
+			v.Type() == pcommon.ValueTypeBytes ||
+			v.Type() == pcommon.ValueTypeSlice {
+			return v.Bytes().Len() == 0
+		}
+		if v.Type() == pcommon.ValueTypeBool {
+			return !v.Bool()
+		}
+		if v.Type() == pcommon.ValueTypeDouble {
+			return v.Double() == 0
+		}
+		if v.Type() == pcommon.ValueTypeInt {
+			return v.Int() == 0
+		}
+
+		if v.Type() == pcommon.ValueTypeEmpty {
+			return true
+		}
+
+	case pcommon.Map:
+		return v.Len() == 0
+	case map[string]any:
+		return v == nil
 	}
+
+	return false
 }