chore: import upstream snapshot with attribution

server/plpgsql/reconcile_labels.go

@@ -0,0 +1,90 @@
+// Copyright 2025 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package plpgsql
+
+import (
+	"github.com/cockroachdb/errors"
+
+	"github.com/dolthub/doltgresql/utils"
+)
+
+// labelStackItem is the stack item used while reconciling labels.
+type labelStackItem struct {
+	label  string
+	start  int
+	isLoop bool
+}
+
+// reconcileLabels handles all GOTO operations that may point to a label, since labels may be nested/shadowed. It's
+// easier to perform this is a final step, rather than trying to reconcile them during the operation conversion step.
+func reconcileLabels(ops []InterpreterOperation) error {
+	labels := utils.NewStack[labelStackItem]()
+	gotos := make(map[int]*InterpreterOperation)
+	for opIndex, operation := range ops {
+		switch operation.OpCode {
+		case OpCode_Goto:
+			// When this is true, we have a label
+			if len(operation.PrimaryData) > 0 {
+				if operation.Index < 0 {
+					// This is a CONTINUE, so we already know the index that we need to go to
+					found := false
+					for i := 0; i < labels.Len(); i++ {
+						stackItem := labels.PeekDepth(i)
+						if stackItem.label == operation.PrimaryData {
+							if !stackItem.isLoop {
+								return errors.New("CONTINUE cannot be used outside a loop")
+							}
+							found = true
+							ops[opIndex].Index = stackItem.start
+							ops[opIndex].PrimaryData = ""
+							break
+						}
+					}
+					if !found {
+						return errors.Errorf(`there is no label "%s" attached to any block or loop enclosing this statement`, operation.PrimaryData)
+					}
+				} else {
+					// This is an EXIT, so we'll save it for later
+					gotos[opIndex] = &ops[opIndex]
+				}
+			}
+		case OpCode_ScopeBegin:
+			// We'll push the label and loop status to the stack
+			labels.Push(labelStackItem{
+				label:  operation.PrimaryData,
+				start:  opIndex + 1, // We want to go to the operation after this one, else we'll continually increase the scope
+				isLoop: len(operation.Target) > 0,
+			})
+			// We clear the label and loop status since we only set them for reconciliation
+			ops[opIndex].PrimaryData = ""
+			ops[opIndex].Target = ""
+		case OpCode_ScopeEnd:
+			stackItem := labels.Pop()
+			for gotoIdx, gotoOp := range gotos {
+				if gotoOp.PrimaryData == stackItem.label {
+					gotoOp.Index = opIndex // We want to go to this operation, as we want to exit the scope
+					gotoOp.PrimaryData = ""
+					delete(gotos, gotoIdx)
+				}
+			}
+		}
+	}
+	if len(gotos) > 0 {
+		for _, op := range gotos {
+			return errors.Errorf(`there is no label "%s" attached to any block or loop enclosing this statement`, op.PrimaryData)
+		}
+	}
+	return nil
+}