Update PSQLRowStream.swift

Author: MahdiBM

Sources/PostgresNIO/New/PSQLRowStream.swift

@@ -32,13 +32,17 @@ final class PSQLRowStream: @unchecked Sendable {
         case empty
         case failure(Error)
     }
-    
+
+    private enum Consumed {
+        case tag(String)
+        case emptyResponse
+    }
+
     private enum DownstreamState {
         case waitingForConsumer(BufferState)
         case iteratingRows(onRow: (PostgresRow) throws -> (), EventLoopPromise<Void>, PSQLRowsDataSource)
         case waitingForAll([PostgresRow], EventLoopPromise<[PostgresRow]>, PSQLRowsDataSource)
-        case consumed(Result<String, Error>)
-        case finished
+        case consumed(Result<Consumed, Error>)
         case asyncSequence(AsyncSequenceSource, PSQLRowsDataSource, onFinish: @Sendable () -> ())
     }
 
@@ -108,13 +112,13 @@ final class PSQLRowStream: @unchecked Sendable {
         case .empty:
             source.finish()
             onFinish()
-            self.downstreamState = .finished
+            self.downstreamState = .consumed(.success(.emptyResponse))
 
         case .finished(let buffer, let commandTag):
             _ = source.yield(contentsOf: buffer)
             source.finish()
             onFinish()
-            self.downstreamState = .consumed(.success(commandTag))
+            self.downstreamState = .consumed(.success(.tag(commandTag)))
 
         case .failure(let error):
             source.finish(error)
@@ -139,7 +143,7 @@ final class PSQLRowStream: @unchecked Sendable {
         case .waitingForConsumer, .iteratingRows, .waitingForAll:
             preconditionFailure("Invalid state: \(self.downstreamState)")
 
-        case .consumed, .finished:
+        case .consumed:
             break
 
         case .asyncSequence(_, let dataSource, _):
@@ -164,7 +168,7 @@ final class PSQLRowStream: @unchecked Sendable {
             dataSource.cancel(for: self)
             onFinish()
 
-        case .consumed, .finished:
+        case .consumed:
             return
 
         case .waitingForConsumer, .iteratingRows, .waitingForAll:
@@ -207,15 +211,15 @@ final class PSQLRowStream: @unchecked Sendable {
                 PostgresRow(data: $0, lookupTable: self.lookupTable, columns: self.rowDescription)
             }
 
-            self.downstreamState = .consumed(.success(commandTag))
+            self.downstreamState = .consumed(.success(.tag(commandTag)))
             return self.eventLoop.makeSucceededFuture(rows)
 
         case .failure(let error):
             self.downstreamState = .consumed(.failure(error))
             return self.eventLoop.makeFailedFuture(error)
 
         case .empty:
-            self.downstreamState = .finished
+            self.downstreamState = .consumed(.success(.emptyResponse))
             return self.eventLoop.makeSucceededFuture([])
         }
     }
@@ -265,7 +269,7 @@ final class PSQLRowStream: @unchecked Sendable {
             return promise.futureResult
 
         case .empty:
-            self.downstreamState = .finished
+            self.downstreamState = .consumed(.success(.emptyResponse))
             return self.eventLoop.makeSucceededVoidFuture()
 
         case .finished(let buffer, let commandTag):
@@ -279,7 +283,7 @@ final class PSQLRowStream: @unchecked Sendable {
                     try onRow(row)
                 }
 
-                self.downstreamState = .consumed(.success(commandTag))
+                self.downstreamState = .consumed(.success(.tag(commandTag)))
                 return self.eventLoop.makeSucceededVoidFuture()
             } catch {
                 self.downstreamState = .consumed(.failure(error))
@@ -350,9 +354,6 @@ final class PSQLRowStream: @unchecked Sendable {
 
         case .consumed(.failure):
             break
-
-        case .finished:
-            preconditionFailure("How can we receive further rows, if we are supposed to be done")
         }
     }
 
@@ -376,22 +377,22 @@ final class PSQLRowStream: @unchecked Sendable {
             preconditionFailure("How can we get another end, if an end was already signalled?")
 
         case .iteratingRows(_, let promise, _):
-            self.downstreamState = .consumed(.success(commandTag))
+            self.downstreamState = .consumed(.success(.tag(commandTag)))
             promise.succeed(())
 
         case .waitingForAll(let rows, let promise, _):
-            self.downstreamState = .consumed(.success(commandTag))
+            self.downstreamState = .consumed(.success(.tag(commandTag)))
             promise.succeed(rows)
 
         case .asyncSequence(let source, _, let onFinish):
-            self.downstreamState = .consumed(.success(commandTag))
+            self.downstreamState = .consumed(.success(.tag(commandTag)))
             source.finish()
             onFinish()
 
-        case .consumed:
+        case .consumed(.success(.tag)), .consumed(.failure):
             break
 
-        case .finished, .waitingForConsumer(.empty):
+        case .consumed(.success(.emptyResponse)), .waitingForConsumer(.empty):
             preconditionFailure("How can we get an end for empty query response?")
         }
     }
@@ -417,10 +418,10 @@ final class PSQLRowStream: @unchecked Sendable {
             consumer.finish(error)
             onFinish()
 
-        case .consumed:
+        case .consumed(.success(.tag)), .consumed(.failure):
             break
 
-        case .finished:
+        case .consumed(.success(.emptyResponse)):
             preconditionFailure("How can we get an error for empty query response?")
         }
     }
@@ -442,13 +443,14 @@ final class PSQLRowStream: @unchecked Sendable {
     }
 
     var commandTag: String {
-        switch self.downstreamState {
-        case .consumed(.success(let commandTag)):
-            return commandTag
-        case .finished:
+        guard case .consumed(.success(let consumed)) = self.downstreamState else {
+            preconditionFailure("commandTag may only be called if all rows have been consumed")
+        }
+        switch consumed {
+        case .tag(let tag):
+            return tag
+        case .emptyResponse:
             return ""
-        default:
-            preconditionFailure("commandTag may only be called if there are no more rows to be consumed")
         }
     }
 }