Buffered Iterator Constructor

README.md

@@ -27,7 +27,7 @@ Please check the [releases](https://github.com/mochidev/AsyncSequenceReader/rele
 
 ```swift
 dependencies: [
-    .package(url: "https://github.com/mochidev/AsyncSequenceReader.git", .upToNextMinor(from: "0.4.0")),
+    .package(url: "https://github.com/mochidev/AsyncSequenceReader.git", .upToNextMinor(from: "0.4.1")),
 ],
 ...
 targets: [

Sources/AsyncSequenceReader/AsyncBufferedIterator.swift

@@ -76,3 +76,9 @@ public struct AsyncBufferedIterator<BaseIterator: AsyncIteratorProtocol>: AsyncI
 }
 
 extension AsyncBufferedIterator: Sendable where BaseIterator.Element: Sendable {}
+
+extension AsyncSequence {
+    public func makeBufferedIterator() -> AsyncBufferedIterator<AsyncIterator> {
+        AsyncBufferedIterator(makeAsyncIterator())
+    }
+}

Sources/AsyncSequenceReader/AsyncReadSequence.swift

@@ -39,7 +39,7 @@ extension AsyncIteratorProtocol {
             results = try await sequenceTransform(readSequence)
             wrappedIterator = readSequence.baseIterator
         }
-        precondition(wrappedIterator.unconsumedBuffer.isEmpty, "A transform was requested, but the sequence was left in a state where the next value will never be read (fix: Use AnyReadableSequence(iterator) instead of calling `.transform` on `iterator` directly)")
+        precondition(wrappedIterator.unconsumedBuffer.isEmpty, "A transform was requested, but the sequence was left in a state where the next value will never be read (fix: Use `sequence.makeBufferedIterator()` instead of calling `.transform` on `iterator` directly)")
         self = wrappedIterator.baseIterator
 
         return results

Tests/AsyncSequenceReaderTests/AsyncBufferedIteratorTests.swift

@@ -48,6 +48,37 @@ import Testing
         #expect(await bufferedIterator.next() == nil)
     }
 
+    @Test func bufferIteratorFromStreamConstructor() async throws {
+        let testStream = AsyncStream<Int> { continuation in
+            for value in 0..<10 {
+                continuation.yield(value)
+            }
+            continuation.finish()
+        }
+
+        var iterator = testStream.makeBufferedIterator()
+
+        #expect(await iterator.next() == 0)
+        #expect(await iterator.next() == 1)
+        #expect(await iterator.next() == 2)
+        #expect(await iterator.next() == 3)
+        #expect(await iterator.next() == 4)
+        #expect(await iterator.hasMoreData() == true)
+        #expect(await iterator.hasMoreData() == true)
+        #expect(await iterator.hasMoreData() == true)
+        #expect(await iterator.next() == 5)
+        #expect(try await iterator.nonIsolatedNext() == 6)
+        #expect(await iterator.next() == 7)
+        #expect(await iterator.next() == 8)
+        #expect(await iterator.hasMoreData() == true)
+        #expect(await iterator.next() == 9)
+        #expect(await iterator.hasMoreData() == false)
+        #expect(await iterator.next() == nil)
+        #expect(await iterator.hasMoreData() == false)
+        #expect(await iterator.hasMoreData() == false)
+        #expect(await iterator.next() == nil)
+    }
+
     @Test func bufferIteratorFromTestSequence() async throws {
         let testStream = TestSequence(base: 0..<10)
 

Tests/AsyncSequenceReaderTests/AsyncSequenceReaderTests.swift

@@ -294,7 +294,7 @@ import Testing
             })
         }
         #if DEBUG
-        #expect(result?.standardErrorUTF8Lines.first == "AsyncSequenceReader/AsyncReadSequence.swift:42: Precondition failed: A transform was requested, but the sequence was left in a state where the next value will never be read (fix: Use AnyReadableSequence(iterator) instead of calling `.transform` on `iterator` directly)")
+        #expect(result?.standardErrorUTF8Lines.first == "AsyncSequenceReader/AsyncReadSequence.swift:42: Precondition failed: A transform was requested, but the sequence was left in a state where the next value will never be read (fix: Use `sequence.makeBufferedIterator()` instead of calling `.transform` on `iterator` directly)")
         #endif
     }
 
@@ -313,7 +313,7 @@ import Testing
             })
         }
         #if DEBUG
-        #expect(result?.standardErrorUTF8Lines.first == "AsyncSequenceReader/AsyncReadSequence.swift:42: Precondition failed: A transform was requested, but the sequence was left in a state where the next value will never be read (fix: Use AnyReadableSequence(iterator) instead of calling `.transform` on `iterator` directly)")
+        #expect(result?.standardErrorUTF8Lines.first == "AsyncSequenceReader/AsyncReadSequence.swift:42: Precondition failed: A transform was requested, but the sequence was left in a state where the next value will never be read (fix: Use `sequence.makeBufferedIterator()` instead of calling `.transform` on `iterator` directly)")
         #endif
     }
 }