stream: align Readable.toWeb termination with eos

lib/internal/streams/end-of-stream.js

@@ -7,6 +7,7 @@ const {
   Promise,
   PromisePrototypeThen,
   ReflectApply,
+  Symbol,
   SymbolDispose,
 } = primordials;
 
@@ -66,6 +67,125 @@ function bindAsyncResource(fn, type) {
   };
 }
 
+const kEosImmediateClose = Symbol('kEosImmediateClose');
+
+/**
+ * Returns the current stream error tracked by eos(), if any.
+ * @param {import('stream').Stream} stream
+ * @returns {Error | null}
+ */
+function getEosErrored(stream) {
+  const errored = isWritableErrored(stream) || isReadableErrored(stream);
+  return typeof errored !== 'boolean' && errored || null;
+}
+
+/**
+ * Returns the error eos() would report from an immediate close, including
+ * premature close detection for unfinished readable or writable sides.
+ * @param {import('stream').Stream} stream
+ * @param {boolean} readable
+ * @param {boolean | null} readableFinished
+ * @param {boolean} writable
+ * @param {boolean | null} writableFinished
+ * @returns {Error | typeof kEosImmediateClose}
+ */
+function getEosOnCloseError(stream, readable, readableFinished, writable, writableFinished) {
+  const errored = getEosErrored(stream);
+  if (errored) {
+    return errored;
+  }
+
+  if (readable && !readableFinished && isReadableNodeStream(stream, true)) {
+    if (!isReadableFinished(stream, false)) {
+      return new ERR_STREAM_PREMATURE_CLOSE();
+    }
+  }
+  if (writable && !writableFinished) {
+    if (!isWritableFinished(stream, false)) {
+      return new ERR_STREAM_PREMATURE_CLOSE();
+    }
+  }
+
+  return kEosImmediateClose;
+}
+
+function getEosInitialState(stream, options = kEmptyObject) {
+  const readable = options.readable ?? isReadableNodeStream(stream);
+  const writable = options.writable ?? isWritableNodeStream(stream);
+
+  // TODO (ronag): Improve soft detection to include core modules and
+  // common ecosystem modules that do properly emit 'close' but fail
+  // this generic check.
+  const willEmitClose = (
+    _willEmitClose(stream) &&
+    isReadableNodeStream(stream) === readable &&
+    isWritableNodeStream(stream) === writable
+  );
+
+  return {
+    readable,
+    writable,
+    willEmitClose,
+    writableFinished: isWritableFinished(stream, false),
+    readableFinished: isReadableFinished(stream, false),
+    closed: isClosed(stream),
+  };
+}
+
+/**
+ * Classifies whether eos() can synchronously determine the result for the
+ * current stream snapshot, or if it must defer to future events.
+ * @param {import('stream').Stream} stream
+ * @param {object} [options]
+ * @param {boolean} [options.readable]
+ * @param {boolean} [options.writable]
+ * @param {ReturnType<typeof getEosInitialState>} [state]
+ * @returns {Error | typeof kEosImmediateClose | null}
+ */
+function getEosImmediateResult(stream, options = kEmptyObject, state = getEosInitialState(stream, options)) {
+  const {
+    readable,
+    writable,
+    willEmitClose,
+    writableFinished,
+    readableFinished,
+    closed,
+  } = state;
+  const wState = stream._writableState;
+  const rState = stream._readableState;
+
+  if (closed) {
+    return getEosOnCloseError(
+      stream,
+      readable,
+      readableFinished,
+      writable,
+      writableFinished,
+    );
+  } else if (wState?.errorEmitted || rState?.errorEmitted) {
+    if (!willEmitClose) {
+      return getEosErrored(stream) ?? kEosImmediateClose;
+    }
+  } else if (
+    !readable &&
+    (!willEmitClose || isReadable(stream)) &&
+    (writableFinished || isWritable(stream) === false) &&
+    (wState == null || wState.pendingcb === undefined || wState.pendingcb === 0)
+  ) {
+    return getEosErrored(stream) ?? kEosImmediateClose;
+  } else if (
+    !writable &&
+    (!willEmitClose || isWritable(stream)) &&
+    (readableFinished || isReadable(stream) === false)
+  ) {
+    return getEosErrored(stream) ?? kEosImmediateClose;
+  } else if ((rState && stream.req && stream.aborted)) {
+    return getEosErrored(stream) ?? kEosImmediateClose;
+  }
+
+  return null;
+}
+
 function eos(stream, options, callback) {
   if (arguments.length === 2) {
     callback = options;
@@ -94,28 +214,22 @@ function eos(stream, options, callback) {
     throw new ERR_INVALID_ARG_TYPE('stream', ['ReadableStream', 'WritableStream', 'Stream'], stream);
   }
 
-  const readable = options.readable ?? isReadableNodeStream(stream);
-  const writable = options.writable ?? isWritableNodeStream(stream);
-
+  const eosState = getEosInitialState(stream, options);
   const wState = stream._writableState;
-  const rState = stream._readableState;
 
   const onlegacyfinish = () => {
     if (!stream.writable) {
       onfinish();
     }
   };
 
-  // TODO (ronag): Improve soft detection to include core modules and
-  // common ecosystem modules that do properly emit 'close' but fail
-  // this generic check.
-  let willEmitClose = (
-    _willEmitClose(stream) &&
-    isReadableNodeStream(stream) === readable &&
-    isWritableNodeStream(stream) === writable
-  );
-
-  let writableFinished = isWritableFinished(stream, false);
+  const { readable, writable } = eosState;
+  let {
+    willEmitClose,
+    writableFinished,
+    readableFinished,
+    closed,
+  } = eosState;
   const onfinish = () => {
     writableFinished = true;
     // Stream should not be destroyed here. If it is that
@@ -134,7 +248,6 @@ function eos(stream, options, callback) {
     }
   };
 
-  let readableFinished = isReadableFinished(stream, false);
   const onend = () => {
     readableFinished = true;
     // Stream should not be destroyed here. If it is that
@@ -157,41 +270,15 @@ function eos(stream, options, callback) {
     callback.call(stream, err);
   };
 
-  let closed = isClosed(stream);
-
   const onclose = () => {
     closed = true;
 
-    const errored = isWritableErrored(stream) || isReadableErrored(stream);
-
-    if (errored && typeof errored !== 'boolean') {
-      return callback.call(stream, errored);
-    }
-
-    if (readable && !readableFinished && isReadableNodeStream(stream, true)) {
-      if (!isReadableFinished(stream, false))
-        return callback.call(stream,
-                             new ERR_STREAM_PREMATURE_CLOSE());
-    }
-    if (writable && !writableFinished) {
-      if (!isWritableFinished(stream, false))
-        return callback.call(stream,
-                             new ERR_STREAM_PREMATURE_CLOSE());
-    }
-
-    callback.call(stream);
-  };
-
-  const onclosed = () => {
-    closed = true;
-
-    const errored = isWritableErrored(stream) || isReadableErrored(stream);
-
-    if (errored && typeof errored !== 'boolean') {
-      return callback.call(stream, errored);
+    const error = getEosOnCloseError(stream, readable, readableFinished, writable, writableFinished);
+    if (error === kEosImmediateClose) {
+      callback.call(stream);
+    } else {
+      callback.call(stream, error);
     }
-
-    callback.call(stream);
   };
 
   const onrequest = () => {
@@ -225,27 +312,13 @@ function eos(stream, options, callback) {
   }
   stream.on('close', onclose);
 
-  if (closed) {
-    process.nextTick(onclose);
-  } else if (wState?.errorEmitted || rState?.errorEmitted) {
-    if (!willEmitClose) {
-      process.nextTick(onclosed);
+  const immediateResult = getEosImmediateResult(stream, options, eosState);
+  if (immediateResult !== null) {
+    if (immediateResult === kEosImmediateClose) {
+      process.nextTick(() => callback.call(stream));
+    } else {
+      process.nextTick(() => callback.call(stream, immediateResult));
     }
-  } else if (
-    !readable &&
-    (!willEmitClose || isReadable(stream)) &&
-    (writableFinished || isWritable(stream) === false) &&
-    (wState == null || wState.pendingcb === undefined || wState.pendingcb === 0)
-  ) {
-    process.nextTick(onclosed);
-  } else if (
-    !writable &&
-    (!willEmitClose || isWritable(stream)) &&
-    (readableFinished || isReadable(stream) === false)
-  ) {
-    process.nextTick(onclosed);
-  } else if ((rState && stream.req && stream.aborted)) {
-    process.nextTick(onclosed);
   }
 
   const cleanup = () => {
@@ -347,4 +420,6 @@ function finished(stream, opts) {
 module.exports = {
   eos,
   finished,
+  getEosImmediateResult,
+  kEosImmediateClose,
 };