From 9573b64b99bc44c62cd5e6cd9e3ef7e525c77f5a Mon Sep 17 00:00:00 2001 From: Domenic Denicola Date: Wed, 17 Jun 2015 20:56:12 -0400 Subject: [PATCH] Use "perform" for abstract ops that cannot throw Closes #342, by making it clear that the promise-returning methods do not throw since they always call out to "perform"s or similar. Also found a couple cases of unnecessary exception guarding, and a few unnecessary ReturnIfAbrupts. Leaves out ReadableByteStream for now, pending #361. --- index.bs | 111 ++++++++++-------- .../lib/writable-stream.js | 16 +-- 2 files changed, 62 insertions(+), 65 deletions(-) diff --git a/index.bs b/index.bs index 05eb8ae69..1f4769768 100644 --- a/index.bs +++ b/index.bs @@ -394,9 +394,9 @@ Instances of ReadableStream are created with the internal slots des 1. Resolve _startResult_ as a promise: 1. Upon fulfillment, 1. Set *this*@[[started]] to *true*. - 1. Return RequestReadableStreamPull(*this*). + 1. Perform RequestReadableStreamPull(*this*). 1. Upon rejection with reason _r_, - 1. If *this*@[[state]] is "readable", return ErrorReadableStream(*this*, _r_). + 1. If *this*@[[state]] is "readable", perform ErrorReadableStream(*this*, _r_).

Properties of the ReadableStream Prototype

@@ -652,7 +652,8 @@ Instances of ReadableStreamController are created with the internal 1. Let _stream_ be *this*@[[controlledReadableStream]]. 1. If _stream_@[[closeRequested]] is *true*, throw a *TypeError* exception. 1. If _stream_@[[state]] is "errored", throw a *TypeError* exception. - 1. Return CloseReadableStream(_stream_). + 1. Perform CloseReadableStream(_stream_). + 1. Return *undefined*.
enqueue(chunk)
@@ -679,7 +680,8 @@ Instances of ReadableStreamController are created with the internal 
   1. If IsReadableStreamController(*this*) is *false*, throw a *TypeError* exception.
   1. If *this*@[[controlledReadableStream]]@[[state]] is not "readable", throw a *TypeError* exception.
-  1. Return ErrorReadableStream(*this*@[[controlledReadableStream]]).
+  1. Perform ErrorReadableStream(*this*@[[controlledReadableStream]]).
+  1. Return *undefined*.

Class ReadableStreamReader

@@ -760,7 +762,7 @@ Instances of ReadableStreamReader are created with the internal slo 1. Set *this*@[[storedError]] to *undefined*. 1. Set *this*@[[readRequests]] to a new empty List. 1. Set *this*@[[closedPromise]] to a new promise. - 1. If _stream_@[[state]] is "closed" or "errored", call-with-rethrow ReleaseReadableStreamReader(*this*). + 1. If _stream_@[[state]] is "closed" or "errored", perform ReleaseReadableStreamReader(*this*).

Properties of the ReadableStreamReader Prototype

@@ -832,7 +834,8 @@ Instances of ReadableStreamReader are created with the internal slo 1. If IsReadableStreamReader(*this*) is *false*, throw a *TypeError* exception. 1. If *this*@[[ownerReadableStream]] is *undefined*, return *undefined*. 1. If *this*@[[readRequests]] is not empty, throw a *TypeError* exception. - 1. Return ReleaseReadableStreamReader(*this*). + 1. Perform ReleaseReadableStreamReader(*this*). + 1. Return *undefined*.

Readable Stream Abstract Operations

@@ -852,7 +855,7 @@ reader for a given stream. 1. If _stream_@[[state]] is "closed", return a new promise resolved with *undefined*. 1. If _stream_@[[state]] is "errored", return a new promise rejected with _stream_@[[storedError]]. 1. Set _stream_@[[queue]] to a new empty List. - 1. Call-with-rethrow FinishClosingReadableStream(_stream_). + 1. Perform FinishClosingReadableStream(_stream_). 1. Let _sourceCancelPromise_ be PromiseInvokeOrNoop(_stream_@[[underlyingSource]], "cancel", «‍_reason_»). 1. Return the result of transforming _sourceCancelPromise_ by a fulfillment handler that returns *undefined*. @@ -868,7 +871,8 @@ this to streams they did not create, and must ensure they have obeyed the precon 1. Assert: _stream_@[[state]] is not "errored". 1. If _stream_@[[state]] is "closed", return *undefined*. 1. Set _stream_@[[closeRequested]] to *true*. - 1. If _stream_@[[queue]] is empty, return FinishClosingReadableStream(_stream_). + 1. If _stream_@[[queue]] is empty, perform FinishClosingReadableStream(_stream_). + 1. Return *undefined*.
@@ -884,7 +888,7 @@ this to streams they did not create, and must ensure they have obeyed the precon 
   1. Assert: _stream_@[[state]] is "readable".
   1. Set _stream_@[[state]] to "closed".
-  1. If IsReadableStreamLocked(_stream_) is *true*, return ReleaseReadableStreamReader(_stream_@[[reader]]).
+  1. If IsReadableStreamLocked(_stream_) is *true*, perform ReleaseReadableStreamReader(_stream_@[[reader]]).
   1. Return *undefined*.
@@ -908,14 +912,14 @@ asserts). 1. If _stream_@[[strategySize]] is not *undefined*, 1. Set _chunkSize_ to Call(_stream_@[[strategySize]], *undefined*, «‍_chunk_»). 1. If _chunkSize_ is an abrupt completion, - 1. Call-with-rethrow ErrorReadableStream(_stream_, ‍_chunkSize_.[[value]]). + 1. Perform ErrorReadableStream(_stream_, ‍_chunkSize_.[[value]]). 1. Return _chunkSize_. 1. Let _chunkSize_ be _chunkSize_.[[value]]. 1. Let _enqueueResult_ be EnqueueValueWithSize(_stream_@[[queue]], _chunk_, _chunkSize_). 1. If _enqueueResult_ is an abrupt completion, - 1. Call-with-rethrow ErrorReadableStream(_stream_, ‍_enqueueResult_.[[value]]). + 1. Perform ErrorReadableStream(_stream_, ‍_enqueueResult_.[[value]]). 1. Return _enqueueResult_. - 1. Call-with-rethrow RequestReadableStreamPull(_stream_). + 1. Perform RequestReadableStreamPull(_stream_). 1. Return *undefined*. @@ -939,14 +943,14 @@ an assert). 1. Let _stream_@[[queue]] be a new empty List. 1. Set _stream_@[[storedError]] to _e_. 1. Set _stream_@[[state]] to "errored". - 1. If IsReadableStreamLocked(_stream_) is *true*, return ReleaseReadableStreamReader(_stream_@[[reader]]). + 1. If IsReadableStreamLocked(_stream_) is *true*, perform ReleaseReadableStreamReader(_stream_@[[reader]]). + 1. Return *undefined*.

GetReadableStreamDesiredSize ( stream )

   1. Let _queueSize_ be GetTotalQueueSize(_stream_@[[queue]]).
-  1. ReturnIfAbrupt(_queueSize_).
   1. Return _stream_@[[strategyHWM]] − _queueSize_.
@@ -994,13 +998,13 @@ readable stream is locked to a reader. 1. Assert: _reader_@[[ownerReadableStream]]@[[state]] is "readable". 1. If _reader_@[[ownerReadableStream]]@[[queue]] is not empty, 1. Let _chunk_ be DequeueValue(_reader_@[[ownerReadableStream]]@[[queue]]). - 1. If _reader_@[[ownerReadableStream]]@[[closeRequested]] is *true* and _reader_@[[ownerReadableStream]]@[[queue]] is now empty, call-with-rethrow FinishClosingReadableStream(_reader_@[[ownerReadableStream]]). - 1. Otherwise, call-with-rethrow RequestReadableStreamPull(_reader_@[[ownerReadableStream]]). + 1. If _reader_@[[ownerReadableStream]]@[[closeRequested]] is *true* and _reader_@[[ownerReadableStream]]@[[queue]] is now empty, perform FinishClosingReadableStream(_reader_@[[ownerReadableStream]]). + 1. Otherwise, perform RequestReadableStreamPull(_reader_@[[ownerReadableStream]]). 1. Return a new promise resolved with CreateIterResultObject(_chunk_, *false*). 1. Otherwise, 1. Let _readRequestPromise_ be a new promise. 1. Append _readRequestPromise_ as the last element of _reader_@[[readRequests]]. - 1. Call-with-rethrow RequestReadableStreamPull(_reader_@[[ownerReadableStream]]). + 1. Perform RequestReadableStreamPull(_reader_@[[ownerReadableStream]]). 1. Return _readRequestPromise_. @@ -1023,13 +1027,13 @@ readable stream is locked to a reader. 1. Set _reader_@[[readRequests]] to a new empty List. 1. Set _reader_@[[ownerReadableStream]]@[[reader]] to *undefined*. 1. Set _reader_@[[ownerReadableStream]] to *undefined*. + 1. Return *undefined*.

RequestReadableStreamPull ( stream )

   1. Let _shouldPull_ be ShouldReadableStreamPull(stream).
-  1. ReturnIfAbrupt(_shouldPull_).
   1. If _shouldPull_ is *false*, return *undefined*.
   1. If _stream_@[[pulling]] is *true*,
     1. Set _stream_@[[pullAgain]] to *true*.
@@ -1040,9 +1044,9 @@ readable stream is locked to a reader.
     1. Set _stream_@[[pulling]] to *false*.
     1. If _stream_@[[pullAgain]] is *true*,
       1. Set _stream_@[[pullAgain]] to *false*.
-      1. Return RequestReadableStreamPull(_stream_).
+      1. Perform RequestReadableStreamPull(_stream_).
   1. Upon rejection of _pullPromise_ with reason _e_,
-    1. If _stream_@[[state]] is "readable", return ErrorReadableStream(_stream_, _e_).
+    1. If _stream_@[[state]] is "readable", perform ErrorReadableStream(_stream_, _e_).
   1. Return *undefined*.
@@ -1054,7 +1058,6 @@ readable stream is locked to a reader. 1. If _stream_@[[started]] is *false*, return *false*. 1. If IsReadableStreamLocked(_stream_) is *true* and _stream_@[[reader]]@[[readRequests]] is not empty, return *true*. 1. Let _desiredSize_ be GetReadableStreamDesiredSize(_stream_). - 1. ReturnIfAbrupt(_desiredSize_). 1. If _desiredSize_ > 0, return *true*. 1. Return *false*. @@ -1090,8 +1093,8 @@ branches. 1. Set _pull_@[[branch2]] to _branch2_. 1. Upon rejection of _reader_@[[closedPromise]] with reason _r_, 1. If _teeState_.[[closedOrErrored]] is *true*, return *undefined*. - 1. Call-with-rethrow ErrorReadableStream(_branch1_, _r_). - 1. Call-with-rethrow ErrorReadableStream(_branch2_, _r_). + 1. Perform ErrorReadableStream(_branch1_, _r_). + 1. Perform ErrorReadableStream(_branch2_, _r_). 1. Set _teeState_.[[closedOrErrored]] to *true*. 1. Return «branch1, branch2». @@ -1124,8 +1127,8 @@ TeeReadableStream pull function F is called, it performs the followin 1. ReturnIfAbrupt(_done_). 1. Assert: Type(_done_) is Boolean. 1. If _done_ is *true* and _teeState_.[[closedOrErrored]] is *false*, - 1. Call-with-rethrow CloseReadableStream(_branch1_). - 1. Call-with-rethrow CloseReadableStream(_branch2_). + 1. Perform CloseReadableStream(_branch1_). + 1. Perform CloseReadableStream(_branch2_). 1. Set _teeState_.[[closedOrErrored]] to *true*. 1. If _teeState_.[[closedOrErrored]] is *true*, return *undefined*. 1. If _teeState_.[[canceled1]] is *false*, @@ -1382,7 +1385,7 @@ Instances of WritableStream are created with the internal slots des 1. Set *this*@[[started]] and *this*@[[writing]] to *false*. 1. Let _normalizedStrategy_ be ValidateAndNormalizeQueuingStrategy(_size_, _highWaterMark_). 1. Set *this*@[[strategySize]] to _normalizedStrategy_.[[size]] and *this*@[[strategyHWM]] to _normalizedStrategy_.[[highWaterMark]]. - 1. Call-with-rethrow SyncWritableStreamStateWithQueue(*this*). + 1. Perform SyncWritableStreamStateWithQueue(*this*). 1. Let _error_ be a new WritableStream error function. 1. Set _error_@[[stream]] to *this*. 1. Let _startResult_ be InvokeOrNoop(_underlyingSink_, "start", «_error_»). @@ -1391,7 +1394,7 @@ Instances of WritableStream are created with the internal slots des 1. Upon fulfillment, 1. Set *this*@[[started]] to *true*. 1. Set *this*@[[startedPromise]] to *undefined*. - 1. Upon rejection with reason _r_, return ErrorWritableStream(*this*, _r_). + 1. Upon rejection with reason _r_, perform ErrorWritableStream(*this*, _r_). A WritableStream error function is an anonymous built-in function that is used to allow @@ -1401,7 +1404,8 @@ a \[[stream]] internal slot. When a WritableStream error function < 
   1. Let _stream_ be _F_@[[stream]].
-  1. Return ErrorWritableStream(_stream_, _e_).
+  1. Perform ErrorWritableStream(_stream_, _e_).
+  1. Return *undefined*.

Properties of the WritableStream Prototype

@@ -1477,7 +1481,7 @@ a \[[stream]] internal slot. When a WritableStream error function < 1. If IsWritableStream(*this*) is *false*, return a promise rejected with a *TypeError* exception. 1. If *this*@[[state]] is "closed", return a new promise resolved with *undefined*. 1. If *this*@[[state]] is "errored", return a new promise rejected with *this*@[[storedError]]. - 1. Call-with-rethrow ErrorWritableStream(*this*, _reason_). + 1. Perform ErrorWritableStream(*this*, _reason_). 1. Let _sinkAbortPromise_ be PromiseInvokeOrFallbackOrNoop(*this*@[[underlyingSink]], "abort", «_reason_», "close", «»). 1. Return the result of transforming _sinkAbortPromise_ by a fulfillment handler that returns *undefined*. @@ -1497,8 +1501,8 @@ a \[[stream]] internal slot. When a WritableStream error function < 1. If *this*@[[state]] is "errored", return a promise rejected with *this*@[[storedError]]. 1. If *this*@[[state]] is "waiting", resolve *this*@[[readyPromise]] with *undefined*. 1. Set *this*@[[state]] to "closing". - 1. Call-with-rethrow EnqueueValueWithSize(*this*@[[queue]], "close", *0*). - 1. Call-with-rethrow CallOrScheduleWritableStreamAdvanceQueue(*this*). + 1. Perform EnqueueValueWithSize(*this*@[[queue]], "close", *0*). + 1. Perform CallOrScheduleWritableStreamAdvanceQueue(*this*). 1. Return *this*@[[closedPromise]]. @@ -1524,20 +1528,17 @@ a \[[stream]] internal slot. When a WritableStream error function < 1. If *this*@[[strategySize]] is not *undefined*, then 1. Set _chunkSize_ to Call(*this*@[[strategySize]], *undefined*, «‍_chunk_»). 1. If _chunkSize_ is an abrupt completion, - 1. Call-with-rethrow ErrorWritableStream(*this*, _chunkSize_.[[value]]). + 1. Perform ErrorWritableStream(*this*, _chunkSize_.[[value]]). 1. Return a new promise rejected with _chunkSize_.[[value]]. 1. Set _chunkSize_ to _chunkSize_.[[value]]. 1. Let _promise_ be a new promise. 1. Let _writeRecord_ be Record{[[promise]]: _promise_, [[chunk]]: _chunk_}. 1. Let _enqueueResult_ be EnqueueValueWithSize(*this*@[[queue]], _writeRecord_, _chunkSize_). 1. If _enqueueResult_ is an abrupt completion, - 1. Call-with-rethrow ErrorWritableStream(*this*, _enqueueResult_.[[value]]). + 1. Perform ErrorWritableStream(*this*, _enqueueResult_.[[value]]). 1. Return a new promise rejected with _enqueueResult_.[[value]]. - 1. Let _syncResult_ be SyncWritableStreamStateWithQueue(*this*). - 1. If _syncResult_ is an abrupt completion, - 1. Call-with-rethrow ErrorWritableStream(*this*, _syncResult_.[[value]]). - 1. Return _promise_. - 1. Call-with-rethrow CallOrScheduleWritableStreamAdvanceQueue(*this*). + 1. Perform SyncWritableStreamStateWithQueue(*this*). + 1. Perform CallOrScheduleWritableStreamAdvanceQueue(*this*). 1. Return _promise_. @@ -1547,9 +1548,10 @@ a \[[stream]] internal slot. When a WritableStream error function < 
   1. If _stream_@[[started]] is *false*, then
-    1. Upon fulfillment of _stream_@[[startedPromise]], call-with-rethrow WritableStreamAdvanceQueue(_stream_).
-    1. Return *undefined*.
-  1. Otherwise, return WritableStreamAdvanceQueue(_stream_).
+    1. Upon fulfillment of _stream_@[[startedPromise]], perform WritableStreamAdvanceQueue(_stream_).
+  1. Otherwise,
+    1. Perform WritableStreamAdvanceQueue(_stream_).
+  1. Return *undefined*.

CloseWritableStream ( stream )

@@ -1562,7 +1564,7 @@ a \[[stream]] internal slot. When a WritableStream error function < 1. Assert: _stream_@[[state]] is "closing". 1. Resolve _stream_@[[closedPromise]] with *undefined*. 1. Set _stream_@[[state]] to "closed". - 1. Upon rejection with reason _r_, return ErrorWritableStream(_stream_, _r_). + 1. Upon rejection with reason _r_, perform ErrorWritableStream(_stream_, _r_). 1. Return *undefined*. @@ -1594,7 +1596,6 @@ a \[[stream]] internal slot. When a WritableStream error function < 1. If _stream_@[[state]] is "closing", return *undefined*. 1. Assert: _stream_@[[state]] is either "writable" or "waiting". 1. Let _queueSize_ be GetTotalQueueSize(_stream_@[[queue]]). - 1. ReturnIfAbrupt(_queueSize_). 1. Let _shouldApplyBackpressure_ be *true* if _queueSize_ > _stream_@[[strategyHWM]], and *false* otherwise. 1. If _shouldApplyBackpressure_ is *true* and _stream_@[[state]] is "writable", then 1. Set _stream_@[[state]] to "waiting". @@ -1614,7 +1615,8 @@ a \[[stream]] internal slot. When a WritableStream error function < 1. Assert: _stream_@[[state]] is "closing". 1. DequeueValue(_stream_@[[queue]]). 1. Assert: _stream_@[[queue]] is now empty. - 1. Return CloseWritableStream(_stream_). + 1. Perform CloseWritableStream(_stream_). + 1. Return *undefined*. 1. Set _stream_@[[writing]] to *true*. 1. Let _writeResult_ be PromiseInvokeOrNoop(_stream_@[[underlyingSink]], "write", «_writeRecord_.[[chunk]]»). 1. Upon fulfillment of _writeResult_, @@ -1622,10 +1624,10 @@ a \[[stream]] internal slot. When a WritableStream error function < 1. Set _stream_@[[writing]] to *false*. 1. Resolve _writeRecord_.[[promise]] with *undefined*. 1. DequeueValue(_stream_@[[queue]]). - 1. Let _syncResult_ be SyncWritableStreamStateWithQueue(_stream_). - 1. If _syncResult_ is an abrupt completion, then return ErrorWritableStream(_stream_, ‍_syncResult_.[[value]]). - 1. Otherwise, return WritableStreamAdvanceQueue(_stream_). - 1. Upon rejection of _writeResult_ with reason _r_, return ErrorWritableStream(_stream_, _r_). + 1. Perform SyncWritableStreamStateWithQueue(_stream_). + 1. Perform WritableStreamAdvanceQueue(_stream_). + 1. Upon rejection of _writeResult_ with reason _r_, perform ErrorWritableStream(_stream_, _r_). + 1. Return *undefined*.

Transform Streams

@@ -1811,6 +1813,7 @@ throughout the rest of this standard. 1. ReturnIfAbrupt(_size_). 1. If _size_ is *NaN*, *+∞*, or *−∞*, throw a *RangeError* exception. 1. Append Record{[[value]]: _value_, [[size]]: _size_} as the last element of _queue_. + 1. Return *undefined*.

GetTotalQueueSize ( queue )

@@ -2190,7 +2193,7 @@ Instances of ReadableByteStreamReader are created with the internal 1. Set *this*@[[storedError]] to *undefined*. 1. Set *this*@[[readRequests]] to a new empty List. 1. Set *this*@[[closedPromise]] to a new promise. - 1. If _stream_@[[state]] is "closed" or "errored", call-with-rethrow ReleaseReadableByteStreamReader(*this*). + 1. If _stream_@[[state]] is "closed" or "errored", perform ReleaseReadableByteStreamReader(*this*).

Properties of the ReadableByteStreamReader Prototype

@@ -2225,7 +2228,8 @@ Instances of ReadableByteStreamReader are created with the internal 1. If IsReadableByteStreamReader(*this*) is *false*, throw a *TypeError* exception. 1. If *this*@[[ownerReadableByteStream]] is *undefined*, return *undefined*. 1. If *this*@[[readRequests]] is not empty, throw a *TypeError* exception. - 1. Return ReleaseReadableByteStreamReader(*this*). + 1. Perform ReleaseReadableByteStreamReader(*this*). + 1. Return *undefined*.

Readable Byte Stream Abstract Operations

@@ -2254,7 +2258,7 @@ stream reader for a given stream. 
   1. Assert: _stream_@[[state]] is "readable".
   1. Set _stream_@[[state]] to "closed".
-  1. If IsReadableByteStreamLocked(_stream_) is *true*, return ReleaseReadableByteStreamReader(_stream_@[[reader]]).
+  1. If IsReadableByteStreamLocked(_stream_) is *true*, perform ReleaseReadableByteStreamReader(_stream_@[[reader]]).
   1. Return *undefined*.
@@ -2275,7 +2279,7 @@ stream reader for a given stream. 1. Assert: _stream_@[[state]] is "readable". 1. Set _stream_@[[storedError]] to _e_. 1. Set _stream_@[[state]] to "errored". - 1. If IsReadableByteStreamLocked(_stream_) is *true*, return ReleaseReadableByteStreamReader(_stream_@[[reader]]). + 1. If IsReadableByteStreamLocked(_stream_) is *true*, perform ReleaseReadableByteStreamReader(_stream_@[[reader]]). 1. Return *undefined*. @@ -2929,6 +2933,9 @@ itself will evolve in these ways.
  • We use the phrase "call-with-rethrow AbstractOperation(x, y, z)" as a shorthand for "Let opResult be AbstractOperation(x, y, z). ReturnIfAbrupt(opResult)." +
  • We use the phrase "perform AbstractOperation(x, y, z)" as a shorthand for "Let + opResult be AbstractOperation(x, y, z). Assert: opResult is + not an abrupt completion." (The ECMAScript spec seems to use "perform" this way, but does not define it.)
  • We use the shorthand phrases from the W3C TAG promises guide to operate on promises at a higher level than the ECMAScript spec does. diff --git a/reference-implementation/lib/writable-stream.js b/reference-implementation/lib/writable-stream.js index f84e95a15..728939047 100644 --- a/reference-implementation/lib/writable-stream.js +++ b/reference-implementation/lib/writable-stream.js @@ -148,13 +148,7 @@ export default class WritableStream { return Promise.reject(enqueueResultE); } - try { - SyncWritableStreamStateWithQueue(this); - } catch (syncResultE) { - ErrorWritableStream(this, syncResultE); - return promise; - } - + SyncWritableStreamStateWithQueue(this); CallOrScheduleWritableStreamAdvanceQueue(this); return promise; } @@ -285,12 +279,8 @@ function WritableStreamAdvanceQueue(stream) { writeRecord._resolve(undefined); DequeueValue(stream._queue); - try { - SyncWritableStreamStateWithQueue(stream); - } catch (syncResultE) { - return ErrorWritableStream(stream, syncResultE); - } - return WritableStreamAdvanceQueue(stream); + SyncWritableStreamStateWithQueue(stream); + WritableStreamAdvanceQueue(stream); }, r => ErrorWritableStream(stream, r) )