Rename cb0 to asyncProcName_continue + other improvements to async tracebacks.

lib/pure/asyncfutures.nim

@@ -231,13 +231,9 @@ proc diff[T](a, b: seq[T]): (int, seq[T]) =
       break
   return (lastIndex, b[lastIndex .. ^1])
 
-proc processEntries(entries: seq[StackTraceEntry]): seq[StackTraceEntry] =
-  proc get(entries: seq[StackTraceEntry], i: int): StackTraceEntry =
-    if i >= entries.len:
-      return StackTraceEntry(procName: "", line: 0, filename: "")
-    else:
-      return entries[i]
-
+proc mergeEntries(entries: seq[StackTraceEntry]): seq[StackTraceEntry] =
+  ## Merges stack trace entries containing re-raise entries into one
+  ## continuous stack trace.
   result = @[]
   var i = 0
   while i < entries.len:
@@ -252,7 +248,7 @@ proc processEntries(entries: seq[StackTraceEntry]): seq[StackTraceEntry] =
         reRaiseEnd.inc()
       assert entries[reRaiseEnd].procName.isNil
       assert entries[reRaiseEnd].line == -100 # Signifies end of re-raise block.
-      let reRaisedEntries = processEntries(entries[i+1 .. reRaiseEnd-1])
+      let reRaisedEntries = mergeEntries(entries[i+1 .. reRaiseEnd-1])
 
       let (lastIndex, remainder) = diff(result, reRaisedEntries)
       for i in 0..<remainder.len:
@@ -260,16 +256,34 @@ proc processEntries(entries: seq[StackTraceEntry]): seq[StackTraceEntry] =
       i = reRaiseEnd+1
       continue
 
+    result.add(entry)
+    i.inc
+
+proc shortenEntries(entries: seq[StackTraceEntry]): seq[StackTraceEntry] =
+  ## Analyzes the entries for patterns and processes them.
+  proc get(entries: seq[StackTraceEntry], i: int): StackTraceEntry =
+    if i >= entries.len:
+      return StackTraceEntry(procName: "", line: 0, filename: "")
+    else:
+      return entries[i]
+
+  result = @[]
+  var i = 0
+  while i < entries.len:
+    var entry = entries[i]
+
     # Detect this pattern:
     #   (procname: a, line: 393, filename: asyncmacro.nim)
-    #   (procname: cb0, line: 34, filename: asyncmacro.nim)
+    #   (procname: a_continue, line: 34, filename: asyncmacro.nim)
     #   (procname: aIter, line: 40, filename: tasync_traceback.nim)
     let second = get(entries, i+1)
+
     let third = get(entries, i+2)
     let fitsPattern =
       cmpIgnoreStyle($entry.filename, "asyncmacro.nim") == 0 and
       cmpIgnoreStyle($second.filename, "asyncmacro.nim") == 0 and
-      cmpIgnoreStyle($second.procName, "cb0") == 0 and
+      ($second.procName).startsWith($entry.procName) and
+      ($second.procName).endsWith("continue") and
       cmpIgnoreStyle($third.procName, $entry.procName & "iter") == 0
 
     if fitsPattern:
@@ -287,10 +301,8 @@ proc getHint(entry: StackTraceEntry): string =
   ## We try to provide some hints about stack trace entries that the user
   ## may not be familiar with, in particular calls inside the stdlib.
   result = ""
-  case ($entry.procName).normalize()
-  of "cb0":
-    if cmpIgnoreStyle($entry.filename, "asyncmacro.nim") == 0:
-      return "Resumes an async procedure"
+  let name = ($entry.procName).normalize()
+  case name
   of "processpendingcallbacks":
     if cmpIgnoreStyle($entry.filename, "asyncdispatch.nim") == 0:
       return "Executes pending callbacks"
@@ -298,6 +310,35 @@ proc getHint(entry: StackTraceEntry): string =
     if cmpIgnoreStyle($entry.filename, "asyncdispatch.nim") == 0:
       return "Processes asynchronous completion events"
 
+  if name.endsWith("continue"):
+    if cmpIgnoreStyle($entry.filename, "asyncmacro.nim") == 0:
+      return "Resumes an async procedure"
+
+proc `$`*(entries: seq[StackTraceEntry]): string =
+  result = ""
+  # Find longest filename & line number combo for alignment purposes.
+  var longestLeft = 0
+  for entry in entries:
+    let left = $entry.filename & $entry.line
+    if left.len > longestLeft:
+      longestLeft = left.len
+
+  const indent = 2
+  # Format the entries.
+  for entry in entries:
+    let indentStr = spaces(indent)
+
+    let left = "$#($#)" % [$entry.filename, $entry.line]
+    result.add("$#$#$# $#\n" % [
+      indentStr,
+      left,
+      spaces(longestLeft - left.len + 2),
+      $entry.procName
+    ])
+    let hint = getHint(entry)
+    if hint.len > 0:
+      result.add(indentStr & "└─" & hint & "\n")
+
 proc injectStacktrace[T](future: Future[T]) =
   when not defined(release):
     const header = "\nAsync traceback:\n"
@@ -309,29 +350,15 @@ proc injectStacktrace[T](future: Future[T]) =
       let start = exceptionMsg.find(header)
       exceptionMsg = exceptionMsg[0..<start]
 
-    let entries = getStackTraceEntries(future.error).processEntries()
+
     var newMsg = exceptionMsg & header
 
-    # Find longest filename & line number combo for alignment purposes.
-    var longestLeft = 0
-    for entry in entries:
-      let left = $entry.filename & $entry.line
-      if left.len > longestLeft:
-        longestLeft = left.len
-
-    const indent = "  "
-    # Format the entries.
-    for entry in entries:
-      let left = "$#($#)" % [$entry.filename, $entry.line]
-      newMsg.add("$#$#$# $#\n" % [
-        indent,
-        left,
-        spaces(longestLeft - left.len + 2),
-        $entry.procName
-      ])
-      let hint = getHint(entry)
-      if hint.len > 0:
-        newMsg.add(indent & "└─" & hint & "\n")
+    let entries = getStackTraceEntries(future.error).mergeEntries()
+    let shortEntries = entries.shortenEntries()
+    newMsg.add($shortEntries)
+    if entries.len > shortEntries.len:
+      newMsg.add("\nDetailed Async traceback:\n")
+      newMsg.add($entries)
 
     newMsg.add("Exception message: " & exceptionMsg & "\n")
     newMsg.add("Exception type:")

lib/pure/asyncmacro.nim

@@ -25,10 +25,10 @@ proc skipStmtList(node: NimNode): NimNode {.compileTime.} =
     result = node[0]
 
 template createCb(retFutureSym, iteratorNameSym,
-                  name, futureVarCompletions: untyped) =
+                  strName, identName, futureVarCompletions: untyped) =
   var nameIterVar = iteratorNameSym
   #{.push stackTrace: off.}
-  proc cb0 {.closure.} =
+  proc identName {.closure.} =
     try:
       if not nameIterVar.finished:
         var next = nameIterVar()
@@ -36,11 +36,11 @@ template createCb(retFutureSym, iteratorNameSym,
           if not retFutureSym.finished:
             let msg = "Async procedure ($1) yielded `nil`, are you await'ing a " &
                     "`nil` Future?"
-            raise newException(AssertionError, msg % name)
+            raise newException(AssertionError, msg % strName)
         else:
           {.gcsafe.}:
             {.push hint[ConvFromXtoItselfNotNeeded]: off.}
-            next.callback = (proc() {.closure, gcsafe.})(cb0)
+            next.callback = (proc() {.closure, gcsafe.})(identName)
             {.pop.}
     except:
       futureVarCompletions
@@ -52,7 +52,7 @@ template createCb(retFutureSym, iteratorNameSym,
       else:
         retFutureSym.fail(getCurrentException())
 
-  cb0()
+  identName()
   #{.pop.}
 proc generateExceptionCheck(futSym,
     tryStmt, rootReceiver, fromNode: NimNode): NimNode {.compileTime.} =
@@ -389,9 +389,10 @@ proc asyncSingleProc(prc: NimNode): NimNode {.compileTime.} =
     outerProcBody.add(closureIterator)
 
     # -> createCb(retFuture)
-    #var cbName = newIdentNode("cb")
+    var cbName = genSym(nskProc, prcName & "_continue")
     var procCb = getAst createCb(retFutureSym, iteratorNameSym,
                          newStrLitNode(prcName),
+                         cbName,
                          createFutureVarCompletions(futureVarIdents, nil))
     outerProcBody.add procCb
 

tests/async/tasync_traceback.nim

@@ -1,5 +1,6 @@
 discard """
   exitcode: 0
+  disabled: "windows"
   output: '''
 b failure
 Async traceback: