Raise tracking (#251)

* Exception tracking v2

* some fixes

* Nim 1.2 compat

* simpler things

* Fixes for libp2p

* Fixes for strictException

* better await exception check

* Fix for template async proc

* make async work with procTy

* FuturEx is now a ref object type

* add tests

* update test

* update readme

* Switch to asyncraises pragma

* Address tests review comments

* Rename FuturEx to RaiseTrackingFuture

* Fix typo

* Split asyncraises into async, asyncraises

* Add -d:chronosWarnMissingRaises

* Add comment to RaiseTrackingFuture

* Allow standalone asyncraises

* CheckedFuture.fail type checking

* First cleanup

* Remove useless line

* Review comments

* nimble: Remove #head from unittest2

* Remove implict raises: CancelledError

* Move checkFutureExceptions to asyncfutures2

* Small refacto

* small cleanup

* Complete in closure finally

* cleanup tests, add comment

* bump

* chronos is not compatible with nim 1.2 anymore

* re-add readme modifications

* fix special exception handlers

* also propagate excetion type in `read`

* `RaiseTrackingFuture` -> `InternalRaisesFuture`

Use internal naming scheme for RTF (this type should only be accessed
via asyncraises)

* use `internalError` for error reading

* oops

* 2.0 workarounds

* again

* remove try/finally for non-raising functions

* Revert "remove try/finally for non-raising functions"

This reverts commit 86bfeb5c97.

`finally` is needed if code returns early :/

* fixes

* avoid exposing `newInternalRaisesFuture` in manual macro code
* avoid unnecessary codegen for `Future[void]`
* avoid reduntant block around async proc body
* simplify body generation for forward declarations with comment but no
body
* avoid duplicate `gcsafe` annotiations
* line info for return at end of async proc

* expand tests

* fix comments, add defer test

---------

Co-authored-by: Jacek Sieka <jacek@status.im>
This commit is contained in:
Tanguy 2023-10-17 14:18:14 +02:00 committed by GitHub
parent 253bc3cfc0
commit a759c11ce4
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 637 additions and 225 deletions

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@ -212,6 +212,41 @@ originating from tasks on the dispatcher queue. It is however possible that
`Defect` that happen in tasks bubble up through `poll` as these are not caught
by the transformation.
#### Checked exceptions
By specifying a `asyncraises` list to an async procedure, you can check which
exceptions can be thrown by it.
```nim
proc p1(): Future[void] {.async, asyncraises: [IOError].} =
assert not (compiles do: raise newException(ValueError, "uh-uh"))
raise newException(IOError, "works") # Or any child of IOError
```
Under the hood, the return type of `p1` will be rewritten to another type,
which will convey raises informations to await.
```nim
proc p2(): Future[void] {.async, asyncraises: [IOError].} =
await p1() # Works, because await knows that p1
# can only raise IOError
```
The hidden type (`RaiseTrackingFuture`) is implicitely convertible into a Future.
However, it may causes issues when creating callback or methods
```nim
proc p3(): Future[void] {.async, asyncraises: [IOError].} =
let fut: Future[void] = p1() # works
assert not compiles(await fut) # await lost informations about raises,
# so it can raise anything
# Callbacks
assert not(compiles do: let cb1: proc(): Future[void] = p1) # doesn't work
let cb2: proc(): Future[void] {.async, asyncraises: [IOError].} = p1 # works
assert not(compiles do:
type c = proc(): Future[void] {.async, asyncraises: [IOError, ValueError].}
let cb3: c = p1 # doesn't work, the raises must match _exactly_
)
```
### Platform independence
Several functions in `chronos` are backed by the operating system, such as

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@ -7,7 +7,7 @@ description = "Networking framework with async/await support"
license = "MIT or Apache License 2.0"
skipDirs = @["tests"]
requires "nim >= 1.2.0",
requires "nim >= 1.6.0",
"stew",
"bearssl",
"httputils",

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@ -8,7 +8,7 @@
# Apache License, version 2.0, (LICENSE-APACHEv2)
# MIT license (LICENSE-MIT)
import std/sequtils
import std/[sequtils, macros]
import stew/base10
when chronosStackTrace:
@ -35,6 +35,12 @@ func `[]`*(loc: array[LocationKind, ptr SrcLoc], v: int): ptr SrcLoc {.
else: raiseAssert("Unknown source location " & $v)
type
InternalRaisesFuture*[T, E] = ref object of Future[T]
## Future with a tuple of possible exception types
## eg InternalRaisesFuture[void, (ValueError, OSError)]
## Will be injected by `asyncraises`, should generally
## not be used manually
FutureStr*[T] = ref object of Future[T]
## Future to hold GC strings
gcholder*: string
@ -59,6 +65,11 @@ proc newFutureImpl[T](loc: ptr SrcLoc, flags: FutureFlags): Future[T] =
internalInitFutureBase(fut, loc, FutureState.Pending, flags)
fut
proc newInternalRaisesFutureImpl[T, E](loc: ptr SrcLoc): InternalRaisesFuture[T, E] =
let fut = InternalRaisesFuture[T, E]()
internalInitFutureBase(fut, loc, FutureState.Pending, {})
fut
proc newFutureSeqImpl[A, B](loc: ptr SrcLoc): FutureSeq[A, B] =
let fut = FutureSeq[A, B]()
internalInitFutureBase(fut, loc, FutureState.Pending, {})
@ -70,12 +81,28 @@ proc newFutureStrImpl[T](loc: ptr SrcLoc): FutureStr[T] =
fut
template newFuture*[T](fromProc: static[string] = "",
flags: static[FutureFlags] = {}): Future[T] =
flags: static[FutureFlags] = {}): auto =
## Creates a new future.
##
## Specifying ``fromProc``, which is a string specifying the name of the proc
## that this future belongs to, is a good habit as it helps with debugging.
newFutureImpl[T](getSrcLocation(fromProc), flags)
when declared(InternalRaisesFutureRaises): # injected by `asyncraises`
newInternalRaisesFutureImpl[T, InternalRaisesFutureRaises](getSrcLocation(fromProc))
else:
newFutureImpl[T](getSrcLocation(fromProc), flags)
macro getFutureExceptions(T: typedesc): untyped =
if getTypeInst(T)[1].len > 2:
getTypeInst(T)[1][2]
else:
ident"void"
template newInternalRaisesFuture*[T](fromProc: static[string] = ""): auto =
## Creates a new future.
##
## Specifying ``fromProc``, which is a string specifying the name of the proc
## that this future belongs to, is a good habit as it helps with debugging.
newInternalRaisesFutureImpl[T, getFutureExceptions(typeof(result))](getSrcLocation(fromProc))
template newFutureSeq*[A, B](fromProc: static[string] = ""): FutureSeq[A, B] =
## Create a new future which can hold/preserve GC sequence until future will
@ -188,6 +215,49 @@ template fail*(future: FutureBase, error: ref CatchableError) =
## Completes ``future`` with ``error``.
fail(future, error, getSrcLocation())
macro checkFailureType(future, error: typed): untyped =
let e = getTypeInst(future)[2]
let types = getType(e)
if types.eqIdent("void"):
error("Can't raise exceptions on this Future")
expectKind(types, nnkBracketExpr)
expectKind(types[0], nnkSym)
assert types[0].strVal == "tuple"
assert types.len > 1
expectKind(getTypeInst(error), nnkRefTy)
let toMatch = getTypeInst(error)[0]
# Can't find a way to check `is` in the macro. (sameType doesn't
# work for inherited objects). Dirty hack here, for [IOError, OSError],
# this will generate:
#
# static:
# if not((`toMatch` is IOError) or (`toMatch` is OSError)
# or (`toMatch` is CancelledError) or false):
# raiseAssert("Can't fail with `toMatch`, only [IOError, OSError] is allowed")
var typeChecker = ident"false"
for errorType in types[1..^1]:
typeChecker = newCall("or", typeChecker, newCall("is", toMatch, errorType))
typeChecker = newCall(
"or", typeChecker,
newCall("is", toMatch, ident"CancelledError"))
let errorMsg = "Can't fail with " & repr(toMatch) & ". Only " & repr(types[1..^1]) & " allowed"
result = nnkStaticStmt.newNimNode(lineInfoFrom=error).add(
quote do:
if not(`typeChecker`):
raiseAssert(`errorMsg`)
)
template fail*[T, E](future: InternalRaisesFuture[T, E], error: ref CatchableError) =
checkFailureType(future, error)
fail(future, error, getSrcLocation())
template newCancelledError(): ref CancelledError =
(ref CancelledError)(msg: "Future operation cancelled!")
@ -429,6 +499,53 @@ proc internalCheckComplete*(fut: FutureBase) {.raises: [CatchableError].} =
injectStacktrace(fut.internalError)
raise fut.internalError
macro internalCheckComplete*(f: InternalRaisesFuture): untyped =
# For InternalRaisesFuture[void, (ValueError, OSError), will do:
# {.cast(raises: [ValueError, OSError]).}:
# if isNil(f.error): discard
# else: raise f.error
let e = getTypeInst(f)[2]
let types = getType(e)
if types.eqIdent("void"):
return quote do:
if not(isNil(`f`.internalError)):
raiseAssert("Unhandled future exception: " & `f`.error.msg)
expectKind(types, nnkBracketExpr)
expectKind(types[0], nnkSym)
assert types[0].strVal == "tuple"
assert types.len > 1
let ifRaise = nnkIfExpr.newTree(
nnkElifExpr.newTree(
quote do: isNil(`f`.internalError),
quote do: discard
),
nnkElseExpr.newTree(
nnkRaiseStmt.newNimNode(lineInfoFrom=f).add(
quote do: (`f`.internalError)
)
)
)
nnkPragmaBlock.newTree(
nnkPragma.newTree(
nnkCast.newTree(
newEmptyNode(),
nnkExprColonExpr.newTree(
ident"raises",
block:
var res = nnkBracket.newTree()
for r in types[1..^1]:
res.add(r)
res
)
),
),
ifRaise
)
proc read*[T: not void](future: Future[T] ): lent T {.raises: [CatchableError].} =
## Retrieves the value of ``future``. Future must be finished otherwise
## this function will fail with a ``ValueError`` exception.
@ -452,6 +569,29 @@ proc read*(future: Future[void] ) {.raises: [CatchableError].} =
# TODO: Make a custom exception type for this?
raise newException(ValueError, "Future still in progress.")
proc read*[T: not void, E](future: InternalRaisesFuture[T, E] ): lent T =
## Retrieves the value of ``future``. Future must be finished otherwise
## this function will fail with a ``ValueError`` exception.
##
## If the result of the future is an error then that error will be raised.
if not future.finished():
# TODO: Make a custom exception type for this?
raise newException(ValueError, "Future still in progress.")
internalCheckComplete(future)
future.internalValue
proc read*[E](future: InternalRaisesFuture[void, E]) =
## Retrieves the value of ``future``. Future must be finished otherwise
## this function will fail with a ``ValueError`` exception.
##
## If the result of the future is an error then that error will be raised.
if future.finished():
internalCheckComplete(future)
else:
# TODO: Make a custom exception type for this?
raise newException(ValueError, "Future still in progress.")
proc readError*(future: FutureBase): ref CatchableError {.raises: [ValueError].} =
## Retrieves the exception stored in ``future``.
##

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@ -2,108 +2,144 @@
#
# Nim's Runtime Library
# (c) Copyright 2015 Dominik Picheta
# (c) Copyright 2018-Present Status Research & Development GmbH
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
import std/[macros]
import std/algorithm
proc processBody(node, setResultSym, baseType: NimNode): NimNode {.compileTime.} =
#echo(node.treeRepr)
case node.kind
of nnkReturnStmt:
# `return ...` -> `setResult(...); return`
let
res = newNimNode(nnkStmtList, node)
if node[0].kind != nnkEmpty:
res.add newCall(setResultSym, processBody(node[0], setResultSym, baseType))
res.add newNimNode(nnkReturnStmt, node).add(newNilLit())
res.add newNimNode(nnkReturnStmt, node).add(newEmptyNode())
res
of RoutineNodes-{nnkTemplateDef}:
# skip all the nested procedure definitions
# Skip nested routines since they have their own return value distinct from
# the Future we inject
node
else:
for i in 0 ..< node.len:
# We must not transform nested procedures of any form, since their
# returns are not meant for our futures
node[i] = processBody(node[i], setResultSym, baseType)
node
proc wrapInTryFinally(fut, baseType, body: NimNode): NimNode {.compileTime.} =
proc wrapInTryFinally(fut, baseType, body, raisesTuple: NimNode): NimNode {.compileTime.} =
# creates:
# var closureSucceeded = true
# try: `body`
# except CancelledError: closureSucceeded = false; `castFutureSym`.cancelAndSchedule()
# except CatchableError as exc: closureSucceeded = false; `castFutureSym`.fail(exc)
# except Defect as exc:
# closureSucceeded = false
# raise exc
# [for raise in raisesTuple]:
# except `raise`: closureSucceeded = false; `castFutureSym`.fail(exc)
# finally:
# if closureSucceeded:
# `castFutureSym`.complete(result)
#
# Calling `complete` inside `finally` ensures that all success paths
# (including early returns and code inside nested finally statements and
# defer) are completed with the final contents of `result`
let
closureSucceeded = genSym(nskVar, "closureSucceeded")
nTry = nnkTryStmt.newTree(body)
excName = ident"exc"
# we are completing inside finally to make sure the completion happens even
# after a `return`
let closureSucceeded = genSym(nskVar, "closureSucceeded")
var nTry = nnkTryStmt.newTree(body)
nTry.add nnkExceptBranch.newTree(
ident"CancelledError",
# Depending on the exception type, we must have at most one of each of these
# "special" exception handlers that are needed to implement cancellation and
# Defect propagation
var
hasDefect = false
hasCancelledError = false
hasCatchableError = false
template addDefect =
if not hasDefect:
hasDefect = true
# When a Defect is raised, the program is in an undefined state and
# continuing running other tasks while the Future completion sits on the
# callback queue may lead to further damage so we re-raise them eagerly.
nTry.add nnkExceptBranch.newTree(
nnkInfix.newTree(ident"as", ident"Defect", excName),
nnkStmtList.newTree(
nnkAsgn.newTree(closureSucceeded, ident"false"),
newCall(ident "cancelAndSchedule", fut)
nnkRaiseStmt.newTree(excName)
)
)
nTry.add nnkExceptBranch.newTree(
nnkInfix.newTree(ident"as", ident"CatchableError", ident"exc"),
nnkStmtList.newTree(
nnkAsgn.newTree(closureSucceeded, ident"false"),
newCall(ident "fail", fut, ident"exc")
)
)
nTry.add nnkExceptBranch.newTree(
nnkInfix.newTree(ident"as", ident"Defect", ident"exc"),
nnkStmtList.newTree(
nnkAsgn.newTree(closureSucceeded, ident"false"),
nnkRaiseStmt.newTree(ident"exc")
)
)
when not chronosStrictException:
# adds
# except Exception as exc:
# closureSucceeded = false
# fut.fail((ref ValueError)(msg: exc.msg, parent: exc))
let excName = ident"exc"
nTry.add nnkExceptBranch.newTree(
nnkInfix.newTree(ident"as", ident"Exception", ident"exc"),
nnkStmtList.newTree(
nnkAsgn.newTree(closureSucceeded, ident"false"),
newCall(ident "fail", fut,
quote do: (ref ValueError)(msg: `excName`.msg, parent: `excName`)),
)
)
nTry.add nnkFinally.newTree(
nnkIfStmt.newTree(
nnkElifBranch.newTree(
closureSucceeded,
nnkWhenStmt.newTree(
nnkElifExpr.newTree(
nnkInfix.newTree(ident "is", baseType, ident "void"),
newCall(ident "complete", fut)
),
nnkElseExpr.newTree(
newCall(ident "complete", fut, ident "result")
)
template addCancelledError =
if not hasCancelledError:
hasCancelledError = true
nTry.add nnkExceptBranch.newTree(
ident"CancelledError",
nnkStmtList.newTree(
nnkAsgn.newTree(closureSucceeded, ident"false"),
newCall(ident "cancelAndSchedule", fut)
)
)
template addCatchableError =
if not hasCatchableError:
hasCatchableError = true
nTry.add nnkExceptBranch.newTree(
nnkInfix.newTree(ident"as", ident"CatchableError", excName),
nnkStmtList.newTree(
nnkAsgn.newTree(closureSucceeded, ident"false"),
newCall(ident "fail", fut, excName)
))
for exc in raisesTuple:
if exc.eqIdent("Exception"):
addCancelledError
addCatchableError
addDefect
# Because we store `CatchableError` in the Future, we cannot re-raise the
# original exception
nTry.add nnkExceptBranch.newTree(
nnkInfix.newTree(ident"as", ident"Exception", excName),
newCall(ident "fail", fut,
nnkStmtList.newTree(
nnkAsgn.newTree(closureSucceeded, ident"false"),
quote do: (ref ValueError)(msg: `excName`.msg, parent: `excName`)))
)
elif exc.eqIdent("CancelledError"):
addCancelledError
elif exc.eqIdent("CatchableError"):
# Ensure cancellations are re-routed to the cancellation handler even if
# not explicitly specified in the raises list
addCancelledError
addCatchableError
else:
nTry.add nnkExceptBranch.newTree(
nnkInfix.newTree(ident"as", exc, excName),
nnkStmtList.newTree(
nnkAsgn.newTree(closureSucceeded, ident"false"),
newCall(ident "fail", fut, excName)
))
nTry.add nnkFinally.newTree(
nnkIfStmt.newTree(
nnkElifBranch.newTree(
closureSucceeded,
if baseType.eqIdent("void"): # shortcut for non-generic void
newCall(ident "complete", fut)
else:
nnkWhenStmt.newTree(
nnkElifExpr.newTree(
nnkInfix.newTree(ident "is", baseType, ident "void"),
newCall(ident "complete", fut)
),
nnkElseExpr.newTree(
newCall(ident "complete", fut, ident "result")
)
)
return nnkStmtList.newTree(
)
)
)
nnkStmtList.newTree(
newVarStmt(closureSucceeded, ident"true"),
nTry
)
@ -144,6 +180,54 @@ proc cleanupOpenSymChoice(node: NimNode): NimNode {.compileTime.} =
for child in node:
result.add(cleanupOpenSymChoice(child))
proc getAsyncCfg(prc: NimNode): tuple[raises: bool, async: bool, raisesTuple: NimNode] =
# reads the pragmas to extract the useful data
# and removes them
var
foundRaises = -1
foundAsync = -1
for index, pragma in pragma(prc):
if pragma.kind == nnkExprColonExpr and pragma[0] == ident "asyncraises":
foundRaises = index
elif pragma.eqIdent("async"):
foundAsync = index
elif pragma.kind == nnkExprColonExpr and pragma[0] == ident "raises":
warning("The raises pragma doesn't work on async procedure. " &
"Please remove it or use asyncraises instead")
result.raises = foundRaises >= 0
result.async = foundAsync >= 0
result.raisesTuple = nnkTupleConstr.newTree()
if foundRaises >= 0:
for possibleRaise in pragma(prc)[foundRaises][1]:
result.raisesTuple.add(possibleRaise)
if result.raisesTuple.len == 0:
result.raisesTuple = ident("void")
else:
when defined(chronosWarnMissingRaises):
warning("Async proc miss asyncraises")
const defaultException =
when defined(chronosStrictException): "CatchableError"
else: "Exception"
result.raisesTuple.add(ident(defaultException))
let toRemoveList = @[foundRaises, foundAsync].filterIt(it >= 0).sorted().reversed()
for toRemove in toRemoveList:
pragma(prc).del(toRemove)
proc isEmpty(n: NimNode): bool {.compileTime.} =
# true iff node recursively contains only comments or empties
case n.kind
of nnkEmpty, nnkCommentStmt: true
of nnkStmtList:
for child in n:
if not isEmpty(child): return false
true
else:
false
proc asyncSingleProc(prc: NimNode): NimNode {.compileTime.} =
## This macro transforms a single procedure into a closure iterator.
## The ``async`` macro supports a stmtList holding multiple async procedures.
@ -158,7 +242,8 @@ proc asyncSingleProc(prc: NimNode): NimNode {.compileTime.} =
if returnType.kind == nnkEmpty:
ident "void"
elif not (
returnType.kind == nnkBracketExpr and eqIdent(returnType[0], "Future")):
returnType.kind == nnkBracketExpr and
(eqIdent(returnType[0], "Future") or eqIdent(returnType[0], "InternalRaisesFuture"))):
error(
"Expected return type of 'Future' got '" & repr(returnType) & "'", prc)
return
@ -168,77 +253,111 @@ proc asyncSingleProc(prc: NimNode): NimNode {.compileTime.} =
let
baseTypeIsVoid = baseType.eqIdent("void")
futureVoidType = nnkBracketExpr.newTree(ident "Future", ident "void")
(hasRaises, isAsync, raisesTuple) = getAsyncCfg(prc)
if prc.kind in {nnkProcDef, nnkLambda, nnkMethodDef, nnkDo}:
if hasRaises:
# Store `asyncraises` types in InternalRaisesFuture
prc.params2[0] = nnkBracketExpr.newTree(
newIdentNode("InternalRaisesFuture"),
baseType,
raisesTuple
)
elif baseTypeIsVoid:
# Adds the implicit Future[void]
prc.params2[0] =
newNimNode(nnkBracketExpr, prc).
add(newIdentNode("Future")).
add(newIdentNode("void"))
if prc.kind notin {nnkProcTy, nnkLambda}: # TODO: Nim bug?
prc.addPragma(newColonExpr(ident "stackTrace", ident "off"))
# The proc itself doesn't raise
prc.addPragma(
nnkExprColonExpr.newTree(newIdentNode("raises"), nnkBracket.newTree()))
# `gcsafe` isn't deduced even though we require async code to be gcsafe
# https://github.com/nim-lang/RFCs/issues/435
prc.addPragma(newIdentNode("gcsafe"))
if isAsync == false: # `asyncraises` without `async`
# type InternalRaisesFutureRaises = `raisesTuple`
# `body`
prc.body = nnkStmtList.newTree(
nnkTypeSection.newTree(
nnkTypeDef.newTree(
ident"InternalRaisesFutureRaises",
newEmptyNode(),
raisesTuple
)
),
prc.body
)
return prc
if prc.kind in {nnkProcDef, nnkLambda, nnkMethodDef, nnkDo} and
not isEmpty(prc.body):
# don't do anything with forward bodies (empty)
let
prcName = prc.name.getName
outerProcBody = newNimNode(nnkStmtList, prc.body)
# Copy comment for nimdoc
if prc.body.len > 0 and prc.body[0].kind == nnkCommentStmt:
outerProcBody.add(prc.body[0])
let
setResultSym = ident "setResult"
procBody = prc.body.processBody(setResultSym, baseType)
internalFutureSym = ident "chronosInternalRetFuture"
internalFutureType =
if baseTypeIsVoid: futureVoidType
else: returnType
castFutureSym = nnkCast.newTree(internalFutureType, internalFutureSym)
setResultSym = ident"setResult"
resultIdent = ident "result"
procBody = prc.body.processBody(setResultSym, baseType)
# don't do anything with forward bodies (empty)
if procBody.kind != nnkEmpty:
let
# fix #13899, `defer` should not escape its original scope
procBodyBlck = nnkBlockStmt.newTree(newEmptyNode(), procBody)
resultDecl = nnkWhenStmt.newTree(
# when `baseType` is void:
nnkElifExpr.newTree(
nnkInfix.newTree(ident "is", baseType, ident "void"),
quote do:
template result: auto {.used.} =
{.fatal: "You should not reference the `result` variable inside" &
" a void async proc".}
),
# else:
nnkElseExpr.newTree(
newStmtList(
quote do: {.push warning[resultshadowed]: off.},
# var result {.used.}: `baseType`
# In the proc body, result may or may not end up being used
# depending on how the body is written - with implicit returns /
# expressions in particular, it is likely but not guaranteed that
# it is not used. Ideally, we would avoid emitting it in this
# case to avoid the default initializaiton. {.used.} typically
# works better than {.push.} which has a tendency to leak out of
# scope.
# TODO figure out if there's a way to detect `result` usage in
# the proc body _after_ template exapnsion, and therefore
# avoid creating this variable - one option is to create an
# addtional when branch witha fake `result` and check
# `compiles(procBody)` - this is not without cost though
nnkVarSection.newTree(nnkIdentDefs.newTree(
nnkPragmaExpr.newTree(
ident "result",
nnkPragma.newTree(ident "used")),
baseType, newEmptyNode())
),
quote do: {.pop.},
)
resultDecl = nnkWhenStmt.newTree(
# when `baseType` is void:
nnkElifExpr.newTree(
nnkInfix.newTree(ident "is", baseType, ident "void"),
quote do:
template result: auto {.used.} =
{.fatal: "You should not reference the `result` variable inside" &
" a void async proc".}
),
# else:
nnkElseExpr.newTree(
newStmtList(
quote do: {.push warning[resultshadowed]: off.},
# var result {.used.}: `baseType`
# In the proc body, result may or may not end up being used
# depending on how the body is written - with implicit returns /
# expressions in particular, it is likely but not guaranteed that
# it is not used. Ideally, we would avoid emitting it in this
# case to avoid the default initializaiton. {.used.} typically
# works better than {.push.} which has a tendency to leak out of
# scope.
# TODO figure out if there's a way to detect `result` usage in
# the proc body _after_ template exapnsion, and therefore
# avoid creating this variable - one option is to create an
# addtional when branch witha fake `result` and check
# `compiles(procBody)` - this is not without cost though
nnkVarSection.newTree(nnkIdentDefs.newTree(
nnkPragmaExpr.newTree(
resultIdent,
nnkPragma.newTree(ident "used")),
baseType, newEmptyNode())
),
quote do: {.pop.},
)
)
)
# generates:
# template `setResultSym`(code: untyped) {.used.} =
# when typeof(code) is void: code
# else: result = code
#
# this is useful to handle implicit returns, but also
# to bind the `result` to the one we declare here
setResultDecl =
# generates:
# template `setResultSym`(code: untyped) {.used.} =
# when typeof(code) is void: code
# else: `resultIdent` = code
#
# this is useful to handle implicit returns, but also
# to bind the `result` to the one we declare here
setResultDecl =
if baseTypeIsVoid: # shortcut for non-generic void
newEmptyNode()
else:
nnkTemplateDef.newTree(
setResultSym,
newEmptyNode(), newEmptyNode(),
@ -254,107 +373,91 @@ proc asyncSingleProc(prc: NimNode): NimNode {.compileTime.} =
newEmptyNode(),
nnkWhenStmt.newTree(
nnkElifBranch.newTree(
nnkInfix.newTree(ident"is", nnkTypeOfExpr.newTree(ident"code"), ident"void"),
nnkInfix.newTree(
ident"is", nnkTypeOfExpr.newTree(ident"code"), ident"void"),
ident"code"
),
nnkElse.newTree(
newAssignment(ident"result", ident"code")
newAssignment(resultIdent, ident"code")
)
)
)
completeDecl = wrapInTryFinally(
castFutureSym, baseType,
newCall(setResultSym, procBodyBlck)
)
closureBody = newStmtList(resultDecl, setResultDecl, completeDecl)
internalFutureParameter = nnkIdentDefs.newTree(
internalFutureSym, newIdentNode("FutureBase"), newEmptyNode())
iteratorNameSym = genSym(nskIterator, $prcName)
closureIterator = newProc(
iteratorNameSym,
[newIdentNode("FutureBase"), internalFutureParameter],
closureBody, nnkIteratorDef)
iteratorNameSym.copyLineInfo(prc)
closureIterator.pragma = newNimNode(nnkPragma, lineInfoFrom=prc.body)
closureIterator.addPragma(newIdentNode("closure"))
# `async` code must be gcsafe
closureIterator.addPragma(newIdentNode("gcsafe"))
# TODO when push raises is active in a module, the iterator here inherits
# that annotation - here we explicitly disable it again which goes
# against the spirit of the raises annotation - one should investigate
# here the possibility of transporting more specific error types here
# for example by casting exceptions coming out of `await`..
let raises = nnkBracket.newTree()
closureIterator.addPragma(nnkExprColonExpr.newTree(
newIdentNode("raises"),
raises
))
# If proc has an explicit gcsafe pragma, we add it to iterator as well.
# TODO if these lines are not here, srcloc tests fail (!)
if prc.pragma.findChild(it.kind in {nnkSym, nnkIdent} and
it.strVal == "gcsafe") != nil:
closureIterator.addPragma(newIdentNode("gcsafe"))
outerProcBody.add(closureIterator)
# -> let resultFuture = newFuture[T]()
# declared at the end to be sure that the closure
# doesn't reference it, avoid cyclic ref (#203)
let
retFutureSym = ident "resultFuture"
retFutureSym.copyLineInfo(prc)
# Do not change this code to `quote do` version because `instantiationInfo`
# will be broken for `newFuture()` call.
outerProcBody.add(
newLetStmt(
retFutureSym,
newCall(newTree(nnkBracketExpr, ident "newFuture", baseType),
newLit(prcName))
)
)
# -> resultFuture.internalClosure = iterator
outerProcBody.add(
newAssignment(
newDotExpr(retFutureSym, newIdentNode("internalClosure")),
iteratorNameSym)
# Wrapping in try/finally ensures that early returns are handled properly
# and that `defer` is processed in the right scope
completeDecl = wrapInTryFinally(
castFutureSym, baseType,
if baseTypeIsVoid: procBody # shortcut for non-generic `void`
else: newCall(setResultSym, procBody),
raisesTuple
)
# -> futureContinue(resultFuture))
outerProcBody.add(
newCall(newIdentNode("futureContinue"), retFutureSym)
closureBody = newStmtList(resultDecl, setResultDecl, completeDecl)
internalFutureParameter = nnkIdentDefs.newTree(
internalFutureSym, newIdentNode("FutureBase"), newEmptyNode())
iteratorNameSym = genSym(nskIterator, $prcName)
closureIterator = newProc(
iteratorNameSym,
[newIdentNode("FutureBase"), internalFutureParameter],
closureBody, nnkIteratorDef)
outerProcBody = newNimNode(nnkStmtList, prc.body)
# Copy comment for nimdoc
if prc.body.len > 0 and prc.body[0].kind == nnkCommentStmt:
outerProcBody.add(prc.body[0])
iteratorNameSym.copyLineInfo(prc)
closureIterator.pragma = newNimNode(nnkPragma, lineInfoFrom=prc.body)
closureIterator.addPragma(newIdentNode("closure"))
# `async` code must be gcsafe
closureIterator.addPragma(newIdentNode("gcsafe"))
# Exceptions are caught inside the iterator and stored in the future
closureIterator.addPragma(nnkExprColonExpr.newTree(
newIdentNode("raises"),
nnkBracket.newTree()
))
outerProcBody.add(closureIterator)
# -> let resultFuture = newInternalRaisesFuture[T]()
# declared at the end to be sure that the closure
# doesn't reference it, avoid cyclic ref (#203)
let
retFutureSym = ident "resultFuture"
retFutureSym.copyLineInfo(prc)
# Do not change this code to `quote do` version because `instantiationInfo`
# will be broken for `newFuture()` call.
outerProcBody.add(
newLetStmt(
retFutureSym,
newCall(newTree(nnkBracketExpr, ident "newInternalRaisesFuture", baseType),
newLit(prcName))
)
)
# -> resultFuture.internalClosure = iterator
outerProcBody.add(
newAssignment(
newDotExpr(retFutureSym, newIdentNode("internalClosure")),
iteratorNameSym)
)
# -> return resultFuture
outerProcBody.add newNimNode(nnkReturnStmt, prc.body[^1]).add(retFutureSym)
# -> futureContinue(resultFuture))
outerProcBody.add(
newCall(newIdentNode("futureContinue"), retFutureSym)
)
prc.body = outerProcBody
# -> return resultFuture
outerProcBody.add newNimNode(nnkReturnStmt, prc.body[^1]).add(retFutureSym)
if prc.kind notin {nnkProcTy, nnkLambda}: # TODO: Nim bug?
prc.addPragma(newColonExpr(ident "stackTrace", ident "off"))
# See **Remark 435** in this file.
# https://github.com/nim-lang/RFCs/issues/435
prc.addPragma(newIdentNode("gcsafe"))
prc.addPragma(nnkExprColonExpr.newTree(
newIdentNode("raises"),
nnkBracket.newTree()
))
if baseTypeIsVoid:
if returnType.kind == nnkEmpty:
# Add Future[void]
prc.params2[0] = futureVoidType
prc.body = outerProcBody
when chronosDumpAsync:
echo repr prc
prc
template await*[T](f: Future[T]): untyped =
@ -365,7 +468,8 @@ template await*[T](f: Future[T]): untyped =
# responsible for resuming execution once the yielded future is finished
yield chronosInternalRetFuture.internalChild
# `child` released by `futureContinue`
chronosInternalRetFuture.internalChild.internalCheckComplete()
cast[type(f)](chronosInternalRetFuture.internalChild).internalCheckComplete()
when T isnot void:
cast[type(f)](chronosInternalRetFuture.internalChild).value()
else:
@ -385,8 +489,26 @@ macro async*(prc: untyped): untyped =
if prc.kind == nnkStmtList:
result = newStmtList()
for oneProc in prc:
oneProc.addPragma(ident"async")
result.add asyncSingleProc(oneProc)
else:
prc.addPragma(ident"async")
result = asyncSingleProc(prc)
macro asyncraises*(possibleExceptions, prc: untyped): untyped =
# Add back the pragma and let asyncSingleProc handle it
# Exerimental / subject to change and/or removal
if prc.kind == nnkStmtList:
result = newStmtList()
for oneProc in prc:
oneProc.addPragma(nnkExprColonExpr.newTree(
ident"asyncraises",
possibleExceptions
))
result.add asyncSingleProc(oneProc)
else:
prc.addPragma(nnkExprColonExpr.newTree(
ident"asyncraises",
possibleExceptions
))
result = asyncSingleProc(prc)
when chronosDumpAsync:
echo repr result

View File

@ -1223,11 +1223,11 @@ suite "Future[T] behavior test suite":
test "location test":
# WARNING: This test is very sensitive to line numbers and module name.
proc macroFuture() {.async.} = # LINE POSITION 1
let someVar {.used.} = 5 # LINE POSITION 2
proc macroFuture() {.async.} =
let someVar {.used.} = 5 # LINE POSITION 1
let someOtherVar {.used.} = 4
if true:
let otherVar {.used.} = 3
let otherVar {.used.} = 3 # LINE POSITION 2
template templateFuture(): untyped =
newFuture[void]("template")
@ -1260,8 +1260,8 @@ suite "Future[T] behavior test suite":
(loc.procedure == procedure)
check:
chk(loc10, "testfut.nim", 1226, "macroFuture")
chk(loc11, "testfut.nim", 1227, "")
chk(loc10, "testfut.nim", 1227, "macroFuture")
chk(loc11, "testfut.nim", 1230, "")
chk(loc20, "testfut.nim", 1239, "template")
chk(loc21, "testfut.nim", 1242, "")
chk(loc30, "testfut.nim", 1236, "procedure")

View File

@ -151,6 +151,10 @@ suite "Macro transformations test suite":
check waitFor(nr()) == 42
# There are a few unreacheable statements to ensure that we don't regress in
# generated code
{.push warning[UnreachableCode]: off.}
suite "Macro transformations - completions":
test "Run closure to completion on return": # issue #415
var x = 0
@ -203,6 +207,21 @@ suite "Macro transformations - completions":
testWeirdCase() == waitFor(testWeirdCaseAsync())
testWeirdCase() == 55
test "Correct return value with result assignment in defer":
proc testWeirdCase: int =
defer:
result = 55
result = 33
proc testWeirdCaseAsync: Future[int] {.async.} =
defer:
result = 55
await sleepAsync(1.milliseconds)
return 33
check:
testWeirdCase() == waitFor(testWeirdCaseAsync())
testWeirdCase() == 55
test "Generic & finally calling async":
proc testGeneric(T: type): Future[T] {.async.} =
try:
@ -264,6 +283,7 @@ suite "Macro transformations - completions":
result = 12
result = await a2()
check waitFor(asyncInAsync()) == 12
{.pop.}
suite "Macro transformations - implicit returns":
test "Implicit return":
@ -362,3 +382,98 @@ suite "Closure iterator's exception transformation issues":
waitFor(x())
suite "Exceptions tracking":
template checkNotCompiles(body: untyped) =
check (not compiles(body))
test "Can raise valid exception":
proc test1 {.async.} = raise newException(ValueError, "hey")
proc test2 {.async, asyncraises: [ValueError].} = raise newException(ValueError, "hey")
proc test3 {.async, asyncraises: [IOError, ValueError].} =
if 1 == 2:
raise newException(ValueError, "hey")
else:
raise newException(IOError, "hey")
proc test4 {.async, asyncraises: [], used.} = raise newException(Defect, "hey")
proc test5 {.async, asyncraises: [].} = discard
proc test6 {.async, asyncraises: [].} = await test5()
expect(ValueError): waitFor test1()
expect(ValueError): waitFor test2()
expect(IOError): waitFor test3()
waitFor test6()
test "Cannot raise invalid exception":
checkNotCompiles:
proc test3 {.async, asyncraises: [IOError].} = raise newException(ValueError, "hey")
test "Explicit return in non-raising proc":
proc test(): Future[int] {.async, asyncraises: [].} = return 12
check:
waitFor(test()) == 12
test "Non-raising compatibility":
proc test1 {.async, asyncraises: [ValueError].} = raise newException(ValueError, "hey")
let testVar: Future[void] = test1()
proc test2 {.async.} = raise newException(ValueError, "hey")
let testVar2: proc: Future[void] = test2
# Doesn't work unfortunately
#let testVar3: proc: Future[void] = test1
test "Cannot store invalid future types":
proc test1 {.async, asyncraises: [ValueError].} = raise newException(ValueError, "hey")
proc test2 {.async, asyncraises: [IOError].} = raise newException(IOError, "hey")
var a = test1()
checkNotCompiles:
a = test2()
test "Await raises the correct types":
proc test1 {.async, asyncraises: [ValueError].} = raise newException(ValueError, "hey")
proc test2 {.async, asyncraises: [ValueError, CancelledError].} = await test1()
checkNotCompiles:
proc test3 {.async, asyncraises: [CancelledError].} = await test1()
test "Can create callbacks":
proc test1 {.async, asyncraises: [ValueError].} = raise newException(ValueError, "hey")
let callback: proc() {.async, asyncraises: [ValueError].} = test1
test "Can return values":
proc test1: Future[int] {.async, asyncraises: [ValueError].} =
if 1 == 0: raise newException(ValueError, "hey")
return 12
proc test2: Future[int] {.async, asyncraises: [ValueError, IOError, CancelledError].} =
return await test1()
checkNotCompiles:
proc test3: Future[int] {.async, asyncraises: [CancelledError].} = await test1()
check waitFor(test2()) == 12
test "Manual tracking":
proc test1: Future[int] {.asyncraises: [ValueError].} =
result = newFuture[int]()
result.complete(12)
check waitFor(test1()) == 12
proc test2: Future[int] {.asyncraises: [IOError, OSError].} =
result = newFuture[int]()
result.fail(newException(IOError, "fail"))
result.fail(newException(OSError, "fail"))
checkNotCompiles:
result.fail(newException(ValueError, "fail"))
proc test3: Future[void] {.asyncraises: [].} =
checkNotCompiles:
result.fail(newException(ValueError, "fail"))
# Inheritance
proc test4: Future[void] {.asyncraises: [CatchableError].} =
result.fail(newException(IOError, "fail"))
test "Reversed async, asyncraises":
proc test44 {.asyncraises: [ValueError], async.} = raise newException(ValueError, "hey")
checkNotCompiles:
proc test33 {.asyncraises: [IOError], async.} = raise newException(ValueError, "hey")