597 lines
20 KiB
Nim
597 lines
20 KiB
Nim
#
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#
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# Nim's Runtime Library
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# (c) Copyright 2015 Dominik Picheta
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# (c) Copyright 2018-Present Status Research & Development GmbH
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#
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# See the file "copying.txt", included in this
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# distribution, for details about the copyright.
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#
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import
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std/[macros],
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../[futures, config],
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./raisesfutures
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proc processBody(node, setResultSym: NimNode): NimNode {.compileTime.} =
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case node.kind
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of nnkReturnStmt:
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# `return ...` -> `setResult(...); return`
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let
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res = newNimNode(nnkStmtList, node)
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if node[0].kind != nnkEmpty:
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res.add newCall(setResultSym, processBody(node[0], setResultSym))
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res.add newNimNode(nnkReturnStmt, node).add(newEmptyNode())
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res
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of RoutineNodes-{nnkTemplateDef}:
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# Skip nested routines since they have their own return value distinct from
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# the Future we inject
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node
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else:
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if node.kind == nnkYieldStmt:
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# asyncdispatch allows `yield` but this breaks cancellation
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warning(
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"`yield` in async procedures not supported - use `awaitne` instead",
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node)
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for i in 0 ..< node.len:
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node[i] = processBody(node[i], setResultSym)
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node
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proc wrapInTryFinally(
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fut, baseType, body, raises: NimNode,
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handleException: bool): NimNode {.compileTime.} =
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# creates:
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# try: `body`
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# [for raise in raises]:
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# except `raise`: closureSucceeded = false; `castFutureSym`.fail(exc)
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# finally:
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# if closureSucceeded:
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# `castFutureSym`.complete(result)
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#
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# Calling `complete` inside `finally` ensures that all success paths
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# (including early returns and code inside nested finally statements and
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# defer) are completed with the final contents of `result`
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let
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closureSucceeded = genSym(nskVar, "closureSucceeded")
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nTry = nnkTryStmt.newTree(body)
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excName = ident"exc"
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# Depending on the exception type, we must have at most one of each of these
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# "special" exception handlers that are needed to implement cancellation and
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# Defect propagation
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var
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hasDefect = false
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hasCancelledError = false
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hasCatchableError = false
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template addDefect =
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if not hasDefect:
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hasDefect = true
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# When a Defect is raised, the program is in an undefined state and
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# continuing running other tasks while the Future completion sits on the
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# callback queue may lead to further damage so we re-raise them eagerly.
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nTry.add nnkExceptBranch.newTree(
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nnkInfix.newTree(ident"as", ident"Defect", excName),
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nnkStmtList.newTree(
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nnkAsgn.newTree(closureSucceeded, ident"false"),
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nnkRaiseStmt.newTree(excName)
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)
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)
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template addCancelledError =
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if not hasCancelledError:
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hasCancelledError = true
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nTry.add nnkExceptBranch.newTree(
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ident"CancelledError",
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nnkStmtList.newTree(
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nnkAsgn.newTree(closureSucceeded, ident"false"),
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newCall(ident "cancelAndSchedule", fut)
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)
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)
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template addCatchableError =
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if not hasCatchableError:
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hasCatchableError = true
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nTry.add nnkExceptBranch.newTree(
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nnkInfix.newTree(ident"as", ident"CatchableError", excName),
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nnkStmtList.newTree(
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nnkAsgn.newTree(closureSucceeded, ident"false"),
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newCall(ident "fail", fut, excName)
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))
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var raises = if raises == nil:
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nnkTupleConstr.newTree(ident"CatchableError")
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elif isNoRaises(raises):
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nnkTupleConstr.newTree()
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else:
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raises.copyNimTree()
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if handleException:
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raises.add(ident"Exception")
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for exc in raises:
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if exc.eqIdent("Exception"):
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addCancelledError
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addCatchableError
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addDefect
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# Because we store `CatchableError` in the Future, we cannot re-raise the
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# original exception
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nTry.add nnkExceptBranch.newTree(
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nnkInfix.newTree(ident"as", ident"Exception", excName),
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newCall(ident "fail", fut,
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nnkStmtList.newTree(
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nnkAsgn.newTree(closureSucceeded, ident"false"),
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quote do:
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(ref AsyncExceptionError)(
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msg: `excName`.msg, parent: `excName`)))
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)
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elif exc.eqIdent("CancelledError"):
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addCancelledError
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elif exc.eqIdent("CatchableError"):
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# Ensure cancellations are re-routed to the cancellation handler even if
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# not explicitly specified in the raises list
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addCancelledError
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addCatchableError
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else:
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nTry.add nnkExceptBranch.newTree(
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nnkInfix.newTree(ident"as", exc, excName),
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nnkStmtList.newTree(
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nnkAsgn.newTree(closureSucceeded, ident"false"),
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newCall(ident "fail", fut, excName)
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))
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addDefect # Must not complete future on defect
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nTry.add nnkFinally.newTree(
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nnkIfStmt.newTree(
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nnkElifBranch.newTree(
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closureSucceeded,
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if baseType.eqIdent("void"): # shortcut for non-generic void
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newCall(ident "complete", fut)
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else:
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nnkWhenStmt.newTree(
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nnkElifExpr.newTree(
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nnkInfix.newTree(ident "is", baseType, ident "void"),
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newCall(ident "complete", fut)
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),
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nnkElseExpr.newTree(
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newCall(ident "complete", fut, newCall(ident "move", ident "result"))
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)
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)
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)
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)
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)
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nnkStmtList.newTree(
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newVarStmt(closureSucceeded, ident"true"),
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nTry
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)
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proc getName(node: NimNode): string {.compileTime.} =
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case node.kind
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of nnkSym:
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return node.strVal
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of nnkPostfix:
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return node[1].strVal
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of nnkIdent:
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return node.strVal
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of nnkEmpty:
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return "anonymous"
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else:
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error("Unknown name.")
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macro unsupported(s: static[string]): untyped =
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error s
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proc params2(someProc: NimNode): NimNode {.compileTime.} =
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# until https://github.com/nim-lang/Nim/pull/19563 is available
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if someProc.kind == nnkProcTy:
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someProc[0]
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else:
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params(someProc)
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proc cleanupOpenSymChoice(node: NimNode): NimNode {.compileTime.} =
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# Replace every Call -> OpenSymChoice by a Bracket expr
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# ref https://github.com/nim-lang/Nim/issues/11091
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if node.kind in nnkCallKinds and
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node[0].kind == nnkOpenSymChoice and node[0].eqIdent("[]"):
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result = newNimNode(nnkBracketExpr)
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for child in node[1..^1]:
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result.add(cleanupOpenSymChoice(child))
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else:
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result = node.copyNimNode()
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for child in node:
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result.add(cleanupOpenSymChoice(child))
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type
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AsyncParams = tuple
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raw: bool
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raises: NimNode
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handleException: bool
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proc decodeParams(params: NimNode): AsyncParams =
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# decodes the parameter tuple given in `async: (name: value, ...)` to its
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# recognised parts
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params.expectKind(nnkTupleConstr)
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var
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raw = false
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raises: NimNode = nil
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handleException = false
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hasLocalAnnotations = false
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for param in params:
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param.expectKind(nnkExprColonExpr)
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if param[0].eqIdent("raises"):
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hasLocalAnnotations = true
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param[1].expectKind(nnkBracket)
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if param[1].len == 0:
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raises = makeNoRaises()
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else:
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raises = nnkTupleConstr.newTree()
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for possibleRaise in param[1]:
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raises.add(possibleRaise)
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elif param[0].eqIdent("raw"):
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# boolVal doesn't work in untyped macros it seems..
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raw = param[1].eqIdent("true")
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elif param[0].eqIdent("handleException"):
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hasLocalAnnotations = true
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handleException = param[1].eqIdent("true")
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else:
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warning("Unrecognised async parameter: " & repr(param[0]), param)
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if not hasLocalAnnotations:
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handleException = chronosHandleException
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(raw, raises, handleException)
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proc isEmpty(n: NimNode): bool {.compileTime.} =
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# true iff node recursively contains only comments or empties
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case n.kind
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of nnkEmpty, nnkCommentStmt: true
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of nnkStmtList:
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for child in n:
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if not isEmpty(child): return false
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true
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else:
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false
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proc asyncSingleProc(prc, params: NimNode): NimNode {.compileTime.} =
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## This macro transforms a single procedure into a closure iterator.
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## The ``async`` macro supports a stmtList holding multiple async procedures.
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if prc.kind notin {nnkProcTy, nnkProcDef, nnkLambda, nnkMethodDef, nnkDo}:
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error("Cannot transform " & $prc.kind & " into an async proc." &
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" proc/method definition or lambda node expected.", prc)
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for pragma in prc.pragma():
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if pragma.kind == nnkExprColonExpr and pragma[0].eqIdent("raises"):
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warning("The raises pragma doesn't work on async procedures - use " &
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"`async: (raises: [...]) instead.", prc)
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let returnType = cleanupOpenSymChoice(prc.params2[0])
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# Verify that the return type is a Future[T]
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let baseType =
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if returnType.kind == nnkEmpty:
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ident "void"
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elif not (
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returnType.kind == nnkBracketExpr and
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(eqIdent(returnType[0], "Future") or eqIdent(returnType[0], "InternalRaisesFuture"))):
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error(
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"Expected return type of 'Future' got '" & repr(returnType) & "'", prc)
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return
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else:
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returnType[1]
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let
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# When the base type is known to be void (and not generic), we can simplify
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# code generation - however, in the case of generic async procedures it
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# could still end up being void, meaning void detection needs to happen
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# post-macro-expansion.
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baseTypeIsVoid = baseType.eqIdent("void")
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(raw, raises, handleException) = decodeParams(params)
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internalFutureType =
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if baseTypeIsVoid:
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newNimNode(nnkBracketExpr, prc).
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add(newIdentNode("Future")).
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add(baseType)
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else:
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returnType
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internalReturnType = if raises == nil:
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internalFutureType
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else:
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nnkBracketExpr.newTree(
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newIdentNode("InternalRaisesFuture"),
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baseType,
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raises
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)
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prc.params2[0] = internalReturnType
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if prc.kind notin {nnkProcTy, nnkLambda}:
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prc.addPragma(newColonExpr(ident "stackTrace", ident "off"))
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# The proc itself doesn't raise
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prc.addPragma(
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nnkExprColonExpr.newTree(newIdentNode("raises"), nnkBracket.newTree()))
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# `gcsafe` isn't deduced even though we require async code to be gcsafe
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# https://github.com/nim-lang/RFCs/issues/435
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prc.addPragma(newIdentNode("gcsafe"))
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if raw: # raw async = body is left as-is
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if raises != nil and prc.kind notin {nnkProcTy, nnkLambda} and not isEmpty(prc.body):
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# Inject `raises` type marker that causes `newFuture` to return a raise-
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# tracking future instead of an ordinary future:
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#
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# type InternalRaisesFutureRaises = `raisesTuple`
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# `body`
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prc.body = nnkStmtList.newTree(
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nnkTypeSection.newTree(
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nnkTypeDef.newTree(
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nnkPragmaExpr.newTree(
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ident"InternalRaisesFutureRaises",
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nnkPragma.newTree(ident "used")),
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newEmptyNode(),
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raises,
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)
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),
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prc.body
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)
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elif prc.kind in {nnkProcDef, nnkLambda, nnkMethodDef, nnkDo} and
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not isEmpty(prc.body):
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let
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setResultSym = ident "setResult"
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procBody = prc.body.processBody(setResultSym)
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resultIdent = ident "result"
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fakeResult = quote do:
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template result: auto {.used.} =
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{.fatal: "You should not reference the `result` variable inside" &
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" a void async proc".}
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resultDecl =
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if baseTypeIsVoid: fakeResult
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else: nnkWhenStmt.newTree(
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# when `baseType` is void:
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nnkElifExpr.newTree(
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nnkInfix.newTree(ident "is", baseType, ident "void"),
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fakeResult
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),
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# else:
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nnkElseExpr.newTree(
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newStmtList(
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quote do: {.push warning[resultshadowed]: off.},
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# var result {.used.}: `baseType`
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# In the proc body, result may or may not end up being used
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# depending on how the body is written - with implicit returns /
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# expressions in particular, it is likely but not guaranteed that
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# it is not used. Ideally, we would avoid emitting it in this
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# case to avoid the default initializaiton. {.used.} typically
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# works better than {.push.} which has a tendency to leak out of
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# scope.
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# TODO figure out if there's a way to detect `result` usage in
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# the proc body _after_ template exapnsion, and therefore
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# avoid creating this variable - one option is to create an
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# addtional when branch witha fake `result` and check
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# `compiles(procBody)` - this is not without cost though
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nnkVarSection.newTree(nnkIdentDefs.newTree(
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nnkPragmaExpr.newTree(
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resultIdent,
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nnkPragma.newTree(ident "used")),
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baseType, newEmptyNode())
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),
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quote do: {.pop.},
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)
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)
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)
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# ```nim
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# template `setResultSym`(code: untyped) {.used.} =
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# when typeof(code) is void: code
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# else: `resultIdent` = code
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# ```
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#
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# this is useful to handle implicit returns, but also
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# to bind the `result` to the one we declare here
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setResultDecl =
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if baseTypeIsVoid: # shortcut for non-generic void
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newEmptyNode()
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else:
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nnkTemplateDef.newTree(
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setResultSym,
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newEmptyNode(), newEmptyNode(),
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nnkFormalParams.newTree(
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newEmptyNode(),
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nnkIdentDefs.newTree(
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ident"code",
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ident"untyped",
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newEmptyNode(),
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)
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),
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nnkPragma.newTree(ident"used"),
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newEmptyNode(),
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nnkWhenStmt.newTree(
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nnkElifBranch.newTree(
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nnkInfix.newTree(
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ident"is", nnkTypeOfExpr.newTree(ident"code"), ident"void"),
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ident"code"
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),
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nnkElse.newTree(
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newAssignment(resultIdent, ident"code")
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)
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)
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)
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internalFutureSym = ident "chronosInternalRetFuture"
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castFutureSym = nnkCast.newTree(internalFutureType, internalFutureSym)
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# Wrapping in try/finally ensures that early returns are handled properly
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# and that `defer` is processed in the right scope
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completeDecl = wrapInTryFinally(
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castFutureSym, baseType,
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if baseTypeIsVoid: procBody # shortcut for non-generic `void`
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else: newCall(setResultSym, procBody),
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raises,
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handleException
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)
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closureBody = newStmtList(resultDecl, setResultDecl, completeDecl)
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internalFutureParameter = nnkIdentDefs.newTree(
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internalFutureSym, newIdentNode("FutureBase"), newEmptyNode())
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prcName = prc.name.getName
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iteratorNameSym = genSym(nskIterator, $prcName)
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closureIterator = newProc(
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iteratorNameSym,
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[newIdentNode("FutureBase"), internalFutureParameter],
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closureBody, nnkIteratorDef)
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iteratorNameSym.copyLineInfo(prc)
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closureIterator.pragma = newNimNode(nnkPragma, lineInfoFrom=prc.body)
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closureIterator.addPragma(newIdentNode("closure"))
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# `async` code must be gcsafe
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closureIterator.addPragma(newIdentNode("gcsafe"))
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# Exceptions are caught inside the iterator and stored in the future
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closureIterator.addPragma(nnkExprColonExpr.newTree(
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newIdentNode("raises"),
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nnkBracket.newTree()
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))
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# The body of the original procedure (now moved to the iterator) is replaced
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# with:
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#
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# ```nim
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# let resultFuture = newFuture[T]()
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# resultFuture.internalClosure = `iteratorNameSym`
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# futureContinue(resultFuture)
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# return resultFuture
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# ```
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#
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# Declared at the end to be sure that the closure doesn't reference it,
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# avoid cyclic ref (#203)
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#
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# Do not change this code to `quote do` version because `instantiationInfo`
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# will be broken for `newFuture()` call.
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let
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outerProcBody = newNimNode(nnkStmtList, prc.body)
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# Copy comment for nimdoc
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if prc.body.len > 0 and prc.body[0].kind == nnkCommentStmt:
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outerProcBody.add(prc.body[0])
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outerProcBody.add(closureIterator)
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let
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retFutureSym = ident "resultFuture"
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newFutProc = if raises == nil:
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nnkBracketExpr.newTree(ident "newFuture", baseType)
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else:
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nnkBracketExpr.newTree(ident "newInternalRaisesFuture", baseType, raises)
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retFutureSym.copyLineInfo(prc)
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outerProcBody.add(
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newLetStmt(
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retFutureSym,
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newCall(newFutProc, newLit(prcName))
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)
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)
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outerProcBody.add(
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newAssignment(
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newDotExpr(retFutureSym, newIdentNode("internalClosure")),
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iteratorNameSym)
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)
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outerProcBody.add(
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newCall(newIdentNode("futureContinue"), retFutureSym)
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)
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outerProcBody.add newNimNode(nnkReturnStmt, prc.body[^1]).add(retFutureSym)
|
|
|
|
prc.body = outerProcBody
|
|
|
|
when chronosDumpAsync:
|
|
echo repr prc
|
|
|
|
prc
|
|
|
|
template await*[T](f: Future[T]): T =
|
|
## Ensure that the given `Future` is finished, then return its value.
|
|
##
|
|
## If the `Future` failed or was cancelled, the corresponding exception will
|
|
## be raised instead.
|
|
##
|
|
## If the `Future` is pending, execution of the current `async` procedure
|
|
## will be suspended until the `Future` is finished.
|
|
when declared(chronosInternalRetFuture):
|
|
chronosInternalRetFuture.internalChild = f
|
|
# `futureContinue` calls the iterator generated by the `async`
|
|
# transformation - `yield` gives control back to `futureContinue` which is
|
|
# responsible for resuming execution once the yielded future is finished
|
|
yield chronosInternalRetFuture.internalChild
|
|
# `child` released by `futureContinue`
|
|
cast[type(f)](chronosInternalRetFuture.internalChild).internalRaiseIfError(f)
|
|
|
|
when T isnot void:
|
|
cast[type(f)](chronosInternalRetFuture.internalChild).value()
|
|
else:
|
|
unsupported "await is only available within {.async.}"
|
|
|
|
template await*[T, E](fut: InternalRaisesFuture[T, E]): T =
|
|
## Ensure that the given `Future` is finished, then return its value.
|
|
##
|
|
## If the `Future` failed or was cancelled, the corresponding exception will
|
|
## be raised instead.
|
|
##
|
|
## If the `Future` is pending, execution of the current `async` procedure
|
|
## will be suspended until the `Future` is finished.
|
|
when declared(chronosInternalRetFuture):
|
|
chronosInternalRetFuture.internalChild = fut
|
|
# `futureContinue` calls the iterator generated by the `async`
|
|
# transformation - `yield` gives control back to `futureContinue` which is
|
|
# responsible for resuming execution once the yielded future is finished
|
|
yield chronosInternalRetFuture.internalChild
|
|
# `child` released by `futureContinue`
|
|
cast[type(fut)](
|
|
chronosInternalRetFuture.internalChild).internalRaiseIfError(E, fut)
|
|
|
|
when T isnot void:
|
|
cast[type(fut)](chronosInternalRetFuture.internalChild).value()
|
|
else:
|
|
unsupported "await is only available within {.async.}"
|
|
|
|
template awaitne*[T](f: Future[T]): Future[T] =
|
|
when declared(chronosInternalRetFuture):
|
|
chronosInternalRetFuture.internalChild = f
|
|
yield chronosInternalRetFuture.internalChild
|
|
cast[type(f)](chronosInternalRetFuture.internalChild)
|
|
else:
|
|
unsupported "awaitne is only available within {.async.}"
|
|
|
|
macro async*(params, prc: untyped): untyped =
|
|
## Macro which processes async procedures into the appropriate
|
|
## iterators and yield statements.
|
|
if prc.kind == nnkStmtList:
|
|
result = newStmtList()
|
|
for oneProc in prc:
|
|
result.add asyncSingleProc(oneProc, params)
|
|
else:
|
|
result = asyncSingleProc(prc, params)
|
|
|
|
macro async*(prc: untyped): untyped =
|
|
## Macro which processes async procedures into the appropriate
|
|
## iterators and yield statements.
|
|
|
|
if prc.kind == nnkStmtList:
|
|
result = newStmtList()
|
|
for oneProc in prc:
|
|
result.add asyncSingleProc(oneProc, nnkTupleConstr.newTree())
|
|
else:
|
|
result = asyncSingleProc(prc, nnkTupleConstr.newTree())
|