mirror of
https://github.com/logos-storage/nim-chronos.git
synced 2026-01-05 15:03:09 +00:00
253bc3cfc0
* Complete in closure finally * cleanup tests, add comment * handle defects * don't complete future on defect * complete future in test to avoid failure * fix with strict exceptions * fix regressions * fix nim 1.6
393 lines
14 KiB
Nim
393 lines
14 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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#
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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 std/[macros]
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proc processBody(node, setResultSym, baseType: NimNode): NimNode {.compileTime.} =
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#echo(node.treeRepr)
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case node.kind
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of nnkReturnStmt:
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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, baseType))
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res.add newNimNode(nnkReturnStmt, node).add(newNilLit())
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res
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of RoutineNodes-{nnkTemplateDef}:
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# skip all the nested procedure definitions
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node
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else:
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for i in 0 ..< node.len:
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# We must not transform nested procedures of any form, since their
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# returns are not meant for our futures
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node[i] = processBody(node[i], setResultSym, baseType)
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node
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proc wrapInTryFinally(fut, baseType, body: NimNode): NimNode {.compileTime.} =
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# creates:
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# var closureSucceeded = true
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# try: `body`
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# except CancelledError: closureSucceeded = false; `castFutureSym`.cancelAndSchedule()
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# except CatchableError as exc: closureSucceeded = false; `castFutureSym`.fail(exc)
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# except Defect as exc:
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# closureSucceeded = false
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# raise exc
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# finally:
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# if closureSucceeded:
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# `castFutureSym`.complete(result)
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# we are completing inside finally to make sure the completion happens even
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# after a `return`
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let closureSucceeded = genSym(nskVar, "closureSucceeded")
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var nTry = nnkTryStmt.newTree(body)
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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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nTry.add nnkExceptBranch.newTree(
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nnkInfix.newTree(ident"as", ident"CatchableError", ident"exc"),
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nnkStmtList.newTree(
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nnkAsgn.newTree(closureSucceeded, ident"false"),
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newCall(ident "fail", fut, ident"exc")
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)
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)
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nTry.add nnkExceptBranch.newTree(
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nnkInfix.newTree(ident"as", ident"Defect", ident"exc"),
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nnkStmtList.newTree(
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nnkAsgn.newTree(closureSucceeded, ident"false"),
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nnkRaiseStmt.newTree(ident"exc")
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)
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)
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when not chronosStrictException:
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# adds
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# except Exception as exc:
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# closureSucceeded = false
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# fut.fail((ref ValueError)(msg: exc.msg, parent: exc))
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let excName = ident"exc"
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nTry.add nnkExceptBranch.newTree(
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nnkInfix.newTree(ident"as", ident"Exception", ident"exc"),
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nnkStmtList.newTree(
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nnkAsgn.newTree(closureSucceeded, ident"false"),
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newCall(ident "fail", fut,
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quote do: (ref ValueError)(msg: `excName`.msg, parent: `excName`)),
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)
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)
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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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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, 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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return 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 =
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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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proc asyncSingleProc(prc: 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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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 eqIdent(returnType[0], "Future")):
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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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baseTypeIsVoid = baseType.eqIdent("void")
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futureVoidType = nnkBracketExpr.newTree(ident "Future", ident "void")
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if prc.kind in {nnkProcDef, nnkLambda, nnkMethodDef, nnkDo}:
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let
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prcName = prc.name.getName
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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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let
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internalFutureSym = ident "chronosInternalRetFuture"
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internalFutureType =
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if baseTypeIsVoid: futureVoidType
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else: returnType
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castFutureSym = nnkCast.newTree(internalFutureType, internalFutureSym)
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setResultSym = ident"setResult"
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procBody = prc.body.processBody(setResultSym, baseType)
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# don't do anything with forward bodies (empty)
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if procBody.kind != nnkEmpty:
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let
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# fix #13899, `defer` should not escape its original scope
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procBodyBlck = nnkBlockStmt.newTree(newEmptyNode(), procBody)
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resultDecl = 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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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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),
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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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ident "result",
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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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# generates:
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# template `setResultSym`(code: untyped) {.used.} =
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# when typeof(code) is void: code
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# else: result = code
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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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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(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(ident"result", ident"code")
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)
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)
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)
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completeDecl = wrapInTryFinally(
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castFutureSym, baseType,
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newCall(setResultSym, procBodyBlck)
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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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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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# TODO when push raises is active in a module, the iterator here inherits
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# that annotation - here we explicitly disable it again which goes
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# against the spirit of the raises annotation - one should investigate
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# here the possibility of transporting more specific error types here
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# for example by casting exceptions coming out of `await`..
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let raises = nnkBracket.newTree()
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closureIterator.addPragma(nnkExprColonExpr.newTree(
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newIdentNode("raises"),
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raises
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))
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# If proc has an explicit gcsafe pragma, we add it to iterator as well.
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# TODO if these lines are not here, srcloc tests fail (!)
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if prc.pragma.findChild(it.kind in {nnkSym, nnkIdent} and
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it.strVal == "gcsafe") != nil:
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closureIterator.addPragma(newIdentNode("gcsafe"))
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outerProcBody.add(closureIterator)
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# -> let resultFuture = newFuture[T]()
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# declared at the end to be sure that the closure
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# doesn't reference it, avoid cyclic ref (#203)
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let
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retFutureSym = ident "resultFuture"
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retFutureSym.copyLineInfo(prc)
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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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outerProcBody.add(
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newLetStmt(
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retFutureSym,
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newCall(newTree(nnkBracketExpr, ident "newFuture", baseType),
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newLit(prcName))
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)
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)
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# -> resultFuture.internalClosure = iterator
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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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# -> futureContinue(resultFuture))
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outerProcBody.add(
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newCall(newIdentNode("futureContinue"), retFutureSym)
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)
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# -> return resultFuture
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outerProcBody.add newNimNode(nnkReturnStmt, prc.body[^1]).add(retFutureSym)
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prc.body = outerProcBody
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if prc.kind notin {nnkProcTy, nnkLambda}: # TODO: Nim bug?
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prc.addPragma(newColonExpr(ident "stackTrace", ident "off"))
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# See **Remark 435** in this file.
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# https://github.com/nim-lang/RFCs/issues/435
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prc.addPragma(newIdentNode("gcsafe"))
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prc.addPragma(nnkExprColonExpr.newTree(
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newIdentNode("raises"),
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nnkBracket.newTree()
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))
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if baseTypeIsVoid:
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if returnType.kind == nnkEmpty:
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# Add Future[void]
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prc.params2[0] = futureVoidType
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prc
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template await*[T](f: Future[T]): untyped =
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when declared(chronosInternalRetFuture):
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chronosInternalRetFuture.internalChild = f
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# `futureContinue` calls the iterator generated by the `async`
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# transformation - `yield` gives control back to `futureContinue` which is
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# responsible for resuming execution once the yielded future is finished
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yield chronosInternalRetFuture.internalChild
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# `child` released by `futureContinue`
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chronosInternalRetFuture.internalChild.internalCheckComplete()
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when T isnot void:
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cast[type(f)](chronosInternalRetFuture.internalChild).value()
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else:
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unsupported "await is only available within {.async.}"
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template awaitne*[T](f: Future[T]): Future[T] =
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when declared(chronosInternalRetFuture):
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chronosInternalRetFuture.internalChild = f
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yield chronosInternalRetFuture.internalChild
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cast[type(f)](chronosInternalRetFuture.internalChild)
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else:
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unsupported "awaitne is only available within {.async.}"
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macro async*(prc: untyped): untyped =
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## Macro which processes async procedures into the appropriate
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## iterators and yield statements.
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if prc.kind == nnkStmtList:
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result = newStmtList()
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for oneProc in prc:
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result.add asyncSingleProc(oneProc)
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else:
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result = asyncSingleProc(prc)
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when chronosDumpAsync:
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echo repr result
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