326 lines
11 KiB
Nim
326 lines
11 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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# `quote do` will ruin line numbers so we avoid it using these helpers
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proc completeWithResult(fut, baseType: NimNode): NimNode {.compileTime.} =
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# when `baseType` is void:
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# complete(`fut`)
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# else:
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# complete(`fut`, result)
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if baseType.eqIdent("void"):
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# Shortcut if we know baseType at macro expansion time
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newCall(ident "complete", fut)
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else:
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# `baseType` might be generic and resolve to `void`
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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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proc completeWithNode(fut, baseType, node: NimNode): NimNode {.compileTime.} =
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# when typeof(`node`) is void:
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# `node` # statement / explicit return
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# -> completeWithResult(fut, baseType)
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# else: # expression / implicit return
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# complete(`fut`, `node`)
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if node.kind == nnkEmpty: # shortcut when known at macro expanstion time
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completeWithResult(fut, baseType)
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else:
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# Handle both expressions and statements - since the type is not know at
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# macro expansion time, we delegate this choice to a later compilation stage
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# with `when`.
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nnkWhenStmt.newTree(
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nnkElifExpr.newTree(
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nnkInfix.newTree(
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ident "is", nnkTypeOfExpr.newTree(node), ident "void"),
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newStmtList(
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node,
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completeWithResult(fut, baseType)
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)
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),
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nnkElseExpr.newTree(
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newCall(ident "complete", fut, node)
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)
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)
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proc processBody(node, fut, 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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res.add completeWithNode(fut, baseType, processBody(node[0], fut, 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, otherwise
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# `fut` will be used for all nested procedures as their own
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# `retFuture`.
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node[i] = processBody(node[i], fut, baseType)
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node
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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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procBody = prc.body.processBody(castFutureSym, 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: `baseType`
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nnkVarSection.newTree(
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nnkIdentDefs.newTree(ident "result", baseType, newEmptyNode())),
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quote do: {.pop.},
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)
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)
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)
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completeDecl = completeWithNode(castFutureSym, baseType, procBodyBlck)
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closureBody = newStmtList(resultDecl, 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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when chronosStrictException:
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raises.add(newIdentNode("CatchableError"))
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when (NimMajor, NimMinor) < (1, 4):
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raises.add(newIdentNode("Defect"))
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else:
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raises.add(newIdentNode("Exception"))
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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.closure = iterator
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outerProcBody.add(
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newAssignment(
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newDotExpr(retFutureSym, newIdentNode("closure")),
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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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let raises = nnkBracket.newTree()
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when (NimMajor, NimMinor) < (1, 4):
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raises.add(newIdentNode("Defect"))
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prc.addPragma(nnkExprColonExpr.newTree(
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newIdentNode("raises"),
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raises
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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.child = 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.child
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# `child` is guaranteed to have been `finished` after the yield
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if chronosInternalRetFuture.mustCancel:
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raise newCancelledError()
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# `child` released by `futureContinue`
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chronosInternalRetFuture.child.internalCheckComplete()
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when T isnot void:
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cast[type(f)](chronosInternalRetFuture.child).internalRead()
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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.child = f
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yield chronosInternalRetFuture.child
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if chronosInternalRetFuture.mustCancel:
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raise newCancelledError()
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cast[type(f)](chronosInternalRetFuture.child)
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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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