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core-trace-experimental: add
@withSpan macro
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247 changes: 247 additions & 0 deletions
247
...race-experimental/src/main/scala-2/org/typelevel/otel4s/trace/experimental/withSpan.scala
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,247 @@ | ||
| /* | ||
| * Copyright 2022 Typelevel | ||
| * | ||
| * Licensed under the Apache License, Version 2.0 (the "License"); | ||
| * you may not use this file except in compliance with the License. | ||
| * You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
|
|
||
| package org.typelevel.otel4s.trace.experimental | ||
|
|
||
| import scala.annotation.StaticAnnotation | ||
| import scala.annotation.compileTimeOnly | ||
| import scala.annotation.unused | ||
| import scala.reflect.macros.blackbox | ||
|
|
||
| /** Wraps the body of an annotated method or variable into the span. | ||
| * | ||
| * By default, the span name will be `className.methodName`, unless a name is | ||
| * provided as an argument. | ||
| * | ||
| * {{{ | ||
| * class Service[F[_]: Tracer](db: Database[F]) { | ||
| * @withSpan | ||
| * def findUser(@spanAttribute userId: Long): F[User] = | ||
| * db.findUser(id) | ||
| * } | ||
| * | ||
| * // expands into | ||
| * | ||
| * class Service[F[_]: Tracer](db: Database[F]) { | ||
| * def findUser(userId: Long): F[User] = | ||
| * Tracer[F] | ||
| * .span("Service.findUser", Attribute("userId", userId)) | ||
| * .surround(db.findUser(id)) | ||
| * } | ||
| * }}} | ||
| * | ||
| * @param name | ||
| * the custom name of the span. If not specified, the span name will be | ||
| * `className.methodName` | ||
| * | ||
| * @param debug | ||
| * whether to print the generated code to the console | ||
| */ | ||
| @compileTimeOnly("enable macro to expand macro annotations") | ||
| class withSpan( | ||
| @unused name: String = "", | ||
| @unused debug: Boolean = false | ||
| ) extends StaticAnnotation { | ||
| def macroTransform(annottees: Any*): Any = macro withSpanMacro.impl | ||
| } | ||
|
|
||
| object withSpanMacro { | ||
|
|
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| def impl(c: blackbox.Context)(annottees: c.Expr[Any]*): c.Expr[c.Tree] = { | ||
| import c.universe._ | ||
|
|
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| def abort(message: String) = | ||
| c.abort(c.enclosingPosition, s"@withSpan macro: $message") | ||
|
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| def ensureImplicitExist(tpe: Tree, reason: Throwable => String): c.Tree = | ||
| try { | ||
| val t = c.typecheck(tpe).tpe | ||
| c.inferImplicitValue(t) | ||
| } catch { | ||
| case e: Throwable => abort(reason(e)) | ||
| } | ||
|
|
||
| def resolveEffectType(tpt: Tree): Tree = | ||
| tpt match { | ||
| case tq"$tpe[${_}]" => tpe | ||
| case _ => abort("cannot resolve the type of the effect") | ||
| } | ||
|
|
||
| val macroName: Tree = | ||
| c.prefix.tree match { | ||
| case Apply(Select(New(name), _), _) => name | ||
| case _ => c.abort(c.enclosingPosition, "Unexpected macro application") | ||
| } | ||
|
|
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| val (nameParam, debug) = c.prefix.tree match { | ||
| case q"new ${`macroName`}(..$args)" => | ||
| ( | ||
| args.headOption | ||
| .collect { case Literal(value) => Left(value) } | ||
| .orElse( | ||
| args.collectFirst { case q"name = $value" => Right(value) } | ||
| ), | ||
| args.collectFirst { case q"debug = true" => }.isDefined | ||
| ) | ||
| case _ => | ||
| (None, false) | ||
| } | ||
|
|
||
| def spanName(definition: ValOrDefDef): Tree = | ||
| nameParam match { | ||
| case Some(Left(const)) => | ||
| val literal = Literal(const) | ||
| q"$literal" | ||
|
|
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| case Some(Right(tree)) => | ||
| tree | ||
|
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| case None => | ||
| @annotation.tailrec | ||
| def resolveEnclosingName(symbol: Symbol, output: String): String = | ||
| if (symbol.isClass) { | ||
| val className = symbol.name.toString | ||
| if (className.startsWith("$anon")) | ||
| resolveEnclosingName(symbol.owner, "$anon" + "." + output) | ||
| else | ||
| className + "." + output | ||
| } else { | ||
| resolveEnclosingName(symbol.owner, output) | ||
| } | ||
|
|
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| val prefix = resolveEnclosingName(c.internal.enclosingOwner, "") | ||
|
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| val literal = Literal( | ||
| Constant(prefix + definition.name.decodedName.toString) | ||
| ) | ||
| q"$literal" | ||
| } | ||
|
|
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| def expandDef(defDef: DefDef): Tree = { | ||
| val effectType = resolveEffectType(defDef.tpt) | ||
| val name: Tree = spanName(defDef) | ||
|
|
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| val attributes = defDef.vparamss.flatten.flatMap { | ||
| case ValDef(mods, name, tpt, _) => | ||
| mods.annotations.flatMap { annotation => | ||
| val typed = c.typecheck(annotation) | ||
| if ( | ||
| typed.tpe.typeSymbol.fullName == "org.typelevel.otel4s.trace.experimental.spanAttribute" | ||
| ) { | ||
| val keyArg = typed match { | ||
| case q"new ${_}(${keyArg})" => | ||
| keyArg | ||
| case _ => | ||
| abort("unknown structure of the @spanAttribute annotation.") | ||
| } | ||
|
|
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| val key = keyArg match { | ||
| // the key param is not specified, use param name as a key | ||
| case Select(_, TermName("$lessinit$greater$default$1")) => | ||
| Literal(Constant(name.decodedName.toString)) | ||
|
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| // type of the AttributeKey must match the parameter type | ||
| case q"$_[$tpe]($_)(..$_)" => | ||
| val keyType = c.untypecheck(tpe) | ||
| val argType = c.typecheck(tpt, c.TYPEmode) | ||
|
|
||
| if (!keyType.equalsStructure(argType)) { | ||
| abort( | ||
| s"the argument [${name.toString}] type [$argType] does not match the type of the attribute [$keyType]." | ||
| ) | ||
| } | ||
| keyArg | ||
|
|
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| case _ => | ||
| keyArg | ||
| } | ||
|
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| ensureImplicitExist( | ||
| q"_root_.org.typelevel.otel4s.AttributeKey.KeySelect[$tpt]", | ||
| e => | ||
| s"the argument [${name.decodedName}] cannot be used as an attribute. The type [$tpt] is not supported.${e.getMessage}" | ||
| ) | ||
|
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| List( | ||
| q"_root_.org.typelevel.otel4s.Attribute($key, $name)" | ||
| ) | ||
| } else { | ||
| Nil | ||
| } | ||
| } | ||
|
|
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| case _ => | ||
| Nil | ||
| } | ||
|
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| val body = | ||
| q""" | ||
| _root_.org.typelevel.otel4s.trace.Tracer[$effectType].span($name, ..$attributes).surround { | ||
| ${defDef.rhs} | ||
| } | ||
| """ | ||
|
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||
| DefDef( | ||
| defDef.mods, | ||
| defDef.name, | ||
| defDef.tparams, | ||
| defDef.vparamss, | ||
| defDef.tpt, | ||
| body | ||
| ) | ||
| } | ||
|
|
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| def expandVal(valDef: ValDef): Tree = { | ||
| val effectType = resolveEffectType(valDef.tpt) | ||
| val name: Tree = spanName(valDef) | ||
|
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| val body = | ||
| q""" | ||
| _root_.org.typelevel.otel4s.trace.Tracer[$effectType].span($name).surround { | ||
| ${valDef.rhs} | ||
| } | ||
| """ | ||
|
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| ValDef(valDef.mods, valDef.name, valDef.tpt, body) | ||
| } | ||
|
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| val result = annottees.map(_.tree).toList match { | ||
| case List(defDef: DefDef) => | ||
| expandDef(defDef) | ||
|
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| case List(valDef: ValDef) => | ||
| expandVal(valDef) | ||
|
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| case _ => | ||
| abort( | ||
| "unsupported definition. Only `def` and `val` with explicit result types and defined bodies are supported." | ||
| ) | ||
| } | ||
|
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| if (debug) { | ||
| val at: String = | ||
| if (c.enclosingPosition == NoPosition) | ||
| "" | ||
| else | ||
| s"at ${c.enclosingPosition.source.file.name}:${c.enclosingPosition.line} " | ||
|
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| scala.Predef.println(s"@withSpan $at- expanded into:\n${result}") | ||
| } | ||
|
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| c.Expr(result) | ||
| } | ||
|
|
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| } |
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