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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.") | ||
| } | ||
|
|
||
| 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, $name)" | ||
| ) | ||
| } else { | ||
| Nil | ||
| } | ||
| } | ||
|
|
||
| case _ => | ||
| Nil | ||
| } | ||
|
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| val body = | ||
| q""" | ||
| _root_.org.typelevel.otel4s.trace.Tracer[$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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Since KeySelect is sealed there's no way to define a
spanAttributefor an unsupported type, normally we'd create an Attribute manually likeThis means we can't use the macro at all if we require one attribute that is unsupported. Would it be sensible to expose some way of contramapping an existing KeySelect?
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Though thinking about it still won't be possible without some other function from value => key type 😢
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Valid points. The macro wouldn't work with newtypes/type aliases.
I guess we can provide some utility methods to lift arbitrary types into the Attribute.