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[direct] improve error messages + test coverage #985

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merged 3 commits into from
Jan 9, 2025
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[direct] improve error messages + test coverage #985

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cbffd29
[direct] improve error messages + test coverage
fwbrasil Jan 8, 2025
690dec4
Merge branch 'main' into direct-improvements
fwbrasil Jan 9, 2025
04877f9
fix merge
fwbrasil Jan 9, 2025
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6 changes: 4 additions & 2 deletions kyo-direct/shared/src/main/scala/kyo/Direct.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,8 @@ private def nowImpl[A: Type, S: Type](self: Expr[A < S])(using Quotes): Expr[A]
| val y = IO(2).now // Then get this result
| x + y // Use both results
|}""".stripMargin)}
|""".stripMargin
|""".stripMargin,
self.asTerm.pos
)
end nowImpl

Expand All @@ -95,7 +96,8 @@ private def laterImpl[A: Type, S: Type](self: Expr[A < S])(using Quotes): Expr[A
| val (e1, e2) = combination.now // Get both effects
| e1.now + e2.now // Sequence them here
|}""".stripMargin)}
|""".stripMargin
|""".stripMargin,
self.asTerm.pos
)
end laterImpl

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241 changes: 140 additions & 101 deletions kyo-direct/shared/src/main/scala/kyo/Validate.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -8,8 +8,6 @@ private[kyo] object Validate:
def apply(expr: Expr[Any])(using Quotes): Unit =
import quotes.reflect.*

val tree = expr.asTerm

def fail(tree: Tree, msg: String): Unit =
report.error(msg, tree.pos)

Expand All @@ -19,9 +17,46 @@ private[kyo] object Validate:
case _ => false
}

Trees.traverse(tree) {
case Apply(TypeApply(Ident("now"), _), _) =>
case Apply(TypeApply(Ident("later"), _), _) =>
Trees.traverse(expr.asTerm) {
case Apply(TypeApply(Ident("now" | "later"), _), List(qual)) =>
Trees.traverse(qual) {
case tree @ Apply(TypeApply(Ident("now" | "later"), _), _) =>
fail(
tree,
s"""${".now".cyan} and ${".later".cyan} can only be used directly inside a ${"`defer`".yellow} block.
|
|Common mistake: You may have forgotten to wrap an effectful computation in ${"`defer`".yellow}:
|${highlight("""
|// Missing defer when handling effects:
|val result = Emit.run { // NOT OK - missing defer
| Emit(1).now
| Emit(2).now
|}
|
|// Correctly wrapped in defer:
|val result = Emit.run {
| defer { // OK - effects wrapped in defer
| Emit(1).now
| Emit(2).now
| }
|}""")}
|
|If you're seeing this inside a ${"`defer`".yellow} block, you may have nested ${".now".cyan}/${".later".cyan} calls:
|${highlight("""
|// Instead of nested .now:
|defer {
| (counter.get.now + 1).now // NOT OK - nested .now
|}
|
|// Store intermediate results:
|defer {
| val value = counter.get.now // OK - get value first
| val incr = value + 1 // OK - pure operation
| IO(incr).now // OK - single .now
|}""".stripMargin)}""".stripMargin
)
}

case tree: Term if tree.tpe.typeSymbol.name == "<" =>
fail(
tree,
Expand All @@ -47,97 +82,52 @@ private[kyo] object Validate:
|""".stripMargin
)

case tree @ Apply(TypeApply(Ident("defer"), _), _) =>
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This case was unnecessary. The error message for a missing now triggers first

fail(
tree,
s"""Nested ${"`defer`".yellow} blocks are not allowed.
|
|Instead of nesting defer blocks:
|${highlight("""
|defer {
| defer { // NOT OK - nested defer
| IO(1).now
| }
|}""".stripMargin)}
|
|Define separate operations:
|${highlight("""
|def innerOperation = defer {
| IO(1).now
|}
|
|defer {
| innerOperation.now // OK - composing effects
|}""".stripMargin)}""".stripMargin
)

case tree @ ValDef(_, _, _) if tree.show.startsWith("var ") =>
fail(
tree,
s"""${"`var`".yellow} declarations are not allowed inside a ${"`defer`".yellow} block.
|
|Mutable state can lead to unexpected behavior with effects. Instead, use proper state management tools:
|
|• Var (kyo-prelude)
|• Atomic* classes (kyo-core)
|• TRef and derivatives (kyo-stm)""".stripMargin
)

case Return(_, _) =>
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Also unnecessary, it's not possible to have a return outside of def

fail(
tree,
s"""${"`return`".yellow} statements are not allowed inside a ${"`defer`".yellow} block.
|
|Early returns can break effect sequencing. Instead:
|${highlight("""
|// Instead of return:
|defer {
| if condition then
| return value // NOT OK - early return
| IO(1).now
|}
|
|// Use if expressions:
|defer {
| if condition then value
| else IO(1).now // OK - explicit flow
|}""".stripMargin)}""".stripMargin
|• Most common: Atomic* classes (kyo-core)
|• With transactional behavior: TRef and derivatives (kyo-stm)
|• Advanced pure state management: Var (kyo-prelude)
""".stripMargin
)

case tree @ ValDef(_, _, _) if tree.show.startsWith("lazy val ") =>
fail(
tree,
s"""${"`lazy val`".yellow} declarations are not allowed inside a ${"`defer`".yellow} block.
|
|Lazy evaluation can interfere with effect sequencing. Instead:
|${highlight("""
|// Instead of lazy val:
|defer {
| lazy val x = IO(1).now // NOT OK - lazy
| x + 1
|}
|
|// Use regular val:
|defer {
| val x = IO(1).now // OK - eager
| x + 1
|}""".stripMargin)}""".stripMargin
)

case Lambda(_, body) if !pure(body) =>
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This pattern match is wrong and I couldn't make it work. I've decided to remove because dotty-cps-async already produces an error message for this.

fail(
tree,
s"""Lambda functions containing ${".now".cyan} are not supported.
|
|Effects in lambdas can lead to unexpected ordering:
|${highlight("""
|defer {
| val f = (x: Int) => IO(x).now // NOT OK - effects in lambda
| f(10)
|}""".stripMargin)}""".stripMargin
s"""${"`lazy val`".yellow} and ${"`object`".yellow} declarations are not allowed inside a ${"`defer`".yellow} block.
|
|These interfere with effect sequencing. Define them outside the defer block:
|${highlight("""
|// Instead of lazy declarations in defer:
|defer {
| lazy val x = IO(1).now // NOT OK - lazy val
| object A // NOT OK - object
| x + 1
|}
|
|// Define outside defer:
|lazy val x = IO(1) // OK - outside
|object A // OK - outside
|
|// Use inside defer:
|defer {
| val result = x.now // OK - proper sequencing
| A.method.now
|}""".stripMargin)}
|
|For expensive computations needing caching, consider ${"`Async.memoize`".cyan}:
|${highlight("""
|defer {
| val memoized = Async.memoize(expensiveComputation).now
| memoized().now // First computes, then caches
|}""".stripMargin)}""".stripMargin.stripMargin
)

case DefDef(_, _, _, Some(body)) if !pure(body) =>
case tree @ DefDef(_, _, _, Some(body)) if !pure(body) =>
fail(
tree,
s"""Method definitions containing ${".now".cyan} are not supported inside ${"`defer`".yellow} blocks.
Expand All @@ -160,12 +150,12 @@ private[kyo] object Validate:
|}""".stripMargin)}""".stripMargin
)

case Try(_, _, _) =>
case tree @ Try(_, _, _) =>
fail(
tree,
s"""${"`try`".yellow}/`catch`".yellow} blocks are not supported inside ${"`defer`".yellow} blocks.
s"""${"`try`".yellow}/${"`catch`".yellow} blocks are not supported inside ${"`defer`".yellow} blocks.
|
|Use error handling effects instead. Handle each effect in a separate defer block:
|Use error handling effects instead. You can handle each effect in a separate defer block:
|${highlight("""
|// Instead of try/catch:
|defer {
Expand All @@ -181,7 +171,7 @@ private[kyo] object Validate:
| IO(1).now
|}
|
|// Handle the effect in a separate defer block:
|// Handle the effect defer block:
|defer {
| Abort.run(computation).now match {
| case Result.Success(v) => v
Expand All @@ -194,25 +184,74 @@ private[kyo] object Validate:
|and clearer error handling boundaries.""".stripMargin
)

case ClassDef(_, _, _, _, _) =>
case tree @ ClassDef(_, _, _, _, _) =>
fail(
tree,
s"""${"`class`".yellow} declarations are not supported inside ${"`defer`".yellow} blocks.
|
|Define classes outside defer blocks:
|${highlight("""
|// Instead of class in defer:
|defer {
| class MyClass(x: Int) // NOT OK
| new MyClass(10)
|}
s"""${"`class`".yellow} and ${"`trait`".yellow} declarations are not allowed inside ${"`defer`".yellow} blocks.
|
|Define them outside defer blocks:
|${highlight("""
|// Instead of declarations in defer:
|defer {
| class MyClass(x: Int) // NOT OK
| trait MyTrait // NOT OK
| new MyClass(10)
|}
|
|// Define outside:
|class MyClass(x: Int) // OK - outside defer
|trait MyTrait // OK - outside defer
|
|defer {
| new MyClass(10) // OK - usage in defer
|}""".stripMargin)}""".stripMargin
)

case tree @ Apply(Ident("throw"), _) =>
fail(
tree,
s"""${"`throw`".yellow} expressions are not allowed inside a ${"`defer`".yellow} block.
|
|Exception throwing can break effect sequencing. Use error handling effects instead:
|${highlight("""
|// Instead of throw:
|defer {
| if condition then
| throw new Exception("error") // NOT OK - throws exception
| IO(1).now
|}
|
|// Use Abort effect:
|defer {
| if condition then
| Abort.fail("error").now // OK - proper error handling
| else IO(1).now
|}""".stripMargin)}""".stripMargin
)

case tree @ Select(_, "synchronized") =>
fail(
tree,
s"""${"`synchronized`".yellow} blocks are not allowed inside a ${"`defer`".yellow} block.
|
|// Define outside:
|class MyClass(x: Int)
|Synchronization can lead to deadlocks with effects. Instead, use proper concurrency primitives:
|
|defer {
| new MyClass(10) // OK
|}""".stripMargin)}""".stripMargin
|• Most common: Atomic* classes for thread-safe values (kyo-core)
|• With mutual exclusion: Meter for controlled access (kyo-core)
|• Advanced transactional state: TRef and STM (kyo-stm)
""".stripMargin
)

case tree @ Select(_, _) if tree.symbol.flags.is(Flags.Mutable) =>
fail(
tree,
s"""Mutable field access is not allowed inside a ${"`defer`".yellow} block.
|
|Mutable state can lead to race conditions. Use proper state management instead:
|
|• Most common: Atomic* classes (kyo-core)
|• With transactional behavior: TRef and derivatives (kyo-stm)
|• Advanced pure state management: Var (kyo-prelude)""".stripMargin
)
}
end apply
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