I'm seeing some weird behavior. I have isolated a ...

# webassembly

[kevin.cianfarini]

I'm seeing some weird behavior. I have isolated a reproducer for an exception not being caught in one of my unit tests.

@Test fun foo() {
  assertFails {
    1 / 0
  }
}

The thrown RuntimeError is not caught. Is this expected? Stacktrace in thread 🧵

[kevin.cianfarini]

RuntimeError: divide by zero
      at <alchemist_test>.kotlin.Int__div-impl (<wasm://wasm/><alchemist_test>-004f044e:wasm-function[2105]:0x347ba)
      at <alchemist_test>.io.github.kevincianfarini.alchemist.SaturatingLongTest.dividing_by_double_zero_throws (<wasm://wasm/><alchemist_test>-004f044e:wasm-function[4933]:0x67b62)
      at <alchemist_test>.io.github.kevincianfarini.alchemist.test fun$io.github.kevincianfarini.alchemist test fun$SaturatingLongTest test fun$dividing_by_double_zero_throws test fun.invoke (<wasm://wasm/><alchemist_test>-004f044e:wasm-function[4653]:0x5b3a1)
      at <alchemist_test>.kotlin.test.TeamcityAdapter$test$lambda.invoke (<wasm://wasm/><alchemist_test>-004f044e:wasm-function[4228]:0x57519)
      at <alchemist_test>.kotlin.test.TeamcityAdapterWithPromiseSupport.runOrScheduleNextWithResult (<wasm://wasm/><alchemist_test>-004f044e:wasm-function[4110]:0x55a28)
      at <alchemist_test>.kotlin.test.TeamcityAdapterWithPromiseSupport.runOrScheduleNextWithResult (<wasm://wasm/><alchemist_test>-004f044e:wasm-function[4111]:0x55a66)
      at <alchemist_test>.kotlin.test.TeamcityAdapter.test (<wasm://wasm/><alchemist_test>-004f044e:wasm-function[4251]:0x5908f)
      at <alchemist_test>.kotlin.test.test (<wasm://wasm/><alchemist_test>-004f044e:wasm-function[4254]:0x592aa)
      at <alchemist_test>.io.github.kevincianfarini.alchemist.test fun$io.github.kevincianfarini.alchemist test fun$SaturatingLongTest test fun.invoke (<wasm://wasm/><alchemist_test>-004f044e:wasm-function[4723]:0x5c285)
      at <alchemist_test>.io.github.kevincianfarini.alchemist.test fun$io.github.kevincianfarini.alchemist test fun$SaturatingLongTest test fun.invoke (<wasm://wasm/><alchemist_test>-004f044e:wasm-function[4724]:0x5c2b6)

[Svyatoslav Kuzmich [JB]]

https://youtrack.jetbrains.com/issue/KT-66081/K-WASM-0-0-5-0-and-50throw-not-ArithmeticException-but-RuntimeError

[kevin.cianfarini]

Ooooffff, thanks for calling this out!

[Svyatoslav Kuzmich [JB]]

It is a default Wasm trap, and Wasm can’t catch traps at the moment. Proper exceptions for / are not implemented yet in Kotlin compiler.

[kevin.cianfarini]

Additionally, do you know why 1 / 0 on JS (not wasmJs) doesn't throw at all?

assertFailsWith<ArithmeticException> {
            1.0 / 0.0
        }

output:

io.github.kevincianfarini.alchemist.SaturatingLongTest.dividing_by_double_zero_throws[js, node] FAILED
    AssertionError: Expected an exception of class ArithmeticException to be thrown, but was completed successfully.
        at DefaultJsAsserter.protoOf.fail_zdvzi9(/home/kevin/code/alchemist/build/compileSync/js/test/testDevelopmentExecutable/kotlin/js/src/main/kotlin/kotlin/test/JsImpl.kt:23)
        at DefaultJsAsserter.protoOf.fail_o3vfxl(/home/kevin/code/alchemist/build/compileSync/js/test/testDevelopmentExecutable/kotlin/js/src/main/kotlin/kotlin/test/DefaultJsAsserter.kt:71)
        at <global>.checkResultIsFailure(/home/kevin/code/alchemist/build/compileSync/js/test/testDevelopmentExecutable/kotlin/src/kotlin/util/Result.kt:36)

[Chrimaeon]

beacuse its javascript 😉
1.0/0.0 === Infinity

[kevin.cianfarini]

Not for Long it isn't!

tests:

@Test
    fun int_division_by_zero_fails_arithmetic_exception() {
        assertFailsWith<ArithmeticException> {
            1 / 0
        }
    }

    @Test
    fun long_division_by_zero_fails_artithmetic_exception() {
        assertFailsWith<ArithmeticException> {
            1L / 0L
        }
    }

Output:

io.github.kevincianfarini.alchemist.SaturatingLongTest.int_division_by_zero_fails_arithmetic_exception[js, node] FAILED
    AssertionError: Expected an exception of class ArithmeticException to be thrown, but was completed successfully.
        at DefaultJsAsserter.protoOf.fail_zdvzi9(/home/kevin/code/alchemist/build/compileSync/js/test/testDevelopmentExecutable/kotlin/js/src/main/kotlin/kotlin/test/JsImpl.kt:23)
        at DefaultJsAsserter.protoOf.fail_o3vfxl(/home/kevin/code/alchemist/build/compileSync/js/test/testDevelopmentExecutable/kotlin/js/src/main/kotlin/kotlin/test/DefaultJsAsserter.kt:71)
        at <global>.checkResultIsFailure(/home/kevin/code/alchemist/build/compileSync/js/test/testDevelopmentExecutable/kotlin/src/kotlin/util/Result.kt:36)
        at SaturatingLongTest.protoOf.int_division_by_zero_fails_arithmetic_exception_de063(/home/kevin/code/alchemist/build/compileSync/js/test/testDevelopmentExecutable/kotlin/common/src/main/kotlin/kotlin/test/Assertions.kt:661)
        at <global>.fn(kotlin/alchemist-test.js:4360)
        at Context.<anonymous>(/home/kevin/code/alchemist/build/js/node_modules/kotlin-web-helpers/src/KotlinTestTeamCityConsoleAdapter.ts:72)
        at <global>.processImmediate(node:internal/timers:478)

io.github.kevincianfarini.alchemist.SaturatingLongTest.long_division_by_zero_fails_artithmetic_exception[js, node] FAILED
    AssertionError: Expected an exception of class ArithmeticException to be thrown, but was Exception: division by zero
        at DefaultJsAsserter.protoOf.fail_zdvzi9(/home/kevin/code/alchemist/build/compileSync/js/test/testDevelopmentExecutable/kotlin/js/src/main/kotlin/kotlin/test/JsImpl.kt:23)
        at <global>.checkResultIsFailure(/home/kevin/code/alchemist/build/compileSync/js/test/testDevelopmentExecutable/kotlin/src/kotlin/util/Result.kt:46)
        at SaturatingLongTest.protoOf.long_division_by_zero_fails_artithmetic_exception_2udkyc(/home/kevin/code/alchemist/build/compileSync/js/test/testDevelopmentExecutable/kotlin/common/src/main/kotlin/kotlin/test/Assertions.kt:661)
        at <global>.fn(kotlin/alchemist-test.js:4365)
        at Context.<anonymous>(/home/kevin/code/alchemist/build/js/node_modules/kotlin-web-helpers/src/KotlinTestTeamCityConsoleAdapter.ts:72)
        at <global>.processImmediate(node:internal/timers:478)

[kevin.cianfarini]

This is almost certainly because Long is emulated on JS, but still this is extremely unintuitive.

[Chrimaeon]

For BigInt division, the result is the quotient of the two operands truncated towards zero, and the remainder is discarded. A RangeError is thrown if the divisor y is 0n. This is because number division by zero returns Infinity or -Infinity, but BigInt has no concept of infinity.

I guess Koltins Long is mapped to BigInt

[kevin.cianfarini]

It's not

[kevin.cianfarini]

It's emulated with two Int

[kevin.cianfarini]

https://github.com/JetBrains/kotlin/blob/rrr/2.1.0/core-docs/libraries/stdlib/js/builtins/Primitives.kt#L1176

[kevin.cianfarini]

Looks like the issue on JS is here for Long. This shouldn't throw Exception, but instead ArithmeticExcepion.

[kevin.cianfarini]

https://github.com/JetBrains/kotlin/blob/62cfeef19de48b908e8abbd835422cdb1192576c/libraries/stdlib/js/runtime/longJs.kt#L217

[Svyatoslav Kuzmich [JB]]

https://youtrack.jetbrains.com/issue/KT-17719/JS-integer-division-by-zero-does-not-throw-exception

[kevin.cianfarini]

😄 https://github.com/JetBrains/kotlin/releases/tag/v2.2.0-Beta2