Correct multipleOf assertion to work with small numbers

Author: OptimumCode

src/commonMain/kotlin/io/github/optimumcode/json/schema/internal/factories/number/MultipleOfAssertionFactory.kt

@@ -8,6 +8,11 @@ import kotlinx.serialization.json.JsonElement
 import kotlinx.serialization.json.JsonPrimitive
 import kotlinx.serialization.json.doubleOrNull
 import kotlinx.serialization.json.longOrNull
+import kotlin.math.absoluteValue
+import kotlin.math.floor
+import kotlin.math.log10
+import kotlin.math.max
+import kotlin.math.pow
 
 @Suppress("unused")
 internal object MultipleOfAssertionFactory : AbstractAssertionFactory("multipleOf") {
@@ -39,13 +44,42 @@ private fun isMultipleOf(a: Number, b: Number): Boolean = when (a) {
 }
 
 private infix fun Double.isMultipleOf(number: Number): Boolean = when (number) {
- is Double -> (this % number).let { it == 0.0 && it == -0.0 }
- is Long -> (this % number).let { it == 0.0 && it == -0.0 }
+ is Double -> isZero(rem(this, number))
+ is Long -> isZero((this % number))
  else -> false
 }
 
 private infix fun Long.isMultipleOf(number: Number): Boolean = when (number) {
  is Long -> this % number == 0L
- is Double -> (this % number).let { it == 0.0 && it == -0.0 }
+ is Double -> isZero(rem(this, number))
  else -> false
+}
+
+private fun isZero(first: Double): Boolean {
+ return first == -0.0 || first == 0.0
+}
+
+private tailrec fun rem(first: Double, second: Double): Double {
+ return if (second < 1 && second > -1) {
+ val degree = floor(log10(second))
+ if (first < 1 && first > -1) {
+ val newDegree = max(floor(log10(second)), degree)
+ val newPow = 10.0.pow(-newDegree)
+ rem((first * newPow), (second * newPow))
+ } else {
+ val pow = 10.0.pow(-degree)
+ (first * pow) % (second * pow)
+ }
+ } else {
+ first % second
+ }
+}
+
+private fun rem(first: Long, second: Double): Double {
+ return if (second < 1 && second > -1) {
+ val degree = floor(log10(second))
+ first % (second * 10.0.pow(-degree))
+ } else {
+ first % second
+ }
 }

src/commonTest/kotlin/io/github/optimumcode/json/schema/assertions/number/JsonSchemaMultipleOfValidationTest.kt

@@ -1,10 +1,15 @@
 package io.github.optimumcode.json.schema.assertions.number
 
+import io.github.optimumcode.json.pointer.JsonPointer
+import io.github.optimumcode.json.schema.ErrorCollector
+import io.github.optimumcode.json.schema.ErrorCollector.Companion
 import io.github.optimumcode.json.schema.JsonSchema
 import io.github.optimumcode.json.schema.ValidationError
 import io.github.optimumcode.json.schema.base.KEY
 import io.kotest.assertions.throwables.shouldThrow
 import io.kotest.core.spec.style.FunSpec
+import io.kotest.core.test.TestScope
+import io.kotest.matchers.collections.shouldContainExactly
 import io.kotest.matchers.collections.shouldHaveSize
 import io.kotest.matchers.shouldBe
 import kotlinx.serialization.ExperimentalSerializationApi
@@ -110,5 +115,64 @@ class JsonSchemaMultipleOfValidationTest : FunSpec() {
  errors shouldHaveSize 0
  }
  }
+
+ JsonSchema.fromDefinition(
+ """
+ {
+ "${KEY}schema": "http://json-schema.org/draft-07/schema#",
+ "multipleOf": 0.0001
+ }
+ """.trimIndent(),
+ ).apply {
+ listOf(
+ JsonUnquotedLiteral("0.0075"),
+ JsonUnquotedLiteral("0.075"),
+ JsonUnquotedLiteral("0.75"),
+ JsonUnquotedLiteral("7.5"),
+ JsonUnquotedLiteral("75"),
+ JsonUnquotedLiteral("750"),
+ JsonUnquotedLiteral("12391239123"),
+ JsonUnquotedLiteral("-0.0075"),
+ JsonUnquotedLiteral("-0.075"),
+ JsonUnquotedLiteral("-0.75"),
+ JsonUnquotedLiteral("-7.5"),
+ JsonUnquotedLiteral("-75"),
+ JsonUnquotedLiteral("-750"),
+ JsonUnquotedLiteral("-12391239123"),
+ ).forEach {
+ test("small number $it is multiple of 0.0001") {
+ val errors = mutableListOf<ValidationError>()
+ validate(it, errors::add) shouldBe true
+ errors shouldHaveSize 0
+ }
+ }
+
+ listOf(
+ JsonUnquotedLiteral("0.00001"),
+ JsonUnquotedLiteral("0.00011"),
+ JsonUnquotedLiteral("0.00751"),
+ JsonUnquotedLiteral("0.01751"),
+ JsonUnquotedLiteral("0.71751"),
+ JsonUnquotedLiteral("1.71751"),
+ JsonUnquotedLiteral("-0.00001"),
+ JsonUnquotedLiteral("-0.00011"),
+ JsonUnquotedLiteral("-0.00751"),
+ JsonUnquotedLiteral("-0.01751"),
+ JsonUnquotedLiteral("-0.71751"),
+ JsonUnquotedLiteral("-1.71751"),
+ ).forEach {
+ test("small number $it is not a multiple of 0.0001") {
+ val errors = mutableListOf<ValidationError>()
+ validate(it, errors::add) shouldBe false
+ errors.shouldContainExactly(
+ ValidationError(
+ schemaPath = JsonPointer("/multipleOf"),
+ objectPath = JsonPointer.ROOT,
+ message = "$it is not a multiple of 0.0001",
+ )
+ )
+ }
+ }
+ }
  }
 }