Change Duration.toString scientific exponent formatting

- use 'e+' for positive exponents in scientific format

libraries/stdlib/js/src/kotlin/time/formatToDecimals.kt

@@ -24,5 +24,5 @@ internal actual fun formatUpToDecimals(value: Double, decimals: Int): String {
 }
 
 internal actual fun formatScientific(value: Double): String {
-    return value.asDynamic().toExponential(2).unsafeCast<String>().replace("+", "")
+    return value.asDynamic().toExponential(2).unsafeCast<String>()
 }

libraries/stdlib/jvm/src/kotlin/time/formatToDecimals.kt

@@ -11,10 +11,11 @@ import java.text.DecimalFormatSymbols
 import java.util.*
 import kotlin.concurrent.getOrSet
 
-private val rootFormatSymbols = DecimalFormatSymbols(Locale.ROOT).apply { exponentSeparator = "e" }
+private val rootNegativeExpFormatSymbols = DecimalFormatSymbols(Locale.ROOT).apply { exponentSeparator = "e" }
+private val rootPositiveExpFormatSymbols = DecimalFormatSymbols(Locale.ROOT).apply { exponentSeparator = "e+" }
 private val precisionFormats = Array(4) { ThreadLocal<DecimalFormat>() }
 
-private fun createFormatForDecimals(decimals: Int) = DecimalFormat("0", rootFormatSymbols).apply {
+private fun createFormatForDecimals(decimals: Int) = DecimalFormat("0", rootNegativeExpFormatSymbols).apply {
     if (decimals > 0) minimumFractionDigits = decimals
     roundingMode = RoundingMode.HALF_UP
 }
@@ -34,4 +35,8 @@ internal actual fun formatUpToDecimals(value: Double, decimals: Int): String =
 
 private val scientificFormat = ThreadLocal<DecimalFormat>()
 internal actual fun formatScientific(value: Double): String =
-    scientificFormat.getOrSet { DecimalFormat("0E0", rootFormatSymbols).apply { minimumFractionDigits = 2 } }.format(value)
+    scientificFormat.getOrSet { DecimalFormat("0E0", rootNegativeExpFormatSymbols).apply { minimumFractionDigits = 2 } }
+        .apply {
+            decimalFormatSymbols = if (value >= 1 || value <= -1) rootPositiveExpFormatSymbols else rootNegativeExpFormatSymbols
+        }
+        .format(value)

libraries/stdlib/test/time/DurationTest.kt

@@ -309,12 +309,12 @@ class DurationTest {
         test(DurationUnit.NANOSECONDS, "0ns", "0.0ns", "0.02ns", "0.020ns", "0.0202ns")
 
         d = Double.MAX_VALUE.nanoseconds
-        test(DurationUnit.DAYS, "2.08e294d")
+        test(DurationUnit.DAYS, "2.08e+294d")
-        test(DurationUnit.NANOSECONDS, "1.80e308ns")
+        test(DurationUnit.NANOSECONDS, "1.80e+308ns")
 
         assertEquals("0.500000000000s", 0.5.seconds.toString(DurationUnit.SECONDS, 100))
         assertEquals("99999000000000.000000000000ns", 99_999.seconds.toString(DurationUnit.NANOSECONDS, 15))
-        assertEquals("1.00e14ns", 100_000.seconds.toString(DurationUnit.NANOSECONDS, 9))
+        assertEquals("1.00e+14ns", 100_000.seconds.toString(DurationUnit.NANOSECONDS, 9))
 
         d = Duration.INFINITE
         test(DurationUnit.DAYS, "Infinity", "Infinity")
@@ -378,15 +378,15 @@ class DurationTest {
 
         test(Duration.ZERO, "0s")
         test(365.days * 10000, "3650000d")
-        test(300.days * 100000, "3e7d", "3.00e7d")
+        test(300.days * 100000, "3.00e+7d")
-        test(365.days * 100000, "3.65e7d")
+        test(365.days * 100000, "3.65e+7d")
 
         val universeAge = 365.25.days * 13.799e9
         val planckTime = 5.4e-44.seconds
 
-        test(universeAge, "5.04e12d")
+        test(universeAge, "5.04e+12d")
-        test(planckTime, "5.4e-44s", "5.40e-44s")
+        test(planckTime, "5.40e-44s")
-        test(Double.MAX_VALUE.nanoseconds, "2.08e294d")
+        test(Double.MAX_VALUE.nanoseconds, "2.08e+294d")
         test(Duration.INFINITE, "Infinity")
     }