Wasm/WASI target implementation (#366)

Author: igoriakovlev

README.md

@@ -478,6 +478,24 @@ external object JsJodaTimeZoneModule
 private val jsJodaTz = JsJodaTimeZoneModule
 ```
 
+#### Note about time zones in Wasm/WASI
+
+By default, there's only one time zone available in Kotlin/Wasm WASI: the `UTC` time zone with a fixed offset.
+
+If you want to use all time zones in Kotlin/Wasm WASI platform, you need to add the following dependency:
+
+```kotlin
+kotlin {
+    sourceSets {
+        val wasmWasiMain by getting {
+            dependencies {
+                implementation("kotlinx-datetime-zoneinfo", "2024a-spi.0.6.0-RC.2")
+            }
+        }
+    }
+}
+```
+
 ### Maven
 
 Add a dependency to the `<dependencies>` element. Note that you need to use the platform-specific `-jvm` artifact in Maven.

buildSrc/src/main/kotlin/zoneInfosResourcesGenerator.kt

@@ -0,0 +1,101 @@
+import java.io.File
+
+/*
+ * Copyright 2019-2024 JetBrains s.r.o. and contributors.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+private val pkg = "package kotlinx.datetime.timezones.tzData"
+
+private fun generateByteArrayProperty(tzData: TzData, header: String, propertyName: String): String = buildString {
+    append(header)
+    appendLine()
+    appendLine()
+    appendLine("/* ${tzData.fullTzNames.joinToString(", ")} */")
+    append("internal val $propertyName get() = byteArrayOf(")
+    for (chunk in tzData.data.toList().chunked(16)) {
+        appendLine()
+        append("    ")
+        val chunkText = chunk.joinToString {
+            it.toString().padStart(4, ' ')
+        } + ","
+        append(chunkText)
+    }
+    appendLine()
+    append(")")
+}
+
+private class TzData(val data: ByteArray, val fullTzNames: MutableList<String>)
+private fun loadTzBinaries(
+    zoneInfo: File,
+    currentName: String,
+    result: MutableList<TzData>
+) {
+    val zoneName = if (currentName.isEmpty()) zoneInfo.name else "$currentName/${zoneInfo.name}"
+    if (zoneInfo.isDirectory) {
+        zoneInfo.listFiles()?.forEach {
+            loadTzBinaries(it, zoneName, result)
+        }
+    } else {
+        val bytes = zoneInfo.readBytes()
+        val foundTzData = result.firstOrNull { it.data.contentEquals(bytes) }
+        val tzData: TzData
+        if (foundTzData != null) {
+            tzData = foundTzData
+        } else {
+            tzData = TzData(bytes, mutableListOf())
+            result.add(tzData)
+        }
+
+        tzData.fullTzNames.add(zoneName)
+    }
+}
+
+fun generateZoneInfosResources(zoneInfoDir: File, outputDir: File, version: String) {
+    val header = buildString {
+        appendLine()
+        append("/* AUTOGENERATED FROM ZONE INFO DATABASE v.$version */")
+        appendLine()
+        appendLine()
+        append(pkg)
+    }
+
+    val loadedZones = mutableListOf<TzData>()
+    zoneInfoDir.listFiles()?.forEach { file ->
+        loadTzBinaries(file, "", loadedZones)
+    }
+
+    val zoneDataByNameBody = StringBuilder()
+    val getTimeZonesBody = StringBuilder()
+    loadedZones.forEachIndexed { id, tzData ->
+        val tzDataName = "tzData$id"
+        val data = generateByteArrayProperty(tzData, header, tzDataName)
+        File(outputDir, "$tzDataName.kt").writeText(data)
+        tzData.fullTzNames.forEach { name ->
+            zoneDataByNameBody.appendLine("    \"$name\" -> $tzDataName")
+            getTimeZonesBody.appendLine("    \"$name\",")
+        }
+    }
+
+    val content = buildString {
+        append(header)
+        appendLine()
+        appendLine()
+        appendLine("internal fun zoneDataByName(name: String): ByteArray = when(name) {")
+        append(zoneDataByNameBody)
+        appendLine()
+        append("    else -> throw kotlinx.datetime.IllegalTimeZoneException(\"Invalid timezone name\")")
+        appendLine()
+        append("}")
+        appendLine()
+        appendLine()
+        append("internal val timeZones: Set<String> by lazy { setOf(")
+        appendLine()
+        append(getTimeZonesBody)
+        appendLine()
+        append(")")
+        append("}")
+    }
+
+    File(outputDir, "tzData.kt").writeText(content)
+}

core/build.gradle.kts

@@ -127,6 +127,10 @@ kotlin {
         }
     }
 
+    wasmWasi {
+        nodejs()
+    }
+
     @OptIn(ExperimentalKotlinGradlePluginApi::class)
     compilerOptions {
         freeCompilerArgs.add("-Xexpect-actual-classes")
@@ -207,14 +211,34 @@ kotlin {
             dependsOn(commonJsTest)
         }
 
-        val nativeMain by getting {
+        val commonKotlinMain by creating {
             dependsOn(commonMain.get())
             dependencies {
                 api("org.jetbrains.kotlinx:kotlinx-serialization-core:$serializationVersion")
             }
         }
 
+        val commonKotlinTest by creating {
+            dependsOn(commonTest.get())
+        }
+
+        val nativeMain by getting {
+            dependsOn(commonKotlinMain)
+        }
+
         val nativeTest by getting {
+            dependsOn(commonKotlinTest)
+        }
+
+        val wasmWasiMain by getting {
+            dependsOn(commonKotlinMain)
+        }
+
+        val wasmWasiTest by getting {
+            dependsOn(commonKotlinTest)
+            dependencies {
+                runtimeOnly(project(":kotlinx-datetime-zoneinfo"))
+            }
         }
 
         val darwinMain by getting {

core/common/src/TimeZone.kt

@@ -66,6 +66,8 @@ public expect open class TimeZone {
          * On Linux, this function queries the `/etc/localtime` symbolic link. If the link is missing, [UTC] is used.
          * If the link points to an invalid location, [IllegalTimeZoneException] is thrown.
          *
+         * Always returns the `UTC` timezone on the Wasm WASI platform due to the lack of support for retrieving system timezone information.
+         *
          * @sample kotlinx.datetime.test.samples.TimeZoneSamples.currentSystemDefault
          */
         public fun currentSystemDefault(): TimeZone
@@ -95,6 +97,10 @@ public expect open class TimeZone {
          *
          * @throws IllegalTimeZoneException if [zoneId] has an invalid format or a time-zone with the name [zoneId]
          * is not found.
+         *
+         * @throws IllegalTimeZoneException on the Wasm WASI platform for non-fixed-offset time zones,
+         * unless a dependency on the `kotlinx-datetime-zoneinfo` artifact is added.
+         *
          * @sample kotlinx.datetime.test.samples.TimeZoneSamples.constructorFunction
          */
         public fun of(zoneId: String): TimeZone