KTOR-409 Fix 'crypto is undefined' error in IE11 (#2531)

ktor-utils/build.gradle.kts

@@ -24,6 +24,12 @@ kotlin {
             }
         }
 
+        val jsTest by getting {
+            dependencies {
+                implementation(kotlin("test-js"))
+            }
+        }
+
         // Hack: register the Native interop klibs as outputs of Kotlin source sets:
         if (!ideaActive && rootProject.ext.get("native_targets_enabled") as Boolean) {
             val utilsInterop by creating

ktor-utils/js/src/io/ktor/util/CryptoJs.kt

@@ -48,10 +48,12 @@ public actual fun Digest(name: String): Digest = object : Digest {
 
 // Variable is renamed to `_crypto` so it wouldn't clash with existing `crypto` variable.
 // JS IR backend doesn't reserve names accessed inside js("") calls
-private val _crypto: Crypto = if (PlatformUtils.IS_NODE) {
-    js("eval('require')('crypto')")
-} else {
-    js("(crypto ? crypto : msCrypto)")
+private val _crypto: Crypto by lazy { // lazy because otherwise it's untestable due to evaluation order
+    if (PlatformUtils.IS_NODE) {
+        js("eval('require')('crypto')")
+    } else {
+        js("(window.crypto ? window.crypto : window.msCrypto)")
+    }
 }
 
 private external class Crypto {

ktor-utils/js/test/io.ktor.util/CryptoTest.kt

@@ -0,0 +1,20 @@
+/*
+ * Copyright 2014-2021 JetBrains s.r.o and contributors. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+package io.ktor.util
+
+import kotlin.test.*
+
+class CryptoTest {
+
+    @Test
+    fun expectCryptoToBeDefinedInIE11() {
+        if (!PlatformUtils.IS_BROWSER) return
+
+        js("window.msCrypto = window.crypto")
+        js("Object.defineProperty(window, 'crypto', {writable: true})")
+        js("delete window.crypto")
+        assertEquals(16, generateNonce().length)
+    }
+}