Create soft assertion sample and fix bugs it exposed

sample/build.gradle.kts

@@ -57,5 +57,11 @@ kotlin {
 }
 
 configure<com.bnorm.power.PowerAssertGradleExtension> {
-  functions = listOf("kotlin.assert", "kotlin.test.assertTrue", "kotlin.require")
+  functions = listOf(
+    "kotlin.assert",
+    "kotlin.test.assertTrue",
+    "kotlin.require",
+    "com.bnorm.power.AssertScope.assert",
+    "com.bnorm.power.assert"
+  )
 }

sample/src/commonMain/kotlin/com/bnorm/power/AssertScope.kt

@@ -0,0 +1,47 @@
+package com.bnorm.power
+
+import kotlin.contracts.*
+
+typealias LazyMessage = () -> Any
+
+interface AssertScope {
+  fun assert(assertion: Boolean, lazyMessage: LazyMessage? = null)
+}
+
+@OptIn(ExperimentalContracts::class)
+fun assert(assertion: Boolean, lazyMessage: LazyMessage? = null) {
+  contract { returns() implies assertion }
+  if (!assertion) {
+    throw AssertionError(lazyMessage?.invoke()?.toString())
+  }
+}
+
+private class SoftAssertScope : AssertScope {
+  private val assertions = mutableListOf<Throwable>()
+
+  override fun assert(assertion: Boolean, lazyMessage: LazyMessage?) {
+    if (!assertion) {
+      assertions.add(AssertionError(lazyMessage?.invoke()?.toString()))
+    }
+  }
+
+  fun close(exception: Throwable? = null) {
+    if (assertions.isNotEmpty()) {
+      val base = exception ?: AssertionError("Multiple failed assertions")
+      for (assertion in assertions) {
+        base.addSuppressed(assertion)
+      }
+      throw base
+    }
+  }
+}
+
+@OptIn(ExperimentalContracts::class)
+fun <R> assertSoftly(block: AssertScope.() -> R): R {
+  contract { callsInPlace(block, InvocationKind.EXACTLY_ONCE) }
+
+  val scope = SoftAssertScope()
+  val result = runCatching { scope.block() }
+  scope.close(result.exceptionOrNull())
+  return result.getOrThrow()
+}

sample/src/commonTest/kotlin/com/bnorm/power/PowerAssertTest.kt

@@ -29,4 +29,22 @@ class PowerAssertTest {
   fun require() {
     require(Person.UNKNOWN.size == 1)
   }
+
+  @Test
+  fun softAssert() {
+    val unknown: List<Person>? = Person.UNKNOWN
+    assert(unknown != null)
+    assert(unknown.size == 2)
+
+    val jane: Person
+    val john: Person
+    assertSoftly {
+      jane = unknown[0]
+      assert(jane.firstName == "Jane")
+      assert(jane.lastName == "Doe") { "bad jane last name" }
+
+      john = unknown[1]
+      assert(john.lastName == "Doe" && john.firstName == "John") { "bad john" }
+    }
+  }
 }