introduce ifNotEmpty, drop own Atrium verb

src/commonMain/kotlin/ch/tutteli/kbox/ifNotEmpty.kt

@@ -0,0 +1,25 @@
+package ch.tutteli.kbox
+
+/**
+ * Checks if this collection is empty and if not applies the given [transformation].
+ *
+ * @param transformation the function which transforms this collection into [SuperTypeOfT] (at least an
+ *   [Iterable])
+ *
+ * @param T The type of the receiver -- a [Collection] or one of its subtypes
+ * @param SuperTypeOfT The result type can also be a super type of [T] as long as it doesn't go
+ *   beyond [Iterable]. In theory, we would not need to establish this constraint but in all cases we came across
+ *   so far we never wanted to end up with [Any]. E.g. if [T] = [List] then we don't want that the
+ *   [transformation] returns an [Array] as otherwise we have a [List] in case it is empty and an [Array] otherwise and
+ *   the least upper bound of those two types is [Any], i.e. we would end up with [SuperTypeOfT] = [Any].
+ *
+ * @return `this` if the given collection is empty, otherwise the result of applying this collection to the given
+ *   [transformation].
+ *
+ * @since 1.2.0
+ */
+@Suppress("BOUNDS_NOT_ALLOWED_IF_BOUNDED_BY_TYPE_PARAMETER")
+inline fun <T, SuperTypeOfT> T.ifNotEmpty(
+    transformation: (T) -> SuperTypeOfT
+): SuperTypeOfT where T : Collection<*>, SuperTypeOfT : Iterable<*>, T : SuperTypeOfT =
+    if (this.isNotEmpty()) transformation(this) else this

src/commonTest/kotlin/ch/tutteli/kbox/AppendToStringBuilderSpec.kt

@@ -2,7 +2,7 @@ package ch.tutteli.kbox
 
 import ch.tutteli.atrium.api.fluent.en_GB.toBeEmpty
 import ch.tutteli.atrium.api.fluent.en_GB.toEqual
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.describe
 import kotlin.reflect.KFunction4

src/commonTest/kotlin/ch/tutteli/kbox/BlankToNullSpec.kt

@@ -1,7 +1,7 @@
 package ch.tutteli.kbox
 
 import ch.tutteli.atrium.api.fluent.en_GB.toEqual
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.describe
 

src/commonTest/kotlin/ch/tutteli/kbox/DynamicTreeTraversalSpec.kt

@@ -1,7 +1,7 @@
 package ch.tutteli.kbox
 
 import ch.tutteli.atrium.api.fluent.en_GB.*
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.describe
 

src/commonTest/kotlin/ch/tutteli/kbox/FailIfTest.kt

@@ -3,7 +3,7 @@ package ch.tutteli.kbox
 import ch.tutteli.atrium.api.fluent.en_GB.messageToContain
 import ch.tutteli.atrium.api.fluent.en_GB.notToThrow
 import ch.tutteli.atrium.api.fluent.en_GB.toThrow
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import kotlin.test.Test
 
 class FailIfTest {

src/commonTest/kotlin/ch/tutteli/kbox/ForEachInSpec.kt

@@ -1,7 +1,7 @@
 package ch.tutteli.kbox
 
 import ch.tutteli.atrium.api.fluent.en_GB.toEqual
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.describe
 

src/commonTest/kotlin/ch/tutteli/kbox/ForEachRemainingSpec.kt

@@ -2,7 +2,7 @@ package ch.tutteli.kbox
 
 import ch.tutteli.atrium.api.fluent.en_GB.toContainExactly
 import ch.tutteli.atrium.api.fluent.en_GB.toBeEmpty
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.describe
 import kotlin.reflect.KFunction2

src/commonTest/kotlin/ch/tutteli/kbox/ForElementAndForEachSpec.kt

@@ -1,7 +1,7 @@
 package ch.tutteli.kbox
 
 import ch.tutteli.atrium.api.fluent.en_GB.toEqual
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.describe
 import kotlin.reflect.KFunction3

src/commonTest/kotlin/ch/tutteli/kbox/IfNotEmptyTest.kt

@@ -0,0 +1,42 @@
+package ch.tutteli.kbox
+
+import ch.tutteli.atrium.api.fluent.en_GB.*
+import ch.tutteli.atrium.api.verbs.expect
+import ch.tutteli.atrium.api.verbs.expectGrouped
+import kotlin.test.Test
+
+class IfNotEmptyTest {
+
+    @Test
+    fun it_returns_the_collection_itself_if_empty() {
+        expectGrouped {
+            listOf<Collection<Int>>(
+                emptyList(),
+                emptySet(),
+            ).forEach { collection ->
+                group("check it works with ${collection::class.simpleName}") {
+                    expect(collection.ifNotEmpty { nonEmptyCollection ->
+                        nonEmptyCollection.map { it + 1 }
+                    }).toBeTheInstance(collection)
+                }
+            }
+        }
+    }
+
+    @Test
+    fun it_returns_the_result_of_the_transformation_if_not_empty() {
+        expectGrouped {
+            listOf(
+                listOf(1),
+                setOf(1),
+            ).forEach { collection ->
+                group("check it works with ${collection::class.simpleName}") {
+                    expect(collection.ifNotEmpty { nonEmptyCollection ->
+                        nonEmptyCollection.map { it + 1 }
+                    }).toContainExactly(2)
+                }
+            }
+        }
+    }
+}
+

src/commonTest/kotlin/ch/tutteli/kbox/IfWithinBoundSpec.kt

@@ -1,7 +1,7 @@
 package ch.tutteli.kbox
 
 import ch.tutteli.atrium.api.fluent.en_GB.toEqual
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.describe
 

src/commonTest/kotlin/ch/tutteli/kbox/IsNotNullAndNotSpec.kt

@@ -1,7 +1,7 @@
 package ch.tutteli.kbox
 
 import ch.tutteli.atrium.api.fluent.en_GB.toEqual
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.describe
 

src/commonTest/kotlin/ch/tutteli/kbox/JoinToStringSpec.kt

@@ -2,7 +2,7 @@ package ch.tutteli.kbox
 
 import ch.tutteli.atrium.api.fluent.en_GB.toBeEmpty
 import ch.tutteli.atrium.api.fluent.en_GB.toEqual
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.describe
 import kotlin.reflect.KFunction3

src/commonTest/kotlin/ch/tutteli/kbox/MapParentsSpec.kt

@@ -1,7 +1,7 @@
 package ch.tutteli.kbox
 
 import ch.tutteli.atrium.api.fluent.en_GB.*
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.Suite
 import org.spekframework.spek2.style.specification.describe

src/commonTest/kotlin/ch/tutteli/kbox/MapRemainingSpec.kt

@@ -2,7 +2,7 @@ package ch.tutteli.kbox
 
 import ch.tutteli.atrium.api.fluent.en_GB.toContainExactly
 import ch.tutteli.atrium.api.fluent.en_GB.toBeEmpty
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.describe
 

src/commonTest/kotlin/ch/tutteli/kbox/MapWithIndexSpec.kt

@@ -2,7 +2,7 @@ package ch.tutteli.kbox
 
 import ch.tutteli.atrium.api.fluent.en_GB.toContainExactly
 import ch.tutteli.atrium.api.fluent.en_GB.toBeEmpty
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.style.specification.describe
 

src/commonTest/kotlin/ch/tutteli/kbox/PeekingIteratorSpec.kt

@@ -3,7 +3,7 @@ package ch.tutteli.kbox
 import ch.tutteli.atrium.api.fluent.en_GB.toBeTheInstance
 import ch.tutteli.atrium.api.fluent.en_GB.toEqual
 import ch.tutteli.atrium.api.fluent.en_GB.toThrow
-import ch.tutteli.kbox.atrium.expect
+import ch.tutteli.atrium.api.verbs.expect
 import org.spekframework.spek2.Spek
 import org.spekframework.spek2.lifecycle.CachingMode
 import org.spekframework.spek2.style.specification.describe

src/commonTest/kotlin/ch/tutteli/kbox/TakeIfTest.kt

@@ -0,0 +1,20 @@
+package ch.tutteli.kbox
+
+import ch.tutteli.atrium.api.fluent.en_GB.toEqual
+import ch.tutteli.atrium.api.verbs.expect
+import kotlin.test.Test
+
+class TakeIfTest {
+
+    @Test
+    fun `it_returns_null_if_predicate_doesnt_hold`() {
+        expect(
+            takeIf<Int>(false) { throw IllegalArgumentException("bla") }
+        ).toEqual(null)
+    }
+
+    @Test
+    fun it_returns_lambda_result_if_predicate_holds() {
+        expect(takeIf(true) { 1 }).toEqual(1)
+    }
+}