Improve objectMatcher

Author: ghostbuster91

core/src/main/scala/com/softwaremill/diffx/ObjectMatcher.scala

@@ -14,6 +14,8 @@ object ObjectMatcher extends LowPriorityObjectMatcher {
     ObjectMatcher[U].isSameObject(f(left), f(right))
 
   def byValue[K, V: ObjectMatcher]: ObjectMatcher[(K, V)] = ObjectMatcher.by[(K, V), V](_._2)
+  def byValue[K, V, U: ObjectMatcher](f: V => U): ObjectMatcher[(K, V)] =
+    ObjectMatcher.by[(K, V), V](_._2)(ObjectMatcher.by[V, U](f))
 
   implicit def optionMatcher[T: ObjectMatcher]: ObjectMatcher[Option[T]] = (left: Option[T], right: Option[T]) => {
     (left, right) match {

docs-sources/usage/replacing.md

@@ -27,4 +27,14 @@ compare(Person(23, 60), Person(23, 62))
 ```
 
 In fact, replacement is so powerful that ignoring is implemented as a replacement 
-with the `Diff.ignore` instance.
+with the `Diff.ignore` instance.
+
+You can use the same mechanism to set particular object matcher for given nested collection in the hierarchy.
+Depending, whether it is list, set or map a respective method needs to be called:
+```scala mdoc:silent
+case class Organization(peopleList: List[Person], peopleSet: Set[Person], peopleMap: Map[String, Person])
+implicit val diffOrg: Derived[Diff[Organization]] = Diff.derived[Organization]
+        .modify(_.peopleList).withListMatcher[Person](ObjectMatcher.byValue(_.age))
+        .modify(_.peopleSet).withSetMatcher[Person](ObjectMatcher.by(_.age))
+        .modify(_.peopleMap).withMapMatcher[String,Person](ObjectMatcher.byValue(_.age))
+```

docs-sources/usage/sequences.md

@@ -54,13 +54,13 @@ import com.softwaremill.diffx._
 import com.softwaremill.diffx.generic.auto._
 case class Person(id: String, name: String)
 
-implicit val personMatcher: ObjectMatcher[(Int, Person)] = 
-    ObjectMatcher.byValue(ObjectMatcher.by(_.id))
+implicit val personMatcher: ObjectMatcher[(Int, Person)] = ObjectMatcher.byValue(_.id)
 val bob = Person("1","Bob")
 val alice = Person("2","Alice")
 ```
 ```scala mdoc
 compare(List(bob, alice), List(alice, bob))
 ```
 
-*Note: `ObjectMatcher` can be also passed explicitly, either upon creation or during modification*
+*Note: `ObjectMatcher` can be also passed explicitly, either upon creation or during modification*
+*See [replacing](replacing.md) for details.*

generated-docs/out/usage/replacing.md

@@ -28,4 +28,14 @@ compare(Person(23, 60), Person(23, 62))
 ```
 
 In fact, replacement is so powerful that ignoring is implemented as a replacement 
-with the `Diff.ignore` instance.
+with the `Diff.ignore` instance.
+
+You can use the same mechanism to set particular object matcher for given nested collection in the hierarchy.
+Depending, whether it is list, set or map a respective method needs to be called:
+```scala
+case class Organization(peopleList: List[Person], peopleSet: Set[Person], peopleMap: Map[String, Person])
+implicit val diffOrg: Derived[Diff[Organization]] = Diff.derived[Organization]
+        .modify(_.peopleList).withListMatcher[Person](ObjectMatcher.byValue(_.age))
+        .modify(_.peopleSet).withSetMatcher[Person](ObjectMatcher.by(_.age))
+        .modify(_.peopleMap).withMapMatcher[String,Person](ObjectMatcher.byValue(_.age))
+```

generated-docs/out/usage/sequences.md

@@ -67,8 +67,7 @@ import com.softwaremill.diffx._
 import com.softwaremill.diffx.generic.auto._
 case class Person(id: String, name: String)
 
-implicit val personMatcher: ObjectMatcher[(Int, Person)] = 
-    ObjectMatcher.byValue(ObjectMatcher.by(_.id))
+implicit val personMatcher: ObjectMatcher[(Int, Person)] = ObjectMatcher.byValue(_.id)
 val bob = Person("1","Bob")
 val alice = Person("2","Alice")
 ```
@@ -79,4 +78,5 @@ compare(List(bob, alice), List(alice, bob))
 // )
 ```
 
-*Note: `ObjectMatcher` can be also passed explicitly, either upon creation or during modification*
+*Note: `ObjectMatcher` can be also passed explicitly, either upon creation or during modification*
+*See [replacing](replacing.md) for details.*