add flatExtracting for map

[joel-costigliola]

Summary

Iterable assertions provide flatMap extraction but map assertions don't, it was suggested in:
https://stackoverflow.com/questions/45081542/assertj-flatmap-list-of-lists-after-calling-extracting

Example

Map<String, List<String>> testMap  = new HashMap<>();
List<String> nameList = newArrayList("Dave", "Jeff");
List<String> jobList = newArrayList("Plumber", "Builder");
List<String> cityList = newArrayList("Dover", "Boston");

testMap.put("name", nameList);
testMap.put("job", jobList);
testMap.put("city", cityList);

assertThat(testMap)
        .flatExtracting("name", "city", "job")
        .contains("Dave", "Jeff", "Plumber", "Builder", "Dover", "Boston");

Java 8 specific ?

• YES : to lambda part (PR on master)
• NO : when extracting by keys (PR on 2.x)

[dafenix]

Hello there,

i am looking at this.

[Vidit-Gupta]

@joel-costigliola This looks pretty sweet. However this would not let you check all unique elements if I understand correctly, no?
For example if I have

class A {
 List<Name> names()
}
A[] = {new A("foo", "bar"), new A("foo")}

then applying flatExtracting on A::names I cannot check that it contains exactly ["foo", "bar"] can I?

[PascalSchumacher]

flatExtracting returns an AbstractObjectArrayAssert. You can use all methods provided by this assertion, e.g. containsExactly, see: https://joel-costigliola.github.io/assertj/core-8/api/org/assertj/core/api/AbstractObjectArrayAssert.html#containsExactly-ELEMENT...-

[Vidit-Gupta]

@PascalSchumacher assertThat(ImmutableList.of("a", "a", "b")).containsExactly("a", "b") will fail.
What I'm saying is flatExtracting gives me back that list with duplicates (["a", "a", "b"]) hence I cannot use it

[PascalSchumacher]

Not sure if I understand you correctly, but if you want to check all unique elements you can use:

String[] abc = {"a", "a", "b"};
assertThat(abc).containsOnly("a", "b")