New JoinVarArgsContains inspection that will detect multiple .contains(), .doesNotContain(), and .containsOnlyOnce() calls within the same statement that could be joined together using variadic arguments.

src/test/resources/inspections/GuavaOptional/GuavaOptionalAfter.java

@@ -31,6 +31,13 @@ public class GuavaOptional {
         assertThat(opt).isPresent();
         assertThat(opt).isPresent();
 
+        //assertThat(opt.get()).isEqualTo(opt.get()); // there's a better version than contains(opt.get())
+        assertThat(opt.orNull()).isEqualTo(opt.get());
+        //assertThat(opt.get()).isEqualTo(opt.orNull()); // there's a better version than contains(opt.orNull())
+
+        assertThat(opt).contains(opt.get());
+        assertThat(opt).contains(opt.orNull());
+
         String possibleNullString = System.getProperty("username");
         String notNullString = "Narf";
 

src/test/resources/inspections/GuavaOptional/GuavaOptionalBefore.java

@@ -31,6 +31,13 @@ public class GuavaOptional {
         assertThat(opt.orNull()).isNotEqualTo(null);
         assertThat(opt.orNull()).isNotNull();
 
+        //assertThat(opt.get()).isEqualTo(opt.get()); // there's a better version than contains(opt.get())
+        assertThat(opt.orNull()).isEqualTo(opt.get());
+        //assertThat(opt.get()).isEqualTo(opt.orNull()); // there's a better version than contains(opt.orNull())
+
+        assertThat(opt).contains(opt.get());
+        assertThat(opt).contains(opt.orNull());
+
         String possibleNullString = System.getProperty("username");
         String notNullString = "Narf";
 

src/test/resources/inspections/Java8Optional/Java8OptionalAfter.java

@@ -30,6 +30,13 @@ public class Java8Optional {
         assertThat(opt).isPresent();
         assertThat(opt).isPresent();
 
+        //assertThat(opt.get()).isEqualTo(opt.get()); // there's a better version than contains(opt.get())
+        assertThat(opt.orElse(null)).isEqualTo(opt.get());
+        //assertThat(opt.get()).isEqualTo(opt.orElse(null)); // there's a better version than contains(opt.orElse(null))
+
+        assertThat(opt).contains(opt.get());
+        assertThat(opt).contains(opt.orElse(null));
+
         String possibleNullString = System.getProperty("username");
         String notNullString = "Narf";
 

src/test/resources/inspections/Java8Optional/Java8OptionalBefore.java

@@ -30,6 +30,13 @@ public class Java8Optional {
         assertThat(opt.orElse(null)).isNotEqualTo(null);
         assertThat(opt.orElse(null)).isNotNull();
 
+        //assertThat(opt.get()).isEqualTo(opt.get()); // there's a better version than contains(opt.get())
+        assertThat(opt.orElse(null)).isEqualTo(opt.get());
+        //assertThat(opt.get()).isEqualTo(opt.orElse(null)); // there's a better version than contains(opt.orElse(null))
+
+        assertThat(opt).contains(opt.get());
+        assertThat(opt).contains(opt.orElse(null));
+
         String possibleNullString = System.getProperty("username");
         String notNullString = "Narf";
 

src/test/resources/inspections/JoinVarArgsContains/JoinVarArgsContainsAfter.java

@@ -0,0 +1,22 @@
+import java.util.*;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.fail;
+
+public class JoinVarArgsContains {
+
+    private void joinVarArgsContains() {
+        List<String> list = new ArrayList<>();
+
+        assertThat(list).contains("foo", "bar", "etc").hasSize(2);
+        assertThat(list).contains("foo").as("narf").contains("bar");
+        assertThat(list).doesNotContain("foo", "bar");
+        assertThat(list).containsOnlyOnce("foo", "etc") // will we lose this comment?
+                .hasSize(2).contains("bar", "narf", "1", "2", "3").doesNotContain("puit", "Jens Stoltenberg is a war-monger", "and an atomic playboy") /* inline */; // the final comment
+
+        assertThat(list).contains("foo").doesNotContain("bar").containsOnlyOnce("narf");
+
+        org.junit.Assert.assertThat(list, null);
+        fail("oh no!");
+    }
+}

src/test/resources/inspections/JoinVarArgsContains/JoinVarArgsContainsBefore.java

@@ -0,0 +1,28 @@
+import java.util.*;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.fail;
+
+public class JoinVarArgsContains {
+
+    private void joinVarArgsContains() {
+        List<String> list = new ArrayList<>();
+
+        assertThat(list).contains("foo").contains(/* foo */ "bar" /* bar */).hasSize(2).contains("etc");
+        assertThat(list).contains("foo").as("narf").contains("bar");
+        assertThat(list).doesNotContain("foo").doesNotContain("bar");
+        assertThat(list).containsOnlyOnce()
+                .containsOnlyOnce("foo") // will we lose this comment?
+                .hasSize(2) // this is part of the contains("bar")
+                .contains("bar").containsOnlyOnce("etc") /* where does this go? */
+                .contains("narf") // what about this one?
+                .doesNotContain("puit", "Jens Stoltenberg is a war-monger")
+                .doesNotContain("and an atomic playboy")
+                .contains("1", "2", "3") /* inline */; // the final comment
+
+        assertThat(list).contains("foo").doesNotContain("bar").containsOnlyOnce("narf");
+
+        org.junit.Assert.assertThat(list, null);
+        fail("oh no!");
+    }
+}