Fail on recursive references in profile groups

Update `Profiles` group expansion logic to fail if recursive
references are found.

See gh-24327

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/context/config/Profiles.java

@@ -27,6 +27,7 @@
 import java.util.List;
 import java.util.Set;
 import java.util.function.Supplier;
+import java.util.stream.Collectors;
 
 import org.springframework.boot.context.properties.bind.Bindable;
 import org.springframework.boot.context.properties.bind.Binder;
@@ -117,18 +118,30 @@ private List<String> expandProfiles(List<String> profiles) {
 		while (!stack.isEmpty()) {
 			String current = stack.pop();
 			expandedProfiles.add(current);
-			asReversedList(this.groups.get(current)).forEach(stack::push);
+			List<String> groupProfiles = asReversedList(this.groups.get(current));
+			Set<String> profileConflicts = getProfileConflicts(groupProfiles, expandedProfiles);
+			if (!profileConflicts.isEmpty()) {
+				String message = String.format("Profiles could not be resolved. Remove profiles %s from group: %s",
+						profileConflicts, current);
+				throw new IllegalStateException(message);
+
+			}
+			groupProfiles.forEach(stack::push);
 		}
 		return asUniqueItemList(StringUtils.toStringArray(expandedProfiles));
 	}
 
+	private Set<String> getProfileConflicts(List<String> groupProfiles, Set<String> expandedProfiles) {
+		return groupProfiles.stream().filter(expandedProfiles::contains).collect(Collectors.toSet());
+	}
+
 	private List<String> asReversedList(List<String> list) {
 		if (list == null || list.isEmpty()) {
 			return Collections.emptyList();
 		}
 		List<String> reversed = new ArrayList<>(list);
 		Collections.reverse(reversed);
-		return Collections.unmodifiableList(reversed);
+		return reversed;
 	}
 
 	private List<String> asUniqueItemList(String[] array) {

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/context/config/ProfilesTests.java

@@ -27,6 +27,7 @@
 import org.springframework.mock.env.MockEnvironment;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
 
 /**
  * Tests for {@link Profiles}.
@@ -359,4 +360,25 @@ void isAcceptedWhenNoActiveAndDefaultWithGroupsContainsProfileReturnsTrue() {
 		assertThat(profiles.isAccepted("x")).isTrue();
 	}
 
+	@Test
+	void simpleRecursiveReferenceInProfileGroupThrowsException() {
+		MockEnvironment environment = new MockEnvironment();
+		environment.setProperty("spring.profiles.active", "a,b,c");
+		environment.setProperty("spring.profiles.group.a", "a,e,f");
+		Binder binder = Binder.get(environment);
+		assertThatIllegalStateException().isThrownBy(() -> new Profiles(environment, binder, null))
+				.withMessageContaining("Profiles could not be resolved. Remove profiles [a] from group: a");
+	}
+
+	@Test
+	void complexRecursiveReferenceInProfileGroupThrowsException() {
+		MockEnvironment environment = new MockEnvironment();
+		environment.setProperty("spring.profiles.active", "a,b,c");
+		environment.setProperty("spring.profiles.group.a", "e,f");
+		environment.setProperty("spring.profiles.group.e", "a,x,y");
+		Binder binder = Binder.get(environment);
+		assertThatIllegalStateException().isThrownBy(() -> new Profiles(environment, binder, null))
+				.withMessageContaining("Profiles could not be resolved. Remove profiles [a] from group: e");
+	}
+
 }