Improve toString() for Profiles.of() implementation

Prior to this commit, the toString() implementation in ProfilesParser
(which is the internal implementation of Profiles.of()) concatenated
profile expressions with " or ".

For example, the string representation of
Profiles.of("spring & framework", "java | kotlin") was
"spring & framework or java | kotlin".

This commit improves the toString() implementation by wrapping
individual profile expressions in parentheses and concatenating them
with " | ".

For example, the string representation from the previous example is now
"(spring & framework) | (java | kotlin)".

This makes it easier to read (for example, when debugging) and
comprehend.

As an additional benefit, the result of invoking toString() can even be
used as a logically equivalent composite profile expression, though
that is not the primary goal of this change.

Closes gh-30374

spring-core/src/main/java/org/springframework/core/env/ProfilesParser.java

@@ -24,10 +24,10 @@
 import java.util.Set;
 import java.util.StringTokenizer;
 import java.util.function.Predicate;
+import java.util.stream.Collectors;
 
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
-import org.springframework.util.StringUtils;
 
 /**
  * Internal parser used by {@link Profiles#of}.
@@ -189,7 +189,14 @@ public boolean equals(@Nullable Object obj) {
 
 		@Override
 		public String toString() {
-			return StringUtils.collectionToDelimitedString(this.expressions, " or ");
+			if (this.expressions.size() == 1) {
+				return this.expressions.iterator().next();
+			}
+			return this.expressions.stream().map(this::wrap).collect(Collectors.joining(" | "));
+		}
+
+		private String wrap(String str) {
+			return "(" + str + ")";
 		}
 
 	}

spring-core/src/test/java/org/springframework/core/env/ProfilesTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2021 the original author or authors.
+ * Copyright 2002-2023 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -272,6 +272,12 @@ void ofComplexExpressionWithoutSpaces() {
 		assertComplexExpression(profiles);
 	}
 
+	@Test
+	void ofComplexExpressionEnclosedInParentheses() {
+		Profiles profiles = Profiles.of("((spring & framework) | (spring & java))");
+		assertComplexExpression(profiles);
+	}
+
 	private void assertComplexExpression(Profiles profiles) {
 		assertThat(profiles.matches(activeProfiles("spring"))).isFalse();
 		assertThat(profiles.matches(activeProfiles("spring", "framework"))).isTrue();
@@ -291,8 +297,27 @@ void sensibleToString() {
 		assertThat(Profiles.of("spring")).hasToString("spring");
 		assertThat(Profiles.of("(spring & framework) | (spring & java)")).hasToString("(spring & framework) | (spring & java)");
 		assertThat(Profiles.of("(spring&framework)|(spring&java)")).hasToString("(spring&framework)|(spring&java)");
-		assertThat(Profiles.of("spring & framework", "java | kotlin")).hasToString("spring & framework or java | kotlin");
-		assertThat(Profiles.of("java | kotlin", "spring & framework")).hasToString("java | kotlin or spring & framework");
+		assertThat(Profiles.of("spring & framework", "java | kotlin")).hasToString("(spring & framework) | (java | kotlin)");
+		assertThat(Profiles.of("java | kotlin", "spring & framework")).hasToString("(java | kotlin) | (spring & framework)");
+		assertThat(Profiles.of("java | kotlin", "spring & framework", "cat | dog")).hasToString("(java | kotlin) | (spring & framework) | (cat | dog)");
+	}
+
+	@Test
+	void toStringGeneratesValidCompositeProfileExpression() {
+		assertThatToStringGeneratesValidCompositeProfileExpression("spring");
+		assertThatToStringGeneratesValidCompositeProfileExpression("(spring & kotlin) | (spring & java)");
+		assertThatToStringGeneratesValidCompositeProfileExpression("spring & kotlin", "spring & java");
+		assertThatToStringGeneratesValidCompositeProfileExpression("spring & kotlin", "spring & java", "cat | dog");
+	}
+
+	private static void assertThatToStringGeneratesValidCompositeProfileExpression(String... profileExpressions) {
+		Profiles profiles = Profiles.of(profileExpressions);
+		assertThat(profiles.matches(activeProfiles("spring", "java"))).isTrue();
+		assertThat(profiles.matches(activeProfiles("kotlin"))).isFalse();
+
+		Profiles compositeProfiles = Profiles.of(profiles.toString());
+		assertThat(compositeProfiles.matches(activeProfiles("spring", "java"))).isTrue();
+		assertThat(compositeProfiles.matches(activeProfiles("kotlin"))).isFalse();
 	}
 
 	@Test