Polish "Add support for List properties in ApplicationProperties"

See gh-1759

Author: mhalbritter

initializr-generator-spring/src/main/java/io/spring/initializr/generator/spring/properties/ApplicationProperties.java

@@ -17,11 +17,12 @@
 package io.spring.initializr.generator.spring.properties;
 
 import java.io.PrintWriter;
-import java.util.ArrayList;
+import java.util.Collection;
 import java.util.HashMap;
-import java.util.List;
 import java.util.Map;
-import java.util.stream.Collectors;
+
+import org.springframework.util.Assert;
+import org.springframework.util.StringUtils;
 
 /**
  * Application properties.
@@ -70,11 +71,20 @@ public void add(String key, String value) {
 		add(key, (Object) value);
 	}
 
+	/**
+	 * Adds a new property.
+	 * @param key the key of the property
+	 * @param value the value of the property
+	 */
+	public void add(String key, Collection<?> value) {
+		add(key, (Object) value);
+	}
+
 	void writeProperties(PrintWriter writer) {
 		for (Map.Entry<String, Object> entry : this.properties.entrySet()) {
-			writer.printf("%s=%s%n", entry.getKey(), (entry.getValue() instanceof List)
-					? ((List<?>) entry.getValue()).stream().map(Object::toString).collect(Collectors.joining(", "))
-					: entry.getValue());
+			Object value = (entry.getValue() instanceof Collection<?> collection)
+					? StringUtils.collectionToCommaDelimitedString(collection) : entry.getValue();
+			writer.printf("%s=%s%n", entry.getKey(), value);
 		}
 	}
 
@@ -120,36 +130,29 @@ private static void writeEntry(Map.Entry<String, Object> entry, PrintWriter writ
 			writeYamlRecursive((Map<String, Object>) nestedMap, writer, indent + 1);
 		}
 		else {
-			if (value instanceof List) {
-				writer.printf("%s%s:%n", indentStr, entry.getKey());
-				writeList((List<?>) value, writer, indent + 1);
+			if (value instanceof Collection<?> collection) {
+				if (collection.isEmpty()) {
+					writer.printf("%s%s: []%n", indentStr, entry.getKey());
+				}
+				else {
+					writer.printf("%s%s:%n", indentStr, entry.getKey());
+					writeCollection(collection, writer, indent + 1);
+				}
 			}
 			else {
 				writer.printf("%s%s: %s%n", indentStr, entry.getKey(), value);
 			}
 		}
 	}
 
-	private static void writeList(List<?> list, PrintWriter writer, int indent) {
+	private static void writeCollection(Collection<?> collection, PrintWriter writer, int indent) {
 		String indentStr = YAML_SPACE.repeat(indent);
-		list.forEach((element) -> writer.printf("%s- %s%n", indentStr, element));
+		collection.forEach((element) -> writer.printf("%s- %s%n", indentStr, element));
 	}
 
 	private void add(String key, Object value) {
-		this.properties.merge(key, value, (oldValue, newValue) -> {
-			var newValues = new ArrayList<>((oldValue instanceof List) ? ((List<?>) oldValue).size() + 1 : 2);
-			if (oldValue instanceof List<?>) {
-				newValues.addAll((List<?>) oldValue);
-			}
-			else {
-				newValues.add(oldValue);
-			}
-			if (!newValues.contains(newValue)) {
-				newValues.add(newValue);
-				return newValues;
-			}
-			return oldValue;
-		});
+		Assert.state(!this.properties.containsKey(key), () -> "Property '%s' already exists".formatted(key));
+		this.properties.put(key, value);
 	}
 
 }

initializr-generator-spring/src/test/java/io/spring/initializr/generator/spring/properties/ApplicationPropertiesTests.java

@@ -18,10 +18,13 @@
 
 import java.io.PrintWriter;
 import java.io.StringWriter;
+import java.util.Collections;
+import java.util.List;
 
 import org.junit.jupiter.api.Test;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
 
 /**
  * Tests for {@link ApplicationProperties}.
@@ -39,21 +42,20 @@ void stringProperty() {
 	}
 
 	@Test
-	void stringPropertyDiffValuesWithSameKey() {
+	void collectionProperty() {
 		ApplicationProperties properties = new ApplicationProperties();
-		properties.add("test", "string");
-		properties.add("test", "string2");
+		List<String> strings = List.of("string1", "string2");
+		properties.add("test", strings);
 		String written = writeProperties(properties);
-		assertThat(written).isEqualToIgnoringNewLines("test=string, string2");
+		assertThat(written).isEqualToIgnoringNewLines("test=string1,string2");
 	}
 
 	@Test
-	void stringPropertySameValuesWithSameKey() {
+	void emptyCollectionProperty() {
 		ApplicationProperties properties = new ApplicationProperties();
-		properties.add("test", "string");
-		properties.add("test", "string");
+		properties.add("test", Collections.emptyList());
 		String written = writeProperties(properties);
-		assertThat(written).isEqualToIgnoringNewLines("test=string");
+		assertThat(written).isEqualToIgnoringNewLines("test=");
 	}
 
 	@Test
@@ -80,6 +82,14 @@ void booleanProperty() {
 		assertThat(written).isEqualToIgnoringNewLines("test=false");
 	}
 
+	@Test
+	void shouldFailOnExistingProperty() {
+		ApplicationProperties properties = new ApplicationProperties();
+		properties.add("test", 1);
+		assertThatIllegalStateException().isThrownBy(() -> properties.add("test", 2))
+			.withMessage("Property 'test' already exists");
+	}
+
 	@Test
 	void writeYaml() {
 		ApplicationProperties properties = new ApplicationProperties();
@@ -105,32 +115,27 @@ void writeYaml() {
 	}
 
 	@Test
-	void writeYamlSameKeyDistinctValues() {
+	void writeYamlCollection() {
 		ApplicationProperties properties = new ApplicationProperties();
-		properties.add("spring.docker.compose.file", "./ollama/docker-compose.yml");
-		properties.add("spring.docker.compose.file", "./qdrant/docker-compose.yml");
+		List<Integer> ints = List.of(1, 2);
+		properties.add("test.sub", ints);
 		String written = writeYaml(properties);
 		assertThat(written).isEqualToNormalizingNewlines("""
-				spring:
-				  docker:
-				    compose:
-				      file:
-				        - ./ollama/docker-compose.yml
-				        - ./qdrant/docker-compose.yml
+				test:
+				  sub:
+				    - 1
+				    - 2
 				""");
 	}
 
 	@Test
-	void writeYamlSameKeySameValues() {
+	void writeEmptyYamlCollection() {
 		ApplicationProperties properties = new ApplicationProperties();
-		properties.add("spring.docker.compose.file", "./ollama/docker-compose.yml");
-		properties.add("spring.docker.compose.file", "./ollama/docker-compose.yml");
+		properties.add("test.sub", Collections.emptyList());
 		String written = writeYaml(properties);
 		assertThat(written).isEqualToNormalizingNewlines("""
-				spring:
-				  docker:
-				    compose:
-				      file: ./ollama/docker-compose.yml
+				test:
+				  sub: []
 				""");
 	}