Clarify when a property was not renamed due to an incompatible type

Closes gh-11794

spring-boot-project/spring-boot-properties-migrator/src/main/java/org/springframework/boot/context/properties/migrator/PropertiesMigrationReport.java

@@ -25,6 +25,7 @@ import java.util.function.Function;
 import java.util.stream.Collectors;
 
 import org.springframework.boot.configurationmetadata.ConfigurationMetadataProperty;
+import org.springframework.boot.configurationmetadata.Deprecation;
 import org.springframework.util.StringUtils;
 
 /**
@@ -74,10 +75,7 @@ class PropertiesMigrationReport {
 		StringBuilder report = new StringBuilder();
 		report.append(String.format("%nThe use of configuration keys that are no longer "
 				+ "supported was found in the environment:%n%n"));
-		append(report, content,
+		append(report, content, this::determineReason);
-				(metadata) -> "Reason: "
-						+ (StringUtils.hasText(metadata.getDeprecation().getShortReason())
-								? metadata.getDeprecation().getShortReason() : "none"));
 		report.append(String.format("%n"));
 		report.append("Please refer to the migration guide or reference guide for "
 				+ "potential alternatives.");
@@ -85,6 +83,18 @@ class PropertiesMigrationReport {
 		return report.toString();
 	}
 
+	private String determineReason(ConfigurationMetadataProperty metadata) {
+		Deprecation deprecation = metadata.getDeprecation();
+		if (StringUtils.hasText(deprecation.getShortReason())) {
+			return deprecation.getShortReason();
+		}
+		if (StringUtils.hasText(deprecation.getReplacement())) {
+			return String.format("Reason: Replacement key '%s' uses an incompatible "
+					+ "target type", deprecation.getReplacement());
+		}
+		return "none";
+	}
+
 	private Map<String, List<PropertyMigration>> getContent(
 			Function<LegacyProperties, List<PropertyMigration>> extractor) {
 		return this.content.entrySet().stream()

spring-boot-project/spring-boot-properties-migrator/src/test/java/org/springframework/boot/context/properties/migrator/PropertiesMigrationReporterTests.java

@@ -141,6 +141,18 @@ public class PropertiesMigrationReporterTests {
 		assertMappedProperty(propertySource, "test.mapped.ttl", 5678L, null);
 	}
 
+	@Test
+	public void reasonIsProvidedIfPropertyCouldNotBeRenamed() throws IOException {
+		this.environment.getPropertySources().addFirst(loadPropertySource("test",
+				"config/config-error-no-compatible-type.properties"));
+		String report = createErrorReport(
+				loadRepository("metadata/type-conversion-metadata.json"));
+		assertThat(report).isNotNull();
+		assertThat(report).containsSubsequence("Property source 'test'",
+				"wrong.inconvertible", "Line: 1", "Reason: Replacement key "
+						+ "'test.inconvertible' uses an incompatible target type");
+	}
+
 	private List<String> mapToNames(PropertySources sources) {
 		List<String> names = new ArrayList<>();
 		for (PropertySource<?> source : sources) {

spring-boot-project/spring-boot-properties-migrator/src/test/resources/config/config-error-no-compatible-type.properties

@@ -0,0 +1 @@
+wrong.inconvertible=abc

spring-boot-project/spring-boot-properties-migrator/src/test/resources/metadata/type-conversion-metadata.json

@@ -12,6 +12,10 @@
       "name": "test.mapped",
       "type": "java.util.Map<java.lang.String, java.time.Duration>"
     },
+    {
+      "name": "test.inconvertible",
+      "type": "com.example.One"
+    },
     {
       "name": "test.cache-seconds",
       "type": "java.lang.Integer",
@@ -35,6 +39,14 @@
         "replacement": "test.mapped.ttl",
         "level": "error"
       }
+    },
+    {
+      "name": "wrong.inconvertible",
+      "type": "com.example.Two",
+      "deprecation": {
+        "replacement": "test.inconvertible",
+        "level": "error"
+      }
     }
   ]
 }