Fail the build if the meta-data are invalid

Make sure to fail the build with a proper compilation error message if
the user-defined meta-data are invalid. For now, this takes care of the
JSON format but other checks may be added in the future.

Closes gh-3329

spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/ConfigurationMetadataAnnotationProcessor.java

@@ -47,6 +47,7 @@ import javax.tools.Diagnostic.Kind;
 import org.springframework.boot.configurationprocessor.fieldvalues.FieldValuesParser;
 import org.springframework.boot.configurationprocessor.fieldvalues.javac.JavaCompilerFieldValuesParser;
 import org.springframework.boot.configurationprocessor.metadata.ConfigurationMetadata;
+import org.springframework.boot.configurationprocessor.metadata.InvalidConfigurationMetadataException;
 import org.springframework.boot.configurationprocessor.metadata.ItemMetadata;
 
 /**
@@ -354,13 +355,15 @@ public class ConfigurationMetadataAnnotationProcessor extends AbstractProcessor
 		}
 		catch (FileNotFoundException ex) {
 			// No additional metadata
-			return metadata;
+		}
+		catch (InvalidConfigurationMetadataException e) {
+			log(e.getKind(), e.getMessage());
 		}
 		catch (Exception ex) {
 			logWarning("Unable to merge additional metadata");
 			logWarning(getStackTrace(ex));
-			return metadata;
 		}
+		return metadata;
 	}
 
 	private String getStackTrace(Exception ex) {
@@ -370,7 +373,11 @@ public class ConfigurationMetadataAnnotationProcessor extends AbstractProcessor
 	}
 
 	private void logWarning(String msg) {
-		this.processingEnv.getMessager().printMessage(Kind.WARNING, msg);
+		log(Kind.WARNING, msg);
+	}
+
+	private void log(Kind kind, String msg) {
+		this.processingEnv.getMessager().printMessage(kind, msg);
 	}
 
 }

spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/MetadataStore.java

@@ -21,12 +21,15 @@ import java.io.FileInputStream;
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
-
 import javax.annotation.processing.ProcessingEnvironment;
+import javax.tools.Diagnostic;
 import javax.tools.FileObject;
 import javax.tools.StandardLocation;
 
+import org.json.JSONException;
+
 import org.springframework.boot.configurationprocessor.metadata.ConfigurationMetadata;
+import org.springframework.boot.configurationprocessor.metadata.InvalidConfigurationMetadataException;
 import org.springframework.boot.configurationprocessor.metadata.JsonMarshaller;
 
 /**
@@ -83,6 +86,10 @@ public class MetadataStore {
 		catch (IOException ex) {
 			return null;
 		}
+		catch (JSONException ex) {
+			throw new InvalidConfigurationMetadataException("Invalid additional meta-data in '" +
+					METADATA_PATH + "': " + ex.getMessage(), Diagnostic.Kind.ERROR);
+		}
 		finally {
 			in.close();
 		}

spring-boot-tools/spring-boot-configuration-processor/src/main/java/org/springframework/boot/configurationprocessor/metadata/InvalidConfigurationMetadataException.java

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2012-2015 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.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.configurationprocessor.metadata;
+
+import javax.tools.Diagnostic;
+
+/**
+ * Thrown to indicate that some meta-data is invalid. Define the
+ * severity to determine whether it has to fail the build.
+ *
+ * @author Stephane Nicoll
+ * @since 1.3.0
+ */
+@SuppressWarnings("serial")
+public class InvalidConfigurationMetadataException extends RuntimeException {
+
+	private final Diagnostic.Kind kind;
+
+	public InvalidConfigurationMetadataException(String message, Diagnostic.Kind kind) {
+		super(message);
+		this.kind = kind;
+	}
+
+	public Diagnostic.Kind getKind() {
+		return kind;
+	}
+
+}

spring-boot-tools/spring-boot-configuration-processor/src/test/java/org/springframework/boot/configurationprocessor/ConfigurationMetadataAnnotationProcessorTests.java

@@ -27,6 +27,7 @@ import org.json.JSONObject;
 import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
+import org.junit.rules.ExpectedException;
 import org.junit.rules.TemporaryFolder;
 import org.springframework.boot.configurationprocessor.metadata.ConfigurationMetadata;
 import org.springframework.boot.configurationprocessor.metadata.ItemHint;
@@ -52,6 +53,7 @@ import org.springframework.boot.configurationsample.specific.InnerClassAnnotated
 import org.springframework.boot.configurationsample.specific.InnerClassProperties;
 import org.springframework.boot.configurationsample.specific.InnerClassRootConfig;
 import org.springframework.boot.configurationsample.specific.SimplePojo;
+import org.springframework.util.FileCopyUtils;
 
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.Matchers.empty;
@@ -78,6 +80,9 @@ public class ConfigurationMetadataAnnotationProcessorTests {
 	@Rule
 	public TemporaryFolder temporaryFolder = new TemporaryFolder();
 
+	@Rule
+	public ExpectedException thrown = ExpectedException.none();
+
 	private TestCompiler compiler;
 
 	@Before
@@ -346,6 +351,16 @@ public class ConfigurationMetadataAnnotationProcessorTests {
 						.fromSource(AdditionalMetadata.class));
 	}
 
+	@Test
+	public void mergeOfInvalidAdditionalMetadata() throws IOException {
+		File additionalMetadataFile = createAdditionalMetadataFile();
+		FileCopyUtils.copy("Hello World", new FileWriter(additionalMetadataFile));
+
+		thrown.expect(IllegalStateException.class);
+		thrown.expectMessage("Compilation failed");
+		compile(SimpleProperties.class);
+	}
+
 	@Test
 	public void mergingOfSimpleHint() throws Exception {
 		writeAdditionalHints(ItemHint.newHint("simple.the-name", new ItemHint.ValueHint(