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Report structured BuilderProblems from compiler diagnostics #1101

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252ca09
Report structured BuilderProblems from compiler diagnostics
gnodet Jul 31, 2026
92a9030
Use per-location dedup keys for compiler diagnostics
gnodet Aug 2, 2026
590e426
Use Log.child() and Log.problem() for hierarchical logging and struct…
gnodet Aug 6, 2026
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2 changes: 1 addition & 1 deletion pom.xml
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Original file line number Diff line number Diff line change
Expand Up @@ -82,7 +82,7 @@ under the License.

<properties>
<javaVersion>17</javaVersion>
<mavenVersion>4.0.0-rc-4</mavenVersion>
<mavenVersion>4.1.0-SNAPSHOT</mavenVersion>

<asmVersion>9.10.1</asmVersion>
<guiceVersion>7.0.0</guiceVersion>
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12 changes: 9 additions & 3 deletions src/main/java/org/apache/maven/plugin/compiler/AbstractCompilerMojo.java
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Expand Up @@ -70,6 +70,7 @@
import org.apache.maven.api.plugin.MojoException;
import org.apache.maven.api.plugin.annotations.Parameter;
import org.apache.maven.api.services.ArtifactManager;
import org.apache.maven.api.services.BuilderProblem;
import org.apache.maven.api.services.DependencyResolver;
import org.apache.maven.api.services.DependencyResolverRequest;
import org.apache.maven.api.services.DependencyResolverResult;
Expand Down Expand Up @@ -944,7 +945,11 @@ final void amendincrementalCompilation(EnumSet<IncrementalBuild.Aspect> aspects,

/**
* The logger for reporting information or warnings to the user.
* Currently, this is also used for console output.
* Also used for structured diagnostic reporting via {@link Log#problem(BuilderProblem)},
* which feeds into the build report, {@code mvnlog --diagnostics}, and warning suppression.
*
* <p>Sub-components receive child loggers (e.g. {@code logger.child("diagnostics")},
* {@code logger.child("options")}) for hierarchical naming in the log output.</p>
*
* <h4>Thread safety</h4>
* This logger should be thread-safe if the {@link ToolExecutor} is executed in a background thread.
Expand Down Expand Up @@ -1333,7 +1338,7 @@ public Options parseParameters(final OptionChecker compiler) {
* For example, Maven will check for illegal values in the "-g" option only if the compiler rejected
* the fully formatted option (e.g. "-g:vars,lines") that we provided to it.
*/
final var configuration = new Options(compiler, logger);
final var configuration = new Options(compiler, logger.child("options"));
configuration.addIfNonBlank("--source", getSource());
targetOrReleaseSet = configuration.addIfNonBlank("--target", getTarget());
targetOrReleaseSet |= configuration.setRelease(getRelease());
Expand Down Expand Up @@ -1463,7 +1468,8 @@ private void compile(final JavaCompiler compiler, final Options configuration) t
Path moduleDescriptor = executor.outputDirectory.resolve(MODULE_INFO + CLASS_FILE_SUFFIX);
if (Files.isRegularFile(moduleDescriptor)) {
byte[] oridinal = Files.readAllBytes(moduleDescriptor);
byte[] modified = ByteCodeTransformer.patchJdkModuleVersion(oridinal, getRelease(), logger);
byte[] modified =
ByteCodeTransformer.patchJdkModuleVersion(oridinal, getRelease(), logger.child("bytecode"));
if (modified != null) {
Files.write(moduleDescriptor, modified);
}
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164 changes: 106 additions & 58 deletions src/main/java/org/apache/maven/plugin/compiler/DiagnosticLogger.java
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Expand Up @@ -30,25 +30,24 @@
import java.util.Optional;

import org.apache.maven.api.plugin.Log;
import org.apache.maven.api.services.MessageBuilder;
import org.apache.maven.api.services.MessageBuilderFactory;
import org.apache.maven.api.services.BuilderProblem;

/**
* A Java compiler diagnostic listener which send the messages to the Maven logger.
* A Java compiler diagnostic listener which sends the messages to the Maven logger.
* When the logger supports structured problem reporting ({@link Log#problem(BuilderProblem)}),
* each diagnostic is also reported as a {@link BuilderProblem} with a per-location dedup key,
* enabling the build report, {@code mvnlog --diagnostics}, and warning suppression.
*
* @author Martin Desruisseaux
*/
final class DiagnosticLogger implements DiagnosticListener<JavaFileObject> {
/**
* The logger where to send diagnostics.
* The logger where to send diagnostics and structured problems.
* This should be a child logger (e.g. {@code "compiler:compile.diagnostics"})
* obtained via {@link Log#child(String)}.
*/
private final Log logger;

/**
* The factory for creating message builders.
*/
private final MessageBuilderFactory messageBuilderFactory;

/**
* The locale for compiler message.
*/
Expand Down Expand Up @@ -76,15 +75,16 @@ final class DiagnosticLogger implements DiagnosticListener<JavaFileObject> {

/**
* Creates a listener which will send the diagnostics to the given logger.
* Structured problems are reported via {@link Log#problem(BuilderProblem)},
* which handles dedup, suppression, and thread-safe interaction with the
* {@code BuildReportCollector} automatically.
*
* @param logger the logger where to send diagnostics
* @param messageBuilderFactory the factory for creating message builders
* @param logger the logger where to send diagnostics (typically a child logger)
* @param locale the locale for compiler message
* @param directory the base directory with which to relativize the paths to source files
*/
DiagnosticLogger(Log logger, MessageBuilderFactory messageBuilderFactory, Locale locale, Path directory) {
DiagnosticLogger(Log logger, Locale locale, Path directory) {
this.logger = logger;
this.messageBuilderFactory = messageBuilderFactory;
this.locale = locale;
this.directory = directory;
codeCount = new LinkedHashMap<>();
Expand All @@ -108,74 +108,121 @@ private String relativize(String file) {
}

/**
* Invoked when the compiler emitted a warning.
* Maps a {@link Diagnostic.Kind} to a {@link BuilderProblem.Severity},
* or {@code null} if the kind has no corresponding severity (e.g. {@code NOTE}).
*/
private static BuilderProblem.Severity mapSeverity(Diagnostic.Kind kind) {
return switch (kind) {
case ERROR -> BuilderProblem.Severity.ERROR;
case WARNING, MANDATORY_WARNING -> BuilderProblem.Severity.WARNING;
default -> null;
};
}

/**
* Invoked when the compiler emitted a diagnostic.
* <p>
* When the diagnostic has a code and a mappable severity (error or warning),
* a structured {@link BuilderProblem} is reported via {@link Log#problem(BuilderProblem)}
* with a per-location dedup key ({@code "compiler:<code>:<source>:<line>"}).
* This avoids double-counting with the {@code BuildReportCollector}'s WARN auto-promotion,
* because {@code Log.problem()} sets the structured-problem flag internally.
* <p>
* Informational diagnostics (notes, other) are logged at INFO level without
* creating a structured problem, since they are not actionable warnings.
*
* @param diagnostic the warning emitted by the Java compiler
* @param diagnostic the diagnostic emitted by the Java compiler
*/
@Override
public void report(Diagnostic<? extends JavaFileObject> diagnostic) {
String message = diagnostic.getMessage(locale);
if (message == null || message.isBlank()) {
return;
}
MessageBuilder record = messageBuilderFactory.builder();
record.a(message);
JavaFileObject source = diagnostic.getSource();
Diagnostic.Kind kind = diagnostic.getKind();
String style;
JavaFileObject source = diagnostic.getSource();
// Track counts for the summary
switch (kind) {
case ERROR:
style = ".error:-bold,f:red";
if (firstError == null) {
firstError = message;
}
numErrors++;
break;
case MANDATORY_WARNING:
case WARNING:
style = ".warning:-bold,f:yellow";
numWarnings++;
break;
default:
style = ".info:-bold,f:blue";
if (diagnostic.getLineNumber() == Diagnostic.NOPOS) {
source = null; // Some messages are generic, e.g. "Recompile with -Xlint:deprecation".
}
break;
}
// Statistics
String code = diagnostic.getCode();
if (code != null) {
codeCount.merge(code, 1, (old, initial) -> old + 1);
}
// Report as a structured problem when we have a diagnostic code and a mappable severity.
// Log.problem() handles both the console log and the build report,
// setting the STRUCTURED_PROBLEM_ACTIVE flag to prevent double-counting.
BuilderProblem.Severity severity = mapSeverity(kind);
if (code != null && severity != null) {
logger.problem(buildProblem(diagnostic, message, code, source, severity));
} else {
// Informational diagnostic or no code — fall back to plain logging
switch (kind) {
case ERROR -> logger.error(message);
case MANDATORY_WARNING, WARNING -> logger.warn(message);
default -> logger.info(message);
}
}
}

/**
* Builds a structured {@link BuilderProblem} from the given compiler diagnostic.
* Each diagnostic gets a per-location key ({@code "compiler:<code>:<source>:<line>"})
* so each unique file+line keeps its own entry in the build report.
* <p>
* The message includes the source location as plain text (e.g.
* {@code "unchecked cast\n at src/main/java/Foo.java[42,10]"})
* so it remains visible in the console output.
*/
private BuilderProblem buildProblem(
Diagnostic<? extends JavaFileObject> diagnostic,
String message,
String code,
JavaFileObject source,
BuilderProblem.Severity severity) {
BuilderProblem.Builder builder = BuilderProblem.builder().severity(severity);
// Build message with source location and per-location dedup key
var fullMessage = new StringBuilder(message);
var keyBuilder = new StringBuilder("compiler:").append(code);
if (source != null) {
record.newline().a(" at ").a(relativize(source.getName()));
String relPath = relativize(source.getName());
builder.source(relPath);
keyBuilder.append(':').append(relPath);
long line = diagnostic.getLineNumber();
long column = diagnostic.getColumnNumber();
fullMessage.append(System.lineSeparator()).append(" at ").append(relPath);
if (line != Diagnostic.NOPOS || column != Diagnostic.NOPOS) {
record.style(style).a('[');
fullMessage.append('[');
if (line != Diagnostic.NOPOS) {
record.a(line);
fullMessage.append(line);
builder.lineNumber((int) line);
keyBuilder.append(':').append(line);
}
if (column != Diagnostic.NOPOS) {
record.a(',').a(column);
fullMessage.append(',').append(column);
builder.columnNumber((int) column);
}
record.a(']').resetStyle();
fullMessage.append(']');
}
}
String log = record.toString();
switch (kind) {
case ERROR:
if (firstError == null) {
firstError = message;
}
logger.error(log);
numErrors++;
break;
case MANDATORY_WARNING:
case WARNING:
logger.warn(log);
numWarnings++;
break;
default:
logger.info(log);
break;
}
// Statistics
String code = diagnostic.getCode();
if (code != null) {
codeCount.merge(code, 1, (old, initial) -> old + 1);
}
return builder.key(keyBuilder.toString())
.message(fullMessage.toString())
.build();
}

/**
Expand All @@ -191,31 +238,32 @@ Optional<String> firstError(Throwable cause) {
* Reports summary after the compilation finished.
*/
void logSummary() {
MessageBuilder message = messageBuilderFactory.builder();
var message = new StringBuilder();
final String patternForCount;
if (!codeCount.isEmpty()) {
@SuppressWarnings("unchecked")
Map.Entry<String, Integer>[] entries = codeCount.entrySet().toArray(Map.Entry[]::new);
Arrays.sort(entries, (a, b) -> Integer.compare(b.getValue(), a.getValue()));
patternForCount = patternForCount(Math.max(entries[0].getValue(), Math.max(numWarnings, numErrors)));
message.strong("Summary of compiler messages:").newline();
message.append("Summary of compiler messages:").append(System.lineSeparator());
for (Map.Entry<String, Integer> entry : entries) {
int count = entry.getValue();
message.format(patternForCount, count, entry.getKey()).newline();
message.append(String.format(patternForCount, count, entry.getKey()))
.append(System.lineSeparator());
}
} else {
patternForCount = patternForCount(Math.max(numWarnings, numErrors));
}
if ((numWarnings | numErrors) != 0) {
message.strong("Total:");
message.append("Total:");
}
if (numWarnings != 0) {
writeCount(message, patternForCount, numWarnings, "warning");
}
if (numErrors != 0) {
writeCount(message, patternForCount, numErrors, "error");
}
logger.info(message.toString());
logger.info(message);
}

/**
Expand All @@ -230,9 +278,9 @@ private static String patternForCount(int n) {
/**
* Appends the count of warnings or errors, making them plural if needed.
*/
private static void writeCount(MessageBuilder message, String patternForCount, int count, String name) {
message.newline();
message.format(patternForCount, count, name);
private static void writeCount(StringBuilder message, String patternForCount, int count, String name) {
message.append(System.lineSeparator());
message.append(String.format(patternForCount, count, name));
if (count > 1) {
message.append('s');
}
Expand Down
2 changes: 1 addition & 1 deletion src/main/java/org/apache/maven/plugin/compiler/ToolExecutor.java
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Expand Up @@ -225,7 +225,7 @@ protected ToolExecutor(final AbstractCompilerMojo mojo, DiagnosticListener<? sup
logger = mojo.logger;
if (listener == null) {
Path root = mojo.project.getRootDirectory();
listener = new DiagnosticLogger(logger, mojo.messageBuilderFactory, LOCALE, root);
listener = new DiagnosticLogger(logger.child("diagnostics"), LOCALE, root);
}
this.listener = listener;
encoding = mojo.charset();
Expand Down
21 changes: 13 additions & 8 deletions src/test/java/org/apache/maven/plugin/compiler/CompilerMojoTestCase.java
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Expand Up @@ -40,20 +40,20 @@
import org.apache.maven.api.model.Build;
import org.apache.maven.api.model.Model;
import org.apache.maven.api.plugin.Log;
import org.apache.maven.api.plugin.testing.Basedir;
import org.apache.maven.api.plugin.testing.InjectMojo;
import org.apache.maven.api.plugin.testing.MojoExtension;
import org.apache.maven.api.plugin.testing.MojoParameter;
import org.apache.maven.api.plugin.testing.MojoTest;
import org.apache.maven.api.plugin.testing.stubs.ProducedArtifactStub;
import org.apache.maven.api.plugin.testing.stubs.ProjectStub;
import org.apache.maven.api.plugin.testing.stubs.SessionMock;
import org.apache.maven.api.services.ArtifactManager;
import org.apache.maven.api.services.MessageBuilderFactory;
import org.apache.maven.api.services.ToolchainManager;
import org.apache.maven.impl.DefaultMessageBuilderFactory;
import org.apache.maven.impl.InternalSession;
import org.apache.maven.plugin.compiler.stubs.CompilerStub;
import org.apache.maven.testing.plugin.Basedir;
import org.apache.maven.testing.plugin.InjectMojo;
import org.apache.maven.testing.plugin.MojoExtension;
import org.apache.maven.testing.plugin.MojoParameter;
import org.apache.maven.testing.plugin.MojoTest;
import org.apache.maven.testing.plugin.stubs.ProducedArtifactStub;
import org.apache.maven.testing.plugin.stubs.ProjectStub;
import org.apache.maven.testing.plugin.stubs.SessionMock;
import org.junit.jupiter.api.Test;

import static org.junit.jupiter.api.Assertions.assertArrayEquals;
Expand All @@ -64,6 +64,7 @@
import static org.junit.jupiter.api.Assertions.assertTrue;
import static org.junit.jupiter.api.Assertions.fail;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.ArgumentMatchers.anyString;
import static org.mockito.ArgumentMatchers.eq;
import static org.mockito.ArgumentMatchers.startsWith;
import static org.mockito.Mockito.clearInvocations;
Expand All @@ -72,6 +73,7 @@
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.never;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;

@MojoTest
public class CompilerMojoTestCase {
Expand Down Expand Up @@ -135,6 +137,7 @@ public void testCompilerBasic(
TestCompilerMojo testCompileMojo) {

Log log = mock(Log.class);
when(log.child(anyString())).thenReturn(log);
compileMojo.logger = log;
compileMojo.execute();
verify(log).warn(startsWith("No explicit value set for --release or --target."));
Expand All @@ -158,6 +161,7 @@ public void testCompilerBasicSourceTarget(
@InjectMojo(goal = "compile", pom = "plugin-config.xml") CompilerMojo compileMojo) {

Log log = mock(Log.class);
when(log.child(anyString())).thenReturn(log);
compileMojo.logger = log;
compileMojo.execute();
verify(log, never()).warn(startsWith("No explicit value set for --release or --target."));
Expand Down Expand Up @@ -196,6 +200,7 @@ public void testCompilerEmptySourceChangeDetection(
Files.write(source, new byte[0]);

Log log = mock(Log.class);
when(log.child(anyString())).thenReturn(log);
compileMojo.logger = log;
compileMojo.execute();

Expand Down