Improve javac error output parsing

Instead of two separate 'while' loops, one inline and one in an extra method, parsing stack traces after finding error messages specific to the English locale of the JDK, now there is generic stack trace parsing, which works in these two cases independent of locale and also in others previously not covered. For backward compatibility, the Javac localized message 'javac.msg.bug' ("An exception has occurred in the compiler ... Please file a bug") is salvaged in a locale-independent way, matching on error reporting URLs always occurring in all JDK locales (English, Japanese, Chinese, German as of JDK 21).

Author: kriegaex

plexus-compilers/plexus-compiler-javac/src/main/java/org/codehaus/plexus/compiler/javac/JavacCompiler.java

@@ -65,6 +65,7 @@
 import java.util.Properties;
 import java.util.StringTokenizer;
 import java.util.concurrent.ConcurrentLinkedDeque;
+import java.util.regex.Pattern;
 
 import org.codehaus.plexus.compiler.AbstractCompiler;
 import org.codehaus.plexus.compiler.CompilerConfiguration;
@@ -627,6 +628,16 @@ private static CompilerResult compileInProcess0(Class<?> javacClass, String[] ar
  return new CompilerResult(success, messages);
  }
 
+ // Match ~95% of existing JDK exception name patterns (last checked for JDK 21)
+ private static final Pattern STACK_TRACE_FIRST_LINE = Pattern.compile("^(?:[\\w+.-]+\\.)[\\w$]*?(?:"
+ + "Exception|Error|Throwable|Failure|Result|Abort|Fault|ThreadDeath|Overflow|Warning|"
+ + "NotSupported|NotFound|BadArgs|BadClassFile|Illegal|Invalid|Unexpected|Unchecked|Unmatched\\w+"
+ + ").*$");
+
+ // Match exception causes, existing and omitted stack trace elements
+ private static final Pattern STACK_TRACE_OTHER_LINE =
+ Pattern.compile("^(?:Caused by:\\s.*|\\s*at .*|\\s*\\.\\.\\.\\s\\d+\\smore)$");
+
  /**
  * Parse the output from the compiler into a list of CompilerMessage objects
  *
@@ -643,6 +654,7 @@ static List<CompilerMessage> parseModernStream(int exitCode, BufferedReader inpu
  StringBuilder buffer = new StringBuilder();
 
  boolean hasPointer = false;
+ int stackTraceLineCount = 0;
 
  while (true) {
  line = input.readLine();
@@ -659,26 +671,44 @@ static List<CompilerMessage> parseModernStream(int exitCode, BufferedReader inpu
  } else if (hasPointer) {
  // A compiler message remains in buffer at end of parse stream
  errors.add(parseModernError(exitCode, bufferAsString));
+ } else if (stackTraceLineCount > 0) {
+ // Extract stack trace from end of buffer
+ String[] lines = bufferAsString.split("\\R");
+ int linesTotal = lines.length;
+ buffer = new StringBuilder();
+ int firstLine = linesTotal - stackTraceLineCount;
+
+ // Salvage Javac localized message 'javac.msg.bug' ("An exception has occurred in the
+ // compiler ... Please file a bug")
+ if (firstLine > 0) {
+ final String lineBeforeStackTrace = lines[firstLine - 1];
+ // One of those two URL substrings should always appear, without regard to JVM locale.
+ // TODO: Update, if the URL changes, last checked for JDK 21.
+ if (lineBeforeStackTrace.contains("java.sun.com/webapps/bugreport")
+ || lineBeforeStackTrace.contains("bugreport.java.com")) {
+ firstLine--;
+ }
+ }
+
+ // Note: For message 'javac.msg.proc.annotation.uncaught.exception' ("An annotation processor
+ // threw an uncaught exception"), there is no locale-independent substring, and the header is
+ // also multi-line. It was discarded in the removed method 'parseAnnotationProcessorStream',
+ // and we continue to do so.
+
+ for (int i = firstLine; i < linesTotal; i++) {
+ buffer.append(lines[i]).append(EOL);
+ }
+ errors.add(new CompilerMessage(buffer.toString(), CompilerMessage.Kind.ERROR));
  }
  }
  return errors;
  }
 
- // A compiler error occurred, treat everything that follows as part of the error.
- if (line.startsWith("An exception has occurred in the compiler")) {
- buffer = new StringBuilder();
-
- while (line != null) {
- buffer.append(line);
- buffer.append(EOL);
- line = input.readLine();
- }
-
- errors.add(new CompilerMessage(buffer.toString(), CompilerMessage.Kind.ERROR));
- return errors;
- } else if (line.startsWith("An annotation processor threw an uncaught exception.")) {
- CompilerMessage annotationProcessingError = parseAnnotationProcessorStream(input);
- errors.add(annotationProcessingError);
+ if (stackTraceLineCount == 0 && STACK_TRACE_FIRST_LINE.matcher(line).matches()
+ || STACK_TRACE_OTHER_LINE.matcher(line).matches()) {
+ stackTraceLineCount++;
+ } else {
+ stackTraceLineCount = 0;
  }
 
  // new error block?
@@ -714,21 +744,6 @@ static List<CompilerMessage> parseModernStream(int exitCode, BufferedReader inpu
  }
  }
 
- private static CompilerMessage parseAnnotationProcessorStream(final BufferedReader input) throws IOException {
- String line = input.readLine();
- final StringBuilder buffer = new StringBuilder();
-
- while (line != null) {
- if (!line.startsWith("Consult the following stack trace for details.")) {
- buffer.append(line);
- buffer.append(EOL);
- }
- line = input.readLine();
- }
-
- return new CompilerMessage(buffer.toString(), CompilerMessage.Kind.ERROR);
- }
-
  private static boolean isMisc(String line) {
  return startsWithPrefix(line, MISC_PREFIXES);
  }