added the assertion logger feature, used for internal debugging only.

src/core/lombok/core/debug/AssertionLogger.java

@@ -0,0 +1,115 @@
+/*
+ * Copyright (C) 2015 The Project Lombok Authors.
+ * 
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+package lombok.core.debug;
+
+import java.io.FileOutputStream;
+import java.io.OutputStream;
+import java.io.PrintWriter;
+import java.io.StringWriter;
+import java.util.Date;
+import java.util.Random;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import lombok.core.Version;
+
+/**
+ * We make a number of assumptions in lombok code, and if these assumptions fail, we try to fall back to a 'least bad' scenario. However, we would prefer to
+ * just know about these cases, without confronting our users with error messages. The 'fix' is to log such assertion failures to this logger, which promptly
+ * ignores them, _unless_ you specifically enable logging them to a file. If you'd like to help out or want to assist in debugging, turn this on.
+ */
+public class AssertionLogger {
+	private static final String LOG_PATH;
+	
+	static {
+		String log = System.getProperty("lombok.assertion.log", null);
+		if (log != null) {
+			LOG_PATH = log.isEmpty() ? null : log;
+		} else {
+			try {
+				log = System.getenv("LOMBOK_ASSERTION_LOG");
+			} catch (Exception e) {
+				log = null;
+			}
+			LOG_PATH = (log == null || log.isEmpty()) ? null : log;
+		}
+	}
+	
+	private static final AtomicBoolean loggedIntro = new AtomicBoolean(false);
+	private static final String PROCESS_ID = generateProcessId();
+	
+	private static final String ID_CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";
+	
+	private static String generateProcessId() {
+		char[] ID = new char[4];
+		Random r = new Random();
+		for (int i = 0; i < ID.length; i++) ID[i] = ID_CHARS.charAt(r.nextInt(ID_CHARS.length()));
+		return new String(ID);
+	}
+	
+	private static synchronized void logToFile(String msg) {
+		if (msg == null) return;
+		
+		try {
+			OutputStream out = new FileOutputStream(LOG_PATH, true);
+			out.write(msg.getBytes("UTF-8"));
+			out.close();
+		} catch (Exception e) {
+			throw new RuntimeException("assertion logging can't write to log file", e);
+		}
+	}
+	
+	private static void logIntro() {
+		if (loggedIntro.getAndSet(true)) return;
+		
+		String version;
+		try {
+			version = Version.getFullVersion();
+		} catch (Exception e) {
+			version = Version.getVersion();
+		}
+		
+		logToFile(String.format("{%s} [%s -- START %s]\n", PROCESS_ID, new Date(), version));
+	}
+	
+	public static <T extends Throwable> T assertLog(String message, T throwable) {
+		if (LOG_PATH == null) return throwable;
+		
+		logIntro();
+		
+		if (message == null) message = "(No message)";
+		String stackMsg = "";
+		if (throwable != null) {
+			StringWriter sw = new StringWriter();
+			PrintWriter pw = new PrintWriter(sw);
+			throwable.printStackTrace(pw);
+			pw.close();
+			stackMsg = "\n  " + sw.toString().replace("\r", "").replace("\n", "\n  ").trim();
+		}
+		logToFile(String.format("{%s} [%ty%<tm%<tdT%<tH%<tM%<tS.%<tL] %s%s\n", PROCESS_ID, new Date(), message, stackMsg));
+		return throwable;
+	}
+	
+	public static void assertLog(String message) {
+		if (LOG_PATH == null) return;
+		assertLog(message, null);
+	}
+}

src/core/lombok/javac/JavacResolution.java

@@ -33,6 +33,7 @@ import java.util.Map;
 import javax.lang.model.type.TypeKind;
 
 import lombok.Lombok;
+import lombok.core.debug.AssertionLogger;
 
 import com.sun.tools.javac.code.BoundKind;
 import com.sun.tools.javac.code.Symbol.TypeSymbol;
@@ -191,6 +192,7 @@ public class JavacResolution {
 			copy.accept(memberEnter);
 		} catch (Exception ignore) {
 			// intentionally ignored; usually even if this step fails, val will work (but not for val in method local inner classes and anonymous inner classes).
+			AssertionLogger.assertLog("member enter failed.", ignore);
 		} finally {
 			setEnvOfMemberEnter(memberEnter, oldEnv);
 		}