fix: add a log warning in verifySourceClasspath (#1937)

src/main/java/spoon/compiler/Environment.java

@@ -240,8 +240,8 @@ void report(Processor<?> processor, Level level,
 	/**
 	 * Sets the source class path of the Spoon model.
 	 * After the class path is set, it can be retrieved by
-	 * {@link #getSourceClasspath()}. Only .jar files or directories
-	 * are accepted.
+	 * {@link #getSourceClasspath()}. Only .jar files or directories with *.class files are accepted.
+	 * The *.jar or *.java files contained in given directories are ignored.
 	 *
 	 * @throws InvalidClassPathException if a given classpath does not exists or
 	 * does not have the right format (.jar file or directory)

src/main/java/spoon/support/StandardEnvironment.java

@@ -434,6 +434,7 @@ private void verifySourceClasspath(String[] sourceClasspath) throws InvalidClass
 				if (javaFiles.size() > 0) {
 					logger.warn("You're trying to give source code in the classpath, this should be given to " + "addInputSource " + javaFiles);
 				}
+				logger.warn("You specified the directory " + classOrJarFolder.getPath() + " in source classpath, please note that only class files will be considered. Jars and subdirectories will be ignored.");
 			} else if (classOrJarFolder.getName().endsWith(".class")) {
 				throw new InvalidClassPathException(".class files are not accepted in source classpath.");
 			}