EclipseHelper: skip unpacked ImageJ1 classes

This is a hacky workaround for the situation where ImageJ1 classes got
loaded prematurely by the Eclipse helper when running from within
Eclipse with a project coupling to ImageJA. Since we know that ImageJ1
will never use SciJava plugin annotations, we can safely skip loading
those classes, thus preventing the premature loading in that scenario.

As usual, thanks to Johannes Schindelin for his help with this fix!

Author: ctrueden

src/main/java/org/scijava/annotations/EclipseHelper.java

@@ -207,9 +207,9 @@ private void maybeIndex(final URL url, final ClassLoader loader) {
 
 	private void index(File directory, ClassLoader loader) {
 		debug("Directory: " + directory);
-		if (!directory.canWrite() || upToDate(directory)) {
-			debug("can write: " + directory.canWrite()
-				+ ", up-to-date: " + upToDate(directory));
+		if (!directory.canWrite() || upToDate(directory) || isIJ1(directory)) {
+			debug("can write: " + directory.canWrite() + ", up-to-date: " +
+				upToDate(directory) + ", : is IJ1: " + isIJ1(directory));
 			return;
 		}
 		final File jsonDirectory = new File(directory, Index.INDEX_PREFIX);
@@ -234,6 +234,14 @@ private void index(File directory, ClassLoader loader) {
 		}
 	}
 
+	/**
+	 * A hacky way of detecting whether the given directory is the root of an
+	 * ImageJ1 codebase containing unpacked ImageJ1 classes.
+	 */
+	private boolean isIJ1(File directory) {
+		return new File(directory, "IJ_Props.txt").exists();
+	}
+
 	private boolean upToDate(final File directory) {
 		final File jsonDirectory = new File(directory, Index.INDEX_PREFIX);
 		if (!jsonDirectory.isDirectory()) {