LocationService: fall back to FileLocation more

Specifically: if the URI resolution returns null, rather than actually
returning null, let's wrap the string into a FileLocation as a fallback.

See imagej/pyimagej#285.

src/main/java/org/scijava/io/location/LocationService.java

@@ -56,14 +56,15 @@ public interface LocationService extends HandlerService<URI, LocationResolver>,
 	 */
 	default Location resolve(final String uriString) throws URISyntaxException {
 	    try {
-	        return resolve(new URI(uriString));
+	        Location loc = resolve(new URI(uriString));
+	        if (loc != null) return loc;
 	    }
 	    catch (final URISyntaxException exc) {
 	        // In general, filenames are not valid URI strings.
 	        // Particularly on Windows, there are backslashes, which are invalid in URIs.
 	        // So we explicitly turn this string into a file if an error happens above.
-	        return resolve(new File(uriString).toURI());
 	    }
+	    return resolve(new File(uriString).toURI());
 	}
 
 	/**

src/test/java/org/scijava/io/location/LocationServiceTest.java

@@ -30,6 +30,7 @@
 package org.scijava.io.location;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
 import static org.junit.Assert.assertTrue;
 
 import java.io.File;
@@ -43,6 +44,7 @@
  * Tests {@link LocationService}.
  * 
  * @author Gabriel Einsdorf
+ * @author Curtis Rueden
  */
 public class LocationServiceTest {
 
@@ -60,6 +62,23 @@ public void testResolve() throws URISyntaxException {
 		assertEquals(uri, loc.resolve(uri.toString()).getURI());
 	}
 
+	@Test
+	public void testResolveWindowsPath() throws URISyntaxException {
+		final Context ctx = new Context(LocationService.class);
+		final LocationService loc = ctx.getService(LocationService.class);
+
+		String pSlash = "C:/Windows/FilePath/image.tif";
+		final Location locSlash = loc.resolve(pSlash);
+		assertTrue(locSlash instanceof FileLocation);
+
+		String pBackslash = pSlash.replace('/', '\\');
+		final Location locBackslash = loc.resolve(pBackslash);
+		assertTrue(locBackslash instanceof FileLocation);
+
+		final Location locSlashURI = loc.resolve(new URI(pSlash));
+		assertNull(locSlashURI);
+	}
+
 	@Test
 	public void testFallBack() throws URISyntaxException {
 		final Context ctx = new Context(LocationService.class);