Fix non-ASCII characters in URI

Author: FlorianKroiss

org.eclipse.lsp4e.test/src/org/eclipse/lsp4e/test/edit/LSPEclipseUtilsTest.java

@@ -342,6 +342,14 @@ public void testToUri_WindowsUNC() {
 		// Ensure there is an authority and no malformed quadruple slashes
 		assertFalse(uriWithSpaces.toString().startsWith("file:////"));
 	}
+    
+	@Test
+	void testFileURIWithNonAsciiPath() throws Exception {
+		// File name contains a German Eszett and a Japanese Kana
+		String fileName = "fooßア";
+		IFile targetFile = project.getFile(fileName);
+		assertEquals(fileName, Paths.get(LSPEclipseUtils.toUri(targetFile)).getFileName().toString());
+	}
 
 	@Test
 	public void testToWorkspaceFolder() {

org.eclipse.lsp4e/src/org/eclipse/lsp4e/LSPEclipseUtils.java

@@ -1353,15 +1353,19 @@ public static URI toUri(File file) {
 				final int slash = path.indexOf('/', 2);
 				final String authority = slash > 2 ? path.substring(2, slash) : path.substring(2);
 				final String absPath = slash > 2 ? path.substring(slash) : "/"; //$NON-NLS-1$
-				return new URI(FILE_SCHEME, authority, absPath, null);
+				return ensureAscii(new URI(FILE_SCHEME, authority, absPath, null));
 			}
-			return new URI(FILE_SCHEME, "", path, null); //$NON-NLS-1$
+			return ensureAscii(new URI(FILE_SCHEME, "", path, null)); //$NON-NLS-1$
 		} catch (URISyntaxException e) {
 			LanguageServerPlugin.logError(e);
 			return file.getAbsoluteFile().toURI();
 		}
 	}
 
+	private static URI ensureAscii(URI uri) {
+		return URI.create(uri.toASCIIString());
+	}
+
 	public static @Nullable IFile getFile(@Nullable IDocument document) {
 		IPath path = toPath(document);
 		return getFile(path);