Fix out-of-bounds error when applying incremental file changes (#113)

---------

Signed-off-by: Ben Sherman <bentshermann@gmail.com>
Co-authored-by: Ben Sherman <bentshermann@gmail.com>

Author: chenyenchung

src/main/java/nextflow/lsp/file/FileCache.java

@@ -92,22 +92,17 @@ public void didChange(DidChangeTextDocumentParams params) {
         }
         else {
             // update file contents with incremental changes
-            var sortedChanges = new ArrayList<>(params.getContentChanges());
-            sortedChanges.sort((a, b) -> {
-                return Positions.COMPARATOR.compare( a.getRange().getStart(), b.getRange().getStart() );
-            });
-            var builder = new StringBuilder();
-            int previousEnd = 0;
-            for( var change : sortedChanges ) {
+            for( var change : params.getContentChanges() ) {
                 var range = change.getRange();
                 var offsetStart = Positions.getOffset(oldText, range.getStart());
                 var offsetEnd = Positions.getOffset(oldText, range.getEnd());
-                builder.append(oldText.substring(previousEnd, offsetStart));
-                builder.append(change.getText());
-                previousEnd = offsetEnd;
+                oldText = new StringBuilder()
+                    .append(oldText.substring(0, offsetStart))
+                    .append(change.getText())
+                    .append(oldText.substring(offsetEnd))
+                    .toString();
             }
-            builder.append(oldText.substring(previousEnd));
-            openFiles.put(uri, builder.toString());
+            openFiles.put(uri, oldText);
         }
         changedFiles.add(uri);
     }

src/test/groovy/nextflow/lsp/file/FileCacheTest.groovy

@@ -61,7 +61,7 @@ class FileCacheTest extends Specification {
                     'hello'
                 ),
                 new TextDocumentContentChangeEvent(
-                    new Range(new Position(0, 8), new Position(0, 8)),
+                    new Range(new Position(0, 11), new Position(0, 11)),
                     ', friend'
                 )
             )