fix(lsp): handle case when cursor is at the end of word

closes #350

fixes
- documentHighlights & rename not working when cursor is at end of word

Author: Mayank1791989

lib/flowLSP/FlowLanguageClient/createMiddleware.js

@@ -123,7 +123,12 @@ export default function createMiddleware(
     provideReferences(document, position, options, token, next) {
       return flowconfigCache.get(document).then(docFlowconfig => {
         if (docFlowconfig === clientFlowconfig) {
-          return next(document, position, options, token);
+          return next(
+            document,
+            fixPosition(document, position),
+            options,
+            token,
+          );
         }
         return null;
       });
@@ -132,7 +137,7 @@ export default function createMiddleware(
     provideDocumentHighlights(document, position, token, next) {
       return flowconfigCache.get(document).then(docFlowconfig => {
         if (docFlowconfig === clientFlowconfig) {
-          return next(document, position, token);
+          return next(document, fixPosition(document, position), token);
         }
         return null;
       });
@@ -150,7 +155,12 @@ export default function createMiddleware(
     provideRenameEdits(document, position, newName, token, next) {
       return flowconfigCache.get(document).then(docFlowconfig => {
         if (docFlowconfig === clientFlowconfig) {
-          return next(document, position, newName, token);
+          return next(
+            document,
+            fixPosition(document, position),
+            newName,
+            token,
+          );
         }
         return null;
       });
@@ -206,3 +216,18 @@ function formatHoverContent(value: ?vscode.Hover): ?vscode.Hover {
 
   return value;
 }
+
+function fixPosition(document, position) {
+  const range = document.getWordRangeAtPosition(position);
+  if (!range) {
+    return position;
+  }
+  // Fix position to handle differences in flow and vscode
+  // [flow] uses `position` as cursor on letter `te` (so only works if cursor on character (t & e))
+  //                                      -------^^----
+  // [vscode] uses `position` as cursor b/w character & character + 1 `|te`, `t|e, `te|` (expect 0, 1, 2 all 3 to work)
+  // @Fix: if position is the end of word move position one char back.
+  return position.isEqual(range.end)
+    ? position.with({ character: position.character - 1 })
+    : position;
+}