refactor: handle commenting on the last line

src/git/diff_line_count.test.ts

@@ -100,6 +100,17 @@ describe('diff_line_count', () => {
     ` 18`,
   ].join('\n');
 
+  const hunkWithoutNewLines = [
+    '@@ -1 +1,4 @@',
+    '-# Initial readme',
+    '\\ No newline at end of file',
+    '+1',
+    '+2',
+    '+3',
+    '+4',
+    '\\ No newline at end of file',
+  ].join('\n');
+
   const testVersion = (diff: string): RestMrVersion => ({
     ...mrVersion,
     diffs: [{ ...diffFile, diff }],
@@ -112,6 +123,8 @@ describe('diff_line_count', () => {
       ${'hunkWithAddedAndRemovedLines'} | ${hunkWithAddedAndRemovedLines} | ${[13, 14, 18, 24]}
       ${'multiHunk'}                    | ${multiHunk}                    | ${[15, 39, 40, 97, 98]}
       ${'hunkWithHunkHeaders'}          | ${hunkWithHunkHeaders}          | ${[15]}
+      ${'hunkWithHunkHeaders'}          | ${hunkWithHunkHeaders}          | ${[15]}
+      ${'hunkWithoutNewLines'}          | ${hunkWithoutNewLines}          | ${[1, 2, 3, 4]}
     `('$hunkName gets correctly parsed', ({ hunk, newLines }) => {
       const ranges = getAddedLinesForFile(testVersion(hunk), diffFile.new_path);
 

src/git/diff_line_count.ts

@@ -16,7 +16,7 @@ const isEmpty = (obj: any): boolean =>
  * `@@ -38,9 +36,8 @@` reads: hunk starts at line 38 of the old version and 36 of the new version.
  */
 const getHunkStartingLine = (headerString = ''): { oldStart: number; newStart: number } | null => {
-  const headerMatch = headerString.match(/@@ -(\d+),\d+ \+(\d+),\d+ @@/);
+  const headerMatch = headerString.match(/@@ -(\d+)(?:,\d+)? \+(\d+)(?:,\d+)? @@/);
   return (
     headerMatch && {
       oldStart: parseInt(headerMatch[1], 10),
@@ -48,6 +48,7 @@ const parseHunk = (hunk: string): HunkLine[] => {
   assert(header);
   const result = remainingLines
     .filter(l => l) // no empty lines
+    .filter(l => !l.startsWith('\\')) // ignore '\ No newline at end of file'
     .reduce(
       ({ oldIndex, newIndex, lines }, line) => {
         const prefix = line[0];

src/review/commenting_range_provider.test.ts

@@ -35,15 +35,31 @@ describe('CommentingRangeProvider', () => {
   });
 
   it('returns full range (all lines in the document) for old file', () => {
-    const testDocument = {
+    const testDocument = ({
       uri: oldFileUrl,
       lineCount: 200,
-    } as vscode.TextDocument;
+      lineAt: () => ({
+        isEmptyOrWhitespace: false,
+      }),
+    } as unknown) as vscode.TextDocument;
     expect(commentingRangeProvider.provideCommentingRanges(testDocument)).toEqual([
       new vscode.Range(new vscode.Position(0, 0), new vscode.Position(199, 0)),
     ]);
   });
 
+  it('returns range without the last line for old file if the last line is empty', () => {
+    const testDocument = ({
+      uri: oldFileUrl,
+      lineCount: 200,
+      lineAt: () => ({
+        isEmptyOrWhitespace: true,
+      }),
+    } as unknown) as vscode.TextDocument;
+    expect(commentingRangeProvider.provideCommentingRanges(testDocument)).toEqual([
+      new vscode.Range(new vscode.Position(0, 0), new vscode.Position(198, 0)),
+    ]);
+  });
+
   const threeNewLinesHunk = ['@@ -0,0 +1,3 @@', '+new file 2', '+', '+12', ''].join('\n');
 
   it('shows correct commenting ranges for a new file', () => {

src/review/commenting_range_provider.ts

@@ -3,6 +3,10 @@ import { REVIEW_URI_SCHEME } from '../constants';
 import { getAddedLinesForFile } from '../git/diff_line_count';
 import { fromReviewUri } from './review_uri';
 
+const lastLineEmpty = (document: vscode.TextDocument): boolean => {
+  const lastLIne = document.lineAt(document.lineCount - 1);
+  return lastLIne.isEmptyOrWhitespace;
+};
 export class CommentingRangeProvider implements vscode.CommentingRangeProvider {
   private mr: RestIssuable;
 
@@ -22,9 +26,8 @@ export class CommentingRangeProvider implements vscode.CommentingRangeProvider {
     }
     const oldFile = params.commit === this.mrVersion.base_commit_sha;
     if (oldFile) {
-      return [
-        new vscode.Range(new vscode.Position(0, 0), new vscode.Position(document.lineCount - 1, 0)),
-      ];
+      const endOfRange = lastLineEmpty(document) ? document.lineCount - 2 : document.lineCount - 1;
+      return [new vscode.Range(new vscode.Position(0, 0), new vscode.Position(endOfRange, 0))];
     }
     const result = getAddedLinesForFile(this.mrVersion, params.path);
     return result.map(