There must always be at least one visible line (#44805)

src/vs/editor/common/viewModel/splitLinesCollection.ts

@@ -288,6 +288,7 @@ export class SplitLinesCollection implements IViewModelLinesCollection {
  let hiddenAreaIdx = -1;
  let nextLineNumberToUpdateHiddenArea = (hiddenAreaIdx + 1 < hiddenAreas.length) ? hiddenAreaEnd + 1 : this.lines.length + 2;
 
+ let hasVisibleLine = false;
  for (let i = 0; i < this.lines.length; i++) {
  let lineNumber = i + 1;
 
@@ -306,6 +307,7 @@ export class SplitLinesCollection implements IViewModelLinesCollection {
  lineChanged = true;
  }
  } else {
+ hasVisibleLine = true;
  // Line should be visible
  if (!this.lines[i].isVisible()) {
  this.lines[i] = this.lines[i].setVisible(true);
@@ -318,6 +320,11 @@ export class SplitLinesCollection implements IViewModelLinesCollection {
  }
  }
 
+ if (!hasVisibleLine) {
+ // Cannot have everything be hidden => reveal everything!
+ this.setHiddenAreas([]);
+ }
+
  return true;
  }
 
@@ -465,6 +472,10 @@ export class SplitLinesCollection implements IViewModelLinesCollection {
 
  public acceptVersionId(versionId: number): void {
  this._validModelVersionId = versionId;
+ if (this.lines.length === 1 && !this.lines[0].isVisible()) {
+ // At least one line must be visible => reset hidden areas
+ this.setHiddenAreas([]);
+ }
  }
 
  public getViewLineCount(): number {

src/vs/editor/test/common/viewModel/viewModelImpl.test.ts

@@ -74,6 +74,39 @@ suite('ViewModel', () => {
  });
  });
 
+ test('issue #44805: No visible lines via API call', () => {
+ const text = [
+ 'line1',
+ 'line2',
+ 'line3'
+ ];
+ testViewModel(text, {}, (viewModel, model) => {
+ assert.equal(viewModel.getLineCount(), 3);
+ viewModel.setHiddenAreas([new Range(1, 1, 3, 1)]);
+ assert.ok(viewModel.getVisibleRanges() !== null);
+ });
+ });
+
+ test('issue #44805: No visible lines via undoing', () => {
+ const text = [
+ ''
+ ];
+ testViewModel(text, {}, (viewModel, model) => {
+ assert.equal(viewModel.getLineCount(), 1);
+
+ model.pushEditOperations([], [{
+ range: new Range(1, 1, 1, 1),
+ text: 'line1\nline2\nline3'
+ }], () => ([]));
+
+ viewModel.setHiddenAreas([new Range(1, 1, 1, 1)]);
+ assert.equal(viewModel.getLineCount(), 2);
+
+ model.undo();
+ assert.ok(viewModel.getVisibleRanges() !== null);
+ });
+ });
+
  function assertGetPlainTextToCopy(text: string[], ranges: Range[], emptySelectionClipboard: boolean, expected: string | string[]): void {
  testViewModel(text, {}, (viewModel, model) => {
  let actual = viewModel.getPlainTextToCopy(ranges, emptySelectionClipboard);