From 9a0709e95ed64a5c3670f9d47db6093b1821471c Mon Sep 17 00:00:00 2001
From: Antonio Scandurra <as-cii@github.com>
Date: Wed, 7 Jun 2017 18:59:23 +0200
Subject: [PATCH] Don't try to measure lines that don't exist

By the time that the animation frame is delivered, the requested
autoscroll
position could not exist anymore. This could cause the editor component
to measure a non-existent line and, as a result, throw an exception.

With this commit we will always ignore measurements for screen lines
that do not exist.
---
 spec/text-editor-component-spec.js | 10 +++++++++-
 src/text-editor-component.js       |  9 +++++++--
 2 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/spec/text-editor-component-spec.js b/spec/text-editor-component-spec.js
index 9163b46a7..1b33e3332 100644
--- a/spec/text-editor-component-spec.js
+++ b/spec/text-editor-component-spec.js
@@ -24,7 +24,7 @@ document.registerElement('text-editor-component-test-element', {
   })
 })
 
-describe('TextEditorComponent', () => {
+fdescribe('TextEditorComponent', () => {
   beforeEach(() => {
     jasmine.useRealClock()
 
@@ -961,6 +961,14 @@ describe('TextEditorComponent', () => {
       expect(component.getScrollLeft()).toBe(component.getScrollWidth() - component.getScrollContainerClientWidth())
     })
 
+    it('does not try to measure lines that do not exist when the animation frame is delivered', async () => {
+      const {component, editor} = buildComponent({autoHeight: false, height: 30, rowsPerTile: 2})
+      editor.scrollToBufferPosition([11, 5])
+      editor.getBuffer().deleteRows(11, 12)
+      await component.getNextUpdatePromise()
+      expect(component.getScrollBottom()).toBe((10 + 1) * component.measurements.lineHeight)
+    })
+
     it('accounts for the presence of horizontal scrollbars that appear during the same frame as the autoscroll', async () => {
       const {component, element, editor} = buildComponent({autoHeight: false})
       const {scrollContainer} = component.refs
diff --git a/src/text-editor-component.js b/src/text-editor-component.js
index 58ab2415f..bdef7130e 100644
--- a/src/text-editor-component.js
+++ b/src/text-editor-component.js
@@ -332,7 +332,7 @@ class TextEditorComponent {
     this.derivedDimensionsCache = {}
     this.updateModelSoftWrapColumn()
     if (this.pendingAutoscroll) {
-      const {screenRange, options} = this.pendingAutoscroll
+      let {screenRange, options} = this.pendingAutoscroll
       this.autoscrollVertically(screenRange, options)
       this.requestHorizontalMeasurement(screenRange.start.row, screenRange.start.column)
       this.requestHorizontalMeasurement(screenRange.end.row, screenRange.end.column)
@@ -2097,7 +2097,12 @@ class TextEditorComponent {
     if (column === 0) return
 
     if (row < this.getRenderedStartRow() || row >= this.getRenderedEndRow()) {
-      this.requestExtraLineToMeasure(row, this.props.model.screenLineForScreenRow(row))
+      const screenLine = this.props.model.screenLineForScreenRow(row)
+      if (screenLine) {
+        this.requestExtraLineToMeasure(row, screenLine)
+      } else {
+        return
+      }
     }
 
     let columns = this.horizontalPositionsToMeasure.get(row)