fix(client): some editor edge cases (#43256)

* fix: handle erm on line zero

* refactor: fix eslint errors

* fix: prevent crash on zero height editable region

client/src/templates/Challenges/classic/editor.tsx

@@ -335,7 +335,7 @@ const Editor = (props: EditorProps): JSX.Element => {
       null,
       () => {}
     );
-    /* eslint-disable */
+    /* eslint-enable */
     editor.addAction({
       id: 'execute-challenge',
       label: 'Run tests',
@@ -365,11 +365,11 @@ const Editor = (props: EditorProps): JSX.Element => {
       keybindings: [monaco.KeyMod.CtrlCmd | monaco.KeyCode.KEY_E],
       run: () => {
         const currentAccessibility = storedAccessibilityMode();
-        
+
         store.set('accessibilityMode', !currentAccessibility);
 
         editor.updateOptions({
-          accessibilitySupport: storedAccessibilityMode() ? 'on' : 'auto',
+          accessibilitySupport: storedAccessibilityMode() ? 'on' : 'auto'
         });
       }
     });
@@ -733,7 +733,6 @@ const Editor = (props: EditorProps): JSX.Element => {
 
   // TODO: TESTS!
   // Make 100% sure this is inclusive.
-  // TODO: pass around monacoRef.current instead of using the global one?
   const getLinesBetweenRanges = (
     firstRange: RangeType,
     secondRange: RangeType
@@ -768,14 +767,17 @@ const Editor = (props: EditorProps): JSX.Element => {
       // editor
       const secondRange = model.getDecorationRange(endEditDecId);
       if (firstRange && secondRange) {
-        const { startLineNumber, endLineNumber } = getLinesBetweenRanges(
+        const editableRegion = getLinesBetweenRanges(firstRange, secondRange);
-          firstRange,
+        const startLineNumber = editableRegion.startLineNumber;
-          secondRange
+
-        );
+        let endLineNumber = editableRegion.endLineNumber;
+
+        // TODO: this prevents the editor from crashing, but it's still possible
+        // for the editable region to become empty and for the editable
+        // decorations to get out of sync with the jaw locations.
+        endLineNumber = Math.max(endLineNumber, startLineNumber + 1);
+        endLineNumber = Math.min(endLineNumber, model.getLineCount());
 
-        // getValueInRange includes column x if
-        // startColumnNumber <= x < endColumnNumber
-        // so we add 1 here
         const endColumn = model.getLineLength(endLineNumber) + 1;
         return new monaco.Range(startLineNumber, 1, endLineNumber, endColumn);
       }
@@ -796,15 +798,11 @@ const Editor = (props: EditorProps): JSX.Element => {
     const { model } = data;
     const monaco = monacoRef.current;
     if (!model || !monaco) return;
-    const forbiddenRanges: [number, number][] = [
+    const forbiddenRegions: [number, number][] = [
       [0, editableRegion[0]],
       [editableRegion[1], model.getLineCount()]
     ];
 
-    const ranges = forbiddenRanges.map(positions => {
-      return positionsToRange(model, monaco, positions);
-    });
-
     const editableRange = positionsToRange(model, monaco, [
       editableRegion[0] + 1,
       editableRegion[1] - 1
@@ -818,34 +816,40 @@ const Editor = (props: EditorProps): JSX.Element => {
 
     // if the forbidden range includes the top of the editor
     // we simply don't add those decorations
-    if (forbiddenRanges[0][1] > 0) {
+    if (forbiddenRegions[0][1] > 0) {
+      const forbiddenRange = positionsToRange(
+        model,
+        monaco,
+        forbiddenRegions[0]
+      );
       // the first range should expand at the top
       // TODO: Unsure what this should be - returns an array, so I added [0] @ojeytonwilliams
       data.startEditDecId = highlightLines(
         monaco.editor.TrackedRangeStickiness.GrowsOnlyWhenTypingBefore,
         model,
-        ranges[0]
+        forbiddenRange
       )[0];
 
       highlightText(
         monaco.editor.TrackedRangeStickiness.GrowsOnlyWhenTypingBefore,
         model,
-        ranges[0]
+        forbiddenRange
       );
     }
 
+    const forbiddenRange = positionsToRange(model, monaco, forbiddenRegions[1]);
     // TODO: handle the case the region covers the bottom of the editor
     // the second range should expand at the bottom
     data.endEditDecId = highlightLines(
       monaco.editor.TrackedRangeStickiness.GrowsOnlyWhenTypingAfter,
       model,
-      ranges[1]
+      forbiddenRange
     )[0];
 
     highlightText(
       monaco.editor.TrackedRangeStickiness.GrowsOnlyWhenTypingAfter,
       model,
-      ranges[1]
+      forbiddenRange
     );
 
     // The deleted line is always considered to be the one that has moved up.
@@ -875,9 +879,7 @@ const Editor = (props: EditorProps): JSX.Element => {
       // edit, then a warned one.  Could it track that they need to make 3
       // undos?
       const newLineRanges = getNewLineRanges(e).map(range => {
-        if (monaco) {
+        return toStartOfLine(monaco.Range.lift(range));
-          return toStartOfLine(monaco.Range.lift(range));
-        }
       });
       const deletedLine = getDeletedLine(e);