(core) Fix JS error when scrolling with a column of hyperlinks, and use stricter types.

Summary:
When scrolling quicly through a column with hyperlinks, null could be passed to
a function that didn't expect it. Added better types would help catch it.

Test Plan: Tested manually

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2813

app/client/models/DataRowModel.ts

@@ -5,7 +5,7 @@ import * as DataTableModel from 'app/client/models/DataTableModel';
 import { IRowModel } from 'app/client/models/DocModel';
 import { ValidationRec } from 'app/client/models/entities/ValidationRec';
 import * as modelUtil from 'app/client/models/modelUtil';
-import { ColValues } from 'app/common/DocActions';
+import { CellValue, ColValues } from 'app/common/DocActions';
 import * as ko from 'knockout';
 
 /**
@@ -16,7 +16,7 @@ export class DataRowModel extends BaseRowModel {
   // Instances of this class are indexable, but that is a little awkward to type.
   // The cells field gives typed access to that aspect of the instance.  This is a
   // bit hacky, and should be cleaned up when BaseRowModel is ported to typescript.
-  public readonly cells: {[key: string]: modelUtil.KoSaveableObservable<any>} = this as any;
+  public readonly cells: {[key: string]: modelUtil.KoSaveableObservable<CellValue>} = this as any;
 
   public _validationFailures: ko.PureComputed<Array<IRowModel<'_grist_Validations'>>>;
   public _isAddRow: ko.Observable<boolean>;

app/client/widgets/ChoiceListCell.ts

@@ -1,6 +1,7 @@
 import {DataRowModel} from 'app/client/models/DataRowModel';
 import {colors} from 'app/client/ui2018/cssVars';
 import {ChoiceTextBox} from 'app/client/widgets/ChoiceTextBox';
+import {CellValue} from 'app/common/DocActions';
 import {decodeObject} from 'app/plugin/objtypes';
 import {Computed, dom, styled} from 'grainjs';
 
@@ -17,7 +18,9 @@ export class ChoiceListCell extends ChoiceTextBox {
       dom.cls('field_clip'),
       cssChoiceList.cls('-wrap', this.wrapping),
       dom.style('justify-content', this.alignment),
-      dom.domComputed((use) => use(row._isAddRow) ? null : [use(value), use(this._choiceSet)], (input) => {
+      dom.domComputed((use) => {
+        return use(row._isAddRow) ? null : [use(value), use(this._choiceSet)] as [CellValue, Set<string>];
+      }, (input) => {
         if (!input) { return null; }
         const [rawValue, choiceSet] = input;
         const val = decodeObject(rawValue);
@@ -27,7 +30,7 @@ export class ChoiceListCell extends ChoiceTextBox {
         return tokens.map(token =>
           cssToken(
             String(token),
-            cssInvalidToken.cls('-invalid', !choiceSet.has(token))
+            cssInvalidToken.cls('-invalid', !choiceSet.has(token as string))
           )
         );
       }),

app/client/widgets/HyperLinkTextBox.ts

@@ -1,3 +1,4 @@
+import {CellValue} from 'app/common/DocActions';
 import {DataRowModel} from 'app/client/models/DataRowModel';
 import {ViewFieldRec} from 'app/client/models/entities/ViewFieldRec';
 import {colors, testId} from 'app/client/ui2018/cssVars';
@@ -20,7 +21,7 @@ export class HyperLinkTextBox extends NTextBox {
     return cssFieldClip(
       dom.style('text-align', this.alignment),
       dom.cls('text_wrapping', this.wrapping),
-      dom.maybe(value, () =>
+      dom.maybe((use) => Boolean(use(value)), () =>
         dom('a',
           dom.attr('href', (use) => _constructUrl(use(value))),
           dom.attr('target', '_blank'),
@@ -40,7 +41,7 @@ export class HyperLinkTextBox extends NTextBox {
 /**
  * Formats value like `foo bar baz` by discarding `baz` and returning `foo bar`.
  */
-function _formatValue(value: string|null|undefined): string {
+function _formatValue(value: CellValue): string {
   if (typeof value !== 'string') { return ''; }
   const index = value.lastIndexOf(' ');
   return index >= 0 ? value.slice(0, index) : value;
@@ -50,7 +51,8 @@ function _formatValue(value: string|null|undefined): string {
  * Given value like `foo bar baz`, constructs URL by checking if `baz` is a valid URL and,
  * if not, prepending `http://`.
  */
-function _constructUrl(value: string): string {
+function _constructUrl(value: CellValue): string {
+  if (typeof value !== 'string') { return ''; }
   const url = value.slice(value.lastIndexOf(' ') + 1);
   try {
     // Try to construct a valid URL