(core) Add rules to eslint to better match our coding conventions.

Summary:
We used tslint earlier, and on switching to eslint, some rules were not
transfered. This moves more rules over, for consistent conventions or helpful
warnings.

- Name private members with a leading underscore.
- Prefer interface over a type alias.
- Use consistent spacing around ':' in type annotations.
- Use consistent spacing around braces of code blocks.
- Use semicolons consistently at the ends of statements.
- Use braces around even one-liner blocks, like conditionals and loops.
- Warn about shadowed variables.

Test Plan: Fixed all new warnings. Should be no behavior changes in code.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D2831

app/client/ui/DocMenu.ts

@@ -245,8 +245,8 @@ function buildWorkspaceDocBlock(home: HomeModel, workspace: Workspace, flashDocI
           // The flash value may change to true, and then immediately to false. We highlight it
           // using a transition, and scroll into view, when it turns back to false.
           transition(flash, {
-            prepare(elem, val) { if (!val) { elem.style.backgroundColor = colors.slate.toString(); }},
-            run(elem, val) { if (!val) { elem.style.backgroundColor = ''; scrollIntoViewIfNeeded(elem); }},
+            prepare(elem, val) { if (!val) { elem.style.backgroundColor = colors.slate.toString(); } },
+            run(elem, val) { if (!val) { elem.style.backgroundColor = ''; scrollIntoViewIfNeeded(elem); } },
           })
         ),
         css.docRowWrapper.cls('-renaming', isRenaming),

app/client/ui/MultiSelector.ts

@@ -45,7 +45,7 @@ export abstract class MultiItemSelector<Item extends BaseItem> extends Disposabl
     return cssMultiSelectorWrapper(
       cssItemList(testId('list'),
         dom.forEach(this._incItems, item => this.buildItemDom(item)),
-        this.buildAddItemDom(this._options.addItemLabel, this._options.addItemText)
+        this._buildAddItemDom(this._options.addItemLabel, this._options.addItemText)
       ),
     );
   }
@@ -60,7 +60,7 @@ export abstract class MultiItemSelector<Item extends BaseItem> extends Disposabl
 
   // Called with an item from `_allItems`
   protected async remove(item: Item): Promise<void> {
-    const idx = this.findIncIndex(item);
+    const idx = this._findIncIndex(item);
     if (idx === -1) { return; }
     this._incItems.splice(idx, 1);
   }
@@ -70,7 +70,7 @@ export abstract class MultiItemSelector<Item extends BaseItem> extends Disposabl
 
   // Replaces an existing item (if found) with a new one
   protected async changeItem(item: Item, newItem: Item): Promise<void> {
-    const idx = this.findIncIndex(item);
+    const idx = this._findIncIndex(item);
     if (idx === -1) { return; }
     this._incItems.splice(idx, 1, newItem);
   }
@@ -82,7 +82,7 @@ export abstract class MultiItemSelector<Item extends BaseItem> extends Disposabl
                            selectCb: (newItem: Item) => void,
                            selectOptions?: {}): Element {
     const obs = computed(use => selectedValue).onWrite(async value => {
-      const newItem = this.findItemByValue(value);
+      const newItem = this._findItemByValue(value);
       if (newItem) {
         selectCb(newItem);
       }
@@ -115,17 +115,17 @@ export abstract class MultiItemSelector<Item extends BaseItem> extends Disposabl
   }
 
   // Returns the index (order) of the item if it's been included, or -1 otherwise.
-  private findIncIndex(item: Item): number {
+  private _findIncIndex(item: Item): number {
     return this._incItems.get().findIndex(_item => _item === item);
   }
 
   // Returns the item object given it's value, or undefined if not found.
-  private findItemByValue(value: string): Item | undefined {
+  private _findItemByValue(value: string): Item | undefined {
     return this._allItems.get().find(_item => _item.value === value);
   }
 
   // Builds the about-to-be-added item
-  private buildAddItemDom(defLabel: string, defText: string): Element {
+  private _buildAddItemDom(defLabel: string, defText: string): Element {
     const addNewItem: Observable<boolean> = observable(false);
     return dom('li', testId('add-item'),
       dom.domComputed(addNewItem, isAdding => isAdding

app/client/ui/PageWidgetPicker.ts

@@ -196,7 +196,7 @@ export function buildPageWidgetPicker(
     dom.create(PageWidgetSelect, value, tables, columns, onSaveCB, options),
 
     // gives focus and binds keydown events
-    (elem: any) => {setTimeout(() => elem.focus(), 0); },
+    (elem: any) => { setTimeout(() => elem.focus(), 0); },
     onKeyDown({
       Escape: () => ctl.close(),
       Enter: () => isValid() && onSaveCB()