(core) Speed up and upgrade build.

Summary:
- Upgrades to build-related packages:
  - Upgrade typescript, related libraries and typings.
  - Upgrade webpack, eslint; add tsc-watch, node-dev, eslint_d.

- Build organization changes:
  - Build webpack from original typescript, transpiling only; with errors still
    reported by a background tsc watching process.

- Typescript-related changes:
  - Reduce imports of AWS dependencies (very noticeable speedup)
  - Avoid auto-loading global @types
  - Client code is now built with isolatedModules flag (for safe transpilation)
  - Use allowJs to avoid copying JS files manually.

- Linting changes
  - Enhance Arcanist ESLintLinter to run before/after commands, and set up to use eslint_d
  - Update eslint config, and include .eslintignore to avoid linting generated files.
  - Include a bunch of eslint-prompted and eslint-generated fixes
  - Add no-unused-expression rule to eslint, and fix a few warnings about it

- Other items:
  - Refactor cssInput to avoid circular dependency
  - Remove a bit of unused code, libraries, dependencies

Test Plan: No behavior changes, all existing tests pass. There are 30 tests fewer reported because `test_gpath.py` was removed (it's been unused for years)

Reviewers: paulfitz

Reviewed By: paulfitz

Subscribers: paulfitz

Differential Revision: https://phab.getgrist.com/D3498

app/client/models/DataRowModel.ts

@@ -21,13 +21,12 @@ export class DataRowModel extends BaseRowModel {
   public _validationFailures: ko.PureComputed<Array<IRowModel<'_grist_Validations'>>>;
   public _isAddRow: ko.Observable<boolean>;
 
-  private _allValidationsList: ko.Computed<KoArray<ValidationRec>>;
   private _isRealChange: ko.Observable<boolean>;
 
   public constructor(dataTableModel: DataTableModel, colNames: string[]) {
     super(dataTableModel, colNames);
 
-    this._allValidationsList = dataTableModel.tableMetaRow.validations;
+    const allValidationsList: ko.Computed<KoArray<ValidationRec>> = dataTableModel.tableMetaRow.validations;
 
     this._isAddRow = ko.observable(false);
 
@@ -36,10 +35,10 @@ export class DataRowModel extends BaseRowModel {
     // changes, those should only be enabled when _isRealChange is true.
     this._isRealChange = ko.observable(true);
 
-    this._validationFailures = this.autoDispose(ko.pureComputed(function() {
-      return this._allValidationsList().all().filter(
+    this._validationFailures = this.autoDispose(ko.pureComputed(() => {
+      return allValidationsList().all().filter(
         validation => !this.cells[this.getValidationNameFromId(validation.id())]());
-    }, this));
+    }));
   }
 
   /**

app/client/models/DocModel.ts

@@ -41,16 +41,8 @@ import {decodeObject} from 'app/plugin/objtypes';
 
 // Re-export all the entity types available. The recommended usage is like this:
 //    import {ColumnRec, ViewFieldRec} from 'app/client/models/DocModel';
-export {ColumnRec} from 'app/client/models/entities/ColumnRec';
-export {DocInfoRec} from 'app/client/models/entities/DocInfoRec';
-export {FilterRec} from 'app/client/models/entities/FilterRec';
-export {PageRec} from 'app/client/models/entities/PageRec';
-export {TabBarRec} from 'app/client/models/entities/TabBarRec';
-export {TableRec} from 'app/client/models/entities/TableRec';
-export {ValidationRec} from 'app/client/models/entities/ValidationRec';
-export {ViewFieldRec} from 'app/client/models/entities/ViewFieldRec';
-export {ViewRec} from 'app/client/models/entities/ViewRec';
-export {ViewSectionRec} from 'app/client/models/entities/ViewSectionRec';
+export type {ColumnRec, DocInfoRec, FilterRec, PageRec, TabBarRec, TableRec, ValidationRec,
+    ViewFieldRec, ViewRec, ViewSectionRec};
 
 
 /**

app/client/models/SectionFilter.ts

@@ -6,7 +6,7 @@ import {buildColFilter, ColumnFilterFunc} from 'app/common/ColumnFilterFunc';
 import {buildRowFilter, RowFilterFunc, RowValueFunc } from 'app/common/RowFilterFunc';
 import {Computed, Disposable, MutableObsArray, obsArray, Observable, UseCB} from 'grainjs';
 
-export {ColumnFilterFunc} from 'app/common/ColumnFilterFunc';
+export type {ColumnFilterFunc};
 
 interface OpenColumnFilter {
   colRef: number;

app/client/models/entities/ViewSectionRec.ts

@@ -306,7 +306,7 @@ export function createViewSectionRec(this: ViewSectionRec, docModel: DocModel):
   // in which case the UI prevents various things like hiding columns or changing the widget type.
   this.isRaw = this.autoDispose(ko.pureComputed(() => this.table().rawViewSectionRef() === this.getRowId()));
 
-  this.borderWidthPx = ko.pureComputed(function() { return this.borderWidth() + 'px'; }, this);
+  this.borderWidthPx = ko.pureComputed(() => this.borderWidth() + 'px');
 
   this.layoutSpecObj = modelUtil.jsonObservable(this.layoutSpec);
 
@@ -487,7 +487,7 @@ export function createViewSectionRec(this: ViewSectionRec, docModel: DocModel):
   this.linkSrcCol = refRecord(docModel.columns, this.activeLinkSrcColRef);
   this.linkTargetCol = refRecord(docModel.columns, this.activeLinkTargetColRef);
 
-  this.activeRowId = ko.observable(null);
+  this.activeRowId = ko.observable<RowId|null>(null);
 
   this._linkingState = Holder.create(this);
   this.linkingState = this.autoDispose(ko.pureComputed(() => {
@@ -506,7 +506,7 @@ export function createViewSectionRec(this: ViewSectionRec, docModel: DocModel):
   }));
 
   // If the view instance for this section is instantiated, it will be accessible here.
-  this.viewInstance = ko.observable(null);
+  this.viewInstance = ko.observable<BaseView|null>(null);
 
   // Describes the most recent cursor position in the section.
   this.lastCursorPos = {
@@ -542,8 +542,8 @@ export function createViewSectionRec(this: ViewSectionRec, docModel: DocModel):
   );
 
   this.hasCustomOptions = ko.observable(false);
-  this.desiredAccessLevel = ko.observable(null);
-  this.columnsToMap = ko.observable(null);
+  this.desiredAccessLevel = ko.observable<AccessLevel|null>(null);
+  this.columnsToMap = ko.observable<ColumnsToMap|null>(null);
   // Calculate mapped columns for Custom Widget.
   this.mappedColumns = ko.pureComputed(() => {
     // First check if widget has requested a custom column mapping and