feat: added tests/typescript to test supported TS examples (#6775)

* feat: added `tests/typescript` to test supported TS examples

* fix: update the test name, description, and output

* chore: remove unused imports in `test_tasks.js`

* fix: wrap README line at 80 characters

* fix: implemented `different_user_input.ts` feedback

* fix: correct mistaken comments

* chore: rename `./eslintrc.json` to `./eslintrc.js`

* feat: added linting for tests/typescript

* chore: cleanup eslintrc lines over 80 characters

* fix: updated `.eslintrc.js` to provide an override for linting itself

* fix: updated tests to build to the `build` directory

* feat: updated `gulp format` to handle formatting `.eslintrc.js`

* fix: updated `.eslintrc.js` to align with both formatter and linter

* fix: updated config comment wording

* fix: removed quotes for valid identifiers

* Revert "fix: removed quotes for valid identifiers"

  This reverts commit 03eff91aea1468e503bc79a90fb139914d3f39d2.

tests/typescript/README.md

@@ -0,0 +1,4 @@
+# TypeScript Tests
+
+Tests pass if all files here compile. Add Blockly use case examples we'd like
+to support, such as subclasses which extend from Blockly classes.

tests/typescript/src/field/different_user_input.ts

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+/**
+ * @license
+ * Copyright 2022 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+/**
+ * Test: Should allow a subclass of Field to have different setValue and
+ * constructor input type than the type that is stored.
+ */
+
+
+import {Field, FieldValidator, fieldRegistry} from 'blockly-test/core';
+
+interface Cell {
+    cellId: string;
+}
+
+interface CellGroup {
+    cells: Cell[];
+}
+
+type FieldMitosisValidator = FieldValidator<CellGroup>;
+
+class FieldMitosis extends Field<CellGroup> {
+    constructor(cell: Cell, validator: FieldMitosisValidator) {
+        super(Field.SKIP_SETUP);
+
+        this.setValue(cell);
+        this.setValidator(validator);
+    }
+
+    // Overwritten Field methods.
+
+    protected doClassValidation_(newCell?: unknown): CellGroup | null {
+        if (!this.isCell(newCell)) return null;
+
+        const cellGroup = this.getValue() ?? {cells: []};
+        cellGroup.cells.push(newCell);
+        return cellGroup;
+    }
+
+    // Example-specific methods.
+
+    private isCell(maybeCell: unknown): maybeCell is Cell {
+        if (!maybeCell) return false;
+        const couldBeCell = maybeCell as { [key: string]: unknown };
+        return 'cellId' in couldBeCell && typeof couldBeCell.cellId === 'string';
+    }
+
+    /**
+     * The cell divides, creating two new cells!
+     */
+    doMitosis(): void {
+        const cellGroup = this.getValue();
+        if (!cellGroup) return;
+    
+        const cells = cellGroup.cells.flatMap((cell) => {
+            const leftCell: Cell = {cellId: `${cell.cellId}-left`};
+            const rightCell: Cell = {cellId: `${cell.cellId}-right`};
+            return [leftCell, rightCell];
+        });
+        this.value_ = {cells};
+    }
+}
+
+fieldRegistry.register('field_mitosis', FieldMitosis);
+
+// Example use of the class.
+
+function cellValidator(cellGroup: CellGroup): CellGroup | undefined {
+    // The cell group is good! Use it as is.
+    if (cellGroup.cells.length > 0) return undefined;
+
+    // Uh oh! No cells.
+    const emergencyCell: Cell = {cellId: 'emergency-cell'};
+    return {cells: [emergencyCell]};
+}
+
+const cellField = new FieldMitosis({cellId: 'cell-A'}, cellValidator);
+cellField.setValue({cellId: 'cell-B'});
+cellField.doMitosis();

tests/typescript/tsconfig.json

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+{
+  "include": [
+    "src/**/*",
+  ],
+  "compilerOptions": {
+    "allowJs": false,
+    "outDir": "dist",
+    "baseUrl": ".",
+    "paths": {
+      "blockly-test/*": ["../../dist/*"],
+    },
+
+    "declaration": false,
+    "declarationMap": false,
+    "sourceMap": false,
+
+    "module": "ES2015",
+    "moduleResolution": "node",
+    "target": "ES2020",
+    "strict": true,
+  }
+}