vscode-extension-samples/notebook-serializer-sample/src/serializer.ts

import * as vscode from 'vscode';
import { TextDecoder, TextEncoder } from 'util';

/**
 * An ultra-minimal sample provider that lets the user type in JSON, and then
 * outputs JSON cells. The outputs are transient and not saved to notebook file on disk.
 */

interface RawNotebookData {
	cells: RawNotebookCell[]
}

interface RawNotebookCell {
	language: string;
	value: string;
	kind: vscode.NotebookCellKind;
	editable?: boolean;
}

export class SampleContentSerializer implements vscode.NotebookSerializer {
	public readonly label: string = 'My Sample Content Serializer';

	public async deserializeNotebook(data: Uint8Array, _token: vscode.CancellationToken): Promise<vscode.NotebookData> {
		const contents = new TextDecoder().decode(data); // convert to String

		// Read file contents
		let raw: RawNotebookData;
		try {
			raw = JSON.parse(contents);
		} catch {
			raw = { cells: [] };
		}

		// Create array of Notebook cells for the VS Code API from file contents
		const cells = raw.cells.map(item => new vscode.NotebookCellData(
			item.kind,
			item.value,
			item.language
		));

		return new vscode.NotebookData(cells);
	}

	public async serializeNotebook(data: vscode.NotebookData, _token: vscode.CancellationToken): Promise<Uint8Array> {
		// Map the Notebook data into the format we want to save the Notebook data as
		const contents: RawNotebookData = { cells: [] };

		for (const cell of data.cells) {
			contents.cells.push({
				kind: cell.kind,
				language: cell.languageId,
				value: cell.value
			});
		}

		return new TextEncoder().encode(JSON.stringify(contents));
	}
}