‘Hide’ jupyter widget metadata

When we round trip jupyter metadata through YAML, it gets pretty badly mutated. Instead, we just encode it and restore it.

Author: dragonstyle

src/core/jupyter/jupyter.ts

@@ -149,6 +149,7 @@ import { pathWithForwardSlashes } from "../path.ts";
 import { convertToHtmlSpans, hasAnsiEscapeCodes } from "../ansi-colors.ts";
 import { ProjectContext } from "../../project/types.ts";
 import { mergeConfigs } from "../config.ts";
+import { encode as encodeBase64 } from "encoding/base64.ts";
 
 export const kJupyterNotebookExtensions = [
   ".ipynb",
@@ -687,9 +688,17 @@ export async function jupyterToMarkdown(
   if (options.toIpynb) {
     const md: string[] = [];
     md.push("---\n");
+
+    // If widgets are present, base64 encode their metadata to prevent true round
+    // tripping through YAML, which heavily mutates the metadata
+    const widgets = nb.metadata.widgets
+      ? encodeBase64(JSON.stringify(nb.metadata.widgets))
+      : undefined;
+
     const jupyterMetadata = {
       jupyter: {
         ...nb.metadata,
+        widgets,
       },
     };
     const yamlText = stringify(jupyterMetadata, {

src/format/ipynb/format-ipynb.ts

@@ -24,6 +24,7 @@ import {
 import { formatResourcePath } from "../../core/resources.ts";
 import { createFormat } from "../formats-shared.ts";
 
+import { decode as base64decode } from "encoding/base64.ts";
 export function ipynbFormat(): Format {
   return createFormat("ipynb", {
     pandoc: {
@@ -69,6 +70,16 @@ export function ipynbFormat(): Format {
           // read notebook
           const nb = jupyterFromFile(output);
 
+          // We 'hide' widget metafrom the YAML by encoding it to
+          // prevent the YAML representation from mangling it. Restore
+          // it here if it is so hidden
+          const widgets = nb.metadata.widgets;
+          if (widgets && typeof (widgets) === "string") {
+            nb.metadata.widgets = JSON.parse(
+              new TextDecoder().decode(base64decode(widgets)),
+            );
+          }
+
           // convert raw cell metadata format to raw_mimetype used by jupyter
           nb.cells = nb.cells.map((cell) => {
             if (cell.cell_type == "raw") {