fixup columns html to use flex (work around pandoc 2.19 regression)

Author: jjallaire

src/format/html/format-html-shared.ts

@@ -27,6 +27,8 @@ import {
 
 import { formatResourcePath } from "../../core/resources.ts";
 import { Document, Element } from "../../core/deno-dom.ts";
+import { HtmlPostProcessResult } from "../../command/render/types.ts";
+import { kHtmlEmptyPostProcessResult } from "../../command/render/constants.ts";
 
 // features that are enabled by default for 'html'. setting
 // all of these to false will yield the minimal html output
@@ -320,6 +322,25 @@ export function insertTitle(
   prependHeading(doc, el, title, level, headingClasses);
 }
 
+export function columnsPostprocessor(
+  doc: Document,
+): Promise<HtmlPostProcessResult> {
+  const columns = doc.querySelectorAll("div.columns div.column");
+  for (const column of columns) {
+    const columnEl = column as Element;
+    const style = columnEl.getAttribute("style");
+    if (style) {
+      columnEl.setAttribute(
+        "style",
+        style.replace(/width:(\d+)%/, (_m: string, pct: string) => {
+          return `flex:0.${pct}`;
+        }),
+      );
+    }
+  }
+  return Promise.resolve(kHtmlEmptyPostProcessResult);
+}
+
 function prependHeading(
   doc: Document,
   el: Element,

src/format/html/format-html.ts

@@ -56,6 +56,7 @@ import { boostrapExtras } from "./format-html-bootstrap.ts";
 
 import {
   clipboardDependency,
+  columnsPostprocessor,
   createCodeCopyButton,
   kAnchorSections,
   kBootstrapDependencyName,
@@ -525,6 +526,7 @@ export async function htmlFormatExtras(
       [kHtmlPostprocessors]: [
         htmlFormatPostprocessor(format, featureDefaults),
         metadataPostProcessor(input, format, offset),
+        columnsPostprocessor,
       ],
     },
   };