fix(ofm): support nested markdown in highlights #2223

kiycoh · 2025-11-25T00:22:01Z

Problem: Previous implementation relied on a regex ==([^=]+)== which attempted to match the highlight within a single text node. This logic fails when the highlighted content contains other Markdown elements (like bold, [[links]], or italics).

Why? When Markdown is nested, the parser splits the content into multiple nodes (e.g., Text Node + Strong Node + Text Node), causing the regex to miss the closing delimiter if it resides in a different node than the opening one.

Solution: I have refactored ofm.ts to move away from regex-based matching on raw text strings to an AST (Abstract Syntax Tree) manipulation approach.

Key changes

AST Traversal: Instead of matching strings, the logic now scans the syntax tree.
Two-Phase Logic (Unified):
- Marking: Identifies == tokens and replaces them with temporary markers, handling text node splits correctly.
- Grouping: Scans children nodes to find marker pairs. It collects all content between the opening and closing markers (including nested HTML/Markdown nodes) and wraps them in the tag.
Complexity: The iteration over children nodes is now done in reverse. This simplifies the logic by preventing index shifting issues when nodes are replaced or modified during the loop, no while loop management. All tests are ok and linted with Prettier.

Before & After

Sample text:

==L'**Ingegneria del software** è una disciplina ingegneristica [[Informatica]] che caratterizza l'intero processo di produzione di un *[[software]]*==

Before:

After:

* Replace regex with AST manipulation to handle split text nodes * Implement marking and grouping logic to wrap mixed content. * Unify plugins

github-actions · 2025-11-25T00:23:07Z

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Name	Status	Preview	Last Commit
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Copilot

Pull request overview

This PR refactors the Obsidian Flavored Markdown highlight feature (==text==) to support nested markdown elements like bold, italics, and wikilinks within highlights. The previous regex-based approach failed when highlighted content was split across multiple AST nodes due to nested markdown syntax.

Key Changes

Changed from regex text matching (==([^=]+)==) to AST-based token replacement and traversal
Implemented a two-phase approach: marking == tokens as temporary nodes, then grouping content between marker pairs
Processes marker pairs in reverse order to avoid index-shifting issues during node replacement

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quartz/plugins/transformers/ofm.ts

Copilot · 2025-11-29T18:35:44Z

quartz/plugins/transformers/ofm.ts

+        plugins.push(() => {
+          return (tree: Root) => {
+            mdastFindReplace(tree, [
+              [highlightRegex, (_value: string) => ({ type: "highlightMarker" }) as any],


The as any type assertion bypasses TypeScript's type safety. Consider defining a proper interface for the custom highlightMarker node type to maintain type safety throughout the transformation pipeline.

interface HighlightMarker { type: "highlightMarker" } // Then use: [highlightRegex, (_value: string): HighlightMarker => ({ type: "highlightMarker" })]

Suggested change

[highlightRegex, (_value: string) => ({ type: "highlightMarker" }) as any],

[highlightRegex, (_value: string): HighlightMarker => ({ type: "highlightMarker" })],

Copilot · 2025-11-29T18:35:45Z

quartz/plugins/transformers/ofm.ts

+
+            visit(tree, (node) => {
+              if (!("children" in node)) return
+              const children = (node as any).children as any[]


Multiple as any type assertions are used here to bypass TypeScript's type checking. Consider properly typing the node types:

import { Parent } from 'mdast' // In the visit callback: if (!('children' in node)) return const parent = node as Parent const children = parent.children

Suggested change

const children = (node as any).children as any[]

const children = (node as Parent).children

Copilot · 2025-11-29T18:35:45Z

quartz/plugins/transformers/ofm.ts

+                const htmlContent = content
+                  .map((n) => {
+                    const hast = toHast(n, { allowDangerousHtml: true })
+                    return toHtml(hast as any, { allowDangerousHtml: true })


Another as any type assertion. The toHtml function returns a string, so this cast is unnecessary. Consider removing it for better type safety.

Suggested change

return toHtml(hast as any, { allowDangerousHtml: true })

return toHtml(hast, { allowDangerousHtml: true })

Copilot · 2025-11-29T18:35:45Z

quartz/plugins/transformers/ofm.ts

+              }
+
+              if (markers.length < 2) return
+


When there's an odd number of == markers, the last unpaired marker will be silently ignored. Consider adding a warning or handling this case explicitly to help users identify unclosed highlight markers in their content. For example:

if (markers.length < 2) return // Check for odd number of markers if (markers.length % 2 !== 0) { // Option 1: Log a warning console.warn(`Unpaired highlight marker found in content`) // Option 2: Remove the last unpaired marker children.splice(markers[markers.length - 1], 1) }

Suggested change

// Check for odd number of markers

if (markers.length % 2 !== 0) {

console.warn("Unpaired highlight marker found in content");

// Remove the last unpaired marker

children.splice(markers[markers.length - 1], 1);

// Remove the last marker from the list

markers.pop();

}

Copilot · 2025-11-29T18:35:45Z

quartz/plugins/transformers/ofm.ts

+            visit(tree, (node) => {
+              if (!("children" in node)) return
+              const children = (node as any).children as any[]
+
+              const markers: number[] = []


[nitpick] Consider adding an early return if there are no markers at all to avoid unnecessary processing:

visit(tree, (node) => { if (!("children" in node)) return const children = (node as any).children as any[] // Early return if no children if (!children || children.length === 0) return const markers: number[] = [] for (let i = 0; i < children.length; i++) { if (children[i].type === "highlightMarker") { markers.push(i) } } if (markers.length < 2) return // ... })

comment fix Co-authored-by: Copilot <[email protected]>

kiycoh

Type Safety Improvements
Safer Node Handling

Copilot

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

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Copilot · 2026-01-03T21:59:53Z

quartz/plugins/transformers/ofm.ts

+              for (let i = 0; i < markers.length - 1; i += 2) {
+                pairs.push([markers[i], markers[i + 1]])
+              }
+


When there is an odd number of highlight markers (e.g., ==text1== some text ==text2), the last unpaired marker remains in the AST as a highlightMarker node. This could cause rendering issues or appear as unexpected content in the output.

Consider adding logic to handle odd markers, such as:

Removing unpaired markers after processing pairs

Converting unpaired markers back to their original == text

Logging a warning about malformed highlight syntax

This would make the behavior more robust and predictable when users have malformed markup.

Suggested change

if (markers.length % 2 === 1) {

const lastMarkerIndex = markers[markers.length - 1]

// Convert the unpaired marker back into its literal representation

children[lastMarkerIndex] = { type: "text", value: "==" } as any

}

Copilot · 2026-01-03T21:59:54Z

quartz/plugins/transformers/ofm.ts

+            visit(tree, (node) => {
+              if (!("children" in node)) return
+              const parent = node as Parent
+              const children = parent.children
+              if (children.length === 0) return
+
+              const markers: number[] = []
+              for (let i = 0; i < children.length; i++) {
+                if (isHighlightMarker(children[i])) {
+                  markers.push(i)
+                }
+              }
+
+              if (markers.length < 2) return
+
+              const pairs: [number, number][] = []
+              for (let i = 0; i < markers.length - 1; i += 2) {
+                pairs.push([markers[i], markers[i + 1]])
+              }
+
+              for (let i = pairs.length - 1; i >= 0; i--) {
+                const [start, end] = pairs[i]
+                const content = children.slice(start + 1, end)
+                const htmlContent = content
+                  .map((n) => {
+                    const hast = toHast(n, { allowDangerousHtml: true })
+                    return hast ? toHtml(hast, { allowDangerousHtml: true }) : ""
+                  })
+                  .join("")
+
+                const newNode: Html = {
+                  type: "html",
+                  value: `<span class="text-highlight">${htmlContent}</span>`,
+                }
+
+                children.splice(start, end - start + 1, newNode)
+              }
+            })


The current implementation only matches highlight markers within a single parent node's immediate children. If a highlight spans across different structural boundaries (e.g., across list items or block quotes), the opening and closing markers won't be paired, leaving unpaired markers in the output.

While this may be acceptable for typical use cases (highlights within paragraphs), it's worth noting this limitation. Consider adding a comment explaining that highlights must be contained within a single parent node, or alternatively, implement a more sophisticated cross-boundary matching algorithm if this is a common use case.

aarnphm · 2026-01-13T17:33:01Z

Going to close this PR, because the proper fix is to implement micromark extensions for all of obsidian features, i.e marker, wikilinks, tags, recursive callout, etc.

but feel free to use this in your own repo (calling toHast and toHtml is considered antipattern within a mdast->hast pipeline afaik and from experience)

fix(ofm): support nested markdown in highlights

fbfaabd

* Replace regex with AST manipulation to handle split text nodes * Implement marking and grouping logic to wrap mixed content. * Unify plugins

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cervoliu approved these changes Dec 10, 2025

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Merge branch 'jackyzha0:v4' into fix/highlight-parsing-logic

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Update quartz/plugins/transformers/ofm.ts

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comment fix Co-authored-by: Copilot <[email protected]>

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Merge branch 'jackyzha0:v4' into fix/highlight-parsing-logic

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feat: new marker interface for highlight parsing logic and validation

23d2cfb

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kiycoh commented Dec 26, 2025

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aarnphm closed this Jan 13, 2026

	[highlightRegex, (_value: string) => ({ type: "highlightMarker" }) as any],
	[highlightRegex, (_value: string): HighlightMarker => ({ type: "highlightMarker" })],

	const children = (node as any).children as any[]
	const children = (node as Parent).children

	return toHtml(hast as any, { allowDangerousHtml: true })
	return toHtml(hast, { allowDangerousHtml: true })

+              // Check for odd number of markers
+              if (markers.length % 2 !== 0) {
+                console.warn("Unpaired highlight marker found in content");
+                // Remove the last unpaired marker
+                children.splice(markers[markers.length - 1], 1);
+                // Remove the last marker from the list
+                markers.pop();
+              }

+              if (markers.length % 2 === 1) {
+                const lastMarkerIndex = markers[markers.length - 1]
+                // Convert the unpaired marker back into its literal representation
+                children[lastMarkerIndex] = { type: "text", value: "==" } as any
+              }

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fix(ofm): support nested markdown in highlights #2223

fix(ofm): support nested markdown in highlights #2223

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kiycoh commented Nov 25, 2025 •

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