bug: Marked treats tabs and spaces differently in lists

[akilesh1706]

Marked version: 11.0.0 (bug reported against 11.0.0). Fix implemented on master.

Markdown flavor: CommonMark / GitHub Flavored Markdown (GFM)

Description

When a list item used a tab after the list marker (e.g. 1.\tText or -\tText), and there was preceding text (a paragraph) before the list, the tokenizer sometimes treated the item content as an indented code block (leading four spaces) instead of normal list content. This produced

...

inside

for the tab-using list, while the same list using spaces produced normal

Text

.

This PR fixes that inconsistency so tabs after the marker are interpreted the same as spaces regardless of text preceding the list.

Fixes the inconsistent tab handling in list items that could make tabbed list items render as indented code blocks. Files changed (key):

Expectation Given input (tabs or spaces after marker):

I am using spaces after the number:

Some Text Some Text Some Text I am using tabs after the number: 1. Some Text 2. Some Text 3. Some Text

Expected HTML (both cases):

(And similar for unordered lists)

Result (before this PR)

Lists that used tabs after the marker were sometimes parsed as indented code blocks and rendered as:

1. Some Text 

...

while the same lists using spaces were parsed/rendered correctly as simple

Some Text

.

What was attempted / what this PR does

Normalizes the first line of a list item by replacing tabs with the same tab normalization used elsewhere in the codebase (tabs -> 4 spaces), then computes indent and slices content from the normalized string so the slice length is correct when tabs are used. Ensures indent detection replaces tabs with spaces consistently when finding the first non-space character. Adds tests to cover: ordered lists using spaces vs tabs, ordered lists that follow a paragraph (the reported scenario), unordered lists using spaces vs tabs.

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Summary of Changes

Hello @akilesh1706, I'm Gemini Code Assist[^1]! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a parsing inconsistency in the Marked library where list items using tabs after their markers were sometimes misinterpreted as indented code blocks, particularly when following a paragraph. The changes normalize tab characters to spaces during the initial processing of list item lines and refine indent calculation, ensuring that Marked consistently renders list items whether tabs or spaces are used after the marker. This improves the robustness and predictability of markdown rendering.

Highlights

• Inconsistent List Parsing: Fixed a bug where Marked inconsistently parsed list items, treating content after a tab-separated marker as an indented code block instead of normal list content, especially when preceded by a paragraph.
• Tab Normalization: Implemented consistent normalization of tabs to 4 spaces within list item parsing logic, ensuring uniform handling of tabs and spaces after list markers.
• Improved Indent Calculation: Enhanced the indent calculation for list items to correctly account for tabs by treating them as 4 spaces when determining the first non-space character.
• Comprehensive Testing: Added new unit tests covering ordered and unordered lists with both tabs and spaces after markers, including the specific scenario of lists following a paragraph, to validate the fix.

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Project	Deployment	Preview	Comments	Updated (UTC)
marked-website	Ready	Preview	Comment	Oct 4, 2025 4:52am

[akilesh1706]

Necessary changes done, requesting for review.

[UziTech]

@akilesh1706 are you planning on continuing to work on this?

[akilesh1706]

@akilesh1706 are you planning on continuing to work on this?

Yes, I'm resolving the CI test passes.