fix(md): require 4 spaces or tab for indented code blocks (#1388)

[joshi-07]

Fixes #1388

Problem

When executing Markdown files (zx file.md), any text indented by 2 or 3 spaces after a blank line (for example, continuation paragraphs in list items or nested documentation notes) was treated as raw JavaScript instead of being commented out:

- item 1
- item 2

  This template assumes you have pnpm installed.

In src/md.ts, tabRe = /^( +|\t)/ matched 2 spaces ( +), incorrectly transitioning state to 'tab' and emitting the text verbatim into the generated script, resulting in syntax errors such as:
SyntaxError: Unexpected identifier 'assumes'

Solution

Per the CommonMark specification, indented code blocks require an indentation of at least four spaces or a tab.

• Updated tabRe to /^( {4,}|\t)/ so lines with 2 or 3 spaces remain regular Markdown prose and are properly commented out with // .

• Retained support for legacy 4-space and tab-indented code blocks.

• Added test coverage in test/md.test.ts for both 4-space indented blocks and list continuation text indented with <4 spaces.

• Setup Set the latest Node.js LTS version.

• Tests: Confirmed transformMarkdown() unit tests succeed. Added tests to cover changes.

• Sign: Follows conventional commits spec.

• CoC: My changes follow the project’s coding guidelines and Code of Conduct.

• Review: This PR represents original work and is not solely generated by AI tools.

[gemini-code-assist]

Code Review

This pull request updates the markdown transformation logic in src/md.ts to ensure that only lines with at least 4 spaces or a tab are treated as indented code blocks, preventing text with fewer spaces from being incorrectly parsed, and adds corresponding test cases in test/md.test.ts. The feedback recommends refining the regular expression to correctly handle cases where 1 to 3 spaces are followed by a tab (which is equivalent to 4 spaces under the CommonMark specification) and adding a test case to verify this behavior.

[gemini-code-assist]

According to the CommonMark specification, a tab character aligns to the next 4-space tab stop. This means that 1 to 3 spaces followed by a tab (e.g., \t) also constitute an indentation of 4 spaces and should start an indented code block.

Updating the regex to /^( {4,}| {0,3}\t)/ ensures that these valid indented code blocks are correctly recognized and preserved, while still preventing 2 or 3 spaces of regular text (without a tab) from being incorrectly treated as code blocks.

Suggested change

	const tabRe = /^( {4,}|\t)/
	const tabRe = /^( {4,}| {0,3}\\t)/

[gemini-code-assist]

Add a test case to verify that blocks indented with 1-3 spaces followed by a tab (which are equivalent to 4 spaces of indentation under CommonMark) are also correctly preserved as indented code blocks.

    test('preserves 4-space indented blocks after a blank line', () => {
      assert.equal(
        transformMarkdown('\\n    console.log("hello")'),
        '// \\n    console.log("hello")'
      )
    })

    test('preserves blocks indented with spaces and a tab (equivalent to 4 spaces)', () => {
      assert.equal(
        transformMarkdown('\\n  \\tconsole.log("hello")'),
        '// \\n  \\tconsole.log("hello")'
      )
    })