FEATURE: Block Leafs

Field	Value
Version	20260815 V1
Description	Parses CommonMark leaf blocks and collects link reference definitions.
Depends On	ARCHITECTURE.md
Provides	leaf block parsing, link reference definitions
Consumes	executable commonmark

Purpose

Implement the leaf-block portion of CommonMark block parsing before inline rendering.

Scope

The parser handles:

thematic breaks;
ATX and setext headings;
indented and fenced code blocks;
HTML blocks;
paragraphs and blank lines;
link reference definitions, including normalization and first-definition precedence.

Leaf blocks must preserve raw inline content for later parsing. Code and raw HTML content must remain literal where required by the specification.

Programmatic Acceptance

=== AC block-leafs-conformance ===
Intent: The implementation passes every supplied conformance example owned by leaf-block parsing.

import subprocess import sys

pattern = ( r"^(Thematic breaks|ATX headings|Setext headings|Indented code blocks|" r"Fenced code blocks|HTML blocks|Link reference definitions|Paragraphs|Blank lines)$" ) result = subprocess.run( [ sys.executable, "sources/spec_tests.py", "--program", "./commonmark", "--spec", "sources/spec.txt", "--pattern", pattern, ], capture_output=True, text=True, ) print(result.stdout) print(result.stderr, file=sys.stderr) assert result.returncode == 0 === END AC block-leafs-conformance ===

=== AC block-leafs-interface ===
Intent: Leaf parsing remains reachable through the required executable interface.

import subprocess

source = "# heading\n\n code\n" result = subprocess.run( ["./commonmark"], input=source, capture_output=True, text=True, ) print(result.stdout) print(result.stderr) assert result.returncode == 0 === END AC block-leafs-interface ===

=== AC block-leafs-reference-input ===
Intent: Link-reference-definition input is accepted through the executable interface.

import subprocess

source = "[label]: /destination\n\n[label]\n" result = subprocess.run( ["./commonmark"], input=source, capture_output=True, text=True, ) print(result.stdout) print(result.stderr) assert result.returncode == 0 === END AC block-leafs-reference-input ===

User Acceptance

None.

Guardrails

Build block structure before inline parsing.
Do not modify sources/spec.txt, sources/spec_tests.py, sources/cmark.py, or sources/normalize.py.
Do not interpret code blocks or HTML blocks as ordinary inline content.