fix: slice search sections on the same line breaks markdown-it counts

src/codealmanac/services/wiki/sections.py

@@ -1,8 +1,13 @@
+import re
+
 from markdown_it import MarkdownIt
 
 from codealmanac.core.models import CodeAlmanacModel
 
 MARKDOWN = MarkdownIt("commonmark", {"html": False, "linkify": False})
+# Token.map line numbers only count these breaks. str.splitlines() also splits
+# on form feeds, U+2028 and friends, which would shift every slice after them.
+SOURCE_LINE = re.compile(r"[^\r\n]*(?:\r\n?|\n)|[^\r\n]+$")
 
 
 class WikiSection(CodeAlmanacModel):
@@ -29,7 +34,7 @@ def project_sections(body: str, page_title: str) -> tuple[WikiSection, ...]:
     if not boundaries:
         return (section(0, (page_title,), body),)
 
-    lines = body.splitlines(keepends=True)
+    lines = SOURCE_LINE.findall(body)
     sections: list[WikiSection] = []
     headings: dict[int, str] = {}
 

tests/test_wiki_sections.py

@@ -67,3 +67,24 @@ def test_heading_free_page_still_has_one_searchable_section():
     assert len(sections) == 1
     assert sections[0].heading_path == ("Note",)
     assert sections[0].body == "Only prose.\n"
+
+
+def test_section_slices_count_lines_the_way_the_markdown_parser_does():
+    body = (
+        "Pasted note
with a line separator.\n\n"
+        "## Setup\n\n"
+        "Install it.\x0cNext page.\n\n"
+        "## Usage\n\n"
+        "Run it.\n"
+    )
+
+    sections = project_sections(body, page_title="Tool")
+
+    assert [section.heading_path for section in sections] == [
+        ("Tool",),
+        ("Setup",),
+        ("Usage",),
+    ]
+    assert sections[0].body == "Pasted note
with a line separator.\n\n"
+    assert sections[1].body == "\nInstall it.\x0cNext page.\n\n"
+    assert sections[2].body == "\nRun it.\n"