Preserve single-line code spans in fallback docstrings

pylsp/_utils.py

@@ -210,14 +210,43 @@ def escape_plain_text(contents: str) -> str:
 
 
 def escape_markdown(contents: str) -> str:
+    """Escape Markdown syntax outside single-line code spans.
+
+    Keep the previous escaping behavior when paired backticks cross a line.
     """
-    Format plain text to display nicely in Markdown environment.
-    """
-    # escape markdown syntax
-    contents = re.sub(r"([\\*_#[\]])", r"\\\1", contents)
-    # preserve white space characters
-    contents = escape_plain_text(contents)
-    return contents
+
+    def escape_text(text):
+        return escape_plain_text(re.sub(r"([\\*_#[\]])", r"\\\1", text))
+
+    runs = list(re.finditer(r"`+", contents))
+    closing_runs = {}
+    next_run_by_length = {}
+    # Index equal-length runs once instead of repeatedly searching the suffix.
+    for index in range(len(runs) - 1, -1, -1):
+        length = runs[index].end() - runs[index].start()
+        if length in next_run_by_length:
+            closing_runs[index] = next_run_by_length[length]
+        next_run_by_length[length] = index
+
+    parts = []
+    offset = index = 0
+    while index < len(runs):
+        closing_index = closing_runs.get(index)
+        if closing_index is None:
+            index += 1
+            continue
+        start, end = runs[index].start(), runs[closing_index].end()
+        span = contents[start:end]
+        if "\n" in span or "\r" in span:
+            # Multiline spans interact with Markdown block parsing. Preserve
+            # the whole input's previous behavior rather than re-pairing ticks.
+            return escape_text(contents)
+        parts.append(escape_text(contents[offset:start]))
+        parts.append(span)
+        offset = end
+        index = closing_index + 1
+    parts.append(escape_text(contents[offset:]))
+    return "".join(parts)
 
 
 def wrap_signature(signature):

test/test_utils.py

@@ -9,6 +9,7 @@
 from typing import Any
 from unittest import mock
 
+import pytest
 from docstring_to_markdown import UnknownFormatError
 from flaky import flaky
 
@@ -234,6 +235,54 @@ def test_clip_column() -> None:
     assert _utils.clip_column(4, ["123\n", "123"], 1) == 3
 
 
+@pytest.mark.parametrize(
+    ("contents", "expected"),
+    [
+        (
+            "Use ``object_hook`` and object_hook.",
+            r"Use ``object_hook`` and object\_hook.",
+        ),
+        ("`*a_b*[c]#d` *a_b*[c]#d", r"`*a_b*[c]#d` \*a\_b\*\[c\]\#d"),
+        ("``a `b_c` d_e`` f_g", r"``a `b_c` d_e`` f\_g"),
+        ("`a_b` ``c_d``", "`a_b` ``c_d``"),
+        ("`  `", "`  `"),
+        (r"\`a_b`", r"\\`a_b`"),
+        (r"\\`a_b`", r"\\\\`a_b`"),
+        (r"`path\name`", r"`path\name`"),
+        (r"`a\` tail_word", r"`a\` tail\_word"),
+        ("`a_b`` c_d", r"`a\_b`` c\_d"),
+        ("``a_b` c_d`", r"``a\_b` c_d`"),
+        ("`a_b\nc_d`", "`a\\_b\nc\\_d`"),
+        ("`a\nb` *outside* `c_d`", "`a\nb` \\*outside\\* `c\\_d`"),
+        ("`a_b`\n`c_d`", "`a_b`\n`c_d`"),
+        ("`*a_b*\n# c_d\nend`", "`\\*a\\_b\\*\n\\# c\\_d\nend`"),
+        ("`a_b\n\nc_d`", "`a\\_b\n\nc\\_d`"),
+        ("`a_b\n  \nc_d`", "`a\\_b\n\u00a0\u00a0\nc\\_d`"),
+        ("`a_b\r\n\r\nc_d`", "`a\\_b\r\n\r\nc\\_d`"),
+        ("`a_b\rc_d`", "`a\\_b\rc\\_d`"),
+        ("`a  b\t_c` tail  _word", "`a  b\t_c` tail\u00a0\u00a0\\_word"),
+        (r"unmatched `path\name_value", r"unmatched `path\\name\_value"),
+    ],
+)
+def test_escape_markdown_code_spans(contents, expected) -> None:
+    assert _utils.escape_markdown(contents) == expected
+
+
+@pytest.mark.parametrize(
+    ("markup_kind", "contents", "expected"),
+    [
+        ("markdown", "Use ``object_hook``.", "Use ``object_hook``."),
+        ("markdown", "Use object_hook.", r"Use object\_hook."),
+        ("plaintext", "Use ``object_hook``.", "Use ``object_hook``."),
+        ("markdown", r"Use ``path\name``.", r"Use ``path\name``."),
+    ],
+)
+def test_format_docstring_code_spans(markup_kind, contents, expected) -> None:
+    assert _utils.format_docstring(
+        contents, markup_kind, signature_config={"formatter": None}
+    ) == {"kind": markup_kind, "value": expected}
+
+
 @mock.patch("docstring_to_markdown.convert")
 def test_format_docstring_valid_rst_signature(mock_convert) -> None:
     """Test that a valid RST docstring includes the function signature."""