Fix line numbers of code fences in docstrings

The docstring line offset assumed that the opening quotes are on their
own line. Fences in docstrings with a summary on the opening line
reported the line after the actual one, and fences in module docstrings
reported the line before it. Docstrings with a string prefix (r""") were
matched against their closing quotes, or not collected at all when the
closing quotes share a line with other text.

Author: RaphaelFakhri

src/pytest_markdown_docs/plugin.py

@@ -36,18 +36,41 @@ class FenceSyntax(Enum):
     superfences = "superfences"
 
 
+# Opening quotes of a docstring, with an optional string prefix (e.g. r""")
+DOCSTRING_OPENINGS = tuple(
+    prefix + quotes for prefix in ("", "r", "R", "u", "U") for quotes in ('"""', "'''")
+)
+
+
 def get_docstring_start_line(obj) -> typing.Optional[int]:
+    """Get the line offset of the docstring text returned by `inspect.getdoc`
+
+    The offset is the line number of the first line of that text, minus one.
+    """
     # Get the source lines and the starting line number of the object
     try:
         source_lines, start_line = inspect.getsourcelines(obj)
     except OSError:
         return None
 
+    # getsourcelines returns 0 as the starting line number of a module
+    start_line = max(start_line, 1)
+
+    # inspect.getdoc strips the leading blank lines of the docstring
+    leading_blank_lines = 0
+    raw_docstring = getattr(obj, "__doc__", None)
+    if isinstance(raw_docstring, str):
+        for raw_line in raw_docstring.split("\n"):
+            if raw_line.strip():
+                break
+            leading_blank_lines += 1
+
     # Find the line in the source code that starts with triple quotes (""" or ''')
     for idx, line in enumerate(source_lines):
         line = line.strip()
-        if line.startswith(('"""', "'''")):
-            return start_line + idx  # Return the starting line number
+        if line.startswith(DOCSTRING_OPENINGS):
+            # idx is 0-based, so start_line + idx is the line of the opening quotes
+            return start_line + idx - 1 + leading_blank_lines
 
     return None  # Docstring not found in source
 

tests/plugin_test.py

@@ -489,6 +489,71 @@ def test_error_origin_before_docstring_traceback(testdir, support_dir):
     )
 
 
+def test_docstring_line_numbers(testdir):
+    testdir.makepyfile(
+        docstring_lines='''
+        def summary_on_first_line():
+            """Summary line.
+
+            ```python
+            raise Exception("foo")
+            ```
+            """
+
+
+        def raw_docstring():
+            r"""Matches \\d.
+
+            ```python
+            raise Exception("bar")
+            ```"""
+        '''
+    )
+    result = testdir.runpytest("-v", "--markdown-docs")
+    result.assert_outcomes(failed=2)
+    result.stdout.re_match_lines(
+        [
+            r".*::raw_docstring\[CodeFence#1\]\[line:13\] FAILED.*",
+            r".*::summary_on_first_line\[CodeFence#1\]\[line:4\] FAILED.*",
+        ],
+        consecutive=True,
+    )
+    result.stdout.re_match_lines(
+        [
+            r'\s*File ".*/docstring_lines.py", line 14, in <module>',
+            r'\s*raise Exception\("bar"\)',
+        ],
+        consecutive=True,
+    )
+    result.stdout.re_match_lines(
+        [
+            r'\s*File ".*/docstring_lines.py", line 5, in <module>',
+            r'\s*raise Exception\("foo"\)',
+        ],
+        consecutive=True,
+    )
+
+
+def test_module_docstring_line_numbers(testdir):
+    testdir.makepyfile(
+        module_docstring='''
+        """
+        ```python
+        raise Exception("foo")
+        ```
+        """
+        '''
+    )
+    result = testdir.runpytest("-v", "--markdown-docs")
+    result.assert_outcomes(failed=1)
+    result.stdout.re_match_lines(
+        [
+            r".*::module_docstring\[CodeFence#1\]\[line:2\] FAILED.*",
+            r'\s*File ".*/module_docstring.py", line 3, in <module>',
+        ]
+    )
+
+
 def test_custom_runner(testdir):
     testdir.makeconftest(
         """