Fix internal error when source is modified (#13884)

Fix IndexError when retrieving start lineno

Author: solaluset

changelog/13884.bugfix.rst

@@ -0,0 +1 @@
+Fixed rare internal IndexError caused by `builtins.compile` being overridden in client code.

src/_pytest/_code/source.py

@@ -168,6 +168,8 @@ def get_statement_startend2(lineno: int, node: ast.AST) -> tuple[int, int | None
                     values.append(val[0].lineno - 1 - 1)
     values.sort()
     insert_index = bisect_right(values, lineno)
+    if insert_index == 0:
+        return 0, None
     start = values[insert_index - 1]
     if insert_index >= len(values):
         end = None
@@ -216,6 +218,7 @@ def getstatementrange_ast(
             pass
 
     # The end might still point to a comment or empty line, correct it.
+    end = min(end, len(source.lines))
     while end:
         line = source.lines[end - 1].lstrip()
         if line.startswith("#") or not line:

testing/code/test_source.py

@@ -7,6 +7,7 @@
 import sys
 import textwrap
 from typing import Any
+from unittest.mock import patch
 
 from _pytest._code import Code
 from _pytest._code import Frame
@@ -647,3 +648,27 @@ def __init__(self, *args):
     # fmt: on
     values = [i for i in x.source.lines if i.strip()]
     assert len(values) == 4
+
+
+def test_patched_compile() -> None:
+    # ensure Source doesn't break
+    # when compile() modifies code dynamically
+    from builtins import compile
+
+    def patched_compile1(_, *args, **kwargs):
+        return compile("", *args, **kwargs)
+
+    with patch("builtins.compile", new=patched_compile1):
+        Source(patched_compile1).getstatement(1)
+
+    # fmt: off
+    def patched_compile2(_, *args, **kwargs):
+
+        # first line of this function (the one above this one) must be empty
+        # LINES must be equal or higher than number of lines of this function
+        LINES = 99
+        return compile("\ndef a():\n" + "\n" * LINES + "    pass", *args, **kwargs)
+    # fmt: on
+
+    with patch("builtins.compile", new=patched_compile2):
+        Source(patched_compile2).getstatement(1)