fix: multi-line conditions used to ruin branch descriptions. #1875

CHANGES.rst

@@ -23,6 +23,10 @@ upgrading your version of coverage.py.
 Unreleased
 ----------
 
+- Fix: some descriptions of missing branches in HTML and LCOV reports were
+  incorrect for multi-line conditions, as reported in `issue 1875`_.  This is
+  now fixed.
+
 - Fix: Python 3.14 `defers evaluation of annotations <pep649_>`_ by moving them
   into separate code objects.  That code is rarely executed, so coverage.py
   would mark them as missing, as reported in `issue 1908`_.  Now they are
@@ -33,6 +37,7 @@ Unreleased
   understand the problem or the solution, but ``git bisect`` helped find it,
   and now it's fixed.
 
+.. _issue 1875: https://github.com/nedbat/coveragepy/issues/1875
 .. _issue 1902: https://github.com/nedbat/coveragepy/issues/1902
 .. _issue 1908: https://github.com/nedbat/coveragepy/issues/1908
 .. _pep649: https://docs.python.org/3.14/whatsnew/3.14.html#pep-649-deferred-evaluation-of-annotations

coverage/parser.py

@@ -764,6 +764,8 @@ def add_arc(
         action_msg: str | None = None,
     ) -> None:
         """Add an arc, including message fragments to use if it is missing."""
+        start = self.multiline.get(start, start)
+        end = self.multiline.get(end, end)
         if self.debug:                      # pragma: debugging
             print(f"Adding possible arc: ({start}, {end}): {missing_cause_msg!r}, {action_msg!r}")
             print(short_stack(), end="\n\n")

tests/test_lcov.py

@@ -558,3 +558,17 @@ def test_always_raise(self) -> None:
             """)
         actual_result = self.get_lcov_report_content()
         assert expected_result == actual_result
+
+    def test_multiline_conditions(self) -> None:
+        self.make_file("multi.py", """\
+            def fun(x):
+                if (
+                    x
+                ):
+                    print("got here")
+            """)
+        cov = coverage.Coverage(source=".", branch=True)
+        self.start_import_stop(cov, "multi")
+        cov.lcov_report()
+        lcov = self.get_lcov_report_content()
+        assert "BRDA:2,0,return from function 'fun',-" in lcov