fix: `class` statements shouldn't be branches. #1449

Revert "refactor: we no longer need to treat 'class' lines specially"

This reverts commit 79f9f4575321fafc2ef770e3255f874db3d4b037.

5 files changed, 26 insertions, 7 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index 01d9f33e..2eba01dd 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -20,6 +20,9 @@ development at the same time, such as 4.5.x and 5.0.
 Unreleased
 ----------
 
+- Starting with coverage.py 6.2, ``class`` statements were marked as a branch.
+  This wasn't right, and has been reverted, fixing `issue 1449`_.
+
 - Packaging is now compliant with `PEP 517`_, closing `issue 1395`_.
 
 - A new debug option ``--debug=pathmap`` shows details of the remapping of
@@ -31,6 +34,7 @@ Unreleased
 .. _bug 50381: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=50381
 .. _PEP 517: https://peps.python.org/pep-0517/
 .. _issue 1395: https://github.com/nedbat/coveragepy/issues/1395
+.. _issue 1449: https://github.com/nedbat/coveragepy/issues/1449
 
 
 .. _changes_6-4-4:
diff --git a/coverage/parser.py b/coverage/parser.py
index 3dbfbf30..8b2a9ac5 100644
--- a/coverage/parser.py
+++ b/coverage/parser.py
@@ -67,6 +67,9 @@ class PythonParser:
         # The raw line numbers of excluded lines of code, as marked by pragmas.
         self.raw_excluded = set()
 
+        # The line numbers of class definitions.
+        self.raw_classdefs = set()
+
         # The line numbers of docstring lines.
         self.raw_docstrings = set()
 
@@ -130,6 +133,12 @@ class PythonParser:
                 indent += 1
             elif toktype == token.DEDENT:
                 indent -= 1
+            elif toktype == token.NAME:
+                if ttext == 'class':
+                    # Class definitions look like branches in the bytecode, so
+                    # we need to exclude them.  The simplest way is to note the
+                    # lines with the 'class' keyword.
+                    self.raw_classdefs.add(slineno)
             elif toktype == token.OP:
                 if ttext == ':' and nesting == 0:
                     should_exclude = (elineno in self.raw_excluded) or excluding_decorators
@@ -292,6 +301,12 @@ class PythonParser:
                 continue
             exit_counts[l1] += 1
 
+        # Class definitions have one extra exit, so remove one for each:
+        for l in self.raw_classdefs:
+            # Ensure key is there: class definitions can include excluded lines.
+            if l in exit_counts:
+                exit_counts[l] -= 1
+
         return exit_counts
 
     def missing_arc_description(self, start, end, executed_arcs=None):
diff --git a/lab/parser.py b/lab/parser.py
index 43f3da52..ebd4e7f3 100644
--- a/lab/parser.py
+++ b/lab/parser.py
@@ -108,6 +108,8 @@ class ParserMain:
                         marks[2] = str(exits)
                     if lineno in pyparser.raw_docstrings:
                         marks[3] = '"'
+                    if lineno in pyparser.raw_classdefs:
+                        marks[3] = 'C'
                     if lineno in pyparser.raw_excluded:
                         marks[4] = 'x'
 
diff --git a/tests/test_lcov.py b/tests/test_lcov.py
index 09bb99aa..ed7706fb 100644
--- a/tests/test_lcov.py
+++ b/tests/test_lcov.py
@@ -203,10 +203,8 @@ class LcovTest(CoverageTest):
             DA:9,0,FPTWzd68bDx76HN7VHu1wA
             LF:6
             LH:4
-            BRDA:0,0,0,1
-            BRDA:7,0,1,1
-            BRF:2
-            BRH:2
+            BRF:0
+            BRH:0
             end_of_record
             """)
         actual_result = self.get_lcov_report_content()
diff --git a/tests/test_parser.py b/tests/test_parser.py
index 48f5ade3..6d181c9e 100644
--- a/tests/test_parser.py
+++ b/tests/test_parser.py
@@ -43,7 +43,7 @@ class PythonParserTest(CoverageTest):
                 pass
             """)
         assert parser.exit_counts() == {
-            2:2, 3:1, 4:2, 5:1, 7:1, 9:2, 10:1
+            2:1, 3:1, 4:2, 5:1, 7:1, 9:1, 10:1
         }
 
     def test_generator_exit_counts(self):
@@ -89,7 +89,7 @@ class PythonParserTest(CoverageTest):
                     pass
             """)
         assert parser.exit_counts() == {
-            1:1, 2:1, 3:1
+            1:0, 2:1, 3:1
         }
 
     def test_missing_branch_to_excluded_code(self):
@@ -472,7 +472,7 @@ class ParserFileTest(CoverageTest):
             class Bar:
                 pass
             """
-        counts = { 2:2, 3:1, 4:2, 5:1, 7:1, 9:2, 10:1 }
+        counts = { 2:1, 3:1, 4:2, 5:1, 7:1, 9:1, 10:1 }
         fname = slug + ".py"
         self.make_file(fname, text, newline=newline)
         parser = self.parse_file(fname)