fix: don't report branches to exclusions as missing. #1271

3 files changed, 22 insertions, 2 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index 8a64f773..9028a0de 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -22,9 +22,14 @@ This list is detailed and covers changes in each pre-release version.
 Unreleased
 ----------
 
+- Fix: Complex conditionals over excluded lines could have incorrectly reported
+  a missing branch (`issue 1271`_). This is now fixed.
+
 - Fix: Removed another vestige of jQuery from the source tarball
   (`issue 840`_).
 
+.. _issue 1271: https://github.com/nedbat/coveragepy/issues/1271
+
 
 .. _changes_611:
 
diff --git a/coverage/results.py b/coverage/results.py
index 3daa3e8e..11c4b09b 100644
--- a/coverage/results.py
+++ b/coverage/results.py
@@ -84,13 +84,14 @@ class Analysis:
 
     @contract(returns='list(tuple(int, int))')
     def arcs_missing(self):
-        """Returns a sorted list of the arcs in the code not executed."""
+        """Returns a sorted list of the unexecuted arcs in the code."""
         possible = self.arc_possibilities()
         executed = self.arcs_executed()
         missing = (
             p for p in possible
                 if p not in executed
                     and p[0] not in self.no_branch
+                    and p[1] not in self.excluded
         )
         return sorted(missing)
 
diff --git a/tests/test_coverage.py b/tests/test_coverage.py
index 1ae927bd..d69a0418 100644
--- a/tests/test_coverage.py
+++ b/tests/test_coverage.py
@@ -1492,7 +1492,7 @@ class ExcludeTest(CoverageTest):
             """,
             [1,2,3,7,8], "", excludes=['#pragma: NO COVER'],
             arcz=".1 12 23 37 45 58 78 8.",
-            arcz_missing="45 58",
+            arcz_missing="58",
         )
 
     def test_excluding_try_except_stranded_else(self):
@@ -1599,6 +1599,20 @@ class ExcludeTest(CoverageTest):
             [1, 6], "", excludes=['assert'],
         )
 
+    def test_excluded_comprehension_branches(self):
+        # https://github.com/nedbat/coveragepy/issues/1271
+        self.check_coverage("""\
+            x, y = [0], [1]
+            if x == [2]:
+                raise NotImplementedError   # pragma: NO COVER
+            if all(_ == __ for _, __ in zip(x, y)):
+                raise NotImplementedError   # pragma: NO COVER
+            """,
+            [1,2,4], "", excludes=['#pragma: NO COVER'],
+            arcz=".1 12 23 24 45 4.  -44 4-4",
+            arcz_missing="4-4",
+        )
+
 
 class Py24Test(CoverageTest):
     """Tests of new syntax in Python 2.4."""