Fix #496, while-true loop with a continue.

3 files changed, 28 insertions, 5 deletions

diff --git a/CHANGES.rst b/CHANGES.rst
index 98cdbea6..40f82e61 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -18,10 +18,16 @@ Unreleased
   data, leaving you with an empty .coverage data file. Fixes issues
   `issue 525`_, `issue 412`_, `issue 516`_, and probably `issue 511`_.
 
-- Branch coverage could misunderstand a finally clause on a try block that
-  never continued on to the following statement, as described in `issue 493`_.
-  This is now fixed. Thanks to Joe Doherty for the report and Loïc Dachary for
-  the fix.
+- Branch coverage fixes:
+
+  - Branch coverage could misunderstand a finally clause on a try block that
+    never continued on to the following statement, as described in `issue
+    493`_.  This is now fixed. Thanks to Joe Doherty for the report and Loïc
+    Dachary for the fix.
+
+  - A while-loop with a constant condition (while True) and a continue
+    statement would be mis-analyzed, as described in `issue 496`_. This is now
+    fixed, thanks to a bug report by Eli Skeggs and a fix by Loïc Dachary.
 
 - Options can now be read from a tox.ini file, if any. Like setup.cfg, sections
   are prefixed with "coverage:", so ``[run]`` options will be read from the
@@ -91,6 +97,7 @@ Unreleased
 .. _issue 265: https://bitbucket.org/ned/coveragepy/issues/265/when-using-source-include-is-silently
 .. _issue 412: https://bitbucket.org/ned/coveragepy/issues/412/coverage-combine-should-error-if-no
 .. _issue 493: https://bitbucket.org/ned/coveragepy/issues/493/confusing-branching-failure
+.. _issue 496: https://bitbucket.org/ned/coveragepy/issues/496/incorrect-coverage-with-branching-and
 .. _issue 505: https://bitbucket.org/ned/coveragepy/issues/505/use-canonical-filename-for-debounce
 .. _issue 514: https://bitbucket.org/ned/coveragepy/issues/514/path-to-problem-file-not-reported-when
 .. _issue 510: https://bitbucket.org/ned/coveragepy/issues/510/erase-still-needed-in-42
diff --git a/coverage/parser.py b/coverage/parser.py
index 8b71b51c..f65e4abb 100644
--- a/coverage/parser.py
+++ b/coverage/parser.py
@@ -952,7 +952,7 @@ class AstArcAnalyzer(object):
         start = to_top = self.line_for_node(node.test)
         if constant_test:
             to_top = self.line_for_node(node.body[0])
-        self.block_stack.append(LoopBlock(start=start))
+        self.block_stack.append(LoopBlock(start=to_top))
         from_start = ArcStart(start, cause="the condition on line {lineno} was never true")
         exits = self.add_body_arcs(node.body, from_start=from_start)
         for xit in exits:
diff --git a/tests/test_arcs.py b/tests/test_arcs.py
index 5baf9476..36eb4faa 100644
--- a/tests/test_arcs.py
+++ b/tests/test_arcs.py
@@ -270,6 +270,22 @@ class LoopArcTest(CoverageTest):
             arcz=arcz,
         )
 
+    def test_bug_496_continue_in_constant_while(self):
+        # https://bitbucket.org/ned/coveragepy/issue/496
+        if env.PY3:
+            arcz = ".1 12     23 34 43 45 5."
+        else:
+            arcz = ".1 12 2-1 23 34 42 45 5."
+        self.check_coverage("""\
+            up = iter('ta')
+            while True:
+                char = next(up)
+                if char == 't': continue
+                break
+            """,
+            arcz=arcz
+            )
+
     def test_for_if_else_for(self):
         self.check_coverage("""\
             def branches_2(l):