Exit arcs have to be corrected to first lines

We've long remapped line numbers to the first line of a multi-line
statement.  But exit line numbers (negative numbers) were not remapped.
This meant we were needlessly chasing weirdnesses in implementations.

But the actual results of running coverage always remapped results to
the first line, so there's no point in tracking the unmapped line
numbers in our tests.

2 files changed, 30 insertions, 46 deletions

diff --git a/coverage/parser.py b/coverage/parser.py
index 12c2d0a5..f0d378c6 100644
--- a/coverage/parser.py
+++ b/coverage/parser.py
@@ -207,7 +207,11 @@ class PythonParser(object):
 
     def first_line(self, line):
         """Return the first line number of the statement including `line`."""
-        return self._multiline.get(line, line)
+        if line < 0:
+            line = -self._multiline.get(-line, -line)
+        else:
+            line = self._multiline.get(line, line)
+        return line
 
     def first_lines(self, lines):
         """Map the line numbers in `lines` to the correct first line of the
diff --git a/tests/test_arcs.py b/tests/test_arcs.py
index 638478ab..bf17f712 100644
--- a/tests/test_arcs.py
+++ b/tests/test_arcs.py
@@ -103,7 +103,7 @@ class SimpleArcTest(CoverageTest):
             b = \\
                 6
             """,
-            arcz="-21 15 5-2",
+            arcz=".1 15 5.",
         )
 
     def test_if_return(self):
@@ -444,10 +444,6 @@ class LoopArcTest(CoverageTest):
         )
 
     def test_multiline_dict_comp(self):
-        if env.PYVERSION < (3, 5):
-            arcz = "-42 2B B-4   2-4"
-        else:
-            arcz = "-32 2B B-3   2-3"
         # Multiline dict comp:
         self.check_coverage("""\
             # comment
@@ -462,13 +458,9 @@ class LoopArcTest(CoverageTest):
             }
             x = 11
             """,
-            arcz=arcz,
+            arcz="-22 2B B-2   2-2"
         )
         # Multi dict comp:
-        if env.PYVERSION < (3, 5):
-            arcz = "-42 2F F-4   2-4"
-        else:
-            arcz = "-32 2F F-3   2-3"
         self.check_coverage("""\
             # comment
             d = \\
@@ -486,7 +478,7 @@ class LoopArcTest(CoverageTest):
             }
             x = 15
             """,
-            arcz=arcz,
+            arcz="-22 2F F-2   2-2"
         )
 
 
@@ -1204,11 +1196,6 @@ class MiscArcTest(CoverageTest):
     """Miscellaneous arc-measuring tests."""
 
     def test_dict_literal(self):
-        if env.PYVERSION < (3, 5):
-            arcz = ".1 19 9."
-        else:
-            # Python 3.5 changed how dict literals are constructed.
-            arcz = "-21 19 9-2"
         self.check_coverage("""\
             d = {
                 'a': 2,
@@ -1220,7 +1207,7 @@ class MiscArcTest(CoverageTest):
                 }
             assert d
             """,
-            arcz=arcz,
+            arcz=".1 19 9.",
         )
         self.check_coverage("""\
             d = \\
@@ -1233,7 +1220,7 @@ class MiscArcTest(CoverageTest):
                 }
             assert d
             """,
-            arcz="-21 19 9-2",
+            arcz=".1 19 9.",
         )
 
     def test_unpacked_literals(self):
@@ -1251,7 +1238,7 @@ class MiscArcTest(CoverageTest):
             }
             assert weird['b'] == 3
             """,
-            arcz="-21 15 5A A-2"
+            arcz=".1 15 5A A."
         )
         self.check_coverage("""\
             l = [
@@ -1265,40 +1252,35 @@ class MiscArcTest(CoverageTest):
             ]
             assert weird[1] == 3
             """,
-            arcz="-21 15 5A A-2"
+            arcz=".1 15 5A A."
         )
 
     def test_pathologically_long_code_object(self):
-        if env.JYTHON:
-            self.skipTest("Bytecode concerns are irrelevant on Jython")
-
         # https://bitbucket.org/ned/coveragepy/issue/359
         # The structure of this file is such that an EXTENDED_ARG bytecode is
         # needed to encode the jump at the end.  We weren't interpreting those
         # opcodes.
         # Note that we no longer interpret bytecode at all, but it couldn't
         # hurt to keep the test...
-        code = """\
-            data = [
-            """ + "".join("""\
-                [
-                    {i}, {i}, {i}, {i}, {i}, {i}, {i}, {i}, {i}, {i}],
-            """.format(i=i) for i in range(2000)
-            ) + """\
-            ]
-
-            print(len(data))
-            """
-        self.check_coverage(
-            code,
-            arcs=[(-3, 1), (1, 4004), (4004, -3)],
-            arcs_missing=[], arcs_unpredicted=[],
-            )
+        for n in [10, 50, 100, 500, 1000, 2000]:
+            code = """\
+                data = [
+                """ + "".join("""\
+                    [
+                        {i}, {i}, {i}, {i}, {i}, {i}, {i}, {i}, {i}, {i}],
+                """.format(i=i) for i in range(n)
+                ) + """\
+                ]
+
+                print(len(data))
+                """
+            self.check_coverage(code, arcs=[(-1, 1), (1, 2*n+4), (2*n+4, -1)])
+            self.assertEqual(self.stdout().split()[-1], str(n))
 
     def test_partial_generators(self):
         # https://bitbucket.org/ned/coveragepy/issues/475/generator-expression-is-marked-as-not
         # Line 2 is executed completely.
-        # Line 3 is started but not finished, because zip ends when #2 ends.
+        # Line 3 is started but not finished, because zip ends before it finishes.
         # Line 4 is never started.
         cov = self.check_coverage("""\
             def f(a, b):
@@ -1307,7 +1289,7 @@ class MiscArcTest(CoverageTest):
                 e = (k for k in b)          # 4
                 return dict(zip(c, d))
 
-            f(['a', 'b'], [1, 2])
+            f(['a', 'b'], [1, 2, 3])
             """,
             arcz=".1 17 7.  .2 23 34 45 5.  -22 2-2  -33 3-3  -44 4-4",
             arcz_missing="3-3 -44 4-4",
@@ -1441,7 +1423,7 @@ class LambdaArcTest(CoverageTest):
             )
             assert fn(10) == 18
             """,
-            arcz="-42 2A A-4   2-4",
+            arcz="-22 2A A-2   2-2",
         )
 
     def test_unused_lambdas_are_confusing_bug_90(self):
@@ -1489,9 +1471,7 @@ class LambdaArcTest(CoverageTest):
                 if k & 1:
                     v()
             """,
-            arcz=".1 12 23 3A AB BC BA CA A.  -43 -53 -63 -73 3-4 3-5 3-6 3-7",
-            arcz_missing="-43 3-4 -63 3-6",
-            arcz_unpredicted="",
+            arcz=".1 12 23 3A AB BC BA CA A.  -33  3-3",
         )