From 30a6a037158eebf062c7da735e0cb905a489d21c Mon Sep 17 00:00:00 2001
From: Ned Batchelder <ned@nedbatchelder.com>
Date: Mon, 20 Apr 2015 12:15:37 -0400
Subject: Fix branch coverage for yield statements. #308 #324

Turns out the "call" and "return" trace events are really "start frame" and
"end frame".  They happen not only when functions are entered and left, but
when generators yield and resume.  We aren't interested in arcs into and out
of yield statements, so the trace functions look more closely to see what's
really happening, and record an arc in human-friendly terms.

Thanks for Mickie Betz for pushing on this bug, although her code is no
longer here. :(
---
 tests/test_arcs.py | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 87 insertions(+)

(limited to 'tests/test_arcs.py')

diff --git a/tests/test_arcs.py b/tests/test_arcs.py
index d3717a8..1098dbd 100644
--- a/tests/test_arcs.py
+++ b/tests/test_arcs.py
@@ -558,6 +558,93 @@ class ExceptionArcTest(CoverageTest):
             arcz_missing="67 7B", arcz_unpredicted="68")
 
 
+class YieldTest(CoverageTest):
+    """Arc tests for generators."""
+
+    def test_yield_in_loop(self):
+        self.check_coverage("""\
+            def gen(inp):
+                for n in inp:
+                    yield n
+
+            list(gen([1,2,3]))
+            """,
+            arcz=".1 .2 23 2. 32 15 5.",
+            arcz_missing="",
+            arcz_unpredicted="")
+
+    def test_padded_yield_in_loop(self):
+        self.check_coverage("""\
+            def gen(inp):
+                i = 2
+                for n in inp:
+                    i = 4
+                    yield n
+                    i = 6
+                i = 7
+
+            list(gen([1,2,3]))
+            """,
+            arcz=".1 19 9.  .2 23 34 45 56 63 37 7.",
+            arcz_missing="",
+            arcz_unpredicted="")
+
+    def test_bug_308(self):
+        self.check_coverage("""\
+            def run():
+                for i in range(10):
+                    yield lambda: i
+
+            for f in run():
+                print(f())
+            """,
+            arcz=".1 15 56 65 5.  .2 23 32 2.  .3 3-3",
+            arcz_missing="",
+            arcz_unpredicted="")
+
+        self.check_coverage("""\
+            def run():
+                yield lambda: 100
+                for i in range(10):
+                    yield lambda: i
+
+            for f in run():
+                print(f())
+            """,
+            arcz=".1 16 67 76 6.  .2 23 34 43 3.   2-2  .4 4-4",
+            arcz_missing="",
+            arcz_unpredicted="")
+
+        self.check_coverage("""\
+            def run():
+                yield lambda: 100  # no branch miss
+
+            for f in run():
+                print(f())
+            """,
+            arcz=".1 14 45 54 4.  .2 2.  2-2",
+            arcz_missing="",
+            arcz_unpredicted="")
+
+    def test_bug_324(self):
+        # This code is tricky: the list() call pulls all the values from gen(),
+        # but each of them is a generator itself that is never iterated.  As a
+        # result, the generator expression on line 3 is never entered or run.
+        self.check_coverage("""\
+            def gen(inp):
+                for n in inp:
+                    yield (i * 2 for i in range(n))
+
+            list(gen([1,2,3]))
+            """,
+            arcz=
+                ".1 15 5. "     # The module level
+                ".2 23 32 2. "  # The gen() function
+                ".3 3-3",       # The generator expression
+            arcz_missing=".3 3-3",
+            arcz_unpredicted="")
+
+
 class MiscArcTest(CoverageTest):
     """Miscellaneous arc-measuring tests."""
 
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