py/objgenerator: Implement PEP479, StopIteration convs to RuntimeError.

This commit implements PEP479 which disallows raising StopIteration inside
a generator to signal that it should be finished.  Instead, the generator
should simply return when it is complete.

See https://www.python.org/dev/peps/pep-0479/ for details.

10 files changed, 56 insertions, 85 deletions

diff --git a/tests/basics/gen_yield_from.py b/tests/basics/gen_yield_from.py
index 4e68aec63..037644e1e 100644
--- a/tests/basics/gen_yield_from.py
+++ b/tests/basics/gen_yield_from.py
@@ -13,34 +13,6 @@ g = gen2()
 print(list(g))
 
 
-# Like above, but terminate subgen using StopIteration
-def gen3():
-    yield 1
-    yield 2
-    raise StopIteration
-
-def gen4():
-    print("here1")
-    print((yield from gen3()))
-    print("here2")
-
-g = gen4()
-print(list(g))
-
-# Like above, but terminate subgen using StopIteration with value
-def gen5():
-    yield 1
-    yield 2
-    raise StopIteration(123)
-
-def gen6():
-    print("here1")
-    print((yield from gen5()))
-    print("here2")
-
-g = gen6()
-print(list(g))
-
 # StopIteration from within a Python function, within a native iterator (map), within a yield from
 def gen7(x):
     if x < 3:
diff --git a/tests/basics/gen_yield_from.py.exp b/tests/basics/gen_yield_from.py.exp
deleted file mode 100644
index 507f2b9ca..000000000
--- a/tests/basics/gen_yield_from.py.exp
+++ /dev/null
@@ -1,14 +0,0 @@
-here1
-3
-here2
-[1, 2]
-here1
-None
-here2
-[1, 2]
-here1
-123
-here2
-[1, 2]
-444
-[0, 1, 2]
diff --git a/tests/basics/gen_yield_from_close.py b/tests/basics/gen_yield_from_close.py
index 833986105..e3e0116ff 100644
--- a/tests/basics/gen_yield_from_close.py
+++ b/tests/basics/gen_yield_from_close.py
@@ -55,14 +55,14 @@ except StopIteration:
 
 
 # Yet another variation - leaf generator gets GeneratorExit,
-# but raises StopIteration instead. This still should close chain properly.
+# and reraises a new GeneratorExit. This still should close chain properly.
 def gen5():
     yield 1
     try:
         yield 2
     except GeneratorExit:
-        print("leaf caught GeneratorExit and raised StopIteration instead")
-        raise StopIteration(123)
+        print("leaf caught GeneratorExit and reraised GeneratorExit")
+        raise GeneratorExit(123)
     yield 3
     yield 4
 
diff --git a/tests/basics/gen_yield_from_close.py.exp b/tests/basics/gen_yield_from_close.py.exp
deleted file mode 100644
index a44d1353d..000000000
--- a/tests/basics/gen_yield_from_close.py.exp
+++ /dev/null
@@ -1,20 +0,0 @@
--1
-1
-StopIteration
--1
-1
-2
-leaf caught GeneratorExit and swallowed it
-delegating caught GeneratorExit
-StopIteration
--1
-1
-2
-leaf caught GeneratorExit and raised StopIteration instead
-delegating caught GeneratorExit
-StopIteration
-123
-RuntimeError
-0
-1
-close
diff --git a/tests/basics/gen_yield_from_throw.py b/tests/basics/gen_yield_from_throw.py
index 829bf0f3b..4d65b3c17 100644
--- a/tests/basics/gen_yield_from_throw.py
+++ b/tests/basics/gen_yield_from_throw.py
@@ -25,6 +25,20 @@ def gen3():
 g3 = gen3()
 print(next(g3))
 try:
-    g3.throw(StopIteration)
+    g3.throw(KeyError)
+except KeyError:
+    print('got KeyError from downstream!')
+
+# case where a thrown exception is caught and stops the generator
+def gen4():
+    try:
+        yield 1
+        yield 2
+    except:
+        pass
+g4 = gen4()
+print(next(g4))
+try:
+    g4.throw(ValueError)
 except StopIteration:
-    print('got StopIteration from downstream!')
+    print('got StopIteration')
diff --git a/tests/basics/gen_yield_from_throw.py.exp b/tests/basics/gen_yield_from_throw.py.exp
deleted file mode 100644
index 6ce97ad86..000000000
--- a/tests/basics/gen_yield_from_throw.py.exp
+++ /dev/null
@@ -1,6 +0,0 @@
-1
-got ValueError from upstream!
-str1
-got TypeError from downstream!
-123
-got StopIteration from downstream!
diff --git a/tests/basics/generator_close.py b/tests/basics/generator_close.py
index aa563f2a8..1ccc78dbe 100644
--- a/tests/basics/generator_close.py
+++ b/tests/basics/generator_close.py
@@ -31,13 +31,14 @@ except StopIteration:
     print("StopIteration")
 
 
-# Throwing StopIteration in response to close() is ok
+# Throwing GeneratorExit in response to close() is ok
 def gen2():
     try:
         yield 1
         yield 2
     except:
-        raise StopIteration
+        print('raising GeneratorExit')
+        raise GeneratorExit
 
 g = gen2()
 next(g)
diff --git a/tests/basics/generator_close.py.exp b/tests/basics/generator_close.py.exp
deleted file mode 100644
index fcd583935..000000000
--- a/tests/basics/generator_close.py.exp
+++ /dev/null
@@ -1,10 +0,0 @@
-None
-StopIteration
-1
-None
-StopIteration
-[1, 2]
-None
-StopIteration
-None
-ValueError
diff --git a/tests/basics/generator_pep479.py b/tests/basics/generator_pep479.py
new file mode 100644
index 000000000..e422c349e
--- /dev/null
+++ b/tests/basics/generator_pep479.py
@@ -0,0 +1,29 @@
+# tests for correct PEP479 behaviour (introduced in Python 3.5)
+
+# basic case: StopIteration is converted into a RuntimeError
+def gen():
+    yield 1
+    raise StopIteration
+g = gen()
+print(next(g))
+try:
+    next(g)
+except RuntimeError:
+    print('RuntimeError')
+
+# trying to continue a failed generator now raises StopIteration
+try:
+    next(g)
+except StopIteration:
+    print('StopIteration')
+
+# throwing a StopIteration which is uncaught will be converted into a RuntimeError
+def gen():
+    yield 1
+    yield 2
+g = gen()
+print(next(g))
+try:
+    g.throw(StopIteration)
+except RuntimeError:
+    print('RuntimeError')
diff --git a/tests/basics/generator_pep479.py.exp b/tests/basics/generator_pep479.py.exp
new file mode 100644
index 000000000..c64fe4956
--- /dev/null
+++ b/tests/basics/generator_pep479.py.exp
@@ -0,0 +1,5 @@
+1
+RuntimeError
+StopIteration
+1
+RuntimeError