refactor visit_Output

* `finalize` is generated once and cached for all nodes.
* Extract common behavior for native env.

Removed the compiler behavior where groups of nodes would generate a
format string. Instead, individual nodes are always yielded. This made
rendering 30% faster in the examples, and simplifies the code. It also
removes the issue where Python would report either the first or last
line of the multi-line format expression, messing up the traceback line
number mapping.

2 files changed, 21 insertions, 22 deletions

diff --git a/tests/test_api.py b/tests/test_api.py
index ec93db2..2eb9ce7 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -11,6 +11,7 @@
 import os
 import tempfile
 import shutil
+from io import StringIO
 
 import pytest
 from jinja2 import Environment, Undefined, ChainableUndefined, \
@@ -206,25 +207,24 @@ class TestMeta(object):
 @pytest.mark.api
 @pytest.mark.streaming
 class TestStreaming(object):
-
     def test_basic_streaming(self, env):
-        tmpl = env.from_string("<ul>{% for item in seq %}<li>{{ loop.index "
-                               "}} - {{ item }}</li>{%- endfor %}</ul>")
-        stream = tmpl.stream(seq=list(range(4)))
-        assert next(stream) == '<ul>'
-        assert next(stream) == '<li>1 - 0</li>'
-        assert next(stream) == '<li>2 - 1</li>'
-        assert next(stream) == '<li>3 - 2</li>'
-        assert next(stream) == '<li>4 - 3</li>'
-        assert next(stream) == '</ul>'
+        t = env.from_string(
+            "<ul>{% for item in seq %}<li>{{ loop.index }} - {{ item }}</li>"
+            "{%- endfor %}</ul>"
+        )
+        stream = t.stream(seq=list(range(3)))
+        assert next(stream) == "<ul>"
+        assert "".join(stream) == "<li>1 - 0</li><li>2 - 1</li><li>3 - 2</li></ul>"
 
     def test_buffered_streaming(self, env):
-        tmpl = env.from_string("<ul>{% for item in seq %}<li>{{ loop.index "
-                               "}} - {{ item }}</li>{%- endfor %}</ul>")
-        stream = tmpl.stream(seq=list(range(4)))
+        tmpl = env.from_string(
+            "<ul>{% for item in seq %}<li>{{ loop.index }} - {{ item }}</li>"
+            "{%- endfor %}</ul>"
+        )
+        stream = tmpl.stream(seq=list(range(3)))
         stream.enable_buffering(size=3)
-        assert next(stream) == u'<ul><li>1 - 0</li><li>2 - 1</li>'
-        assert next(stream) == u'<li>3 - 2</li><li>4 - 3</li></ul>'
+        assert next(stream) == u'<ul><li>1'
+        assert next(stream) == u' - 0</li>'
 
     def test_streaming_behavior(self, env):
         tmpl = env.from_string("")
diff --git a/tests/test_async.py b/tests/test_async.py
index 5f331a5..b71f094 100644
--- a/tests/test_async.py
+++ b/tests/test_async.py
@@ -102,13 +102,12 @@ def test_async_iteration_in_templates():
 
 
 def test_async_iteration_in_templates_extended():
-    t = Template('{% for x in rng %}{{ loop.index0 }}/{{ x }}{% endfor %}',
-                 enable_async=True)
-    async def async_iterator():
-        for item in [1, 2, 3]:
-            yield item
-    rv = list(t.generate(rng=async_iterator()))
-    assert rv == ['0/1', '1/2', '2/3']
+    t = Template(
+        "{% for x in rng %}{{ loop.index0 }}/{{ x }}{% endfor %}", enable_async=True
+    )
+    stream = t.generate(rng=auto_aiter(range(1, 4)))
+    assert next(stream) == "0"
+    assert "".join(stream) == "/11/22/3"
 
 
 @pytest.fixture