wip: make dot objects iterables of unicode lines including newline

docs/manual.rst

@@ -339,14 +339,14 @@ Custom DOT statements
 
 To add arbitrary statements to the created DOT_ source, use the
 :attr:`~.Graph.body` attribute of the :class:`.Graph` or :class:`.Digraph`
-object. It holds the verbatim list of lines to be written to the source file.
-Use its ``append()`` or ``extend()`` method:
+object. It holds the verbatim list of lines to be written to the source file
+(including their newline). Use its ``append()`` or ``extend()`` method:
 
 .. code:: python
 
     >>> rt = Digraph(comment='The Round Table')
 
-    >>> rt.body.append('\t"King Arthur" -> {\n\t\t"Sir Bedevere", "Sir Lancelot"\n\t}')
+    >>> rt.body.append('\t"King Arthur" -> {\n\t\t"Sir Bedevere", "Sir Lancelot"\n\t}\n')
     >>> rt.edge('Sir Bedevere', 'Sir Lancelot', constraint='false')
 
     >>> print(rt.source)  # doctest: +NORMALIZE_WHITESPACE

graphviz/backend.py

@@ -146,6 +146,15 @@ def pipe(engine, format, data, quiet=False):
         graphviz.ExecutableNotFound: If the Graphviz executable is not found.
         subprocess.CalledProcessError: If the exit status is non-zero.
     """
+    piped = open_pipe(engine, format, quiet)
+    with piped as fd:
+        fd.write(data)
+    with piped as outs:
+        return outs
+
+
+@tools.multi_contextmanager
+def open_pipe(engine, format, quiet=False):
     args, _ = command(engine, format)
 
     try:
@@ -158,14 +167,16 @@ def pipe(engine, format, data, quiet=False):
         else:  # pragma: no cover
             raise
 
-    outs, errs = proc.communicate(data)
+    yield proc.stdin
+
+    outs, errs = proc.communicate()
     if proc.returncode:
         if not quiet:
             stderr_write_binary(errs)
             sys.stderr.flush()
         raise subprocess.CalledProcessError(proc.returncode, args, output=outs)
 
-    return outs
+    yield outs
 
 
 def version():

graphviz/dot.py

@@ -36,12 +36,12 @@
 class Dot(files.File):
     """Assemble, save, and render DOT source code, open result in viewer."""
 
-    _comment = '// %s'
-    _subgraph = 'subgraph %s{'
-    _subgraph_plain = '%s{'
-    _node = _attr = '\t%s%s'
+    _comment = u'// %s\n'
+    _subgraph = u'subgraph %s{\n'
+    _subgraph_plain = u'%s{\n'
+    _node = _attr = u'\t%s%s\n'
     _attr_plain = _attr % ('%s', '')
-    _tail = '}'
+    _tail = u'}\n'
 
     _quote = staticmethod(lang.quote)
     _quote_edge = staticmethod(lang.quote_edge)
@@ -115,7 +115,7 @@ def __iter__(self, subgraph=False):
 
     def __str__(self):
         """The DOT source code as string."""
-        return '\n'.join(self)
+        return ''.join(self)
 
     source = property(__str__, doc=__str__.__doc__)
 
@@ -255,9 +255,9 @@ class Graph(Dot):
         corresponding attribute name after instance creation.
     """
 
-    _head = 'graph %s{'
-    _head_strict = 'strict %s' % _head
-    _edge = '\t%s -- %s%s'
+    _head = u'graph %s{\n'
+    _head_strict = u'strict %s' % _head
+    _edge = u'\t%s -- %s%s\n'
     _edge_plain = _edge % ('%s', '%s', '')
 
     @property
@@ -271,9 +271,9 @@ class Digraph(Dot):
 
     __doc__ += Graph.__doc__.partition('.')[2]
 
-    _head = 'digraph %s{'
-    _head_strict = 'strict %s' % _head
-    _edge = '\t%s -> %s%s'
+    _head = u'digraph %s{\n'
+    _head_strict = u'strict %s' % _head
+    _edge = u'\t%s -> %s%s\n'
     _edge_plain = _edge % ('%s', '%s', '')
 
     @property

graphviz/files.py

@@ -119,11 +119,14 @@ def pipe(self, format=None):
         if format is None:
             format = self._format
 
-        data = text_type(self.source).encode(self._encoding)
+        piped = backend.open_pipe(self._engine, format)
 
-        outs = backend.pipe(self._engine, format, data)
+        with piped as fd:
+            for uline in self:
+                fd.write((uline).encode(self._encoding))
 
-        return outs
+        with piped as outs:
+            return outs
 
     @property
     def filepath(self):
@@ -146,12 +149,9 @@ def save(self, filename=None, directory=None):
         filepath = self.filepath
         tools.mkdirs(filepath)
 
-        data = text_type(self.source)
-
         with io.open(filepath, 'w', encoding=self.encoding) as fd:
-            fd.write(data)
-            if not data.endswith(u'\n'):
-                fd.write(u'\n')
+            for uline in self:
+                fd.write(uline)
 
         return filepath
 
@@ -266,3 +266,8 @@ def _kwargs(self):
         result = super(Source, self)._kwargs()
         result['source'] = self.source
         return result
+
+    def __iter__(self):
+        yield text_type(self.source)
+        if not self.source.endswith(u'\n'):
+            yield u'\n'

graphviz/tools.py

@@ -1,10 +1,11 @@
 # tools.py
 
 import os
+import functools
 
 from . import _compat
 
-__all__ = ['attach', 'mkdirs', 'mapping_items']
+__all__ = ['attach', 'mkdirs', 'mapping_items', 'multi_contextmanager']
 
 
 def attach(object, name):
@@ -44,3 +45,39 @@ def mapping_items(mapping, _iteritems=_compat.iteritems):
     if type(mapping) is dict:
         return iter(sorted(_iteritems(mapping)))
     return _iteritems(mapping)
+
+
+def multi_contextmanager(func):
+    """
+
+    >>> @multi_contextmanager
+    ... def spam():
+    ...      yield 'spam'
+    ...      print('and')
+    ...      yield 'eggs'
+
+    >>> s = spam()
+    >>> with s as x:
+    ...    print(x)
+    spam
+    >>> with s as x:
+    ...    print(x)
+    and
+    eggs
+    """
+    @functools.wraps(func)
+    def wrapper(*args, **kwargs):
+        return GeneratorContextmanager(func(*args, **kwargs))
+    return wrapper
+
+
+class GeneratorContextmanager(object):
+
+    def __init__(self, generator):
+        self._iter = iter(generator)
+
+    def __enter__(self):
+        return next(self._iter)
+
+    def __exit__(self, type, value, tb):
+        pass

tests/conftest.py

@@ -70,8 +70,8 @@ def quiet(request):
 
 
 @pytest.fixture
-def pipe(mocker):
-    yield mocker.patch('graphviz.backend.pipe')
+def open_pipe(mocker):
+    yield mocker.patch('graphviz.backend.open_pipe')
 
 
 @pytest.fixture

tests/test_backend.py

@@ -103,7 +103,8 @@ def test_pipe_pipe_invalid_data_mocked(mocker, py2, Popen, quiet):  # noqa: N803
     Popen.assert_called_once_with(['dot', '-Tpng'],
                                   stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                                   stderr=subprocess.PIPE, startupinfo=STARTUPINFO)
-    proc.communicate.assert_called_once_with(b'nongraph')
+    proc.stdin.write.assert_called_once_with(b'nongraph')
+    proc.communicate.assert_called_once_with()
     if not quiet:
         if py2:
             stderr.write.assert_called_once_with(errs)
@@ -123,7 +124,8 @@ def test_pipe_mocked(mocker, Popen):  # noqa: N803
     Popen.assert_called_once_with(['dot', '-Tpng'],
                                   stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                                   stderr=subprocess.PIPE, startupinfo=STARTUPINFO)
-    proc.communicate.assert_called_once_with(b'nongraph')
+    proc.stdin.write.assert_called_once_with(b'nongraph')
+    proc.communicate.assert_called_once_with()
 
 
 @pytest.mark.usefixtures('empty_path')

tests/test_dot.py

@@ -63,8 +63,8 @@ def test_iter_subgraph_strict(cls):
 
 
 def test_iter_strict():
-    assert Graph(strict=True).source == 'strict graph {\n}'
-    assert Digraph(strict=True).source == 'strict digraph {\n}'
+    assert Graph(strict=True).source == 'strict graph {\n}\n'
+    assert Digraph(strict=True).source == 'strict digraph {\n}\n'
 
 
 def test_attr_invalid_kw(cls):
@@ -75,14 +75,14 @@ def test_attr_invalid_kw(cls):
 def test_attr_kw_none():
     dot = Graph()
     dot.attr(spam='eggs')
-    assert dot.source == 'graph {\n\tspam=eggs\n}'
+    assert dot.source == 'graph {\n\tspam=eggs\n}\n'
 
 
 def test_subgraph_graph_none():
     dot = Graph()
     with dot.subgraph(name='name', comment='comment'):
         pass
-    assert dot.source == 'graph {\n\t// comment\n\tsubgraph name {\n\t}\n}'
+    assert dot.source == 'graph {\n\t// comment\n\tsubgraph name {\n\t}\n}\n'
 
 
 def test_subgraph_graph_notsole(cls):
@@ -99,7 +99,7 @@ def test_subgraph_mixed(classes):
 def test_subgraph_reflexive():  # guard against potential infinite loop
     dot = Graph()
     dot.subgraph(dot)
-    assert dot.source == 'graph {\n\t{\n\t}\n}'
+    assert dot.source == 'graph {\n\t{\n\t}\n}\n'
 
 
 def test_subgraph():
@@ -144,7 +144,8 @@ def test_subgraph():
 	A -- D
 	B -- E
 	C -- F
-}'''
+}
+'''
 
 
 def test_label_html():
@@ -220,4 +221,5 @@ def test_label_html():
 </TABLE>>]
 	struct1:f1 -> struct2:f0
 	struct1:f2 -> struct3:here
-}'''
+}
+'''

tests/test_files.py

@@ -60,20 +60,25 @@ def test__repr_svg_(mocker, source):
     pipe.return_value.decode.assert_called_once_with(source.encoding)
 
 
-def test_pipe_format(pipe, source, format_='svg'):
+def test_pipe_format(open_pipe, source, format_='svg'):
     assert source.format != format_
+    multi_context = open_pipe.return_value.__enter__.return_value
 
-    assert source.pipe(format=format_) is pipe.return_value
+    assert source.pipe(format=format_) is multi_context
 
     data = source.source.encode(source.encoding)
-    pipe.assert_called_once_with(source.engine, format_, data)
+    open_pipe.assert_called_once_with(source.engine, format_)
+    multi_context.write.call_args_list == [((data,), {}), ((b'\n',), {})]
 
 
-def test_pipe(pipe, source):
-    assert source.pipe() is pipe.return_value
+def test_pipe(open_pipe, source):
+    multi_context = open_pipe.return_value.__enter__.return_value
+
+    assert source.pipe() is multi_context
 
     data = source.source.encode(source.encoding)
-    pipe.assert_called_once_with(source.engine, source.format, data)
+    open_pipe.assert_called_once_with(source.engine, source.format)
+    multi_context.write.call_args_list == [((data,), {}), ((b'\n',), {})]
 
 
 def test_filepath(test_platform, source):