Fix for table stdout detection in some cases.

When a table is created prior to sys.stdout being changed to some other
file object, as can be the case when a pager is used, the table would
incorrectly assume it was not drawing to a tty when it came time to
print output and would not use the proper terminal size, despite using
the correct renderer class.

This patch changes the Table.file attr to be a lazy property that checks
the user override value and otherwise returns the current value of
sys.stdout.

shellish/layout/table.py

@@ -149,18 +149,13 @@ def __init__(self, columns=None, headers=None, accessors=None, width=None,
         self.headers = tuple(headers or ())
         self.width = width
         self.flex = flex
-        self.file = file if file is not None else sys.stdout
+        self._file = file
         self.hide_header = hide_header
         self.hide_footer = hide_footer
         self.column_mask = column_mask
         self.align_rows = align_rows
         self.default_renderer = None
-        if not renderer:
-            if not self.file.isatty():
-                renderer = 'plain'
-            else:
-                renderer = 'terminal'
-        self.renderer_class = self.lookup_renderer(renderer)
+        self.renderer = renderer
         if cliptext is not None:
             self.cliptext = cliptext
         if column_padding is not None:
@@ -184,8 +179,23 @@ def close(self, exception=None):
         if self.default_renderer:
             self.default_renderer.close(exception=exception)
 
-    def lookup_renderer(self, name):
-        return self.renderer_types[name]
+    @property
+    def file(self):
+        if self._file is not None:
+            return self._file
+        else:
+            return sys.stdout
+
+    def make_renderer(self):
+        if not self.renderer:
+            if not self.file.isatty():
+                renderer = 'plain'
+            else:
+                renderer = 'terminal'
+        else:
+            renderer = self.renderer
+        Renderer = self.renderer_types[renderer]
+        return Renderer(self)
 
     @classmethod
     def register_renderer(cls, renderer):
@@ -317,6 +327,7 @@ def ns2table(ns):
             }
         return ns2table
 
+
     def make_accessors(self, columns):
         """ Accessors can be numeric keys for sequence row data, string keys
         for mapping row data, or a callable function.  For numeric and string
@@ -370,7 +381,7 @@ def print(self, rows):
         rendered yet, we will make a renderer instance which will freeze
         state. """
         if not self.default_renderer:
-            self.default_renderer = self.renderer_class(self)
+            self.default_renderer = self.make_renderer()
         self.default_renderer.print(rows)
 
     def print_row(self, row):

test/layout.py

@@ -11,7 +11,7 @@
 def calc_table(*columns, width=100, data=None, flex=False, **kwargs):
     t = L.Table(columns=columns, width=width, flex=flex, column_padding=0,
                 **kwargs)
-    renderer = t.renderer_class(t)
+    renderer = t.make_renderer()
     renderer.print(data or [])
     return renderer.widths
 
@@ -190,11 +190,11 @@ def test_columns_from_accessors(self):
 
     def test_columns_width_spec_only(self):
         output, t = self.table(columns=[None, None, None])
-        t.renderer_class(t)
+        t.make_renderer()
 
     def test_columns_empty_style_spec(self):
         output, t = self.table(columns=[{}, {}, {}])
-        t.renderer_class(t)
+        t.make_renderer()
 
     def test_empty_iter(self):
         output, t = self.table([None])
@@ -412,7 +412,7 @@ class JSONTableRenderer(unittest.TestCase):
 
     def setUp(self):
         t = L.Table([None], renderer='json')
-        self.r = t.renderer_class(t)
+        self.r = t.make_renderer()
 
     def test_make_key_snakecase(self):
         self.assertEqual(self.r.make_key('snake_case'), 'snakeCase')