Merge pull request scrapy#141 from Gallaecio/selector-data-preview

Shorten selector representations using an ellipsis

parsel/selector.py

@@ -7,7 +7,7 @@
 import six
 from lxml import etree, html
 
-from .utils import flatten, iflatten, extract_regex
+from .utils import flatten, iflatten, extract_regex, shorten
 from .csstranslator import HTMLTranslator, GenericTranslator
 
 
@@ -358,6 +358,6 @@ def __bool__(self):
     __nonzero__ = __bool__
 
     def __str__(self):
-        data = repr(self.get()[:40])
+        data = repr(shorten(self.get(), width=40))
         return "<%s xpath=%r data=%s>" % (type(self).__name__, self._expr, data)
     __repr__ = __str__

parsel/utils.py

@@ -80,4 +80,15 @@ def extract_regex(regex, text, replace_entities=True):
     strings = flatten(strings)
     if not replace_entities:
         return strings
-    return [w3lib_replace_entities(s, keep=['lt', 'amp']) for s in strings]
+    return [w3lib_replace_entities(s, keep=['lt', 'amp']) for s in strings]
+
+
+def shorten(text, width, suffix='...'):
+    """Truncate the given text to fit in the given width."""
+    if len(text) <= width:
+        return text
+    if width > len(suffix):
+        return text[:width-len(suffix)] + suffix
+    if width >= 0:
+        return suffix[len(suffix)-width:]
+    raise ValueError('width must be equal or greater than 0')

tests/test_selector.py

@@ -133,9 +133,9 @@ def test_representation_slice(self):
         body = u"<p><input name='{}' value='\xa9'/></p>".format(50 * 'b')
         sel = self.sscls(text=body)
 
-        representation = "<Selector xpath='//input/@name' data='{}'>".format(40 * 'b')
+        representation = "<Selector xpath='//input/@name' data='{}...'>".format(37 * 'b')
         if six.PY2:
-            representation = "<Selector xpath='//input/@name' data=u'{}'>".format(40 * 'b')
+            representation = "<Selector xpath='//input/@name' data=u'{}...'>".format(37 * 'b')
 
         self.assertEqual(
             [repr(it) for it in sel.xpath('//input/@name')],

tests/test_utils.py

@@ -0,0 +1,26 @@
+from parsel.utils import shorten
+
+from pytest import mark, raises
+import six
+
+
+@mark.parametrize(
+    'width,expected',
+    (
+        (-1, ValueError),
+        (0, u''),
+        (1, u'.'),
+        (2, u'..'),
+        (3, u'...'),
+        (4, u'f...'),
+        (5, u'fo...'),
+        (6, u'foobar'),
+        (7, u'foobar'),
+    )
+)
+def test_shorten(width, expected):
+    if isinstance(expected, six.string_types):
+        assert shorten(u'foobar', width) == expected
+    else:
+        with raises(expected):
+            shorten(u'foobar', width)