Warn when SoupStrainer is used with the html5lib tree builder.

4 files changed, 23 insertions, 25 deletions

diff --git a/NEWS.txt b/NEWS.txt
index c93541e..bcffd61 100644
--- a/NEWS.txt
+++ b/NEWS.txt
@@ -1,4 +1,4 @@
-= 4.0.0b8 () =
+= 4.0.0b8 (20110224) =
 
 * All tree builders now preserve namespace information in the
   documents they parse.
@@ -10,6 +10,10 @@
 
 * The string representation of a DOCTYPE always ends in a newline.
 
+* Issue a warning if the user tries to use a SoupStrainer in
+  conjunction with the html5lib tree builder, which doesn't support
+  them.
+
 = 4.0.0b7 (20110223) =
 
 * Upon decoding to string, any characters that can't be represented in
diff --git a/TODO.txt b/TODO.txt
index 61f9aee..e57d799 100644
--- a/TODO.txt
+++ b/TODO.txt
@@ -1,29 +1,14 @@
-Bugs
-----
-
-* html5lib doesn't support SoupStrainers, which is OK, but there
-  should be a warning about it.
-
-Big features
-------------
-
-* Add namespace support.
-
 Optimizations
 -------------
 
-markup_attr_map can be optimized since it's always a map now.
-
-BS3 features not yet ported
----------------------------
+The html5lib tree builder doesn't use the standard tree-building API,
+which worries me. (This may also be why the tree builder doesn't
+support SoupStrainers, but I think that has more to do with the fact
+that the html5lib tree builder is constantly rearranging the tree, and
+will crash if something it parsed earlier didn't actually make it into
+the tree.)
 
-* In BS3, "soup.aTag" is the same as 'soup.find("a")'. This lets you
-locate a tag called (let's say) "find" with attribute
-access. "soup.find" won't do what you want, but "soup.findTag" will.
-
-This still works In BS4 but it's deprecated. I could make
-"soup.find_tag" work the same way as "soup.find('find')", but I don't
-think it's worth it.
+markup_attr_map can be optimized since it's always a map now.
 
 CDATA
 -----
diff --git a/bs4/builder/_html5lib.py b/bs4/builder/_html5lib.py
index 26b1773..cf716df 100644
--- a/bs4/builder/_html5lib.py
+++ b/bs4/builder/_html5lib.py
@@ -2,6 +2,7 @@ __all__ = [
     'HTML5TreeBuilder',
     ]
 
+import warnings
 from bs4.builder import (
     PERMISSIVE,
     HTML,
@@ -30,6 +31,8 @@ class HTML5TreeBuilder(HTMLTreeBuilder):
 
     # These methods are defined by Beautiful Soup.
     def feed(self, markup):
+        if self.soup.parse_only is not None:
+            warnings.warn("You provided a value for parse_only, but the html5lib tree builder doesn't support parse_only. The entire document will be parsed.")
         parser = html5lib.HTMLParser(tree=self.create_treebuilder)
         doc = parser.parse(markup, encoding=self.user_specified_encoding)
 
diff --git a/bs4/tests/test_html5lib.py b/bs4/tests/test_html5lib.py
index 0828cfd..f195f7d 100644
--- a/bs4/tests/test_html5lib.py
+++ b/bs4/tests/test_html5lib.py
@@ -1,5 +1,7 @@
 """Tests to ensure that the html5lib tree builder generates good trees."""
 
+import warnings
+
 try:
     from bs4.builder import HTML5TreeBuilder
     HTML5LIB_PRESENT = True
@@ -26,11 +28,15 @@ class HTML5LibBuilderSmokeTest(SoupTest, HTML5TreeBuilderSmokeTest):
         # The html5lib tree builder does not support SoupStrainers.
         strainer = SoupStrainer("b")
         markup = "<p>A <b>bold</b> statement.</p>"
-        soup = self.soup(markup,
-                         parse_only=strainer)
+        with warnings.catch_warnings(record=True) as w:
+            soup = self.soup(markup, parse_only=strainer)
         self.assertEqual(
             soup.decode(), self.document_for(markup))
 
+        self.assertTrue(
+            "the html5lib tree builder doesn't support parse_only" in
+            str(w[0].message))
+
     def test_correctly_nested_tables(self):
         """html5lib inserts <tbody> tags where other parsers don't."""
         markup = ('<table id="1">'