Fixed an incorrectly raised exception when inserting a tag before or

  after an identical tag. [bug=1810692]

3 files changed, 20 insertions, 2 deletions

diff --git a/CHANGELOG b/CHANGELOG
index b778f6d..389b949 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,13 @@
+= 4.7.1 (Unreleased)
+
+* Fixed a significant performance problem introduced in 4.7.0. [bug=1810617]
+
+* Fixed an incorrectly raised exception when inserting a tag before or
+  after an identical tag. [bug=1810692]
+
+* Beautiful Soup will no longer try to keep track of namespaces that
+  are not defined with a prefix; this can confuse soupselect. [bug=1810680]
+
 = 4.7.0 (20181231)
 
 * Beautiful Soup's CSS Selector implementation has been replaced by a
diff --git a/bs4/element.py b/bs4/element.py
index c367dee..5718d31 100644
--- a/bs4/element.py
+++ b/bs4/element.py
@@ -455,7 +455,7 @@ class PageElement(object):
         if parent is None:
             raise ValueError(
                 "Element has no parent, so 'before' has no meaning.")
-        if self in args:
+        if any(x is self for x in args):
                 raise ValueError("Can't insert an element before itself.")
         for predecessor in args:
             # Extract first so that the index won't be screwed up if they
@@ -476,7 +476,7 @@ class PageElement(object):
         if parent is None:
             raise ValueError(
                 "Element has no parent, so 'after' has no meaning.")
-        if self in args:
+        if any(x is self for x in args):
             raise ValueError("Can't insert an element after itself.")
         
         offset = 0
diff --git a/bs4/tests/test_tree.py b/bs4/tests/test_tree.py
index 2290558..6d79454 100644
--- a/bs4/tests/test_tree.py
+++ b/bs4/tests/test_tree.py
@@ -971,6 +971,10 @@ class TestTreeModification(SoupTest):
         # Can't insert before if an element has no parent.
         b.extract()
         self.assertRaises(ValueError, b.insert_before, "nope")
+
+        # Can insert an identical element
+        soup = self.soup("<a>")
+        soup.a.insert_before(soup.new_tag("a"))
         
     def test_insert_multiple_before(self):
         soup = self.soup("<a>foo</a><b>bar</b>")
@@ -1000,6 +1004,10 @@ class TestTreeModification(SoupTest):
         # Can't insert after if an element has no parent.
         b.extract()
         self.assertRaises(ValueError, b.insert_after, "nope")
+
+        # Can insert an identical element
+        soup = self.soup("<a>")
+        soup.a.insert_before(soup.new_tag("a"))
         
     def test_insert_multiple_after(self):
         soup = self.soup("<a>foo</a><b>bar</b>")