push() now swallows syntax errors and immediately produces a 'ready'

state.

This is intended, as the invalid input may in fact be OK with ipython
extensions, but that can only be ascertained by the kernel, so the
client should send this right away to the kernel.

IPython/core/blockbreaker.py

@@ -179,14 +179,21 b' class BlockBreaker(object):'
         # exception is raised in compilation, we don't mislead by having
         # inconsistent code/source attributes.
         self.code, self.is_complete = None, None
+        try:
         self.code = self.compile(source)
+        # Invalid syntax can produce any of a number of different errors from
+        # inside the compiler, so we have to catch them all.  Syntax errors
+        # immediately produce a 'ready' block, so the invalid Python can be
+        # sent to the kernel for evaluation with possible ipython
+        # special-syntax conversion.
+        except (SyntaxError, OverflowError, ValueError, TypeError, MemoryError):
+            self.is_complete = True
+        else:
         # Compilation didn't produce any exceptions (though it may not have
         # given a complete code object)
-        if self.code is None:
-            self.is_complete = False
-        else:
-            self.is_complete = True
+            self.is_complete = self.code is not None
         self._update_indent(lines)
+
         return self.is_complete
 
     def interactive_block_ready(self):

IPython/core/tests/test_blockbreaker.py

@@ -181,3 +181,11 b' class BlockBreakerTestCase(unittest.TestCase):'
         self.assertFalse(bb.interactive_block_ready())
         bb.push('')
         self.assertTrue(bb.interactive_block_ready())
+
+    def test_syntax_error(self):
+        bb = self.bb
+        # Syntax errors immediately produce a 'ready' block, so the invalid
+        # Python can be sent to the kernel for evaluation with possible ipython
+        # special-syntax conversion.
+        bb.push('run foo')
+        self.assertTrue(bb.interactive_block_ready())