Swallow warnings during anonymous compilation of source

changelog/4260.bugfix.rst

@@ -0,0 +1 @@
+Swallow warnings during anonymous compilation of source.

src/_pytest/_code/source.py

@@ -8,14 +8,13 @@
 import sys
 import textwrap
 import tokenize
+import warnings
 from ast import PyCF_ONLY_AST as _AST_FLAG
 from bisect import bisect_right
 
 import py
 import six
 
-cpy_compile = compile
-
 
 class Source(object):
     """ an immutable object holding a source code fragment,
@@ -161,7 +160,7 @@ def compile(
                 filename = base + "%r %s:%d>" % (filename, fn, lineno)
         source = "\n".join(self.lines) + "\n"
         try:
-            co = cpy_compile(source, filename, mode, flag)
+            co = compile(source, filename, mode, flag)
         except SyntaxError:
             ex = sys.exc_info()[1]
             # re-represent syntax errors from parsing python strings
@@ -195,7 +194,7 @@ def compile_(source, filename=None, mode="exec", flags=0, dont_inherit=0):
     """
     if isinstance(source, ast.AST):
         # XXX should Source support having AST?
-        return cpy_compile(source, filename, mode, flags, dont_inherit)
+        return compile(source, filename, mode, flags, dont_inherit)
     _genframe = sys._getframe(1)  # the caller
     s = Source(source)
     co = s.compile(filename, mode, flags, _genframe=_genframe)
@@ -290,7 +289,11 @@ def get_statement_startend2(lineno, node):
 def getstatementrange_ast(lineno, source, assertion=False, astnode=None):
     if astnode is None:
         content = str(source)
-        astnode = compile(content, "source", "exec", 1024)  # 1024 for AST
+        # See #4260:
+        # don't produce duplicate warnings when compiling source to find ast
+        with warnings.catch_warnings():
+            warnings.simplefilter("ignore")
+            astnode = compile(content, "source", "exec", _AST_FLAG)
 
     start, end = get_statement_startend2(lineno, astnode)
     # we need to correct the end: