Merge branch 'master' into master

6 files changed, 58 insertions, 11 deletions

diff --git a/.travis.yml b/.travis.yml
index ce324be..696c1c0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,6 +17,8 @@ matrix:
       env: TOXENV=py36
     - python: 3.7
       env: TOXENV=py37
+    - python: 3.8
+      env: TOXENV=py38
     - python: pypy2.7-6.0
       env: TOXENV=pypy
     - python: pypy3.5-6.0
diff --git a/pycodestyle.py b/pycodestyle.py
index 7b5b4f8..b7e0b2f 100755
--- a/pycodestyle.py
+++ b/pycodestyle.py
@@ -117,11 +117,13 @@ ARITHMETIC_OP = frozenset(['**', '*', '/', '//', '+', '-'])
 WS_OPTIONAL_OPERATORS = ARITHMETIC_OP.union(['^', '&', '|', '<<', '>>', '%'])
 # Warn for -> function annotation operator in py3.5+ (issue 803)
 FUNCTION_RETURN_ANNOTATION_OP = ['->'] if sys.version_info >= (3, 5) else []
+ASSIGNMENT_EXPRESSION_OP = [':='] if sys.version_info >= (3, 8) else []
 WS_NEEDED_OPERATORS = frozenset([
     '**=', '*=', '/=', '//=', '+=', '-=', '!=', '<>', '<', '>',
     '%=', '^=', '&=', '|=', '==', '<=', '>=', '<<=', '>>=', '=',
     'and', 'in', 'is', 'or'] +
-    FUNCTION_RETURN_ANNOTATION_OP)
+    FUNCTION_RETURN_ANNOTATION_OP +
+    ASSIGNMENT_EXPRESSION_OP)
 WHITESPACE = frozenset(' \t')
 NEWLINE = frozenset([tokenize.NL, tokenize.NEWLINE])
 SKIP_TOKENS = NEWLINE.union([tokenize.INDENT, tokenize.DEDENT])
@@ -134,7 +136,7 @@ RAISE_COMMA_REGEX = re.compile(r'raise\s+\w+\s*,')
 RERAISE_COMMA_REGEX = re.compile(r'raise\s+\w+\s*,.*,\s*\w+\s*$')
 ERRORCODE_REGEX = re.compile(r'\b[A-Z]\d{3}\b')
 DOCSTRING_REGEX = re.compile(r'u?r?["\']')
-EXTRANEOUS_WHITESPACE_REGEX = re.compile(r'[\[({] | [\]}),;:]')
+EXTRANEOUS_WHITESPACE_REGEX = re.compile(r'[\[({] | [\]}),;]| :(?!=)')
 WHITESPACE_AFTER_COMMA_REGEX = re.compile(r'[,;:]\s*(?:  |\t)')
 COMPARE_SINGLETON_REGEX = re.compile(r'(\bNone|\bFalse|\bTrue)?\s*([=!]=)'
                                      r'\s*(?(1)|(None|False|True))\b')
@@ -495,13 +497,16 @@ def missing_whitespace(logical_line):
     line = logical_line
     for index in range(len(line) - 1):
         char = line[index]
-        if char in ',;:' and line[index + 1] not in WHITESPACE:
+        next_char = line[index + 1]
+        if char in ',;:' and next_char not in WHITESPACE:
             before = line[:index]
             if char == ':' and before.count('[') > before.count(']') and \
                     before.rfind('{') < before.rfind('['):
                 continue  # Slice syntax, no space required
-            if char == ',' and line[index + 1] == ')':
+            if char == ',' and next_char == ')':
                 continue  # Allow tuple with only one element: (3,)
+            if char == ':' and next_char == '=' and sys.version_info >= (3, 8):
+                continue  # Allow assignment expression
             yield index, "E231 missing whitespace after '%s'" % char
 
 
@@ -1077,7 +1082,8 @@ def module_imports_on_top_of_file(
             line = line[1:]
         return line and (line[0] == '"' or line[0] == "'")
 
-    allowed_try_keywords = ('try', 'except', 'else', 'finally')
+    allowed_keywords = (
+        'try', 'except', 'else', 'finally', 'with', 'if', 'elif')
 
     if indent_level:  # Allow imports in conditional statement/function
         return
@@ -1091,9 +1097,9 @@ def module_imports_on_top_of_file(
             yield 0, "E402 module level import not at top of file"
     elif re.match(DUNDER_REGEX, line):
         return
-    elif any(line.startswith(kw) for kw in allowed_try_keywords):
-        # Allow try, except, else, finally keywords intermixed with
-        # imports in order to support conditional importing
+    elif any(line.startswith(kw) for kw in allowed_keywords):
+        # Allow certain keywords intermixed with imports in order to
+        # support conditional or filtered importing
         return
     elif is_string_literal(line):
         # The first literal is a docstring, allow it. Otherwise, report
@@ -1145,7 +1151,9 @@ def compound_statements(logical_line):
         update_counts(line[prev_found:found], counts)
         if ((counts['{'] <= counts['}'] and   # {'a': 1} (dict)
              counts['['] <= counts[']'] and   # [1:2] (slice)
-             counts['('] <= counts[')'])):    # (annotation)
+             counts['('] <= counts[')']) and  # (annotation)
+            not (sys.version_info >= (3, 8) and
+                 line[found + 1] == '=')):  # assignment expression
             lambda_kw = LAMBDA_REGEX.search(line, 0, found)
             if lambda_kw:
                 before = line[:lambda_kw.start()].rstrip()
@@ -1209,13 +1217,16 @@ def explicit_line_join(logical_line, tokens):
                 parens -= 1
 
 
+_SYMBOLIC_OPS = frozenset("()[]{},:.;@=%~") | frozenset(("...",))
+
+
 def _is_binary_operator(token_type, text):
     is_op_token = token_type == tokenize.OP
     is_conjunction = text in ['and', 'or']
     # NOTE(sigmavirus24): Previously the not_a_symbol check was executed
     # conditionally. Since it is now *always* executed, text may be
     # None. In that case we get a TypeError for `text not in str`.
-    not_a_symbol = text and text not in "()[]{},:.;@=%~"
+    not_a_symbol = text and text not in _SYMBOLIC_OPS
     # The % character is strictly speaking a binary operator, but the
     # common usage seems to be to put it next to the format parameters,
     # after a line break.
diff --git a/testsuite/E40.py b/testsuite/E40.py
index f9a18fc..6c71fa2 100644
--- a/testsuite/E40.py
+++ b/testsuite/E40.py
@@ -34,6 +34,21 @@ finally:
     print('made attempt to import foo')
 
 import bar
+#: Okay
+with warnings.catch_warnings():
+    warnings.filterwarnings("ignore", DeprecationWarning)
+    import foo
+
+import bar
+#: Okay
+if False:
+    import foo
+elif not True:
+    import bar
+else:
+    import mwahaha
+
+import bar
 #: E402
 VERSION = '1.2.3'
 
diff --git a/testsuite/python3.py b/testsuite/python3.py
index be7c58f..709695a 100644
--- a/testsuite/python3.py
+++ b/testsuite/python3.py
@@ -37,3 +37,10 @@ class Class:
 
     def m(self):
         xs: List[int] = []
+
+
+# Used to trigger W504
+def f(
+    x: str = ...
+):
+    ...
diff --git a/testsuite/python38.py b/testsuite/python38.py
index adf217d..5f62a3f 100644
--- a/testsuite/python38.py
+++ b/testsuite/python38.py
@@ -1,3 +1,15 @@
 #: Okay
 def f(a, /, b):
     pass
+#: Okay
+if x := 1:
+    print(x)
+if m and (token := m.group(1)):
+    pass
+stuff = [[y := f(x), x / y] for x in range(5)]
+#: E225:1:5
+if x:= 1:
+    pass
+#: E225:1:18
+if False or (x :=1):
+    pass
diff --git a/tox.ini b/tox.ini
index 742888c..fc42fc1 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = py27, py34, py35, py36, py37, pypy, pypy3, jython
+envlist = py27, py34, py35, py36, py37, py38, pypy, pypy3, jython
 skipsdist = True
 skip_missing_interpreters = True