Merge pull request #256 from thatch/issue249

Better validate `except` without a space after it.
Instagram · Mar 5, 2020 · b31cf0c · b31cf0c
2 parents 196a4f6 + d9f0666
commit b31cf0c
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Showing 3 changed files with 56 additions and 5 deletions.
diff --git a/libcst/_nodes/statement.py b/libcst/_nodes/statement.py
@@ -785,10 +785,15 @@ def _validate(self) -> None:
             raise CSTValidationError(
                 "Must use a Name node for AsName name inside ExceptHandler."
             )
-        if self.type is not None and self.whitespace_after_except.empty:
-            raise CSTValidationError(
-                "Must have at least one space after except when ExceptHandler has a type."
-            )
+        type_ = self.type
+        if type_ is not None and self.whitespace_after_except.empty:
+            # Space is only required when the first char in `type` could start
+            # an identifier.  In the most common cases, we want to allow
+            # grouping or tuple parens.
+            if isinstance(type_, Name) and not type_.lpar:
+                raise CSTValidationError(
+                    "Must have at least one space after except when ExceptHandler has a type."
+                )
 
     def _visit_and_replace_children(self, visitor: CSTVisitorT) -> "ExceptHandler":
         return ExceptHandler(

diff --git a/libcst/_nodes/tests/test_try.py b/libcst/_nodes/tests/test_try.py
@@ -281,6 +281,50 @@ class TryTest(CSTNodeTest):
                 + "        pass\n",
                 "parser": None,
             },
+            # No space when using grouping parens
+            {
+                "node": cst.Try(
+                    cst.SimpleStatementSuite((cst.Pass(),)),
+                    handlers=(
+                        cst.ExceptHandler(
+                            cst.SimpleStatementSuite((cst.Pass(),)),
+                            whitespace_after_except=cst.SimpleWhitespace(""),
+                            type=cst.Name(
+                                "Exception",
+                                lpar=(cst.LeftParen(),),
+                                rpar=(cst.RightParen(),),
+                            ),
+                        ),
+                    ),
+                ),
+                "code": "try: pass\nexcept(Exception): pass\n",
+                "parser": parse_statement,
+            },
+            # No space when using tuple
+            {
+                "node": cst.Try(
+                    cst.SimpleStatementSuite((cst.Pass(),)),
+                    handlers=(
+                        cst.ExceptHandler(
+                            cst.SimpleStatementSuite((cst.Pass(),)),
+                            whitespace_after_except=cst.SimpleWhitespace(""),
+                            type=cst.Tuple(
+                                [
+                                    cst.Element(
+                                        cst.Name("IOError"),
+                                        comma=cst.Comma(
+                                            whitespace_after=cst.SimpleWhitespace(" ")
+                                        ),
+                                    ),
+                                    cst.Element(cst.Name("ImportError")),
+                                ]
+                            ),
+                        ),
+                    ),
+                ),
+                "code": "try: pass\nexcept(IOError, ImportError): pass\n",
+                "parser": parse_statement,
+            },
         )
     )
     def test_valid(self, **kwargs: Any) -> None:

diff --git a/libcst/_parser/conversions/params.py b/libcst/_parser/conversions/params.py
@@ -90,7 +90,9 @@
     ),
     version="<=3.5",
 )
-def convert_argslist(config: ParserConfig, children: Sequence[Any]) -> Any:
+def convert_argslist(  # noqa: C901
+    config: ParserConfig, children: Sequence[Any]
+) -> Any:
     posonly_params: List[Param] = []
     posonly_ind: Union[ParamSlash, MaybeSentinel] = MaybeSentinel.DEFAULT
     params: List[Param] = []