Fix crash with NameError through decorator during collection (#243)

This was a quick hack/fix, without knowing what I was doing, could need more tests likely.

src/_pytest/_code/code.py

@@ -244,12 +244,14 @@ def getsource(self, astcache=None) -> Optional["Source"]:
                 astnode = astcache.get(key, None)
         start = self.getfirstlinesource()
         try:
-            astnode, _, end = getstatementrange_ast(
+            astnode, ast_start, end = getstatementrange_ast(
                 self.lineno, source, astnode=astnode
             )
         except SyntaxError:
             end = self.lineno + 1
         else:
+            if ast_start - 1 < start:
+                start = ast_start
             if key is not None:
                 astcache[key] = astnode
         return source[start:end]

src/_pytest/_code/source.py

@@ -352,6 +352,8 @@ def get_statement_startend2(lineno: int, node: ast.AST) -> Tuple[int, Optional[i
     # AST's line numbers start indexing at 1
     values = []  # type: List[int]
     for x in ast.walk(node):
+        if isinstance(x, (ast.FunctionDef)):
+            values.extend(deco.lineno - 1 for deco in x.decorator_list)
         if isinstance(x, (ast.stmt, ast.ExceptHandler)):
             values.append(x.lineno - 1)
             for name in ("finalbody", "orelse"):

testing/code/test_code.py

@@ -229,3 +229,23 @@ def test_not_raise_exception_with_mixed_encoding(self, tw_mock) -> None:
             tw_mock.lines[0]
             == r"unicode_string = São Paulo, utf8_string = b'S\xc3\xa3o Paulo'"
         )
+
+
+def test_nameerror_with_decorator(testdir):
+    # TODO: unittest with Code (additionally)?!
+    source = """
+        @nameerror_deco1
+        def test():
+            pass
+        """
+    p1 = testdir.makepyfile(source)
+    result = testdir.runpytest(str(p1), "-rf")
+    result.stdout.fnmatch_lines(
+        [
+            "*_ ERROR collecting test_nameerror_with_decorator.py _*",
+            "test_nameerror_with_decorator.py:1: in <module>",
+            "    @nameerror_deco1",
+            "E   NameError: name 'nameerror_deco1' is not defined",
+            "*= 1 error in *",
+        ]
+    )