Re: [PATCH 07/22] qapi/parser: assert object keys are strings

[John Snow]

On 4/25/21 3:27 AM, Markus Armbruster wrote:
John Snow <js...@redhat.com> writes:
The single quote token implies the value is a string. Assert this to be
the case.

Signed-off-by: John Snow <js...@redhat.com>
---
  scripts/qapi/parser.py | 2 ++
  1 file changed, 2 insertions(+)

diff --git a/scripts/qapi/parser.py b/scripts/qapi/parser.py
index 6b443b1247e..8d1fe0ddda5 100644
--- a/scripts/qapi/parser.py
+++ b/scripts/qapi/parser.py
@@ -246,6 +246,8 @@ def get_members(self):
              raise QAPIParseError(self, "expected string or '}'")
          while True:
              key = self.val
+            assert isinstance(key, str)  # Guaranteed by tok == "'"
+
              self.accept()
              if self.tok != ':':
                  raise QAPIParseError(self, "expected ':'")

The assertion is correct, but I wonder why mypy needs it.  Can you help?


The lexer value can also be True/False (Maybe None? I forget) based on 
the Token returned. Here, since the token was the single quote, we know 
that value must be a string.

Mypy has no insight into the correlation between the Token itself and 
the token value, because that relationship is not expressed via the type 
system.

--js