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[PATCH v2 06/12] qapi/source: Add builtin null-object sentinel
From: |
John Snow |
Subject: |
[PATCH v2 06/12] qapi/source: Add builtin null-object sentinel |
Date: |
Wed, 16 Dec 2020 20:59:21 -0500 |
We use None to represent an object that has no source information
because it's a builtin. This complicates interface typing, since many
interfaces expect that there is an info object available to print errors
with.
Introduce a special QAPISourceInfo that represents these built-ins so
that if an error should so happen to occur relating to one of these
builtins that we will be able to print its information, and interface
typing becomes simpler: you will always have a source info object.
This object will evaluate as False, so "if info" remains a valid
idiomatic construct.
NB: It was intentional to not allow empty constructors or similar to
create "empty" source info objects; callers must explicitly invoke
'builtin()' to pro-actively opt into using the sentinel. This should
prevent use-by-accident.
Signed-off-by: John Snow <jsnow@redhat.com>
---
scripts/qapi/source.py | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
diff --git a/scripts/qapi/source.py b/scripts/qapi/source.py
index d7a79a9b8ae..a049b73b57b 100644
--- a/scripts/qapi/source.py
+++ b/scripts/qapi/source.py
@@ -11,7 +11,12 @@
import copy
import sys
-from typing import List, Optional, TypeVar
+from typing import (
+ List,
+ Optional,
+ Type,
+ TypeVar,
+)
class QAPISchemaPragma:
@@ -41,6 +46,17 @@ def __init__(self, fname: str, line: int,
self.defn_meta: Optional[str] = None
self.defn_name: Optional[str] = None
+ @classmethod
+ def builtin(cls: Type[T]) -> T:
+ """
+ Create an instance corresponding to a built-in definition.
+ """
+ return cls('', -1, None)
+
+ def __bool__(self) -> bool:
+ # "if info" is false if @info corresponds to a built-in definition.
+ return bool(self.fname)
+
def set_defn(self, meta: str, name: str) -> None:
self.defn_meta = meta
self.defn_name = name
@@ -73,4 +89,6 @@ def include_path(self) -> str:
return ret
def __str__(self) -> str:
+ if not bool(self):
+ return '[builtin]'
return self.include_path() + self.in_defn() + self.loc()
--
2.26.2
- [PATCH v2 01/12] qapi/commands: assert arg_type is not None, (continued)
- [PATCH v2 01/12] qapi/commands: assert arg_type is not None, John Snow, 2020/12/16
- [PATCH v2 02/12] qapi/events: fix visit_event typing, John Snow, 2020/12/16
- [PATCH v2 03/12] qapi/main: handle theoretical None-return from re.match(), John Snow, 2020/12/16
- [PATCH v2 10/12] tests/qapi-schema: Add quotes to module name in test output, John Snow, 2020/12/16
- [PATCH v2 04/12] qapi/gen: assert that _start_if is not None in _wrap_ifcond, John Snow, 2020/12/16
- [PATCH v2 08/12] qapi/gen: write _genc/_genh access shims, John Snow, 2020/12/16
- [PATCH v2 12/12] qapi: enable strict-optional checks, John Snow, 2020/12/16
- [PATCH v2 07/12] qapi/schema: make QAPISourceInfo mandatory, John Snow, 2020/12/16
- [PATCH v2 05/12] qapi/gen: use './builtin' for the built-in module name, John Snow, 2020/12/16
- [PATCH v2 09/12] qapi/gen: move write method to QAPIGenC, make fname a str, John Snow, 2020/12/16
- [PATCH v2 06/12] qapi/source: Add builtin null-object sentinel,
John Snow <=
- [PATCH v2 11/12] qapi/schema: Name the builtin module "" instead of None, John Snow, 2020/12/16