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" is 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 <[email protected]> --- 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 d7a79a9b8aee..64af7318cb67 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 a SourceInfo object corresponding to a builtin definition. + """ + return cls('', -1, None) + + def __bool__(self) -> bool: + # "if info: ..." is false if info is the builtin sentinel. + 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
