cc39ae57dc
Here's an example of one of these errors:
```
INVALID_KEY predicate py_cobjectnames(@py_cobject obj, string name)
The key set {obj} does not functionally determine all fields. Here is a
pair of tuples that agree on the key set but differ at index 1: Tuple 1
in row 63874: (72088,"u'<X>'") Tuple 2 in row 63875: (72088,"u'<?>'")
```
(Here, the substring `X` should really be the Unicode character U+FFFD,
but for some reason I'm not allowed to put that in this commit message.)
Inside the extractor, we assign IDs based on the string type (bytestring
or Unicode) and a hash of the UTF-8 encoded content of the string. In
this case, however, certain _different_ strings were receiving the same
hash, due to replacement characters in the encoding process.
In particular, we were converting unencodable characters to question
marks in one place, and to U+FFFD in another place. This caused a
discrepancy that lead to the dataset check error.
To fix this, we put in a custom error handler that always puts the
U+FFFD character in place of unencodable characters. With this, the
strings now agree, and hence there is no clash.
CodeQL
This open source repository contains the standard CodeQL libraries and queries that power GitHub Advanced Security and the other application security products that GitHub makes available to its customers worldwide.
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