Escape rename keys when generating (un)structuring code - #771
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Tinche merged 3 commits intoSep 1, 2026
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The generated (un)structuring code interpolated a field's rename target into
the source inside single quotes (o['{kn}'], res['{kn}'], etc). A rename key is
an arbitrary dict key, so one containing a quote (for example "it's") produced
invalid source and raised SyntaxError. Interpolate the key with repr ({kn!r})
so any key string is embedded safely.
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Done, parametrized in |
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Great, thanks! |
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`make_hetero_tuple_structure_fn` builds the per-index note by interpolating
`str(cl)` into a single-quoted string literal in the generated source, at
`src/cattrs/gen/__init__.py` line 903 on main:
`f"__c_ivn('Structuring {cl} @ index {ix}', {ix}, {type_name})]"`. When a type
argument has a quote in its `repr`, such as `Literal["a"]`, the quote closes
the literal early and compiling the hook raises `SyntaxError` before any data
is looked at. This only affects the generated path, so `Converter()` fails
where `BaseConverter()` and `Converter(detailed_validation=False)` succeed.
`NamedTuple`s structure through the same factory, so they crash the same way.
This is the same class of bug as #769 and #771, and the fix is the same shape
already used in `src/cattrs/gen/typeddicts.py` line 394: build the note text in
Python and embed it with `repr`. The note text is byte-identical to before, so
nothing that reads `IterableValidationNote` changes.
The test covers a quote from `Literal`, the same quote nested inside a `List`,
an `Annotated` whose metadata repr contains both quote characters, and a
`NamedTuple` field, then triggers a real validation failure and checks the note
reads exactly as it does for a tuple whose arguments have no quotes. The
expected note is built from the same type expression so the assertion does not
depend on how a given Python version renders typing objects.
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Summary
A field's
renametarget is a dictionary key, so it can legitimately contain any character. But the generated (un)structuring code interpolates it into the source inside single quotes:So a rename to a key containing a quote produces invalid source and blows up when it's compiled:
Fix
Interpolate the key with
repr({kn!r}) instead of hand-written single quotes, so any key string is embedded as a valid, correctly-escaped literal. This only affects therenamekey (kn); attrs already rejects aliases that aren't valid identifiers, so the alias-based keys can't hit this.After the change,
it's, keys with double quotes, and keys that look like code all round-trip as plain string keys.Tests
Added
test_renaming_to_key_with_special_characters(structure + unstructure round-trip for a rename containing a quote and a couple of other awkward keys). It raisesSyntaxErroronmainand passes here. Fulltest_gen_dict.py/test_gen.pystay green (63 passed).