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Document the parse_constant -NaN caveat in load/loads/parse docstrings #157

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Merged
dpranke merged 1 commit into from
Nov 2, 2026
Merged

Document the parse_constant -NaN caveat in load/loads/parse docstrings #157

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14 changes: 13 additions & 1 deletion json5/lib.py
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Original file line number Diff line number Diff line change
Expand Up @@ -143,6 +143,11 @@ def load(
string as written, and must be able to handle both decimal and
hexadecimal literals (e.g. `0x1F`); only the default parser
decodes hexadecimal literals automatically.
- the `parse_constant` parameter does not have the same semantics
as in the `json` module either: a custom callback is passed the
constant's spelling as written, so in addition to `NaN`,
`Infinity` and `-Infinity` it must also accept the `-NaN` form
of negative NaN, which is legal JSON5.

`load()` reads the entire remaining stream into memory, even when
`consume_trailing=False`. That option controls whether the parser
Expand Down Expand Up @@ -224,6 +229,11 @@ def loads(
string as written, and must be able to handle both decimal and
hexadecimal literals (e.g. `0x1F`); only the default parser
decodes hexadecimal literals automatically.
- the `parse_constant` parameter does not have the same semantics
as in the `json` module either: a custom callback is passed the
constant's spelling as written, so in addition to `NaN`,
`Infinity` and `-Infinity` it must also accept the `-NaN` form
of negative NaN, which is legal JSON5.

Raises
- `ValueError` if given an invalid document. This is different
Expand Down Expand Up @@ -281,7 +291,9 @@ def parse(
optional `start` parameter that specifies a zero-based offset to start
parsing from in the string, (d) the `parse_int` parameter does not have
the same semantics as in the `json` module (see `loads()` for details),
and (e) the return value is different, as described below.
(e) the `parse_constant` parameter also differs from the `json` module
(see `loads()` for details), and (f) the return value is different,
as described below.

`parse()` is useful if you have a string that might contain multiple
values and you need to extract all of them; you can do so by repeatedly
Expand Down