Bug report

Bug description:

For an invalid \escape in a string, the pure Python decoder reports the position of the character after the backslash. The C decoder reports the position of the backslash.

from test.support import import_helper

cjson = import_helper.import_fresh_module("json", fresh=["_json"])
pyjson = import_helper.import_fresh_module("json", blocked=["_json"])

for json in cjson, pyjson:
    try:
        json.loads('"\\a"')
    except ValueError as e:
        print(e.pos)
# C: 1
# Python: 2

This is the same kind of difference that gh-154936 fixed for control characters.

CPython versions tested on:

CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-162028: Fix the pure Python JSON decoder error position for invalid escapes #162029