"\u0000" is in fact legal

[nicowilliams]

From RFC7159:

Any character may be escaped. If the character is in the Basic Multilingual Plane (U+0000 through U+FFFF), then it may be represented as a six-character sequence: [...]

but parsers/test_ccan_json/json/_test/nst_files/n_223.json is an n_* test and contains "\u0000", which means it should be a y_* test, that is, expected to parse successfully.

[pineapplemachine]

Agreed. This JSON file looks valid to me.