How can I freeze an unknown data structure, ignoring all errors ?

[behrica]

Related to https://github.com/ptaoussanis/nippy/issues/141, but more focussed question.

Is there a way to freeze an arbitrary data structure, while ignoring all errors due to non freezable types ? "ignoring" could mean putting nil or leaving out or replace by "dummy".

[ptaoussanis]

Hi Carsten,

Yes, you have two options:

1. Set *freeze-fallback* to the keyword value :write-unfreezable.
2. Set *freeze-fallback* to the function value taoensso.nippy/write-unfreezable.

There's an important difference between these:

1. Will try to freeze an object using Java Serializable (which can be error-prone). If that fails, it'll try using Clojure's reader (which can be slow, and sometimes also error-prone). If that fails, it'll use taoensso.nippy/write-unfreezable to essentially serialize an error message (always works, but of limited value if you want to be able to reconstruct the frozen object).

2. Will just immediately resort to using taoensso.nippy/write-unfreezable - i.e. will always work and always be fast, but you'll basically just be serializing an error message.

Put it differently:

• Use (1) if you want Nippy to make a best effort to retain all data. Downsides are potential speed and thawing issues.
• Use (2) if you don't mind dropping unserializable data.

[behrica]

thanks, very helpfull