[smile] Feature enabling / disabling

[ghost]

SmileGenerator offers the possibility to configure its features after it has been constructed. If you want to enable / disable features on a per-generator approach the following code looks reasonable:

   try (OutputStream os = // ...
        JsonGenerator out = smileFactory.createGenerator(os).
                  configure(Feature.CHECK_SHARED_NAMES, false)) {
        out.startObject();

However changing Features after construction is mostly unsupported:

• WRITE_HEADER, CHECK_SHARED_NAMES, CHECK_SHARED_STRING_VALUES are only used before / during object construction, any changes in the above manner will be ignored
• ENCODE_BINARY_AS_7BIT is checked during writing, which means the content of the document might differ from the header. This would happen in the example above.
• WRITE_END_MARKER is checked during writing and will work as intended

All in all three features cannot be changed, one change is possibly harmful and the last one marginally useful. In my opinion the possibility to change Features for a constructed Generator should be deprecated. At the very least the noop of changing most features after construction should be documented.

[cowtowncoder]

I thought I had commented but apparently not.

So, yes, this is problematic. What is missing currently is ability to pass per-serialization settings, especially from databinding (and to a degree from streaming too, since changes to factory can not be done safely wrt multi-threading). I have plans to change this in future, but that'll be Jackson 3.x (after 2.9). In the meantime it would probably make sense to block dangerous change (second one) for sure, and possibly throw exception for misleading case (where call ignored).

[cowtowncoder]

I will have to do 2.9.0 without more work, but hope to add some checks/exceptions as per comments. And with 3.0 jackson-core interaction will be changed in such a way to that parsers and generators will be passed feature settings through constructor, without need to (or ability) to change them. This will allow efficient and safe handling.

[cowtowncoder]

As per comments, this now works in master (for 3.0). (but note that it will be months until it gets released; and there is no easy fix for 2.x)