MRG: New schema generator

[jakevdp]

This is a rewrite of the core of the altair library, targeting Vega-Lite 1.2, based on the more complete schema parser at http://github.com/altair-viz/schemapi

The reason for this rewrite is that it will make it easier to transition to Vega-Lite 2.0 and other future Vega-Lite versions.

Still TODO

• decide on final name for altair_parser package & update references here (now schemapi)
• fix non-ASCII characters for Python 2.7
• re-organize utilities used in altair.schema
• make traitlet shorthand types more meaningful (currently all instances just say "object")
• check for required traits in ToPython() visitor
• fix references to deprecated names in docs (e.g. BaseObject, to_altair)
• use required_traits rather than allow_undefined=False in order to not error on intermediate steps
• specialize ToCode() generator to configure charts using methods like mark_point().

Summary of Changes

• The bulk of the code used to generate the Altair API code has been removed from this package, and put in schemapi. Note that everything in altair/schema/_interface is automatically generated by schemapi and its extensions in tools/generate_schema_interface.py

• User-facing API should be identical to current master. This is confirmed by the fact that all existing tests pass

• all traitlets objects are now based on the JSONTraitlets extensions provided by schemapi. One big reason for this is that the default value is now undefined, and a value of None will be interpreted as an explicit null in the JSON output.

• deprecated to_altair() in favor of to_python()

• put all schema API classes in a single file _interface/schema.py, rather than separating them out into individual files

• skip changed to _skip_on_export

• Addition of _required_traits; an error will be raised if these traits are undefined at export.

• change Travis doc build to use Python 3.x, as there was a unicode error somewhere in sphinx for 2.x (tried debugging for an hour or so, but didn't make any progress)

[jakevdp]

Chose to go with schemapi for the jsonschema API generator. The package is renamed; I still need to change references in this PR

[jakevdp]

OK, this is ready to merge! It's a relatively large change to the code-base, but all previous API tests are passing so I think it's pretty safe. The executive summary of changes is in the description above. @ellisonbg, would you mind taking a look?

[ellisonbg]

Sure, will have a look!

[ellisonbg]

Wow, this is very nice. Overall, the changes to the code base are very minimal, which is a good sign. I think we should merge and iterate. What version do you think we should release this as?

[jakevdp]

Let's plan to release as 1.3.0, once #370 is merged as well. I think the addition of mimetype rendering support from master warrants a minor release.

Then we can push for a 2.0 release built on vega-lite 2.0

[ellisonbg]

Sounds good.

…

On Wed, Aug 9, 2017 at 9:42 AM, Jake Vanderplas ***@***.***> wrote: Let's plan to release as 1.3.0, once #370 <#370> is merged as well. I think the addition of mimetype rendering support from master warrants a minor release. Then we can push for a 2.0 release built on vega-lite 2.0 — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#364 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AABr0Dl7nxETL9_wZpQCXI1ziFw382Iqks5sWeFqgaJpZM4OqO8X> .

-- Brian E. Granger Associate Professor of Physics and Data Science Cal Poly State University, San Luis Obispo @ellisonbg on Twitter and GitHub bgranger@calpoly.edu and ellisonbg@gmail.com

[jakevdp]

I'll merge and we can go from there