Experimental V2 renderer

[jhollinger]

An experimental serializer/renderer for the proposed V2 base. Rapidly evolving. I know it looks large, but most of that is tests. It's broken up into small commits so we can easily pull out pieces and PR them individually if we want. Notes:

• Added a ton of extension hooks for V2 and a better hook runner.
• A simple formatter DSL in Blueprints (plus an extension hook).
• Extractors are still their own thing - extensions don't seem a great fit.
• The serializer dogfoods the reflection API.
• The serializer dogfoods our hooks: most logic and all options come from built-in extensions.
• "Outer" and "inner" serializer calls to solve [Bug] Data is lost on nested associations when preload is enabled for new records blueprinter-activerecord#30.
• Can be significantly faster than V1 - up to 65%! (details below).
• Blueprints and extractors get instantiated:
  • During each render.
  • A single instance is shared throughout the render (e.g. a single WidgetBlueprint instance).
  • Field blocks, if blocks, formatter blocks, etc. are instance-evaled against the blueprint instance.
  • This allows for helper methods and state during the render.

Performance

The perf characteristics of V1 and V2 vary greatly based on:

1. The total number of fields and associations in a Blueprint.
2. The relative number of fields vs associations in a Blueprint.
3. How many items are being rendered overall.

# 2 fields, 1 objects, 0 collections
10,000 widgets 10x: V2 39.33% faster (0.2439 sec)
1,000 widgets 100x: V2 33.85% faster (0.1908 sec)
500 widgets 100x: V2 35.08% faster (0.0995 sec)
250 widgets 100x: V2 35.07% faster (0.0494 sec)
100 widgets 250x: V2 33.96% faster (0.0481 sec)
25 widgets 500x: V2 28.38% faster (0.0198 sec)
5 widgets 1000x: V2 00.55% faster (0.0001 sec)
1 widgets 1000x: V2 49.95% slower (0.0061 sec)

# 10 fields, 5 objects, 2 collections
10,000 widgets 10x: V2 52.72% faster (3.5379 sec)
1,000 widgets 100x: V2 49.02% faster (3.0312 sec)
500 widgets 100x: V2 48.19% faster (1.4554 sec)
250 widgets 100x: V2 47.73% faster (0.7174 sec)
100 widgets 250x: V2 46.12% faster (0.6754 sec)
25 widgets 500x: V2 44.38% faster (0.3056 sec)
5 widgets 1000x: V2 36.58% faster (0.0934 sec)
1 widgets 1000x: V2 19.83% slower (0.0098 sec)

# 100 fields, 50 objects, 25 collections
10,000 widgets 10x: V2 57.36% faster (64.8405 sec)
1,000 widgets 100x: V2 65.60% faster (74.7372 sec)
500 widgets 100x: V2 65.64% faster (37.2329 sec)
250 widgets 100x: V2 64.54% faster (17.7782 sec)
100 widgets 250x: V2 53.74% faster (11.3225 sec)
25 widgets 500x: V2 57.40% faster (5.8170 sec)
5 widgets 1000x: V2 53.44% faster (2.1441 sec)
1 widgets 1000x: V2 37.89% faster (0.3217 sec)

Note that on the very small end of things (few items with few fields) V2 is actually slower. But we're talking fractions of a ms.