Writing an on-boarding guide for contributors

[doanduyhai]

Because Achilles is using heavily annotation processor to generate source code at compile time, sometimes external contributors find it very hard to handle and understand the code.

The on-boarding guide will make their life easier by explaining the main design choices of Achilles that are not explicit:

• the multi-module Maven project
• why the need to have a separated achilles-model module
• the configuration of annotation processors on each module
• Tell, don't ask design philosophy
• the design of the meta data classes
• a walkthrough on
  • compile time entities & annotations parsing (AnnotationTree)
  • compile time generation of source code
• the codec system
• the type-safe function supports in Achilles
• the code design for the DSL source code generation
  • inner classes & variable sharing for DSL
  • behavior multi-inheritance through interface default methods
  • generation of combinatory WHERE clause
• the tricks to support ECJ compiler
• testing infrastructure
  • mvn compile on achilles-core to copy .java source file to target directory
  • usage of compile-testing library and special annotation to trigger annotation processor
• Cassandra version-aware feature toggle using rich enums
• Doc generation with pandoc on Linux & Mac
• TestSchemaGenerator to be put in the latest integration test module