This folder is a place to extract modular functionality from
canvas. Canvas's Gemfile arrangement is enabled to read gems
from this path locally without installing from a remote source. This is valuable for a few reasons:
it prevents circular dependencies (bundler won't allow it)
modularized code cannot bind to specific domain concepts on canvas models
gems can have their specs run independently, without needing to load all
of canvas, saving iteration time
it allows for eventual build optimization via only running specs for the
transitive closure of parents depending on a gem where a change is.
it gives ENGINES extracted from canvas (see the "engines" directory) a place
to reference code shared with canvas without it being packaged into the canvas
monolith directly.
There are some tradeoffs:
spreads canvas over more subdirectories, giving some mental overhad to traversing
the entire codebase.
modular tests necessarily don't test integration with canvas concepts, so solid integration tests in the app are still a requirement.
total SERIALIZED build time goes up because each gem loads it's specs in a new process rather than all running within an already booted canvas process.
[TODO] eventually write more on whether we feel like those tradeoffs are good ones,
and what the best practices are to leverage this pattern for max-gain/min-pain.
Testing
To test all the gems:
cd gems
./test_all_gems.sh
To test an individual gem
Run ./test.sh inside the gem's folder. This is basically the same as:
75fa608fc9