Cache for parsing the schema

[koddsson]

👋 Hey hey!

When working with large GraphQL schemas (like GitHubs v4 API schema) we've noticed that eslint could run a bit slower. We narrowed it down to eslint-plugin-graphql adding ~500ms per file to the run time of eslint.

By adding a simple cache object for the schema results of parseOptions we can bring that time down pretty signifigantly.

Here's a example eslint run in one of our projects at GitHub:

Before this patch:

⚡ time TIMING=1 ./node_modules/.bin/eslint .
Rule                            | Time (ms) | Relative
:-------------------------------|----------:|--------:
prettier/prettier               |  5956.319 |    57.1%
graphql/no-deprecated-fields    |  1427.804 |    13.7%
import/namespace                |   810.107 |     7.8%
no-unused-vars                  |   274.724 |     2.6%
import/no-deprecated            |   148.324 |     1.4%
react/no-direct-mutation-state  |   124.988 |     1.2%
react/no-unused-prop-types      |   117.736 |     1.1%
react/prefer-stateless-function |   115.713 |     1.1%
import/named                    |    86.341 |     0.8%
react/no-deprecated             |    77.588 |     0.7%
TIMING=1 ./node_modules/.bin/eslint .  174.30s user 4.23s system 97% cpu 3:02.83 total

After this patch:

⚡ time TIMING=1 ./node_modules/.bin/eslint .
cache miss
Rule                                | Time (ms) | Relative
:-----------------------------------|----------:|--------:
prettier/prettier                   |  2788.298 |    65.9%
import/namespace                    |   415.556 |     9.8%
no-unused-vars                      |    68.644 |     1.6%
import/no-deprecated                |    60.269 |     1.4%
react/no-unused-prop-types          |    52.729 |     1.2%
graphql/no-deprecated-fields        |    52.299 |     1.2%
import/named                        |    48.913 |     1.2%
react/no-direct-mutation-state      |    45.669 |     1.1%
react/void-dom-elements-no-children |    45.446 |     1.1%
react/prefer-stateless-function     |    38.467 |     0.9%
TIMING=1 ./node_modules/.bin/eslint .  10.07s user 0.43s system 125% cpu 8.356 total

(There seems to be some prettier/prettier weirdness going on here as well)

I wasn't quite sure on how to test this but am open for suggestions if you've got any.

TODO:

• Make sure all of the significant new logic is covered by tests
• Rebase your changes on master so that they can be merged easily
• Make sure all tests pass
• Update CHANGELOG.md with your change
• If this was a change that affects the external API, update the README

Pull Request Labels

• feature
• blocking
• docs

/label performance

[jnwng]

simple enough — thank you for providing benchmarks to make this easier to merge! live in eslint-plugin-graphql@2.1.0

[patsissons]

looks like this has broken support for graphql-config with multiple schemas defined, as the cache hits are short circuiting schema selection. I'll write up a proper issue and create a PR to fix this shortly.