## Summary:
In this commit I refactor the argument-generation logic to move most of
the code out of the template and into the type-generator. This logic
predates #51, and I didn't think to update it there, but I think it
benefits from similar treatment, for similar reasons.
Specifically, the main change is to treat variables as another struct
type we can generate, rather than handling them inline as a
`map[string]interface{}`. Users still pass them the same way, but
instead of putting them into a `map[string]interface{}` and JSONifying
that, we generate a struct and put them there.
This turns out to simplify things quite a lot, because we already have a
lot of code to generate types. Notably, the omitempty code goes from a
dozen lines to basically two, and fixes a bug (#43) in the process,
because now that we have a struct, `json.Marshal` will do our work for
us! (And, once we have syntax for it (#14), we'll be able to handle
field-level omitempty basically for free.) More importantly, it will
simplify custom marshalers (#38, forthcoming) significantly, since we do
all that logic at the containing-struct level, but will need to apply it
to arguments.
It does require two breaking changes:
1. For folks implementing the `graphql.Client` API (rather than just
calling `NewClient`): we now pass them variables as an `interface{}`
rather than a `map[string]interface{}`. For most callers, including
Khan/webapp, this is basically a one-line change to the signature of
their `MakeRequest`, and it should be a lot more future-proof.
2. genqlient's handling of the `omitempty` option has changed to match
that of `encoding/json`, in particular it now never considers structs
"empty". The difference was never intentional (I just didn't realize
that behavior of `encoding/json`); arguably our behavior was more
useful but I think that's outweighed by the value of consistency with
`encoding/json` as well as the simpler and more correct
implementation (fixing #43 is actually quite nontrivial otherwise).
Once we have custom unmarshaler support (#38), users will be able to
map a zero value to JSON null if they wish, which is mostly if not
entirely equivalent for GraphQL's purposes.
Issue: https://github.com/Khan/genqlient/issues/38
Issue: https://github.com/Khan/genqlient/issues/43
## Test plan:
make check
Author: benjaminjkraft
Reviewers: StevenACoffman, dnerdy, aberkan, jvoll, mahtabsabet, MiguelCastillo
Required Reviewers:
Approved By: StevenACoffman, dnerdy
Checks: ✅ Test (1.17), ✅ Test (1.16), ✅ Test (1.15), ✅ Test (1.14), ✅ Lint, ✅ Lint, ✅ Test (1.17), ✅ Test (1.16), ✅ Test (1.15), ✅ Test (1.14)
Pull Request URL: https://github.com/Khan/genqlient/pull/103
