Document second breaking change

docs/CHANGELOG.md

@@ -23,12 +23,13 @@ When releasing a new version:
 ### Breaking changes:
 
 - The [`graphql.Client`](https://pkg.go.dev/github.com/Khan/genqlient/graphql#Client) interface now accepts `variables interface{}` (containing a JSON-marshalable value) rather than `variables map[string]interface{}`.  Clients implementing the interface themselves will need to change the signature; clients who simply call `graphql.NewClient` are unaffected.
+- genqlient's handling of the `omitempty` option has changed to match that of `encoding/json`, from which it had inadvertently differed.  In particular, this means struct-typed arguments with `# @genqlient(omitempty: true)` will no longer be omitted if they are the zero value.  (Struct-pointers are still omitted if nil, so adding `pointer: true` will typically work fine.)
 
 ### New features:
 
 ### Bug fixes:
 
-- The `omitempty` option now works correctly for struct- and map-typed variables, which is to say it never considers them empty (matching `encoding/json`). (#43)
+- The `omitempty` option now works correctly for struct- and map-typed variables, matching `encoding/json`, which is to say it never omits structs, and omits empty maps.
 
 ## v0.1.0
 

generate/types.go

@@ -203,6 +203,9 @@ func (typ *goStructType) WriteDefinition(w io.Writer, g *generator) error {
 	// select the same field, or several fragments select the same field -- the
 	// JSON library will only fill one of those (the least-nested one); we want
 	// to fill them all.
+	//
+	// TODO(benkraft): If/when proposal #5901 is implemented (Go 1.18 at the
+	// earliest), we may be able to do some of this a simpler way.
 	if !needUnmarshaler {
 		return nil
 	}