chore: add integration test for omitempty encoding at ingress (#1450)

Addresses
#1441 (comment)

Tested with `go test --tags=integration ./integration/... -run
TestHTTPEncodeOmitempty`

go-runtime/encoding/encoding_test.go

@@ -37,6 +37,11 @@ func TestMarshal(t *testing.T) {
 		ShouldntOmit string `json:""`
 		NotTagged    string
 	}
+	type validateOmitemptyOption struct {
+		ShouldOmit   ftl.Option[string] `json:",omitempty"`
+		ShouldntOmit ftl.Option[string] `json:""`
+		NotTagged    ftl.Option[string]
+	}
 	tests := []struct {
 		name     string
 		input    any
@@ -65,6 +70,11 @@ func TestMarshal(t *testing.T) {
 		{name: "UnregisteredSumType", input: struct{ D unregistered }{variant{"hello"}}, err: `the only supported interface types are enums or any, not encoding_test.unregistered`},
 		{name: "OmitEmptyNotNull", input: validateOmitempty{"foo", "bar", "baz"}, expected: `{"shouldOmit":"foo","shouldntOmit":"bar","notTagged":"baz"}`},
 		{name: "OmitEmptyNull", input: validateOmitempty{}, expected: `{"shouldntOmit":"","notTagged":""}`},
+		{name: "OmitEmptyOptionNone", input: validateOmitemptyOption{
+			ShouldOmit:   ftl.None[string](),
+			ShouldntOmit: ftl.None[string](),
+			NotTagged:    ftl.None[string](),
+		}, expected: `{"shouldntOmit":null,"notTagged":null}`},
 	}
 
 	tr := typeregistry.NewTypeRegistry()

integration/integration_test.go

@@ -108,6 +108,17 @@ func TestSchemaGenerate(t *testing.T) {
 	)
 }
 
+func TestHttpEncodeOmitempty(t *testing.T) {
+	run(t,
+		copyModule("omitempty"),
+		deploy("omitempty"),
+		httpCall(http.MethodGet, "/get", jsonData(t, obj{}), func(resp *httpResponse) error {
+			assert.Equal(t, "{\"mustset\":\"\"}", repr.String(resp.jsonBody))
+			return nil
+		}),
+	)
+}
+
 func TestHttpIngress(t *testing.T) {
 	run(t,
 		copyModule("httpingress"),

integration/testdata/go/omitempty/ftl.toml

@@ -0,0 +1,2 @@
+module = "omitempty"
+language = "go"

integration/testdata/go/omitempty/go.mod

@@ -0,0 +1,43 @@
+module ftl/omitempty
+
+go 1.22.2
+
+require github.com/TBD54566975/ftl v0.206.1
+
+require (
+	connectrpc.com/connect v1.16.1 // indirect
+	connectrpc.com/grpcreflect v1.2.0 // indirect
+	connectrpc.com/otelconnect v0.7.0 // indirect
+	github.com/alecthomas/concurrency v0.0.2 // indirect
+	github.com/alecthomas/participle/v2 v2.1.1 // indirect
+	github.com/alecthomas/types v0.14.0 // indirect
+	github.com/alessio/shellescape v1.4.2 // indirect
+	github.com/danieljoos/wincred v1.2.0 // indirect
+	github.com/go-logr/logr v1.4.1 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/godbus/dbus/v5 v5.1.0 // indirect
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20221227161230-091c0ba34f0a // indirect
+	github.com/jackc/pgx/v5 v5.5.5 // indirect
+	github.com/jackc/puddle/v2 v2.2.1 // indirect
+	github.com/jpillora/backoff v1.0.0 // indirect
+	github.com/kballard/go-shellquote v0.0.0-20180428030007-95032a82bc51 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/multiformats/go-base36 v0.2.0 // indirect
+	github.com/swaggest/jsonschema-go v0.3.70 // indirect
+	github.com/swaggest/refl v1.3.0 // indirect
+	github.com/zalando/go-keyring v0.2.4 // indirect
+	go.opentelemetry.io/otel v1.26.0 // indirect
+	go.opentelemetry.io/otel/metric v1.26.0 // indirect
+	go.opentelemetry.io/otel/trace v1.26.0 // indirect
+	golang.org/x/crypto v0.22.0 // indirect
+	golang.org/x/exp v0.0.0-20240416160154-fe59bbe5cc7f // indirect
+	golang.org/x/mod v0.17.0 // indirect
+	golang.org/x/net v0.24.0 // indirect
+	golang.org/x/sync v0.7.0 // indirect
+	golang.org/x/sys v0.20.0 // indirect
+	golang.org/x/text v0.14.0 // indirect
+	google.golang.org/protobuf v1.34.0 // indirect
+)
+
+replace github.com/TBD54566975/ftl => ../../../..

integration/testdata/go/omitempty/omitempty.go

@@ -0,0 +1,20 @@
+package omitempty
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/TBD54566975/ftl/go-runtime/ftl" // Import the FTL SDK.
+)
+
+type EchoRequest struct{}
+
+type EchoResponse struct {
+	Error   string `json:"error,omitempty"` // Should be omitted from marshaled JSON
+	MustSet string `json:"mustset"`         // Should marshal to `"mustset":""`
+}
+
+//ftl:ingress http GET /get
+func Get(ctx context.Context, req builtin.HttpRequest[EchoRequest]) (builtin.HttpResponse[EchoResponse, string], error) {
+	return EchoResponse{}, nil
+}