Configurator to be SetterMethods

This commit changes Configurator's methods to be SetterMethods instead
of IOMethods, as Configurator is specifically made for frontend-managed
settings just for the backend, so no storing/loading is needed on the
backend's side.

This commit also changes SetterMethod to allow methods done to the
backend to error out, in case the setting value is invalid somehow.
Setter methods that are called by the backend (as opposed to the
frontend) must never error.

cchat.go

@@ -318,12 +318,10 @@ type Completer interface {
 }
 
 // Configurator is an interface which the backend can implement for a primitive
-// configuration API. Since these methods do return an error, they are allowed
-// to do IO. The frontend should handle this appropriately, including running
-// them asynchronously.
+// configuration API.
 type Configurator interface {
-	SetConfiguration(context.Context, map[string]string) error // Blocking
-	Configuration(context.Context) (map[string]string, error)  // Blocking
+	SetConfiguration(map[string]string) error
+	Configuration() map[string]string
 }
 
 // Editor adds message editing to the messenger. Only EditMessage can do IO.

cmd/internal/cchat-generator/generate_interface.go

@@ -66,6 +66,7 @@ func generateInterfaces(ifaces []repository.Interface) jen.Code {
 					stmt.Params(generateFuncParams(method.Returns, method.ErrorType)...)
 				case repository.SetterMethod:
 					stmt.Params(generateFuncParams(method.Parameters, "")...)
+					stmt.Params(generateFuncParamsErr(repository.NamedType{}, method.ErrorType)...)
 				case repository.IOMethod:
 					stmt.Params(generateFuncParamsCtx(method.Parameters, "")...)
 					stmt.Params(generateFuncParamsErr(method.ReturnValue, method.ErrorType)...)

repository/interface.go

@@ -78,6 +78,10 @@ type SetterMethod struct {
 	// Parameters is the list of parameters in the function. These parameters
 	// should be the parameters to set.
 	Parameters []NamedType
+	// ErrorType is non-empty if the function returns an error at the end of
+	// returns. An error may be returned from the backend if the input is
+	// invalid, but it must not do IO. Frontend setters must never error.
+	ErrorType string
 }
 
 // IOMethod is a regular method that can do IO and thus is blocking. These

repository/main.go

@@ -817,18 +817,15 @@ var Main = Packages{
 		}, {
 			Comment: Comment{`
 				Configurator is an interface which the backend can implement for a
-				primitive configuration API. Since these methods do return an error,
-				they are allowed to do IO. The frontend should handle this
-				appropriately, including running them asynchronously.
+				primitive configuration API.
 			`},
 			Name: "Configurator",
 			Methods: []Method{
-				IOMethod{
-					method:      method{Name: "Configuration"},
-					ReturnValue: NamedType{Type: "map[string]string"},
-					ErrorType:   "error",
+				GetterMethod{
+					method:  method{Name: "Configuration"},
+					Returns: []NamedType{{Type: "map[string]string"}},
 				},
-				IOMethod{
+				SetterMethod{
 					method:     method{Name: "SetConfiguration"},
 					Parameters: []NamedType{{Type: "map[string]string"}},
 					ErrorType:  "error",