Make subscriptions unstable feature (#1025)

<!-- The PR description should answer 2 important questions: -->

### What

Put subscriptions API behind unstable feature.

V3_GIT_ORIGIN_REV_ID: 4eb454009c2e9658d899efbb81488faac3674e48

v3/crates/engine/src/internal_flags.rs

@@ -19,6 +19,7 @@
 pub enum UnstableFeature {
     EnableOrderByExpressions,
     EnableNdcV02Support,
+    EnableSubscriptions,
 }
 
 pub fn resolve_unstable_features(
@@ -34,8 +35,10 @@ pub fn resolve_unstable_features(
             UnstableFeature::EnableNdcV02Support => {
                 features.enable_ndc_v02_support = true;
             }
+            UnstableFeature::EnableSubscriptions => {
+                features.enable_subscriptions = true;
+            }
         }
     }
-
     features
 }

v3/crates/engine/tests/common.rs

@@ -486,6 +486,7 @@ pub fn test_execute_explain(
             unstable_features: metadata_resolve::configuration::UnstableFeatures {
                 enable_order_by_expressions: false,
                 enable_ndc_v02_support: true,
+                enable_subscriptions: false,
             },
             ..Default::default()
         };
@@ -547,6 +548,7 @@ pub(crate) fn test_metadata_resolve_configuration() -> metadata_resolve::configu
         unstable_features: metadata_resolve::configuration::UnstableFeatures {
             enable_order_by_expressions: false,
             enable_ndc_v02_support: true,
+            enable_subscriptions: false,
         },
     }
 }

v3/crates/metadata-resolve/src/stages/mod.rs

@@ -224,6 +224,7 @@ pub fn resolve(
         &order_by_expressions,
         &graphql_types,
         &graphql_config,
+        configuration,
     )?;
 
     let commands_with_permissions = command_permissions::resolve(

v3/crates/metadata-resolve/src/stages/models_graphql/graphql.rs

@@ -9,6 +9,7 @@ use super::types::{
     SelectAggregateGraphQlDefinition, SelectManyGraphQlDefinition, SelectUniqueGraphQlDefinition,
     SubscriptionGraphQlDefinition, UniqueIdentifierField,
 };
+use crate::configuration::Configuration;
 use crate::helpers::types::{mk_name, store_new_graphql_type};
 use crate::stages::order_by_expressions::OrderByExpressions;
 use crate::stages::{data_connector_scalar_types, graphql_config, models, object_types};
@@ -32,6 +33,7 @@ pub(crate) fn resolve_model_graphql_api(
     aggregate_expression_name: &Option<Qualified<AggregateExpressionName>>,
     order_by_expressions: &OrderByExpressions,
     graphql_config: &graphql_config::GraphqlConfig,
+    configuration: &Configuration,
 ) -> Result<ModelGraphQlApi, Error> {
     let model_name = &model.name;
     let mut graphql_api = ModelGraphQlApi::default();
@@ -88,7 +90,7 @@ pub(crate) fn resolve_model_graphql_api(
         let subscription = select_unique
             .subscription
             .as_ref()
-            .map(resolve_subscription_graphql_api)
+            .map(|s| resolve_subscription_graphql_api(s, configuration))
             .transpose()?;
         graphql_api
             .select_uniques
@@ -165,7 +167,7 @@ pub(crate) fn resolve_model_graphql_api(
             let subscription = gql_definition
                 .subscription
                 .as_ref()
-                .map(resolve_subscription_graphql_api)
+                .map(|s| resolve_subscription_graphql_api(s, configuration))
                 .transpose()?;
             mk_name(gql_definition.query_root_field.as_str()).map(|f: ast::Name| {
                 let select_many_description = if gql_definition.description.is_some() {
@@ -236,7 +238,7 @@ pub(crate) fn resolve_model_graphql_api(
                 let subscription = graphql_aggregate
                     .subscription
                     .as_ref()
-                    .map(resolve_subscription_graphql_api)
+                    .map(|s| resolve_subscription_graphql_api(s, configuration))
                     .transpose()?;
                 Ok(SelectAggregateGraphQlDefinition {
                     query_root_field: mk_name(graphql_aggregate.query_root_field.as_str())?,
@@ -329,7 +331,12 @@ fn is_model_used_in_any_aggregate_relationship(
 
 fn resolve_subscription_graphql_api(
     subscription: &open_dds::models::SubscriptionGraphQlDefinition,
+    configuration: &Configuration,
 ) -> Result<SubscriptionGraphQlDefinition, Error> {
+    // Subscriptions are currently unstable.
+    if !configuration.unstable_features.enable_subscriptions {
+        return Err(Error::UnstableFeatureSubscriptions);
+    }
     let open_dds::models::SubscriptionGraphQlDefinition {
         root_field,
         description,

v3/crates/metadata-resolve/src/stages/models_graphql/mod.rs

@@ -9,6 +9,7 @@ use indexmap::IndexMap;
 use lang_graphql::ast::common as ast;
 use open_dds::{data_connector::DataConnectorName, models::ModelName, types::CustomTypeName};
 
+use crate::configuration::Configuration;
 use crate::stages::{
     boolean_expressions, data_connector_scalar_types, graphql_config, models,
     object_boolean_expressions, relationships,
@@ -40,6 +41,7 @@ pub fn resolve(
     order_by_expressions: &order_by_expressions::OrderByExpressions,
     existing_graphql_types: &BTreeSet<ast::TypeName>,
     graphql_config: &graphql_config::GraphqlConfig,
+    configuration: &Configuration,
 ) -> Result<types::ModelsWithGraphql, Error> {
     let mut models_with_graphql = types::ModelsWithGraphql::new();
 
@@ -83,6 +85,7 @@ pub fn resolve(
                 &model.aggregate_expression,
                 order_by_expressions,
                 graphql_config,
+                configuration,
             )?,
             None => types::ModelGraphQlApi::default(),
         };

v3/crates/metadata-resolve/src/types/configuration.rs

@@ -16,4 +16,5 @@ pub struct Configuration {
 pub struct UnstableFeatures {
     pub enable_order_by_expressions: bool,
     pub enable_ndc_v02_support: bool,
+    pub enable_subscriptions: bool,
 }

v3/crates/metadata-resolve/src/types/error.rs

@@ -300,6 +300,8 @@ pub enum Error {
     CompatibilityError {
         warnings_as_errors: SeparatedBy<crate::Warning>,
     },
+    #[error("Subscriptions are currently unstable. Please add 'subscriptions' to unstable features to enable them.")]
+    UnstableFeatureSubscriptions,
 }
 
 pub trait ShouldBeAnError {

v3/crates/metadata-resolve/tests/metadata_golden_tests.rs

@@ -83,6 +83,7 @@ fn read_test_configuration(
     let unstable_features = configuration::UnstableFeatures {
         enable_order_by_expressions: false,
         enable_ndc_v02_support: false,
+        enable_subscriptions: false,
     };
 
     let configuration_path = directory.join("configuration.json");

v3/justfile

@@ -83,6 +83,7 @@ watch: start-docker-test-deps start-docker-run-deps
       --otlp-endpoint http://localhost:4317 \
       --authn-config-path static/auth/auth_config.json \
       --metadata-path static/sample-schema.json \
+      --unstable-feature enable-subscriptions \
       --expose-internal-errors'
 
 # check the code is fine
@@ -148,4 +149,5 @@ run: start-docker-test-deps start-docker-run-deps
     --otlp-endpoint http://localhost:4317 \
     --authn-config-path static/auth/auth_config.json \
     --metadata-path static/sample-schema.json \
+    --unstable-feature enable-subscriptions \
     --expose-internal-errors