re-add support for reuse fragments for JS QP

apollo-router/src/configuration/metrics.rs

@@ -49,6 +49,7 @@ impl Metrics {
         data.populate_user_plugins_instrument(configuration);
         data.populate_query_planner_experimental_parallelism(configuration);
         data.populate_deno_or_rust_mode_instruments(configuration);
+        data.populate_legacy_fragment_usage(configuration);
 
         data.into()
     }
@@ -497,6 +498,18 @@ impl InstrumentData {
         );
     }
 
+    pub(crate) fn populate_legacy_fragment_usage(&mut self, configuration: &Configuration) {
+        // Fragment generation takes precedence over fragment reuse. Only report when fragment reuse is *actually active*.
+        if configuration.supergraph.reuse_query_fragments == Some(true)
+            && !configuration.supergraph.generate_query_fragments
+        {
+            self.data.insert(
+                "apollo.router.config.reuse_query_fragments".to_string(),
+                (1, HashMap::new()),
+            );
+        }
+    }
+
     pub(crate) fn populate_query_planner_experimental_parallelism(
         &mut self,
         configuration: &Configuration,

apollo-router/src/configuration/mod.rs

@@ -394,7 +394,7 @@ impl Configuration {
 
     pub(crate) fn js_query_planner_config(&self) -> router_bridge::planner::QueryPlannerConfig {
         router_bridge::planner::QueryPlannerConfig {
-            reuse_query_fragments: None,
+            reuse_query_fragments: self.supergraph.reuse_query_fragments,
             generate_query_fragments: Some(self.supergraph.generate_query_fragments),
             incremental_delivery: Some(router_bridge::planner::IncrementalDeliverySupport {
                 enable_defer: Some(self.supergraph.defer_support),
@@ -416,6 +416,14 @@ impl Configuration {
     pub(crate) fn rust_query_planner_config(
         &self,
     ) -> apollo_federation::query_plan::query_planner::QueryPlannerConfig {
+        if self
+            .supergraph
+            .reuse_query_fragments
+            .is_some_and(|flag| flag)
+        {
+            // warn the user that reuse query fragments is unsupported for RS QP
+            tracing::warn!("'experimental_reuse_query_fragments' is not supported by the Rust QP and this configuration option will be removed in the next release. Use 'generate_query_fragments' instead.");
+        }
         apollo_federation::query_plan::query_planner::QueryPlannerConfig {
             subgraph_graphql_validation: false,
             generate_query_fragments: self.supergraph.generate_query_fragments,
@@ -682,6 +690,13 @@ pub(crate) struct Supergraph {
     /// Default: false
     pub(crate) introspection: bool,
 
+    /// Enable reuse of query fragments
+    ///
+    /// This feature is deprecated and will be removed in next release. It is only available in JS QP.
+    /// Use generate_query_fragments instead.
+    #[serde(rename = "experimental_reuse_query_fragments")]
+    pub(crate) reuse_query_fragments: Option<bool>,
+
     /// Enable QP generation of fragments for subgraph requests
     /// Default: true
     pub(crate) generate_query_fragments: bool,
@@ -739,6 +754,7 @@ impl Supergraph {
         introspection: Option<bool>,
         defer_support: Option<bool>,
         query_planning: Option<QueryPlanning>,
+        reuse_query_fragments: Option<bool>,
         generate_query_fragments: Option<bool>,
         early_cancel: Option<bool>,
         experimental_log_on_broken_pipe: Option<bool>,
@@ -749,6 +765,15 @@ impl Supergraph {
             introspection: introspection.unwrap_or_else(default_graphql_introspection),
             defer_support: defer_support.unwrap_or_else(default_defer_support),
             query_planning: query_planning.unwrap_or_default(),
+            reuse_query_fragments: generate_query_fragments.and_then(|v|
+                if v {
+                    if reuse_query_fragments.is_some_and(|v| v) {
+                        // warn the user that both are enabled and it's overridden
+                        tracing::warn!("Both 'generate_query_fragments' and 'experimental_reuse_query_fragments' are explicitly enabled, 'experimental_reuse_query_fragments' will be overridden to false");
+                    }
+                    Some(false)
+                } else { reuse_query_fragments }
+            ),
             generate_query_fragments: generate_query_fragments
                 .unwrap_or_else(default_generate_query_fragments),
             early_cancel: early_cancel.unwrap_or_default(),
@@ -767,6 +792,7 @@ impl Supergraph {
         introspection: Option<bool>,
         defer_support: Option<bool>,
         query_planning: Option<QueryPlanning>,
+        reuse_query_fragments: Option<bool>,
         generate_query_fragments: Option<bool>,
         early_cancel: Option<bool>,
         experimental_log_on_broken_pipe: Option<bool>,
@@ -777,6 +803,15 @@ impl Supergraph {
             introspection: introspection.unwrap_or_else(default_graphql_introspection),
             defer_support: defer_support.unwrap_or_else(default_defer_support),
             query_planning: query_planning.unwrap_or_default(),
+            reuse_query_fragments: generate_query_fragments.and_then(|v|
+                if v {
+                    if reuse_query_fragments.is_some_and(|v| v) {
+                        // warn the user that both are enabled and it's overridden
+                        tracing::warn!("Both 'generate_query_fragments' and 'experimental_reuse_query_fragments' are explicitly enabled, 'experimental_reuse_query_fragments' will be overridden to false");
+                    }
+                    Some(false)
+                } else { reuse_query_fragments }
+            ),
             generate_query_fragments: generate_query_fragments
                 .unwrap_or_else(default_generate_query_fragments),
             early_cancel: early_cancel.unwrap_or_default(),

apollo-router/src/configuration/snapshots/apollo_router__configuration__tests__schema_generation.snap

@@ -6617,6 +6617,12 @@ snapshot_kind: text
           "description": "Log a message if the client closes the connection before the response is sent. Default: false.",
           "type": "boolean"
         },
+        "experimental_reuse_query_fragments": {
+          "default": null,
+          "description": "Enable reuse of query fragments\n\nThis feature is deprecated and will be removed in next release. It is only available in JS QP. Use generate_query_fragments instead.",
+          "nullable": true,
+          "type": "boolean"
+        },
         "generate_query_fragments": {
           "default": true,
           "description": "Enable QP generation of fragments for subgraph requests Default: true",