Add query planner configuration option generate_query_fragments (#460)

Ref: apollographql/federation#2958

Adopting this in router should take into consideration that both
`reuse_query_fragments` and `generate_query_fragments` should not both
be set to true. Since `reuse_` currently defaults to true, it should be
disabled when `generate_` is enabled.

---------

Co-authored-by: apollo-bot2 <apollo-bot2@users.noreply.github.com>

federation-2/router-bridge/src/introspect.rs

@@ -309,6 +309,7 @@ fragment TypeRef on __Type {
                 }),
                 graphql_validation: true,
                 reuse_query_fragments: None,
+                generate_query_fragments: None,
                 debug: Default::default(),
             },
         )

federation-2/router-bridge/src/planner.rs

@@ -677,6 +677,12 @@ pub struct QueryPlannerConfig {
     /// planner's default.
     pub reuse_query_fragments: Option<bool>,
 
+    /// If enabled, the query planner will extract inline fragments into
+    /// fragment definitions before sending queries to subgraphs. This can
+    /// significantly reduce the size of the query sent to subgraphs, but may
+    /// increase the time it takes to plan the query.
+    pub generate_query_fragments: Option<bool>,
+
     /// A sub-set of configurations that are meant for debugging or testing. All the configurations in this
     /// sub-set are provided without guarantees of stability (they may be dangerous) or continued support (they
     /// may be removed without warning).
@@ -691,6 +697,7 @@ impl Default for QueryPlannerConfig {
             }),
             graphql_validation: true,
             reuse_query_fragments: None,
+            generate_query_fragments: None,
             debug: Default::default(),
         }
     }
@@ -764,6 +771,8 @@ mod tests {
     const NO_OPERATION: &str = include_str!("testdata/no_operation.graphql");
     const QUERY_REUSE_QUERY_FRAGMENTS: &str =
         include_str!("testdata/query_reuse_query_fragments.graphql");
+    const QUERY_GENERATE_QUERY_FRAGMENTS: &str =
+        include_str!("testdata/query_generate_query_fragments.graphql");
 
     const MULTIPLE_ANONYMOUS_QUERIES: &str =
         include_str!("testdata/query_with_multiple_anonymous_operations.graphql");
@@ -773,6 +782,8 @@ mod tests {
         include_str!("testdata/schema_without_review_body.graphql");
     const SCHEMA_REUSE_QUERY_FRAGMENTS: &str =
         include_str!("testdata/schema_reuse_query_fragments.graphql");
+    const SCHEMA_GENERATE_QUERY_FRAGMENTS: &str =
+        include_str!("testdata/schema_generate_query_fragments.graphql");
     const CORE_IN_V0_1: &str = include_str!("testdata/core_in_v0.1.graphql");
     const UNSUPPORTED_FEATURE: &str = include_str!("testdata/unsupported_feature.graphql");
     const UNSUPPORTED_FEATURE_FOR_EXECUTION: &str =
@@ -970,6 +981,78 @@ mod tests {
         insta::assert_snapshot!(serde_json::to_string_pretty(&payload.data).unwrap());
     }
 
+    #[tokio::test]
+    async fn generate_query_fragments_defaults_to_false() {
+        let planner = Planner::<serde_json::Value>::new(
+            SCHEMA_GENERATE_QUERY_FRAGMENTS.to_string(),
+            QueryPlannerConfig::default(),
+        )
+        .await
+        .unwrap();
+
+        let payload = planner
+            .plan(
+                QUERY_GENERATE_QUERY_FRAGMENTS.to_string(),
+                None,
+                PlanOptions::default(),
+            )
+            .await
+            .unwrap()
+            .into_result()
+            .unwrap();
+        insta::assert_snapshot!(serde_json::to_string_pretty(&payload.data).unwrap());
+    }
+
+    #[tokio::test]
+    async fn generate_query_fragments_explicit_false() {
+        let planner = Planner::<serde_json::Value>::new(
+            SCHEMA_GENERATE_QUERY_FRAGMENTS.to_string(),
+            QueryPlannerConfig {
+                generate_query_fragments: Some(false),
+                ..Default::default()
+            },
+        )
+        .await
+        .unwrap();
+
+        let payload = planner
+            .plan(
+                QUERY_GENERATE_QUERY_FRAGMENTS.to_string(),
+                None,
+                PlanOptions::default(),
+            )
+            .await
+            .unwrap()
+            .into_result()
+            .unwrap();
+        insta::assert_snapshot!(serde_json::to_string_pretty(&payload.data).unwrap());
+    }
+
+    #[tokio::test]
+    async fn generate_query_fragments_true() {
+        let planner = Planner::<serde_json::Value>::new(
+            SCHEMA_GENERATE_QUERY_FRAGMENTS.to_string(),
+            QueryPlannerConfig {
+                generate_query_fragments: Some(true),
+                ..Default::default()
+            },
+        )
+        .await
+        .unwrap();
+
+        let payload = planner
+            .plan(
+                QUERY_GENERATE_QUERY_FRAGMENTS.to_string(),
+                None,
+                PlanOptions::default(),
+            )
+            .await
+            .unwrap()
+            .into_result()
+            .unwrap();
+        insta::assert_snapshot!(serde_json::to_string_pretty(&payload.data).unwrap());
+    }
+
     #[tokio::test]
     async fn parse_errors_return_the_right_usage_reporting_data() {
         let planner =
@@ -2034,6 +2117,7 @@ feature https://specs.apollo.dev/unsupported-feature/v0.1 is for: SECURITY but i
                 }),
                 graphql_validation: true,
                 reuse_query_fragments: None,
+                generate_query_fragments: None,
                 debug: Default::default(),
             },
         )
@@ -2113,6 +2197,7 @@ feature https://specs.apollo.dev/unsupported-feature/v0.1 is for: SECURITY but i
                 }),
                 graphql_validation: true,
                 reuse_query_fragments: None,
+                generate_query_fragments: None,
                 debug: Default::default(),
             },
         )

federation-2/router-bridge/src/snapshots/router_bridge__planner__tests__generate_query_fragments_defaults_to_false.snap

@@ -0,0 +1,18 @@
+---
+source: router-bridge/src/planner.rs
+assertion_line: 1003
+expression: "serde_json::to_string_pretty(&payload.data).unwrap()"
+---
+{
+  "queryPlan": {
+    "kind": "QueryPlan",
+    "node": {
+      "kind": "Fetch",
+      "serviceName": "Subgraph1",
+      "variableUsages": [],
+      "operation": "{t{__typename ...on A{x y t{__typename ...on A{x y}...on B{z}}}}}",
+      "operationKind": "query"
+    }
+  },
+  "formattedQueryPlan": "QueryPlan {\n  Fetch(service: \"Subgraph1\") {\n    {\n      t {\n        __typename\n        ... on A {\n          x\n          y\n          t {\n            __typename\n            ... on A {\n              x\n              y\n            }\n            ... on B {\n              z\n            }\n          }\n        }\n      }\n    }\n  },\n}"
+}

federation-2/router-bridge/src/snapshots/router_bridge__planner__tests__generate_query_fragments_explicit_false.snap

@@ -0,0 +1,18 @@
+---
+source: router-bridge/src/planner.rs
+assertion_line: 1028
+expression: "serde_json::to_string_pretty(&payload.data).unwrap()"
+---
+{
+  "queryPlan": {
+    "kind": "QueryPlan",
+    "node": {
+      "kind": "Fetch",
+      "serviceName": "Subgraph1",
+      "variableUsages": [],
+      "operation": "{t{__typename ...on A{x y t{__typename ...on A{x y}...on B{z}}}}}",
+      "operationKind": "query"
+    }
+  },
+  "formattedQueryPlan": "QueryPlan {\n  Fetch(service: \"Subgraph1\") {\n    {\n      t {\n        __typename\n        ... on A {\n          x\n          y\n          t {\n            __typename\n            ... on A {\n              x\n              y\n            }\n            ... on B {\n              z\n            }\n          }\n        }\n      }\n    }\n  },\n}"
+}

federation-2/router-bridge/src/snapshots/router_bridge__planner__tests__generate_query_fragments_true.snap

@@ -0,0 +1,18 @@
+---
+source: router-bridge/src/planner.rs
+assertion_line: 1054
+expression: "serde_json::to_string_pretty(&payload.data).unwrap()"
+---
+{
+  "queryPlan": {
+    "kind": "QueryPlan",
+    "node": {
+      "kind": "Fetch",
+      "serviceName": "Subgraph1",
+      "variableUsages": [],
+      "operation": "{t{__typename ..._generated_onA3_0}}fragment _generated_onA2_0 on A{x y}fragment _generated_onA3_0 on A{x y t{__typename ..._generated_onA2_0 ...on B{z}}}",
+      "operationKind": "query"
+    }
+  },
+  "formattedQueryPlan": "QueryPlan {\n  Fetch(service: \"Subgraph1\") {\n    {\n      t {\n        __typename\n        ..._generated_onA3_0\n      }\n    }\n    \n    fragment _generated_onA2_0 on A {\n      x\n      y\n    }\n    \n    fragment _generated_onA3_0 on A {\n      x\n      y\n      t {\n        __typename\n        ..._generated_onA2_0\n        ... on B {\n          z\n        }\n      }\n    }\n  },\n}"
+}

federation-2/router-bridge/src/testdata/query_generate_query_fragments.graphql

@@ -0,0 +1,17 @@
+query {
+  t {
+    ... on A {
+      x
+      y
+      t {
+        ... on A {
+          x
+          y
+        }
+        ... on B {
+          z
+        }
+      }
+    }
+  }
+}

federation-2/router-bridge/src/testdata/schema_generate_query_fragments.graphql

@@ -0,0 +1,94 @@
+schema
+  @link(url: "https://specs.apollo.dev/link/v1.0")
+  @link(url: "https://specs.apollo.dev/join/v0.4", for: EXECUTION) {
+  query: Query
+}
+
+directive @join__directive(
+  graphs: [join__Graph!]
+  name: String!
+  args: join__DirectiveArguments
+) repeatable on SCHEMA | OBJECT | INTERFACE | FIELD_DEFINITION
+
+directive @join__enumValue(graph: join__Graph!) repeatable on ENUM_VALUE
+
+directive @join__field(
+  graph: join__Graph
+  requires: join__FieldSet
+  provides: join__FieldSet
+  type: String
+  external: Boolean
+  override: String
+  usedOverridden: Boolean
+  overrideLabel: String
+) repeatable on FIELD_DEFINITION | INPUT_FIELD_DEFINITION
+
+directive @join__graph(name: String!, url: String!) on ENUM_VALUE
+
+directive @join__implements(
+  graph: join__Graph!
+  interface: String!
+) repeatable on OBJECT | INTERFACE
+
+directive @join__type(
+  graph: join__Graph!
+  key: join__FieldSet
+  extension: Boolean! = false
+  resolvable: Boolean! = true
+  isInterfaceObject: Boolean! = false
+) repeatable on OBJECT | INTERFACE | UNION | ENUM | INPUT_OBJECT | SCALAR
+
+directive @join__unionMember(
+  graph: join__Graph!
+  member: String!
+) repeatable on UNION
+
+directive @link(
+  url: String
+  as: String
+  for: link__Purpose
+  import: [link__Import]
+) repeatable on SCHEMA
+
+type A @join__type(graph: SUBGRAPH1) {
+  x: Int
+  y: Int
+  t: T
+}
+
+type B @join__type(graph: SUBGRAPH1) {
+  z: Int
+}
+
+scalar join__DirectiveArguments
+
+scalar join__FieldSet
+
+enum join__Graph {
+  SUBGRAPH1 @join__graph(name: "Subgraph1", url: "")
+}
+
+scalar link__Import
+
+enum link__Purpose {
+  """
+  \`SECURITY\` features provide metadata necessary to securely resolve fields.
+  """
+  SECURITY
+  """
+  \`EXECUTION\` features provide metadata necessary for operation execution.
+  """
+  EXECUTION
+}
+
+type Query @join__type(graph: SUBGRAPH1) {
+  t: T
+  t2: T
+}
+
+union T
+  @join__type(graph: SUBGRAPH1)
+  @join__unionMember(graph: SUBGRAPH1, member: "A")
+  @join__unionMember(graph: SUBGRAPH1, member: "B") =
+    A
+  | B