implemented basic correctness check of query plans

- comparison of two response shapes
- query plans analysis, deriving plan's overall response shape

apollo-federation/cli/src/main.rs

@@ -250,8 +250,10 @@ fn cmd_plan(
         ExecutableDocument::parse_and_validate(planner.api_schema().schema(), query, query_path)?;
     let query_plan = planner.build_query_plan(&query_doc, None, Default::default())?;
     println!("{query_plan}");
+    // Use the supergraph schema, not the API schema, for correctness check,
+    // since the plan may access hidden fields.
     apollo_federation::query_plan::correctness::check_plan(
-        planner.api_schema(),
+        &supergraph.schema,
         &query_doc,
         &query_plan,
     )?;

apollo-federation/src/query_plan/correctness/mod.rs

@@ -1,10 +1,15 @@
+pub mod query_plan_analysis;
+#[cfg(test)]
+pub mod query_plan_analysis_test;
 pub mod response_shape;
+pub mod response_shape_compare;
 #[cfg(test)]
 pub mod response_shape_test;
 
 use apollo_compiler::validation::Valid;
 use apollo_compiler::ExecutableDocument;
 
+use crate::internal_error;
 use crate::query_plan::QueryPlan;
 use crate::schema::ValidFederationSchema;
 use crate::FederationError;
@@ -15,9 +20,16 @@ use crate::FederationError;
 pub fn check_plan(
     schema: &ValidFederationSchema,
     operation_doc: &Valid<ExecutableDocument>,
-    _plan: &QueryPlan,
+    plan: &QueryPlan,
 ) -> Result<(), FederationError> {
-    let rs = response_shape::compute_response_shape(operation_doc, schema)?;
-    println!("\nResponse shape from operation:\n{rs}");
-    Ok(())
+    let op_rs = response_shape::compute_response_shape_for_operation(operation_doc, schema)?;
+
+    let root_type = response_shape::compute_the_root_type_condition_for_operation(operation_doc)?;
+    let plan_rs = query_plan_analysis::interpret_query_plan(schema, &root_type, plan)?;
+
+    response_shape_compare::compare_response_shapes(&op_rs, &plan_rs)
+        .map_err(|e| internal_error!(
+            "Response shape from query plan does not match response shape from input operation:\n{}",
+            e.description()
+        ))
 }