chore(federation): address two TODOs in build_query_plan (#5876)

apollo-federation/src/error/mod.rs

@@ -4,6 +4,7 @@ use std::fmt::Display;
 use std::fmt::Formatter;
 use std::fmt::Write;
 
+use apollo_compiler::executable::GetOperationError;
 use apollo_compiler::validation::DiagnosticList;
 use apollo_compiler::validation::WithErrors;
 use apollo_compiler::InvalidNameError;
@@ -56,6 +57,8 @@ pub enum SingleFederationError {
     InvalidGraphQLName(#[from] InvalidNameError),
     #[error("Subgraph invalid: {message}")]
     InvalidSubgraph { message: String },
+    #[error("Operation name not found")]
+    UnknownOperation,
     #[error("{message}")]
     DirectiveDefinitionInvalid { message: String },
     #[error("{message}")]
@@ -225,6 +228,7 @@ impl SingleFederationError {
             SingleFederationError::InvalidGraphQL { .. }
             | SingleFederationError::InvalidGraphQLName(_) => ErrorCode::InvalidGraphQL,
             SingleFederationError::InvalidSubgraph { .. } => ErrorCode::InvalidGraphQL,
+            SingleFederationError::UnknownOperation => ErrorCode::InvalidGraphQL,
             SingleFederationError::DirectiveDefinitionInvalid { .. } => {
                 ErrorCode::DirectiveDefinitionInvalid
             }
@@ -406,6 +410,12 @@ impl From<InvalidNameError> for FederationError {
     }
 }
 
+impl From<GetOperationError> for FederationError {
+    fn from(_: GetOperationError) -> Self {
+        SingleFederationError::UnknownOperation.into()
+    }
+}
+
 impl From<FederationSpecError> for FederationError {
     fn from(err: FederationSpecError) -> Self {
         // TODO: When we get around to finishing the composition port, we should really switch it to

apollo-federation/src/query_plan/query_planner.rs

@@ -332,13 +332,11 @@ impl QueryPlanner {
     ) -> Result<QueryPlan, FederationError> {
         let operation = document
             .operations
-            .get(operation_name.as_ref().map(|name| name.as_str()))
-            // TODO(@goto-bus-stop) this is not an internal error, but a user error
-            .map_err(|_| FederationError::internal("requested operation does not exist"))?;
+            .get(operation_name.as_ref().map(|name| name.as_str()))?;
 
-        if operation.selection_set.selections.is_empty() {
+        if operation.selection_set.is_empty() {
             // This should never happen because `operation` comes from a known-valid document.
-            // TODO(@goto-bus-stop) it's probably fair to panic here :)
+            // We could panic here but we are returning a `Result` already anyways, so shrug!
             return Err(FederationError::internal(
                 "Invalid operation: empty selection set",
             ));
@@ -413,7 +411,7 @@ impl QueryPlanner {
         };
         */
 
-        if normalized_operation.selection_set.selections.is_empty() {
+        if normalized_operation.selection_set.is_empty() {
             return Ok(QueryPlan::default());
         }