always merge distinct steps.

plan.go

@@ -2,6 +2,7 @@ package bramble
 
 import (
 	"context"
+	"strings"
 	"encoding/json"
 	"fmt"
 
@@ -206,15 +207,32 @@ func extractSelectionSet(ctx *PlanningContext, insertionPoint []string, parentTy
 		}
 	}
 
-	// Create child steps for all remote field selections
 	if len(remoteSelections) > 0 {
+		// Create child steps for all remote field selections
 		childrenSteps, err := createSteps(ctx, insertionPoint, parentType, location, remoteSelections, true)
 		if err != nil {
 			return nil, nil, err
 		}
 		childrenStepsResult = append(childrenStepsResult, childrenSteps...)
 	}
 
+	if len(childrenStepsResult) > 1 {
+		// Merge steps targeting distinct service/path locations
+		mergedSteps := []*QueryPlanStep{}
+		mergedStepsMap := map[string]*QueryPlanStep{}
+		for _, step := range childrenStepsResult {
+			key := strings.Join(append([]string{step.ServiceURL}, step.InsertionPoint...), "/")
+			if existingStep, ok := mergedStepsMap[key]; ok {
+				existingStep.SelectionSet = append(existingStep.SelectionSet, step.SelectionSet...)
+				existingStep.Then = append(existingStep.Then, step.Then...)
+			} else {
+				mergedStepsMap[key] = step
+				mergedSteps = append(mergedSteps, step)
+			}
+		}
+		childrenStepsResult = mergedSteps
+	}
+
 	parentDef := ctx.Schema.Types[parentType]
 	// For abstract types, add an id fragment for all possible boundary
 	// implementations. This assures that abstract boundaries always return
@@ -241,6 +259,7 @@ func extractSelectionSet(ctx *PlanningContext, insertionPoint []string, parentTy
 					ObjectDefinition: implementationType,
 				}
 				selectionSetResult = append([]ast.Selection{possibleId}, selectionSetResult...)
+				break
 			}
 		}
 	// Otherwise, add an id selection to boundary types where the result

plan_test.go

@@ -118,7 +118,7 @@ func TestQueryPlanABA2(t *testing.T) {
 				"SelectionSet": "{ _id: id compTitles(limit: 42) { id compTitles(limit: 666) { id } } }",
 				"InsertionPoint": ["movies"],
 				"Then": [
-					{
+				  {
 					"ServiceURL": "A",
 					"ParentType": "Movie",
 					"SelectionSet": "{ _id: id title }",
@@ -408,7 +408,7 @@ func TestQueryPlanFragmentSpread2(t *testing.T) {
 	PlanTestFixture1.Check(t, query, plan)
 }
 
-func TestQueryPlanMergeDeepTraversal(t *testing.T) {
+func TestQueryPlanCompleteDeepTraversal(t *testing.T) {
 	query := `
 	{
 		shop1 {
@@ -451,6 +451,40 @@ func TestQueryPlanMergeDeepTraversal(t *testing.T) {
 	PlanTestFixture6.Check(t, query, plan)
 }
 
+func TestQueryPlanMergeInsertionPointSteps(t *testing.T) {
+	query := `
+	{
+		shop1 {
+			products {
+				name
+			}
+			products {
+				name
+			}
+		}
+	}`
+	plan := `{
+		"RootSteps": [
+			{
+				"ServiceURL": "A",
+				"ParentType": "Query",
+				"SelectionSet": "{ shop1 { products { _id: id } products { _id: id } } }",
+				"InsertionPoint": null,
+				"Then": [
+					{
+					"ServiceURL": "B",
+					"ParentType": "Product",
+					"SelectionSet": "{ _id: id name _id: id name }",
+					"InsertionPoint": ["shop1", "products"],
+					"Then": null
+					}
+				]
+			}
+		]
+	}`
+	PlanTestFixture6.Check(t, query, plan)
+}
+
 func TestQueryPlanExpandAbstractTypesWithPossibleBoundaryIds(t *testing.T) {
 	query := `
 	{
@@ -490,7 +524,7 @@ func TestQueryPlanInlineFragmentSpreadOfInterface(t *testing.T) {
 			{
 				"ServiceURL": "A",
 				"ParentType": "Query",
-				"SelectionSet": "{ animals { ... on Snake { _id: id } ... on Lion { _id: id } name ... on Lion { maneColor __typename } ... on Snake { _id: id __typename } } }",
+				"SelectionSet": "{ animals { ... on Lion { _id: id } ... on Snake { _id: id } name ... on Lion { maneColor __typename } ... on Snake { _id: id __typename } } }",
 				"InsertionPoint": null,
 				"Then": [
 					{