From d35d38ae92c76a1b6c58cf9ebdd90c40da700fe7 Mon Sep 17 00:00:00 2001
From: Dmitriy Lazarev <w@kich.dev>
Date: Fri, 23 Feb 2024 00:41:46 +0400
Subject: [PATCH] Add postTransform option to allow apply custom
 transformations after schema mapping

Signed-off-by: Dmitriy Lazarev <w@kich.dev>
---
 .changeset/clean-badgers-tie.md |  5 +++++
 src/transformSchema.ts          | 17 ++++++++++++++---
 src/types.ts                    |  2 ++
 3 files changed, 21 insertions(+), 3 deletions(-)
 create mode 100644 .changeset/clean-badgers-tie.md

diff --git a/.changeset/clean-badgers-tie.md b/.changeset/clean-badgers-tie.md
new file mode 100644
index 0000000..4ae6dc7
--- /dev/null
+++ b/.changeset/clean-badgers-tie.md
@@ -0,0 +1,5 @@
+---
+"@frontside/hydraphql": patch
+---
+
+Add postTransform option to allow apply custom transformations after schema mapping
diff --git a/src/transformSchema.ts b/src/transformSchema.ts
index 6d4874e..e354e16 100644
--- a/src/transformSchema.ts
+++ b/src/transformSchema.ts
@@ -11,11 +11,17 @@ export function transformSchema(
   additionalModules: (GraphQLModule | Module)[] = [],
   { generateOpaqueTypes }: { generateOpaqueTypes?: boolean } = {},
 ) {
+  const postTransformers: GraphQLModule["postTransform"][] = [];
   const modules = [CoreSync(), ...additionalModules];
   const directiveMappers: Record<string, FieldDirectiveMapper> = {};
   const typeDefs: DocumentNode[] = modules.flatMap((m) => {
-    const { module: gqlModule, mappers = {} } = "id" in m ? { module: m } : m;
+    const {
+      module: gqlModule,
+      mappers = {},
+      postTransform = undefined,
+    } = "id" in m ? { module: m } : m;
     const documents = gqlModule.typeDefs;
+    postTransformers.push(postTransform);
     documents.forEach((document) => {
       document.definitions.forEach((definition) => {
         if (definition.kind !== Kind.DIRECTIVE_DEFINITION) return;
@@ -36,10 +42,15 @@ export function transformSchema(
     generateOpaqueTypes,
   });
 
-  const errors = validateSchema(schema);
+  const postSchema = postTransformers.reduce(
+    (s, transform) => transform?.(s) ?? s,
+    schema,
+  );
+
+  const errors = validateSchema(postSchema);
 
   if (errors.length > 0) {
     throw new Error(errors.map((e) => e.message).join("\n"));
   }
-  return schema;
+  return postSchema;
 }
diff --git a/src/types.ts b/src/types.ts
index 2a797ad..9c3b120 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -4,6 +4,7 @@ import type {
   GraphQLFieldConfig,
   GraphQLNamedType,
   GraphQLObjectType,
+  GraphQLSchema,
 } from "graphql";
 import type { Application, Module } from "graphql-modules";
 
@@ -64,5 +65,6 @@ export interface NamedType {
 
 export interface GraphQLModule {
   mappers?: Record<string, FieldDirectiveMapper>;
+  postTransform?: (schema: GraphQLSchema) => GraphQLSchema;
   module: Module;
 }