feat!: In-place setting of Schema Resolvers

This builds the schema at runtime by parsing the SDL and setting the field resolvers in place, as opposed to generated an entire equivalent schema. The previous way could resulted in longer files that caused long compile times, and was more complex and brittle. Compile time improvements have been validated on the large GitHub schema.
This approach does require that we make a change to the GraphQL package that makes field resolvers mutable.

Author: NeedleInAJayStack

Examples/GraphQLDotOrg/Package.resolved

@@ -15,7 +15,8 @@ let package = Package(
     ],
     dependencies: [
         .package(name: "graphql-generator", path: "../.."),
-        .package(url: "https://github.com/GraphQLSwift/GraphQL.git", from: "4.0.0"),
+        // TODO: Mainline when merged: https://github.com/GraphQLSwift/GraphQL/pull/174
+        .package(url: "https://github.com/NeedleInAJayStack/GraphQL.git", revision: "30873303575b92f2395a900869ec8f253efad1b2"),
     ],
     targets: [
         .target(

Examples/GraphQLDotOrg/Package.swift

@@ -9,7 +9,8 @@ let package = Package(
     ],
     dependencies: [
         .package(name: "graphql-generator", path: "../.."),
-        .package(url: "https://github.com/GraphQLSwift/GraphQL.git", from: "4.0.0"),
+        // TODO: Mainline when merged: https://github.com/GraphQLSwift/GraphQL/pull/174
+        .package(url: "https://github.com/NeedleInAJayStack/GraphQL.git", revision: "30873303575b92f2395a900869ec8f253efad1b2"),
     ],
     targets: [
         .target(

Examples/HelloWorldServer/Package.resolved

@@ -29,6 +29,7 @@ struct GraphQLGeneratorPlugin: BuildToolPlugin {
         let outputFiles = [
             outputDirectory.appendingPathComponent("Types.swift"),
             outputDirectory.appendingPathComponent("Schema.swift"),
+            outputDirectory.appendingPathComponent("SDL.swift"),
         ]
 
         let arguments = schemaInputs.flatMap { ["\($0.path)"] } + [

Examples/HelloWorldServer/Package.swift

@@ -218,7 +218,6 @@ public struct EmailAddress: Scalar {
 ## Development Roadmap
 
 1. Directives: Directives are currently not supported
-2. Executable Schema: To work around the immutability of some Schema components, we generate Swift code to fully recreate the defined schema. Instead, we could just add resolver logic to the schema parsed from the `.graphql` file SDL.
 
 ## Contributing
 

Plugins/GraphQLGeneratorPlugin.swift

@@ -42,21 +42,20 @@ struct GraphQLGeneratorCommand: ParsableCommand {
             print("Parsing schema files...")
         }
 
-        // Parse schema files
-        let parser = SchemaParser()
-        let schema = try parser.parseSchemaFiles(schemaFiles)
-
-        if verbose {
-            print("Schema parsed successfully")
-            print("Generating Swift code...")
+        /// Read GraphQL schema files and combine them into a single schema
+        var combinedSource = ""
+        for filePath in schemaFiles {
+            let url = URL(fileURLWithPath: filePath)
+            let content = try String(contentsOf: url, encoding: .utf8)
+            combinedSource += content + "\n"
         }
 
         // Generate code
         let generator = CodeGenerator()
-        let generatedFiles = try generator.generate(schema: schema)
+        let files = try generator.generate(source: combinedSource)
 
         // Write generated files
-        for (filename, content) in generatedFiles {
+        for (filename, content) in files {
             let fileURL = outputURL.appendingPathComponent(filename)
             try content.write(to: fileURL, atomically: true, encoding: .utf8)
 

README.md

@@ -7,7 +7,9 @@ package struct CodeGenerator {
 
     /// Generate all Swift files from the schema
     /// Returns a dictionary of filename -> file content
-    package func generate(schema: GraphQLSchema) throws -> [String: String] {
+    package func generate(source: String) throws -> [String: String] {
+        let schema = try GraphQL.buildSchema(source: source)
+
         var files: [String: String] = [:]
 
         // Generate Types.swift
@@ -18,6 +20,10 @@ package struct CodeGenerator {
         let schemaGenerator = SchemaGenerator()
         files["Schema.swift"] = try schemaGenerator.generate(schema: schema)
 
+        // Generate SDL.swift
+        let sdlGenerator = SDLGenerator()
+        files["SDL.swift"] = try sdlGenerator.generate(source: source)
+
         return files
     }
 }

Sources/GraphQLGenerator/main.swift

@@ -0,0 +1,16 @@
+import Foundation
+import GraphQL
+
+/// Generates a file that simply wraps the SDL so that its available at runtime without moving files.
+package struct SDLGenerator {
+    package func generate(source: String) throws -> String {
+        return """
+        // Generated by GraphQL Generator
+        // DO NOT EDIT - This file is automatically generated
+
+        let graphQLRawSDL = #\"\"\"
+        \(source)
+        \"\"\"#
+        """
+    }
+}