Improve performance by not building schema AST over and over

packages/graphql-codegen-cli/src/codegen.ts

@@ -5,7 +5,7 @@ import { normalizeOutputParam, normalizeInstanceOrArray, normalizeConfig } from
 import { prettify } from './utils/prettier';
 import { Renderer } from './utils/listr-renderer';
 import { loadSchema, loadDocuments } from './load';
-import { GraphQLError, DocumentNode } from 'graphql';
+import { GraphQLError, DocumentNode, buildASTSchema } from 'graphql';
 import { getPluginByName } from './plugins';
 import { getPresetByName } from './presets';
 import { debugLog } from './utils/debugging';
@@ -16,7 +16,7 @@ export async function executeCodegen(config: Types.Config): Promise<Types.FileOu
   function wrapTask(task: () => void | Promise<void>, source?: string) {
     return async () => {
       try {
-        await task();
+        await Promise.resolve(task());
       } catch (error) {
         if (source && !(error instanceof GraphQLError)) {
           error.source = source;
@@ -221,6 +221,7 @@ export async function executeCodegen(config: Types.Config): Promise<Types.FileOu
                           presetConfig: outputConfig.presetConfig || {},
                           plugins: normalizedPluginsArray,
                           schema: outputSchema,
+                          schemaAst: buildASTSchema(outputSchema),
                           documents: outputDocuments,
                           config: mergedConfig,
                           pluginMap,
@@ -231,20 +232,23 @@ export async function executeCodegen(config: Types.Config): Promise<Types.FileOu
                             filename,
                             plugins: normalizedPluginsArray,
                             schema: outputSchema,
+                            schemaAst: buildASTSchema(outputSchema),
                             documents: outputDocuments,
                             config: mergedConfig,
                             pluginMap,
                           },
                         ];
                       }
 
-                      for (const outputArgs of outputs) {
+                      const process = async (outputArgs: Types.GenerateOptions) => {
                         const output = await codegen(outputArgs);
                         result.push({
                           filename: outputArgs.filename,
                           content: await prettify(filename, output),
                         });
-                      }
+                      };
+
+                      await Promise.all(outputs.map(process));
                     }, filename),
                   },
                 ],

packages/graphql-codegen-core/src/codegen.ts

@@ -1,5 +1,5 @@
 import { Types, isComplexPluginOutput } from '@graphql-codegen/plugin-helpers';
-import { DocumentNode, visit } from 'graphql';
+import { DocumentNode, visit, buildASTSchema } from 'graphql';
 import { mergeSchemas } from './merge-schemas';
 import { executePlugin } from './execute-plugin';
 import { DetailedError } from './errors';
@@ -16,10 +16,20 @@ export async function codegen(options: Types.GenerateOptions): Promise<string> {
   const pluginPackages = Object.keys(options.pluginMap).map(key => options.pluginMap[key]);
 
   // merged schema with parts added by plugins
+  let schemaChanged = false;
   const schema = pluginPackages.reduce((schema, plugin) => {
-    return !plugin.addToSchema ? schema : mergeSchemas([schema, plugin.addToSchema]);
+    if (!plugin.addToSchema) {
+      return schema;
+    }
+
+    schemaChanged = true;
+    return mergeSchemas([schema, plugin.addToSchema]);
   }, options.schema);
 
+  if (schemaChanged) {
+    options.schemaAst = buildASTSchema(schema);
+  }
+
   const prepend: Set<string> = new Set<string>();
   const append: Set<string> = new Set<string>();
 
@@ -39,6 +49,7 @@ export async function codegen(options: Types.GenerateOptions): Promise<string> {
                 ...(pluginConfig as object),
               },
         schema,
+        schemaAst: options.schemaAst,
         documents: options.documents,
         outputFilename: options.filename,
         allPlugins: options.plugins,

packages/graphql-codegen-core/src/execute-plugin.ts

@@ -7,6 +7,7 @@ export interface ExecutePluginOptions {
   name: string;
   config: Types.PluginConfig;
   schema: DocumentNode;
+  schemaAst?: GraphQLSchema;
   documents: Types.DocumentFile[];
   outputFilename: string;
   allPlugins: Types.ConfiguredPlugin[];
@@ -30,7 +31,7 @@ export async function executePlugin(options: ExecutePluginOptions, plugin: Codeg
     );
   }
 
-  const outputSchema: GraphQLSchema = buildASTSchema(options.schema);
+  const outputSchema: GraphQLSchema = options.schemaAst || buildASTSchema(options.schema);
   const documents = options.documents || [];
 
   if (outputSchema && documents.length > 0) {
@@ -51,8 +52,10 @@ export async function executePlugin(options: ExecutePluginOptions, plugin: Codeg
     }
   }
 
-  return plugin.plugin(outputSchema, documents, options.config, {
-    outputFile: options.outputFilename,
-    allPlugins: options.allPlugins,
-  });
+  return await Promise.resolve(
+    plugin.plugin(outputSchema, documents, options.config, {
+      outputFile: options.outputFilename,
+      allPlugins: options.allPlugins,
+    })
+  );
 }

packages/presets/near-operation-file/src/index.ts

@@ -162,6 +162,7 @@ export const preset: Types.OutputPreset<NearOperationFileConfig> = {
           pluginMap,
           config,
           schema: options.schema,
+          schemaAst: options.schemaAst,
           documents: [documentFile],
         };
       })

packages/utils/plugins-helpers/src/types.ts

@@ -6,6 +6,7 @@ export namespace Types {
     filename: string;
     plugins: Types.ConfiguredPlugin[];
     schema: DocumentNode;
+    schemaAst?: GraphQLSchema;
     documents: Types.DocumentFile[];
     config: { [key: string]: any };
     pluginMap: {
@@ -64,6 +65,7 @@ export namespace Types {
     baseOutputDir: string;
     plugins: Types.ConfiguredPlugin[];
     schema: DocumentNode;
+    schemaAst?: GraphQLSchema;
     documents: Types.DocumentFile[];
     config: { [key: string]: any };
     pluginMap: {