Deduplicate fragment definition before codegen

.gitignore

@@ -62,6 +62,7 @@ jspm_packages/
 /*.d.ts
 /workers
 !/babel.config.js
+!/jest.config.js
 !/index.js
 !/.pnp.js
 

__tests__/common.test.ts

@@ -0,0 +1,27 @@
+import path from 'path';
+import fs from 'fs';
+import { promisify } from 'util';
+import { visit } from 'graphql';
+import { deduplicateFragmentFromDocuments } from '~/src/common';
+
+const readFile = promisify(fs.readFile);
+
+test('deduplicateFragmentFromDocuments()', async () => {
+  const data = await readFile(path.resolve(__dirname, 'data/gh-33.json'), 'utf-8');
+  const documents = JSON.parse(data);
+  const resultDocuments = deduplicateFragmentFromDocuments(documents);
+
+  const fragmentNames = new Set<string>();
+  for (const { document } of resultDocuments) {
+    visit(document, {
+      FragmentDefinition(node) {
+        const duplicated = fragmentNames.has(node.name.value);
+        expect(duplicated).toBe(false);
+
+        if (!duplicated) {
+          fragmentNames.add(node.name.value);
+        }
+      },
+    });
+  }
+});

jest.config.js

@@ -0,0 +1,6 @@
+module.exports = {
+  verbose: true,
+  transform: {
+    '^.+\\.[t|j]sx?$': 'babel-jest',
+  },
+};

package.json

@@ -34,6 +34,7 @@
     "typescript"
   ],
   "scripts": {
+    "test": "jest",
     "tsc": "tsc --emitDeclarationOnly --skipLibCheck",
     "flowtype": "cp -f src/types.ts src/types.js && babel src/types.js -d . --plugins module:@babel/plugin-transform-flow-comments",
     "build": "babel src -d . --extensions .ts,.tsx",
@@ -58,7 +59,8 @@
     "@graphql-toolkit/common": "^0.9.7",
     "@graphql-toolkit/core": "^0.9.7",
     "async": "^3.1.1",
-    "common-tags": "^1.8.0"
+    "common-tags": "^1.8.0",
+    "~": "link:."
   },
   "devDependencies": {
     "@babel/cli": "^7.8.4",
@@ -68,14 +70,18 @@
     "@babel/plugin-transform-flow-comments": "^7.8.3",
     "@babel/plugin-transform-named-capturing-groups-regex": "^7.8.3",
     "@babel/preset-typescript": "^7.8.3",
+    "@babel/runtime": "^7.8.4",
     "@types/async": "^3.0.7",
     "@types/common-tags": "^1.8.0",
     "@types/graphql": "^14.5.0",
-    "@types/node": "^12.7.3",
+    "@types/jest": "^25.1.2",
+    "@types/node": "^13.7.1",
     "@yarnpkg/pnpify": "^2.0.0-rc.18",
+    "babel-jest": "^25.1.0",
     "babel-preset-gatsby-package": "^0.2.16",
     "gatsby": "^2.19.17",
     "graphql": "^14.6.0",
+    "jest": "^25.1.0",
     "typescript": "^3.7.5",
     "utility-types": "^3.10.0"
   }

src/common.ts

@@ -1,6 +1,7 @@
 import fs from 'fs';
 import { dirname } from 'path';
 import { promisify } from 'util';
+import { Source } from '@graphql-toolkit/common';
 
 const _mkdir = promisify(fs.mkdir);
 const _readFile = promisify(fs.readFile);
@@ -19,3 +20,34 @@ export const formatLanguage = (lang: 'typescript' | 'flow') => (
 );
 
 export type UnwrapPromise<T> = T extends Promise<infer U> ? U : T;
+
+export function deduplicateFragmentFromDocuments(documents: Source[]) {
+  const existFragmentNames = new Set<string>();
+  return documents.map(source => {
+    const { document } = source;
+
+    // Nothing to do for other sources
+    if (!document) {
+      return source;
+    }
+
+    const uniqDefinitions = document.definitions.filter(def => {
+      // De-dup only cares about fragments
+      if (def.kind !== 'FragmentDefinition') {
+        return true;
+      }
+      const fragmentName = def.name.value;
+      const duplicated = existFragmentNames.has(fragmentName);
+      if (!duplicated) existFragmentNames.add(fragmentName);
+      return !duplicated;
+    });
+
+    return {
+      ...source,
+      document: {
+        ...document,
+        definitions: uniqDefinitions,
+      },
+    };
+  });
+}

src/gatsby-node.ts

@@ -9,7 +9,7 @@ import {
 import FileParser from 'gatsby/dist/query/file-parser';
 import { parseGraphQLSDL, Source } from '@graphql-toolkit/common';
 
-import { writeFile, UnwrapPromise, readFile } from './common';
+import { writeFile, UnwrapPromise, readFile, deduplicateFragmentFromDocuments } from './common';
 import { setupCodegenWorker, setupInsertTypeWorker, InsertTypeTask } from './workers';
 import { requirePluginOptions, RequiredPluginOptions } from './plugin-utils';
 import { GatsbyKnownAction } from './gatsby-utils';
@@ -136,8 +136,9 @@ export const onPostBootstrap: GatsbyNode['onPostBootstrap'] = async ({
   });
 
   const pushCodegenTask = () => {
-    // @ts-ignore
-    codegenWorker.push({ documents: [...trackedSource.values()].filter(Boolean) });
+    codegenWorker.push({
+      documents: deduplicateFragmentFromDocuments([...trackedSource.values()].filter(Boolean)),
+    });
   };
 
   pushCodegenTask();

tsconfig.json

@@ -7,7 +7,11 @@
     "esModuleInterop": true,
     "downlevelIteration": true,
     "declaration": true,
-    "outDir": "."
+    "outDir": ".",
+    "baseUrl": ".",
+    "paths": {
+      "~/*": ["./*"]
+    }
   },
   "include": [
     "src",