transform documents hooks

.changeset/short-toes-relax.md

@@ -0,0 +1,102 @@
+---
+"@graphql-codegen/cli": minor
+"@graphql-codegen/core": minor
+"@graphql-codegen/plugin-helpers": minor
+"@graphql-codegen/client-preset": minor
+"@graphql-codegen/gql-tag-operations-preset": minor
+"@graphql-codegen/graphql-modules-preset": minor
+---
+
+Introduce a new feature called DocumentTransform.
+
+DocumentTransform is a functionality that allows you to modify `documents` before they are processed by plugins. You can use functions passed to the `documentTransforms` option to make changes to GraphQL documents.
+
+To use this feature, you can write `documentTransforms` as follows:
+
+```ts
+import type { CodegenConfig } from '@graphql-codegen/cli';
+
+const config: CodegenConfig = {
+  schema: 'https://localhost:4000/graphql',
+  documents: ['src/**/*.tsx'],
+  generates: {
+    './src/gql/': {
+      preset: 'client',
+      documentTransforms: [
+        {
+          transform: ({ documents }) => {
+            // Make some changes to the documents
+            return documents;
+          },
+        },
+      ],
+    },
+  },
+};
+export default config;
+```
+
+For instance, to remove a `@localOnlyDirective` directive from `documents`, you can write the following code:
+
+```js
+import type { CodegenConfig } from '@graphql-codegen/cli';
+import { visit } from 'graphql';
+
+const config: CodegenConfig = {
+  schema: 'https://localhost:4000/graphql',
+  documents: ['src/**/*.tsx'],
+  generates: {
+    './src/gql/': {
+      preset: 'client',
+      documentTransforms: [
+        {
+          transform: ({ documents }) => {
+            return documents.map(documentFile => {
+              documentFile.document = visit(documentFile.document, {
+                Directive: {
+                  leave(node) {
+                    if (node.name.value === 'localOnlyDirective') return null;
+                  },
+                },
+              });
+              return documentFile;
+            });
+          },
+        },
+      ],
+    },
+  },
+};
+export default config;
+```
+
+DocumentTransform can also be specified by file name. You can create a custom file for a specific transformation and pass it to `documentTransforms`.
+
+Let's create the document transform as a file:
+
+```js
+module.exports = {
+  transform: ({ documents }) => {
+    // Make some changes to the documents
+    return documents;
+  },
+};
+```
+
+Then, you can specify the file name as follows:
+
+```ts
+import type { CodegenConfig } from '@graphql-codegen/cli';
+
+const config: CodegenConfig = {
+  schema: 'https://localhost:4000/graphql',
+  documents: ['src/**/*.tsx'],
+  generates: {
+    './src/gql/': {
+      preset: 'client',
+      documentTransforms: ['./my-document-transform.js'],
+    },
+  },
+};
+export default config;
+```

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

@@ -18,6 +18,7 @@ import { CodegenContext, ensureContext, shouldEmitLegacyCommonJSImports } from '
 import { getPluginByName } from './plugins.js';
 import { getPresetByName } from './presets.js';
 import { debugLog, printLogs } from './utils/debugging.js';
+import { getDocumentTransform } from './documentTransforms.js';
 
 /**
  * Poor mans ESM detection.
@@ -316,6 +317,18 @@ export async function executeCodegen(input: CodegenContext | Types.Config): Prom
                             emitLegacyCommonJSImports: shouldEmitLegacyCommonJSImports(config),
                           };
 
+                          const documentTransforms = Array.isArray(outputConfig.documentTransforms)
+                            ? await Promise.all(
+                                outputConfig.documentTransforms.map(async (config, index) => {
+                                  return await getDocumentTransform(
+                                    config,
+                                    makeDefaultLoader(context.cwd),
+                                    `the element at index ${index} of the documentTransforms`
+                                  );
+                                })
+                              )
+                            : [];
+
                           const outputs: Types.GenerateOptions[] = preset
                             ? await context.profiler.run(
                                 async () =>
@@ -330,6 +343,7 @@ export async function executeCodegen(input: CodegenContext | Types.Config): Prom
                                     pluginMap,
                                     pluginContext,
                                     profiler: context.profiler,
+                                    documentTransforms,
                                   }),
                                 `Build Generates Section: ${filename}`
                               )
@@ -344,6 +358,7 @@ export async function executeCodegen(input: CodegenContext | Types.Config): Prom
                                   pluginMap,
                                   pluginContext,
                                   profiler: context.profiler,
+                                  documentTransforms,
                                 },
                               ];
 

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

@@ -0,0 +1,82 @@
+import { resolve } from 'path';
+import { Types } from '@graphql-codegen/plugin-helpers';
+
+export async function getDocumentTransform(
+  documentTransform: Types.OutputDocumentTransform,
+  loader: Types.PackageLoaderFn<Types.DocumentTransformObject>,
+  defaultName: string
+): Promise<Types.ConfiguredDocumentTransform> {
+  if (typeof documentTransform === 'string') {
+    const transformObject = await getDocumentTransformByName(documentTransform, loader);
+    return { name: documentTransform, transformObject };
+  }
+  if (isTransformObject(documentTransform)) {
+    return { name: defaultName, transformObject: documentTransform };
+  }
+  if (isTransformFileConfig(documentTransform)) {
+    const name = Object.keys(documentTransform)[0];
+    const transformObject = await getDocumentTransformByName(name, loader);
+    return { name, transformObject, config: Object.values(documentTransform)[0] };
+  }
+  throw new Error(
+    `
+        An unknown format document transform: '${defaultName}'.
+    `
+  );
+}
+
+function isTransformObject(config: Types.OutputDocumentTransform): config is Types.DocumentTransformObject {
+  return typeof config === 'object' && config.transform && typeof config.transform === 'function';
+}
+
+function isTransformFileConfig(config: Types.OutputDocumentTransform): config is Types.DocumentTransformFileConfig {
+  const keys = Object.keys(config);
+  return keys.length === 1 && typeof keys[0] === 'string';
+}
+
+export async function getDocumentTransformByName(
+  name: string,
+  loader: Types.PackageLoaderFn<Types.DocumentTransformObject>
+): Promise<Types.DocumentTransformObject> {
+  const possibleNames = [
+    `@graphql-codegen/${name}`,
+    `@graphql-codegen/${name}-document-transform`,
+    name,
+    resolve(process.cwd(), name),
+  ];
+
+  const possibleModules = possibleNames.concat(resolve(process.cwd(), name));
+
+  for (const moduleName of possibleModules) {
+    try {
+      return await loader(moduleName);
+    } catch (err) {
+      if (err.code !== 'MODULE_NOT_FOUND' && err.code !== 'ERR_MODULE_NOT_FOUND') {
+        throw new Error(
+          `
+              Unable to load document transform matching '${name}'.
+              Reason:
+                ${err.message}
+            `
+        );
+      }
+    }
+  }
+
+  const possibleNamesMsg = possibleNames
+    .map(name =>
+      `
+        - ${name}
+    `.trimEnd()
+    )
+    .join('');
+
+  throw new Error(
+    `
+        Unable to find document transform matching '${name}'
+        Install one of the following packages:
+
+        ${possibleNamesMsg}
+      `
+  );
+}