feat(cli): add a dry-run mode with --check cli flag (#8149)

* feat(cli): add a dry-run mode with `--check` cli flag

* fix(cli): typo for `check` typing

* Create rude-vans-notice.md

* fix(cli): typo

.changeset/rude-vans-notice.md

@@ -0,0 +1,5 @@
+---
+"@graphql-codegen/cli": minor
+---
+
+feat(cli): add a dry-run mode with `--check` cli flag

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

@@ -5,8 +5,8 @@ import { cliError } from './utils/cli-error.js';
 const [, , cmd] = process.argv;
 
 runCli(cmd)
-  .then(() => {
-    process.exit(0);
+  .then(returnCode => {
+    process.exit(returnCode);
   })
   .catch(error => {
     cliError(error);

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

@@ -4,18 +4,28 @@ import { createContext } from './config.js';
 import { lifecycleHooks } from './hooks.js';
 import { DetailedError } from '@graphql-codegen/plugin-helpers';
 
-export async function runCli(cmd: string): Promise<any> {
+export async function runCli(cmd: string): Promise<number> {
   await ensureGraphQlPackage();
 
   if (cmd === 'init') {
-    return init();
+    init();
+    return 0;
   }
 
   const context = await createContext();
   try {
-    return await generate(context);
+    await generate(context);
+    if (context.checkMode && context.checkModeStaleFiles.length > 0) {
+      // eslint-disable-next-line no-console
+      console.log(
+        `The following stale files were detected:\n${context.checkModeStaleFiles.map(file => `  - ${file}\n`)}`
+      );
+      return 1;
+    }
+    return 0;
   } catch (error) {
     await lifecycleHooks(context.getConfig().hooks).onError(error.toString());
+    return 1;
   }
 }
 

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

@@ -30,6 +30,7 @@ export type YamlCliFlags = {
   silent: boolean;
   errorsOnly: boolean;
   profile: boolean;
+  check?: boolean;
   verbose?: boolean;
   debug?: boolean;
   ignoreNoDocuments?: boolean;
@@ -323,6 +324,10 @@ export function updateContextWithCliFlags(context: CodegenContext, cliFlags: Yam
     context.useProfiler();
   }
 
+  if (cliFlags.check === true) {
+    context.enableCheckMode();
+  }
+
   context.updateConfig(config);
 }
 
@@ -331,12 +336,14 @@ export class CodegenContext {
   private _graphqlConfig?: GraphQLConfig;
   private config: Types.Config;
   private _project?: string;
+  private _checkMode = false;
   private _pluginContext: { [key: string]: any } = {};
 
   cwd: string;
   filepath: string;
   profiler: Profiler;
   profilerOutput?: string;
+  checkModeStaleFiles = [];
 
   constructor({
     config,
@@ -387,6 +394,14 @@ export class CodegenContext {
     };
   }
 
+  enableCheckMode() {
+    this._checkMode = true;
+  }
+
+  get checkMode() {
+    return this._checkMode;
+  }
+
   useProfiler() {
     this.profiler = createProfiler();
 

packages/graphql-codegen-cli/src/generate-and-save.ts

@@ -73,8 +73,10 @@ export async function generate(
 
             if (previousHash && currentHash === previousHash) {
               debugLog(`Skipping file (${result.filename}) writing due to indentical hash...`);
-
               return;
+            } else if (context.checkMode) {
+              context.checkModeStaleFiles.push(result.filename);
+              return; // skip updating file in dry mode
             }
 
             if (content.length === 0) {

website/src/pages/docs/config-reference/codegen-config.mdx

@@ -143,6 +143,21 @@ The Codegen also supports several CLI flags that allow you to override the defau
 
 - **`--project` (`-p`)** - To generate only one project out of a [Multi Project](multiproject-config) config file.
 
+- **`--check`** - Enable dry-run mode (see below)
+
+## Dry-run mode
+
+Codegen can be run in dry-run mode to check if some new changes are detected:
+
+```bash
+yarn run codegen --check
+```
+
+When enabled, codegen will return the following exit code:
+
+- `0`: no changes were detected
+- `1`: some changes are missing in existing files
+
 ## Debug Mode
 
 To enable debug mode, either set the `debug: true` configuration option or use the CLI `--debug` flag.