feat: Add a config plugin for Expo (iOS)

This patch adds an Expo config-plugin to easily embed the library into
an Expo project.

This plugin with insert the code changes described in the README each
time the "prebuild" phase in run.

Author: aurelien-iapp

Diff for: README.md

@@ -434,6 +434,19 @@ If you want to support universal links, add the following to `AppDelegate.m` und
 + }
 ```
 
+##### For Expo projects
+
+Add the following line to your [config plugins declaration](https://docs.expo.dev/config-plugins/introduction/) in the
+`app.json` file at the root of the Expo project (can be `app.config.js` or `app.config.ts` if you are using dynamic config):
+
+```json
+{
+  "expo": {
+    "plugins": ["react-native-app-auth/plugin"]
+  }
+}
+```
+
 #### Integration of the library with a Swift iOS project
 
 The approach mentioned should work with Swift. In this case one should make `AppDelegate` conform to `RNAppAuthAuthorizationFlowManager`. Note that this is not tested/guaranteed by the maintainers.

Diff for: package.json

@@ -47,6 +47,7 @@
     "react-native": ">=0.63.0"
   },
   "devDependencies": {
+    "@expo/config-plugins": "^7.2.5",
     "@svitejs/changesets-changelog-github-compact": "^0.1.1",
     "babel-eslint": "10.0.3",
     "eslint": "6.8.0",

Diff for: plugin/index.js

@@ -0,0 +1,13 @@
+const { withPlugins, createRunOncePlugin } = require('@expo/config-plugins');
+const { withAppAuthAppDelegate, withAppAuthAppDelegateHeader } = require('./ios');
+
+const withAppAuth = config => {
+  return withPlugins(config, [
+    // iOS
+    withAppAuthAppDelegate,
+    withAppAuthAppDelegateHeader, // 👈 ️this one uses withDangerousMod !
+  ]);
+};
+
+const packageJson = require('../package.json');
+module.exports = createRunOncePlugin(withAppAuth, packageJson.name, packageJson.version);

Diff for: plugin/ios/app-delegate-header.js

@@ -0,0 +1,57 @@
+const { IOSConfig, withDangerousMod } = require('@expo/config-plugins');
+const codeModIOs = require('@expo/config-plugins/build/ios/codeMod');
+const {
+  createGeneratedHeaderComment,
+  removeContents,
+} = require('@expo/config-plugins/build/utils/generateCode');
+const fs = require('fs');
+const { insertProtocolDeclaration } = require('./utils/insert-protocol-declaration');
+
+const withAppAuthAppDelegateHeader = rootConfig =>
+  withDangerousMod(rootConfig, [
+    'ios',
+    config => {
+      // find the AppDelegate.h file in the project
+      const headerFilePath = IOSConfig.Paths.getAppDelegateObjcHeaderFilePath(
+        config.modRequest.projectRoot
+      );
+
+      // BEWARE: we update the AppDelegate.h file *outside* of the standard Expo config procedure !
+      let contents = fs.readFileSync(headerFilePath, 'utf-8');
+
+      // add a new import (unless it already exists)
+      contents = codeModIOs.addObjcImports(contents, ['"RNAppAuthAuthorizationFlowManager.h"']);
+
+      // adds a new protocol to the AppDelegate interface (unless it already exists)
+      contents = insertProtocolDeclaration({
+        source: contents,
+        interfaceName: 'AppDelegate',
+        protocolName: 'RNAppAuthAuthorizationFlowManager',
+        baseClassName: 'EXAppDelegateWrapper',
+      });
+
+      // add a new property to the AppDelegate interface (unless it already exists)
+      contents = removeContents({
+        src: contents,
+        tag: 'react-native-app-auth',
+      }).contents;
+      contents = codeModIOs.insertContentsInsideObjcInterfaceBlock(
+        contents,
+        '@interface AppDelegate',
+        `
+${createGeneratedHeaderComment(contents, 'react-native-app-auth', '//')}
+@property(nonatomic, weak) id<RNAppAuthAuthorizationFlowManagerDelegate> authorizationFlowManagerDelegate;
+// @generated end react-native-app-auth`,
+        { position: 'head' }
+      );
+
+      // and finally we write the file back to the disk
+      fs.writeFileSync(headerFilePath, contents, 'utf-8');
+
+      return config;
+    },
+  ]);
+
+module.exports = {
+  withAppAuthAppDelegateHeader,
+};

Diff for: plugin/ios/app-delegate.js

@@ -0,0 +1,55 @@
+const { withAppDelegate } = require('@expo/config-plugins');
+const codeModIOs = require('@expo/config-plugins/build/ios/codeMod');
+const {
+  createGeneratedHeaderComment,
+  removeContents,
+} = require('@expo/config-plugins/build/utils/generateCode');
+
+const withAppAuthAppDelegate = rootConfig =>
+  withAppDelegate(rootConfig, config => {
+    let { contents } = config.modResults;
+
+    // generation tags & headers
+    const tag1 = 'react-native-app-auth custom scheme';
+    const tag2 = 'react-native-app-auth deep linking';
+    const header1 = createGeneratedHeaderComment(contents, tag1, '//');
+    const header2 = createGeneratedHeaderComment(contents, tag2, '//');
+
+    // insert the code that handles the custom scheme redirections
+    contents = removeContents({ src: contents, tag: tag1 }).contents;
+    contents = codeModIOs.insertContentsInsideObjcFunctionBlock(
+      contents,
+      'application:openURL:options:',
+      `  ${header1}
+      if ([self.authorizationFlowManagerDelegate resumeExternalUserAgentFlowWithURL:url]) {
+        return YES;
+      }
+      // @generated end ${tag1}`,
+      { position: 'head' }
+    );
+
+    // insert the code that handles the deep linking continuation
+    contents = removeContents({ src: contents, tag: tag2 }).contents;
+    contents = codeModIOs.insertContentsInsideObjcFunctionBlock(
+      contents,
+      'application:continueUserActivity:restorationHandler:',
+      `  ${header2}
+      if ([userActivity.activityType isEqualToString:NSUserActivityTypeBrowsingWeb]) {
+        if (self.authorizationFlowManagerDelegate) {
+          BOOL resumableAuth = [self.authorizationFlowManagerDelegate resumeExternalUserAgentFlowWithURL:userActivity.webpageURL];
+          if (resumableAuth) {
+            return YES;
+          }
+        }
+      }
+      // @generated end ${tag2}`,
+      { position: 'head' }
+    );
+
+    config.modResults.contents = contents;
+    return config;
+  });
+
+module.exports = {
+  withAppAuthAppDelegate,
+};

Diff for: plugin/ios/index.js

@@ -0,0 +1,7 @@
+const { withAppAuthAppDelegateHeader } = require('./app-delegate-header');
+const { withAppAuthAppDelegate } = require('./app-delegate');
+
+module.exports = {
+  withAppAuthAppDelegate,
+  withAppAuthAppDelegateHeader,
+};

Diff for: plugin/ios/utils/insert-protocol-declaration.js

@@ -0,0 +1,35 @@
+/**
+ * Inserts a protocol into an Objective-C class interface declaration.
+ * @param {string} source source code of the file
+ * @param {string} interfaceName Name of the interface to insert the protocol into (ex: AppDelegate)
+ * @param {string} protocolName Name of the protocol to add to the list of protocols (ex: RNAppAuthAuthorizationFlowManagerDelegate)
+ * @param {string|undefined} baseClassName Base class name of the interface (ex: NSObject)
+ * @returns {string} the patched source code
+ */
+const insertProtocolDeclaration = ({
+  source,
+  interfaceName,
+  protocolName,
+  baseClassName = 'NSObject',
+}) => {
+  const matchInterfaceDeclarationRegexp = new RegExp(
+    `(@interface\\s+${interfaceName}\\s*:\\s*${baseClassName})(\\s*\\<(.*)\\>)?`
+  );
+  const match = source.match(matchInterfaceDeclarationRegexp);
+  if (match) {
+    const [line, interfaceDeclaration, , existingProtocols] = match;
+    if (!existingProtocols || !existingProtocols.includes(protocolName)) {
+      source = source.replace(
+        line,
+        `${interfaceDeclaration} <${
+          existingProtocols ? `${existingProtocols},` : ''
+        }${protocolName}>`
+      );
+    }
+  }
+  return source;
+};
+
+module.exports = {
+  insertProtocolDeclaration,
+};