[BREAKING] Add snap_resolveInterface RPC method (#2509)

This PR adds a new non-restricted RPC method that allows a snap to
resolve a given user interface bound to a `snap_dialog` with a custom
value.

- [x] Add the `resolveInterface` method in the `SnapInterfaceController`
- [x] Add a new `snap_resolveInterface` RPC method
- [x] Update `snap_dialog` RPC method to set the approval ID to the
interface ID
- [x] [BREAKING] `snap_dialog` now takes the `requestUserApproval` hook
which is meant to be bind to the `addAndShowRequest` method of the
`ApprovalController`

packages/snaps-controllers/coverage.json

@@ -1,6 +1,6 @@
 {
   "branches": 92.08,
-  "functions": 96.74,
-  "lines": 97.96,
-  "statements": 97.64
+  "functions": 96.75,
+  "lines": 97.97,
+  "statements": 97.65
 }

packages/snaps-controllers/src/interface/SnapInterfaceController.test.tsx

@@ -14,6 +14,7 @@ import { getJsxElementFromComponent } from '@metamask/snaps-utils';
 import { MOCK_SNAP_ID } from '@metamask/snaps-utils/test-utils';
 
 import {
+  MockApprovalController,
   getRestrictedSnapInterfaceControllerMessenger,
   getRootSnapInterfaceControllerMessenger,
 } from '../test-utils';
@@ -932,4 +933,167 @@ describe('SnapInterfaceController', () => {
       ).toThrow(`Interface with id '${id}' not found.`);
     });
   });
+
+  describe('resolveInterface', () => {
+    it('resolves the interface with the given value', async () => {
+      const rootMessenger = getRootSnapInterfaceControllerMessenger();
+      const controllerMessenger =
+        getRestrictedSnapInterfaceControllerMessenger(rootMessenger);
+
+      /* eslint-disable-next-line no-new */
+      new SnapInterfaceController({
+        messenger: controllerMessenger,
+      });
+
+      const approvalControllerMock = new MockApprovalController();
+
+      rootMessenger.registerActionHandler(
+        'ApprovalController:hasRequest',
+        approvalControllerMock.hasRequest.bind(approvalControllerMock),
+      );
+
+      rootMessenger.registerActionHandler(
+        'ApprovalController:acceptRequest',
+        approvalControllerMock.acceptRequest.bind(approvalControllerMock),
+      );
+
+      const id = await rootMessenger.call(
+        'SnapInterfaceController:createInterface',
+        MOCK_SNAP_ID,
+        <Box>
+          <Text>foo</Text>
+        </Box>,
+      );
+
+      const approvalPromise = approvalControllerMock.addRequest({
+        id,
+      });
+
+      rootMessenger.call(
+        'SnapInterfaceController:resolveInterface',
+        MOCK_SNAP_ID,
+        id,
+        'bar',
+      );
+
+      expect(await approvalPromise).toBe('bar');
+    });
+
+    it('throws if the interface does not exist', async () => {
+      const rootMessenger = getRootSnapInterfaceControllerMessenger();
+      const controllerMessenger =
+        getRestrictedSnapInterfaceControllerMessenger(rootMessenger);
+
+      /* eslint-disable-next-line no-new */
+      new SnapInterfaceController({
+        messenger: controllerMessenger,
+      });
+
+      const approvalControllerMock = new MockApprovalController();
+
+      rootMessenger.registerActionHandler(
+        'ApprovalController:hasRequest',
+        approvalControllerMock.hasRequest.bind(approvalControllerMock),
+      );
+
+      rootMessenger.registerActionHandler(
+        'ApprovalController:acceptRequest',
+        approvalControllerMock.acceptRequest.bind(approvalControllerMock),
+      );
+
+      await expect(
+        rootMessenger.call(
+          'SnapInterfaceController:resolveInterface',
+          MOCK_SNAP_ID,
+          'foo',
+          'bar',
+        ),
+      ).rejects.toThrow(`Interface with id 'foo' not found.`);
+    });
+
+    it('throws if the interface is resolved by another snap', async () => {
+      const rootMessenger = getRootSnapInterfaceControllerMessenger();
+      const controllerMessenger =
+        getRestrictedSnapInterfaceControllerMessenger(rootMessenger);
+
+      /* eslint-disable-next-line no-new */
+      new SnapInterfaceController({
+        messenger: controllerMessenger,
+      });
+
+      const approvalControllerMock = new MockApprovalController();
+
+      rootMessenger.registerActionHandler(
+        'ApprovalController:hasRequest',
+        approvalControllerMock.hasRequest.bind(approvalControllerMock),
+      );
+
+      rootMessenger.registerActionHandler(
+        'ApprovalController:acceptRequest',
+        approvalControllerMock.acceptRequest.bind(approvalControllerMock),
+      );
+
+      const id = await rootMessenger.call(
+        'SnapInterfaceController:createInterface',
+        MOCK_SNAP_ID,
+        <Box>
+          <Text>foo</Text>
+        </Box>,
+      );
+
+      // eslint-disable-next-line @typescript-eslint/no-floating-promises
+      approvalControllerMock.addRequest({
+        id,
+      });
+
+      await expect(
+        rootMessenger.call(
+          'SnapInterfaceController:resolveInterface',
+          'baz' as SnapId,
+          id,
+          'bar',
+        ),
+      ).rejects.toThrow('Interface not created by baz.');
+    });
+
+    it('throws if the interface has no approval request', async () => {
+      const rootMessenger = getRootSnapInterfaceControllerMessenger();
+      const controllerMessenger =
+        getRestrictedSnapInterfaceControllerMessenger(rootMessenger);
+
+      /* eslint-disable-next-line no-new */
+      new SnapInterfaceController({
+        messenger: controllerMessenger,
+      });
+
+      const approvalControllerMock = new MockApprovalController();
+
+      rootMessenger.registerActionHandler(
+        'ApprovalController:hasRequest',
+        approvalControllerMock.hasRequest.bind(approvalControllerMock),
+      );
+
+      rootMessenger.registerActionHandler(
+        'ApprovalController:acceptRequest',
+        approvalControllerMock.acceptRequest.bind(approvalControllerMock),
+      );
+
+      const id = await rootMessenger.call(
+        'SnapInterfaceController:createInterface',
+        MOCK_SNAP_ID,
+        <Box>
+          <Text>foo</Text>
+        </Box>,
+      );
+
+      await expect(
+        rootMessenger.call(
+          'SnapInterfaceController:resolveInterface',
+          MOCK_SNAP_ID,
+          id,
+          'bar',
+        ),
+      ).rejects.toThrow(`Approval request with id '${id}' not found.`);
+    });
+  });
 });

packages/snaps-controllers/src/interface/SnapInterfaceController.ts

@@ -1,3 +1,7 @@
+import type {
+  AcceptRequest,
+  HasApprovalRequest,
+} from '@metamask/approval-controller';
 import type { RestrictedControllerMessenger } from '@metamask/base-controller';
 import { BaseController } from '@metamask/base-controller';
 import type {
@@ -12,6 +16,7 @@ import type {
 } from '@metamask/snaps-sdk';
 import type { JSXElement } from '@metamask/snaps-sdk/jsx';
 import { getJsonSizeUnsafe, validateJsxLinks } from '@metamask/snaps-utils';
+import type { Json } from '@metamask/utils';
 import { assert } from '@metamask/utils';
 import { nanoid } from 'nanoid';
 
@@ -50,16 +55,24 @@ export type UpdateInterfaceState = {
   handler: SnapInterfaceController['updateInterfaceState'];
 };
 
+export type ResolveInterface = {
+  type: `${typeof controllerName}:resolveInterface`;
+  handler: SnapInterfaceController['resolveInterface'];
+};
+
 export type SnapInterfaceControllerAllowedActions =
   | TestOrigin
-  | MaybeUpdateState;
+  | MaybeUpdateState
+  | HasApprovalRequest
+  | AcceptRequest;
 
 export type SnapInterfaceControllerActions =
   | CreateInterface
   | GetInterface
   | UpdateInterface
   | DeleteInterface
-  | UpdateInterfaceState;
+  | UpdateInterfaceState
+  | ResolveInterface;
 
 export type SnapInterfaceControllerMessenger = RestrictedControllerMessenger<
   typeof controllerName,
@@ -135,6 +148,11 @@ export class SnapInterfaceController extends BaseController<
       `${controllerName}:updateInterfaceState`,
       this.updateInterfaceState.bind(this),
     );
+
+    this.messagingSystem.registerActionHandler(
+      `${controllerName}:resolveInterface`,
+      this.resolveInterface.bind(this),
+    );
   }
 
   /**
@@ -232,6 +250,23 @@ export class SnapInterfaceController extends BaseController<
     });
   }
 
+  /**
+   * Resolve the promise of a given interface approval request.
+   * The approval needs to have the same ID as the interface.
+   *
+   * @param snapId - The snap id.
+   * @param id - The interface id.
+   * @param value - The value to resolve the promise with.
+   */
+  async resolveInterface(snapId: SnapId, id: string, value: Json) {
+    this.#validateArgs(snapId, id);
+    this.#validateApproval(id);
+
+    await this.#acceptApprovalRequest(id, value);
+
+    this.deleteInterface(id);
+  }
+
   /**
    * Utility function to validate the args passed to the other methods.
    *
@@ -251,6 +286,18 @@ export class SnapInterfaceController extends BaseController<
     );
   }
 
+  /**
+   * Utility function to validate that the approval request exists.
+   *
+   * @param id - The interface id.
+   */
+  #validateApproval(id: string) {
+    assert(
+      this.#hasApprovalRequest(id),
+      `Approval request with id '${id}' not found.`,
+    );
+  }
+
   /**
    * Trigger a Phishing list update if needed.
    */
@@ -269,6 +316,33 @@ export class SnapInterfaceController extends BaseController<
       .result;
   }
 
+  /**
+   * Check if an approval request exists for a given interface by looking up
+   * if the ApprovalController has a request with the given interface ID.
+   *
+   * @param id - The interface id.
+   * @returns True if an approval request exists, otherwise false.
+   */
+  #hasApprovalRequest(id: string) {
+    return this.messagingSystem.call('ApprovalController:hasRequest', {
+      id,
+    });
+  }
+
+  /**
+   * Accept an approval request for a given interface.
+   *
+   * @param id - The interface id.
+   * @param value - The value to resolve the promise with.
+   */
+  async #acceptApprovalRequest(id: string, value: Json) {
+    await this.messagingSystem.call(
+      'ApprovalController:acceptRequest',
+      id,
+      value,
+    );
+  }
+
   /**
    * Utility function to validate the components of an interface.
    * Throws if something is invalid.

packages/snaps-controllers/src/test-utils/controller.ts

@@ -74,7 +74,11 @@ export class MockApprovalController {
     };
   };
 
-  async addRequest(request: { requestData?: Record<string, Json> }) {
+  async addRequest(request: {
+    id?: string;
+    origin?: string;
+    requestData?: Record<string, Json>;
+  }) {
     const promise = new Promise((resolve, reject) => {
       this.#approval = {
         promise: { resolve, reject },
@@ -85,6 +89,21 @@ export class MockApprovalController {
     return promise;
   }
 
+  hasRequest(
+    opts: { id?: string; origin?: string; type?: string } = {},
+  ): boolean {
+    return this.#approval?.request.id === opts.id;
+  }
+
+  async acceptRequest(_id: string, value: unknown) {
+    if (this.#approval) {
+      this.#approval.promise.resolve(value);
+      return await Promise.resolve({ value });
+    }
+
+    return await Promise.reject(new Error('No request to approve.'));
+  }
+
   updateRequestStateAndApprove({
     requestState,
   }: {
@@ -679,7 +698,10 @@ export const getRestrictedSnapInterfaceControllerMessenger = (
     allowedActions: [
       'PhishingController:testOrigin',
       'PhishingController:maybeUpdateState',
+      'ApprovalController:hasRequest',
+      'ApprovalController:acceptRequest',
     ],
+    allowedEvents: [],
   });
 
   if (mocked) {