feat: Solana Wallet Standard (#31705)

## **Description**

This PR implements [Solana Wallet
Standard](https://github.com/anza-xyz/wallet-standard/) using script
injection, enabling users use MetaMask on Solana dApps.

The communication between the dApp and MetaMask uses the Multichain API.

[![Open in GitHub
Codespaces](https://github.com/codespaces/badge.svg)](https://codespaces.new/MetaMask/metamask-extension/pull/31705?quickstart=1)

## **Related issues**

Fixes:

## **Manual testing steps**

1. Run `yarn` then `yarn start:flask`
2. If you already have a local Flask extension installed, then first
uninstall it from chrome://extensions
3. Install the built flask build by loading `dist/chrome` and setup a
Solana account
4. Go to any Solana Wallet Standard compatible app, such as [Wallet
Standard Demo](https://anza-xyz.github.io/wallet-adapter/example/) or
https://jup.ag/
5. Connect with MetaMask
6. Try the features proposed by the dApp

## **Screenshots/Recordings**
MetaMask icon is the first one (the 2nd being Solflare):
![Screenshot 2025-04-08 at 15 09
48](https://github.com/user-attachments/assets/5d913f75-58da-43cf-9c0b-5e21c01afd0d)
Connection modal:
![Screenshot 2025-04-08 at 15 17
28](https://github.com/user-attachments/assets/38822726-607e-4512-ab98-b06458fc184a)
When connected:
![Screenshot 2025-04-08 at 15 17
46](https://github.com/user-attachments/assets/61f34af4-f469-402d-ab97-f3c1fc79ac89)

## **Pre-merge author checklist**

- [ ] I've followed [MetaMask Contributor
Docs](https://github.com/MetaMask/contributor-docs) and [MetaMask
Extension Coding
Standards](https://github.com/MetaMask/metamask-extension/blob/main/.github/guidelines/CODING_GUIDELINES.md).
- [ ] I've completed the PR template to the best of my ability
- [ ] I’ve included tests if applicable
- [ ] I’ve documented my code using [JSDoc](https://jsdoc.app/) format
if applicable
- [ ] I’ve applied the right labels on the PR (see [labeling
guidelines](https://github.com/MetaMask/metamask-extension/blob/main/.github/guidelines/LABELING_GUIDELINES.md)).
Not required for external contributors.

## **Pre-merge reviewer checklist**

- [ ] I've manually tested the PR (e.g. pull and build branch, run the
app, test code being changed).
- [ ] I confirm that this PR addresses all acceptance criteria described
in the ticket it closes and includes the necessary testing evidence such
as recordings and or screenshots.

---------

Co-authored-by: Christian Montoya <[email protected]>
Co-authored-by: Alex <[email protected]>
Co-authored-by: jiexi <[email protected]>

Author: 4 people

app/scripts/inpage.js

@@ -35,6 +35,17 @@ import log from 'loglevel';
 import { v4 as uuid } from 'uuid';
 import { WindowPostMessageStream } from '@metamask/post-message-stream';
 import { initializeProvider } from '@metamask/providers/initializeInpageProvider';
+
+// this is currently equivalent to process.env.MULTICHAIN_API
+// which can't be used for conditional imports
+///: BEGIN:ONLY_INCLUDE_IF(build-beta,build-flask)
+import {
+  getMultichainClient,
+  getDefaultTransport,
+} from '@metamask/multichain-api-client';
+import { registerSolanaWalletStandard } from '@metamask/solana-wallet-standard';
+///: END:ONLY_INCLUDE_IF
+
 import shouldInjectProvider from '../../shared/modules/provider-injection';
 
 // contexts
@@ -67,4 +78,13 @@ if (shouldInjectProvider()) {
       rdns: process.env.METAMASK_BUILD_APP_ID,
     },
   });
+
+  // this is currently equivalent to process.env.MULTICHAIN_API
+  ///: BEGIN:ONLY_INCLUDE_IF(build-beta,build-flask)
+  getMultichainClient({
+    transport: getDefaultTransport(),
+  }).then((client) => {
+    registerSolanaWalletStandard({ client });
+  });
+  ///: END:ONLY_INCLUDE_IF
 }

package.json

@@ -292,6 +292,7 @@
     "@metamask/message-manager": "^12.0.1",
     "@metamask/message-signing-snap": "^0.6.0",
     "@metamask/metamask-eth-abis": "^3.1.1",
+    "@metamask/multichain-api-client": "^0.1.1",
     "@metamask/multichain-api-middleware": "^0.1.1",
     "@metamask/multichain-network-controller": "^0.1.0",
     "@metamask/multichain-transactions-controller": "^0.7.2",
@@ -324,6 +325,7 @@
     "@metamask/snaps-sdk": "^6.22.0",
     "@metamask/snaps-utils": "^9.2.0",
     "@metamask/solana-wallet-snap": "^1.18.1",
+    "@metamask/solana-wallet-standard": "^0.1.1",
     "@metamask/transaction-controller": "^54.0.0",
     "@metamask/user-operation-controller": "^31.0.0",
     "@metamask/utils": "^11.1.0",

yarn.lock

@@ -5776,6 +5776,13 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@metamask/multichain-api-client@npm:^0.1.1":
+  version: 0.1.1
+  resolution: "@metamask/multichain-api-client@npm:0.1.1"
+  checksum: 10/85d8e7d20389460269ddd07388dcbfdbceb532df0e21d5184f810f90d4e8817318e717b0f6f716fce6ad7c457d54c476c1e7ac209cbb6b0757cbebd747917568
+  languageName: node
+  linkType: hard
+
 "@metamask/multichain-api-middleware@npm:^0.1.1":
   version: 0.1.1
   resolution: "@metamask/multichain-api-middleware@npm:0.1.1"
@@ -6571,6 +6578,20 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@metamask/solana-wallet-standard@npm:^0.1.1":
+  version: 0.1.1
+  resolution: "@metamask/solana-wallet-standard@npm:0.1.1"
+  dependencies:
+    "@solana/wallet-standard-chains": "npm:^1.1.1"
+    "@solana/wallet-standard-features": "npm:^1.3.0"
+    "@wallet-standard/base": "npm:^1.1.0"
+    "@wallet-standard/features": "npm:^1.1.0"
+    "@wallet-standard/wallet": "npm:^1.1.0"
+    bs58: "npm:^6.0.0"
+  checksum: 10/06559ac73f590d360c8b8e053bdfde94077558bc861e4bc03dffa6578d939e3774c94957f95488e9394c75efd3bd0533035f1f10da2f5b8dfba2533e16193af4
+  languageName: node
+  linkType: hard
+
 "@metamask/superstruct@npm:^3.0.0, @metamask/superstruct@npm:^3.1.0, @metamask/superstruct@npm:^3.2.1":
   version: 3.2.1
   resolution: "@metamask/superstruct@npm:3.2.1"
@@ -8876,6 +8897,25 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@solana/wallet-standard-chains@npm:^1.1.1":
+  version: 1.1.1
+  resolution: "@solana/wallet-standard-chains@npm:1.1.1"
+  dependencies:
+    "@wallet-standard/base": "npm:^1.1.0"
+  checksum: 10/8903840e721642e1699dc949f7c9e75e2d6f4c26b7e768e871d91d4006731356dea64426c7351381912671887979ef47193fc17cb8b12ba819334f95f83c0ba6
+  languageName: node
+  linkType: hard
+
+"@solana/wallet-standard-features@npm:^1.3.0":
+  version: 1.3.0
+  resolution: "@solana/wallet-standard-features@npm:1.3.0"
+  dependencies:
+    "@wallet-standard/base": "npm:^1.1.0"
+    "@wallet-standard/features": "npm:^1.1.0"
+  checksum: 10/9c4ef26346ef0b602ad4bde7a32e53716b96a427c4f7120571be949efeefa21a2458e9d6ef41bf1be7a1e3f2a45fa631fc4242503a87043d74bb7213c62509c2
+  languageName: node
+  linkType: hard
+
 "@solana/web3.js@npm:^2.0.0":
   version: 2.0.0
   resolution: "@solana/web3.js@npm:2.0.0"
@@ -12500,6 +12540,31 @@ __metadata:
   languageName: node
   linkType: hard
 
+"@wallet-standard/base@npm:^1.1.0":
+  version: 1.1.0
+  resolution: "@wallet-standard/base@npm:1.1.0"
+  checksum: 10/11dbb8ed80566265916ab193ad5eab1585d55996781a88039d2bc4480428b1e778901b2dcff3e688dcac7de45e8a9272026f37f07f1e75168caff581906c5079
+  languageName: node
+  linkType: hard
+
+"@wallet-standard/features@npm:^1.1.0":
+  version: 1.1.0
+  resolution: "@wallet-standard/features@npm:1.1.0"
+  dependencies:
+    "@wallet-standard/base": "npm:^1.1.0"
+  checksum: 10/e046f813ec4bfea172aeb6c11358a962afe8f9a6961453e621d624f89d8b5fc8a44404dacfe18d33be815df6e9117bbf914009f5a9f9ea91ff90a136043fcac8
+  languageName: node
+  linkType: hard
+
+"@wallet-standard/wallet@npm:^1.1.0":
+  version: 1.1.0
+  resolution: "@wallet-standard/wallet@npm:1.1.0"
+  dependencies:
+    "@wallet-standard/base": "npm:^1.1.0"
+  checksum: 10/b56846709c43b1dee6b44f7a9e15d89a00e4408d3d967eb438f415b42c5c52c4cf33a7b3126d0cf0dc0d78f244755e3d084a05824c1397ce58be169426c5337b
+  languageName: node
+  linkType: hard
+
 "@webassemblyjs/ast@npm:1.12.1, @webassemblyjs/ast@npm:^1.12.1":
   version: 1.12.1
   resolution: "@webassemblyjs/ast@npm:1.12.1"
@@ -27347,6 +27412,7 @@ __metadata:
     "@metamask/message-manager": "npm:^12.0.1"
     "@metamask/message-signing-snap": "npm:^0.6.0"
     "@metamask/metamask-eth-abis": "npm:^3.1.1"
+    "@metamask/multichain-api-client": "npm:^0.1.1"
     "@metamask/multichain-api-middleware": "npm:^0.1.1"
     "@metamask/multichain-network-controller": "npm:^0.1.0"
     "@metamask/multichain-transactions-controller": "npm:^0.7.2"
@@ -27381,6 +27447,7 @@ __metadata:
     "@metamask/snaps-sdk": "npm:^6.22.0"
     "@metamask/snaps-utils": "npm:^9.2.0"
     "@metamask/solana-wallet-snap": "npm:^1.18.1"
+    "@metamask/solana-wallet-standard": "npm:^0.1.1"
     "@metamask/test-bundler": "npm:^1.0.0"
     "@metamask/test-dapp": "npm:9.2.0"
     "@metamask/test-dapp-multichain": "npm:^0.6.0"