Format Snap manifests with Prettier

packages/snaps-cli/package.json

@@ -93,6 +93,7 @@
     "ora": "^5.4.1",
     "os-browserify": "^0.3.0",
     "path-browserify": "^1.0.1",
+    "prettier": "^2.8.8",
     "process": "^0.11.10",
     "punycode": "^2.3.0",
     "querystring-es3": "^0.2.1",
@@ -146,7 +147,6 @@
     "jest-it-up": "^2.0.0",
     "jest-silent-reporter": "^0.6.0",
     "memfs": "^3.4.13",
-    "prettier": "^2.8.8",
     "prettier-plugin-packagejson": "^2.5.2",
     "ts-node": "^10.9.1",
     "tsc-watch": "^4.5.0",

packages/snaps-cli/src/commands/manifest/implementation.test.ts

@@ -118,4 +118,63 @@ describe('manifest', () => {
       expect.stringMatching('The snap manifest file has been updated.'),
     );
   });
+
+  it('formats a snap manifest with Prettier', async () => {
+    const error = jest.spyOn(console, 'error').mockImplementation();
+    const log = jest.spyOn(console, 'log').mockImplementation();
+
+    await fs.writeFile(
+      '/snap/snap.manifest.json',
+      JSON.stringify(
+        getSnapManifest({
+          shasum: 'G/W5b2JZVv+epgNX9pkN63X6Lye9EJVJ4NLSgAw/afd=',
+          initialPermissions: {
+            'endowment:name-lookup': {
+              chains: ['eip155:1', 'eip155:2', 'eip155:3'],
+            },
+          },
+        }),
+      ),
+    );
+
+    const spinner = ora();
+    const result = await manifest('/snap/snap.manifest.json', true, spinner);
+    expect(result).toBe(true);
+
+    expect(error).not.toHaveBeenCalled();
+    expect(log).toHaveBeenCalledWith(
+      expect.stringMatching('The snap manifest file has been updated.'),
+    );
+
+    expect(await fs.readFile('/snap/snap.manifest.json', 'utf8'))
+      .toMatchInlineSnapshot(`
+      "{
+        "version": "1.0.0",
+        "description": "The test example snap!",
+        "proposedName": "@metamask/example-snap",
+        "repository": {
+          "type": "git",
+          "url": "https://github.com/MetaMask/example-snap.git"
+        },
+        "source": {
+          "shasum": "d4W7f1lzpVGMj8jjCn1lYhhHmKc/9TSk5QLH5ldKQoI=",
+          "location": {
+            "npm": {
+              "filePath": "dist/bundle.js",
+              "packageName": "@metamask/example-snap",
+              "registry": "https://registry.npmjs.org",
+              "iconPath": "images/icon.svg"
+            }
+          }
+        },
+        "initialPermissions": {
+          "endowment:name-lookup": {
+            "chains": ["eip155:1", "eip155:2", "eip155:3"]
+          }
+        },
+        "manifestVersion": "0.1"
+      }
+      "
+    `);
+  });
 });

packages/snaps-cli/src/commands/manifest/implementation.ts

@@ -1,11 +1,30 @@
 import { checkManifest, indent } from '@metamask/snaps-utils/node';
 import { assert } from '@metamask/utils';
 import { red, yellow, green } from 'chalk';
+import { promises as fs } from 'fs';
 import type { Ora } from 'ora';
 import { dirname } from 'path';
+import babel from 'prettier/parser-babel';
+import { format } from 'prettier/standalone';
 
 import { error, info, warn } from '../../utils';
 
+/**
+ * Write the manifest to disk.
+ *
+ * @param path - The path to write the manifest to.
+ * @param data - The manifest data.
+ * @returns A promise that resolves when the manifest has been written.
+ */
+async function writeManifest(path: string, data: string) {
+  const formattedManifest = format(data, {
+    parser: 'json',
+    plugins: [babel],
+  });
+
+  await fs.writeFile(path, formattedManifest);
+}
+
 /**
  * Check the snap manifest file at the given path. If `write` is `true`, the
  * manifest will be written to disk if it is invalid. If `write` is `false`,
@@ -24,6 +43,7 @@ export async function manifest(
 ): Promise<boolean> {
   const { reports, updated } = await checkManifest(dirname(path), {
     updateAndWriteManifest: write,
+    writeFileFn: writeManifest,
   });
 
   const errors = [];