Update: Add support for "//" comments in package.json dependencies (#…

…3829)

**Summary**
Fixes #2484. Adds support for the `"//"` package in package.json, by deleting it before we resolve the dependencies.

**Test plan**

Adds a new integration test.

__tests__/commands/install/integration.js

@@ -471,6 +471,12 @@ test.concurrent('install should run install scripts in the order of dependencies
   });
 });
 
+test.concurrent('install with comments in manifest', (): Promise<void> => {
+  return runInstall({noLockfile: true}, 'install-with-comments', async config => {
+    expect(await fs.readFile(path.join(config.cwd, 'node_modules', 'foo', 'index.js'))).toEqual('foobar;\n');
+  });
+});
+
 test.concurrent('run install scripts in the order when one dependency does not have install script', (): Promise<
   void,
 > => {

__tests__/fixtures/install/install-with-comments/bar/index.js

@@ -0,0 +1 @@
+foobar;

__tests__/fixtures/install/install-with-comments/bar/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "bar",
+  "version": "0.0.0",
+  "main": "index.js"
+}

__tests__/fixtures/install/install-with-comments/package.json

@@ -0,0 +1,10 @@
+{
+  "dependencies": {
+    "//": [
+      "This is a",
+      "multiline",
+      "comment"
+    ],
+    "foo": "file:bar"
+  }
+}

__tests__/fixtures/install/install-with-comments/yarn.lock

@@ -0,0 +1,4 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+"foo@file:bar":
+  version "0.0.0"

src/cli/commands/install.js

@@ -227,6 +227,13 @@ export class Install {
 
       this.rootManifestRegistries.push(registry);
       const projectManifestJson = await this.config.readJson(loc);
+
+      ['dependencies', 'devDependencies', 'optionalDependencies', 'peerDependencies'].forEach(dependencyKey => {
+        if (projectManifestJson[dependencyKey]) {
+          delete projectManifestJson[dependencyKey]['//'];
+        }
+      });
+
       await normalizeManifest(projectManifestJson, this.config.cwd, this.config, true);
 
       Object.assign(this.resolutions, projectManifestJson.resolutions);