added another test

__tests__/commands/install/integration-deduping.js

@@ -226,7 +226,7 @@ test.concurrent('install should not copy node_modules when hardlinking', (): Pro
   // A@1 -> B@1 -> C@1
   //     -> C@2
   // B@2
-  // C@2
+  // C@3
   // D@1 -> B@1 (hardlink) -> C@1 (hardlink)
   //     -> C@2
   return runInstall({linkDuplicates: true}, 'hardlink-collision', async config => {
@@ -238,3 +238,22 @@ test.concurrent('install should not copy node_modules when hardlinking', (): Pro
     expect(a_1.ino).toEqual(d_1.ino);
   });
 });
+
+test.concurrent('install should not hardlink full package structure', (): Promise<void> => {
+  // https://github.com/yarnpkg/yarn/issues/2734
+  // A@1 -> B@1 -> C@1
+  //     -> C@2
+  // B@2
+  // C@3
+  // D@1 -> B@1 (hardlink)
+  //     -> C@1 (hardlink)
+  return runInstall({linkDuplicates: true}, 'hardlink-collision-2', async config => {
+    let a_1 = await fs.stat(path.join(config.cwd, 'node_modules/a/node_modules/b/package.json'));
+    let d_1 = await fs.stat(path.join(config.cwd, 'node_modules/d/node_modules/b/package.json'));
+    expect(a_1.ino).toEqual(d_1.ino);
+    a_1 = await fs.stat(path.join(config.cwd, 'node_modules/a/node_modules/b/node_modules/c/package.json'));
+    d_1 = await fs.stat(path.join(config.cwd, 'node_modules/d/node_modules/c/package.json'));
+    expect(a_1.ino).toEqual(d_1.ino);
+    expect(await fs.exists(path.join(config.cwd, 'node_modules/d/node_modules/b/node_modules/c/package.json'))).toBe(false);
+  });
+});

__tests__/fixtures/install/hardlink-collision-2/deps/a-1/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "a",
+  "version": "1.0.0",
+  "dependencies": {
+    "b": "file:../b-1",
+    "c": "file:../c-2"
+  }
+}

__tests__/fixtures/install/hardlink-collision-2/deps/b-1/package.json

@@ -0,0 +1,7 @@
+{
+  "name": "b",
+  "version": "1.0.0",
+  "dependencies": {
+    "c": "file:../c-1"
+  }
+}

__tests__/fixtures/install/hardlink-collision-2/deps/b-2/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "b",
+  "version": "2.0.0"
+}

__tests__/fixtures/install/hardlink-collision-2/deps/c-1/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "c",
+  "version": "1.0.0"
+}

__tests__/fixtures/install/hardlink-collision-2/deps/c-2/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "c",
+  "version": "2.0.0"
+}

__tests__/fixtures/install/hardlink-collision-2/deps/c-3/package.json

@@ -0,0 +1,4 @@
+{
+  "name": "c",
+  "version": "3.0.0"
+}

__tests__/fixtures/install/hardlink-collision-2/deps/d-1/package.json

@@ -0,0 +1,7 @@
+{
+  "name": "a",
+  "version": "2.0.0",
+  "dependencies": {
+    "b": "file:../b-1"
+  }
+}

__tests__/fixtures/install/hardlink-collision-2/package.json

@@ -0,0 +1,8 @@
+{
+  "dependencies": {
+    "a": "file:deps/a-1",
+    "b": "file:deps/b-2",
+    "c": "file:deps/c-3",
+    "d": "file:deps/d-1"
+  }
+}

src/util/fs.js

@@ -450,7 +450,6 @@ async function buildActionsForHardlink(
 
       // push all files to queue
       invariant(srcFiles, 'src files not initialised');
-      // hardlinking is per package, not going into sub packages
       srcFiles = srcFiles.filter(f => f !== 'node_modules');
       let remaining = srcFiles.length;
       if (!remaining) {