`yarn install` ignores `files` from local dependencies

What is the current behavior?

It seems that yarn install ignores files from package.json of projects that are locally depended on.

If the current behavior is a bug, please provide the steps to reproduce.

Using two simple projects that depends on each other locally:

○ → tree
.
|____project1
| |____bad.js
| |____good.js
| |____package.json
|____project2
| |____package.json

project1 specifies which files should be copied by dependent projects:

// project1/package.json
{
    "name" : "project1",
    "version" : "0.0.1",
    "files" : ["good.js"]
}

project2 depends on project1 locally:

// project2/package.json
{
    "name" : "project2",
    "version" : "0.0.1",
    "dependencies" : {
        "project1" : "file:../project1"
    }
}

npm install in project2 only copies the good file:

 2017-03-02 12:43:41 ⌚  turus in ~/tmp/yarn-issue/project2
○ → npm install
project2@0.0.1 /home/phtrivier/tmp/yarn-issue/project2
└── project1@0.0.1 

npm WARN project2@0.0.1 No description
npm WARN project2@0.0.1 No repository field.
npm WARN project2@0.0.1 No license field.

 2017-03-02 12:43:45 ⌚  turus in ~/tmp/yarn-issue/project2
○ → ll node_modules/project1/
total 32
drwxrwxr-x 2 phtrivier phtrivier 4096 mars   2 12:43 .
drwxrwxr-x 3 phtrivier phtrivier 4096 mars   2 12:43 ..
-rw-rw-r-- 1 phtrivier phtrivier   37 mars   2 12:37 good.js
-rw-rw-r-- 1 phtrivier phtrivier 1171 mars   2 12:43 package.json

However, yarn install copies everything, ignoring files:

  2017-03-02 12:43:48 ⌚  turus in ~/tmp/yarn-issue/project2
○ → rm -rf node_modules

 2017-03-02 12:44:55 ⌚  turus in ~/tmp/yarn-issue/project2
○ → yarn install
yarn install v0.21.3
warning project2@0.0.1: No license field
[1/4] Resolving packages...
[2/4] Fetching packages...
[3/4] Linking dependencies...
[4/4] Building fresh packages...
Done in 0.26s.

 2017-03-02 12:44:58 ⌚  turus in ~/tmp/yarn-issue/project2
○ → ll node_modules/project1/
total 44
drwxrwxr-x 2 phtrivier phtrivier 4096 mars   2 12:44 .
drwxrwxr-x 3 phtrivier phtrivier 4096 mars   2 12:44 ..
-rw-rw-r-- 1 phtrivier phtrivier   57 mars   2 12:37 bad.js
-rw-rw-r-- 1 phtrivier phtrivier   37 mars   2 12:37 good.js
-rw-rw-r-- 1 phtrivier phtrivier   80 mars   2 12:38 package.json

 2017-03-02 12:45:03 ⌚  turus in ~/tmp/yarn-issue/project2
○ → 

What is the expected behavior?

Same behavior as npm.

Please mention your node.js, yarn and operating system version.

○ → npm --version
3.10.10
○ → yarn --version
0.21.3
○ → uname -a
Linux turus 4.8.0-39-generic #42-Ubuntu SMP Mon Feb 20 11:47:27 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux