validate-tree: Warn on deps in both dependencies and devDependencies

Fixes: npm#6725
Credit: @TedYav
PR-URL: npm/npm#15772
Reviewed-By: @iarna

.mailmap

@@ -53,6 +53,7 @@ Ryan Emery <[email protected]>
 Sam Mikes <[email protected]>
 Stephanie Snopek <[email protected]>
 Takaya Kobayashi <[email protected]>
+Ted Yavuzkurt <[email protected]> <[email protected]>
 Thomas Reggi <[email protected]>
 Timo Weiß <[email protected]>
 Tony <[email protected]>

lib/install/validate-tree.js

@@ -26,7 +26,8 @@ module.exports = function (idealTree, log, next) {
       ], done)
     }],
     [thenValidateAllPeerDeps, idealTree],
-    [thenCheckTop, idealTree]
+    [thenCheckTop, idealTree],
+    [thenCheckDuplicateDeps, idealTree]
   ], andFinishTracker(log, next))
 }
 
@@ -73,5 +74,22 @@ function thenCheckTop (idealTree, next) {
     warnObj.code = 'ENODEPRE'
     idealTree.warnings.push(warnObj)
   }
+
+  next()
+}
+
+// check for deps duplciated between devdeps and regular deps
+function thenCheckDuplicateDeps (idealTree, next) {
+  var deps = idealTree.package.dependencies || {}
+  var devDeps = idealTree.package.devDependencies || {}
+
+  for (var pkg in devDeps) {
+    if (pkg in deps) {
+      var warnObj = new Error('The package ' + pkg + ' is included as both a dev and production dependency.')
+      warnObj.code = 'EDUPLICATEDEP'
+      idealTree.warnings.push(warnObj)
+    }
+  }
+
   next()
 }

test/tap/install-duplicate-deps-warning.js

@@ -0,0 +1,69 @@
+var fs = require('graceful-fs')
+var path = require('path')
+
+var mkdirp = require('mkdirp')
+var mr = require('npm-registry-mock')
+var osenv = require('osenv')
+var rimraf = require('rimraf')
+var test = require('tap').test
+
+var common = require('../common-tap.js')
+var npm = npm = require('../../')
+
+var pkg = path.resolve(__dirname, path.basename(__filename, '.js'))
+
+var json = {
+  dependencies: {
+    underscore: '1.5.1'
+  },
+  devDependencies: {
+    underscore: '1.3.1'
+  }
+}
+
+test('setup', function (t) {
+  t.comment('test for https://github.com/npm/npm/issues/6725')
+  cleanup()
+  mkdirp.sync(pkg)
+  fs.writeFileSync(
+    path.join(pkg, 'package.json'),
+    JSON.stringify(json, null, 2)
+  )
+  process.chdir(pkg)
+  console.dir(pkg)
+  t.end()
+})
+
+test('npm install with duplicate dependencies, different versions', function (t) {
+  t.plan(1)
+  mr({ port: common.port }, function (er, s) {
+    var opts = {
+      cache: path.resolve(pkg, 'cache'),
+      registry: common.registry
+    }
+
+    npm.load(opts, function (err) {
+      if (err) return t.fail(err)
+
+      npm.install('.', function (err, additions, result) {
+        if (err) return t.fail(err)
+
+        var invalid = result.warnings.filter(function (warning) { return warning.code === 'EDUPLICATEDEP' })
+        t.is(invalid.length, 1, 'got a warning (EDUPLICATEDEP) for duplicate dev/production dependencies')
+
+        s.close()
+        t.end()
+      })
+    })
+  })
+})
+
+test('cleanup', function (t) {
+  cleanup()
+  t.end()
+})
+
+function cleanup () {
+  process.chdir(osenv.tmpdir())
+  rimraf.sync(pkg)
+}