Install transitive dependencies even if listed as devDependencies in the project

__tests__/commands/install/integration.js

@@ -29,7 +29,7 @@ async function mockConstants(base: Config, mocks: Object, cb: (config: Config) =
   // the Yarn environment.
 
   const opts = {};
-  
+
   opts.binLinks = base.binLinks;
   opts.cwd = base.cwd;
   opts.globalFolder = base.globalFolder;
@@ -231,6 +231,17 @@ test.concurrent('--production flag does not link dev dependency bin scripts', ()
   });
 });
 
+test.concurrent('--production flag installs transitive dependencies even if they are top-level devDependencies', () => {
+  // Root package: dependencies: ['a'], devDependencies: ['b']
+  // 'a' package: dependencies: ['b']
+  // 'b' should be installed, even with --production
+  return runInstall({production: true}, 'install-production-transitive-dep', async (config) => {
+    assert.ok(
+      await fs.exists(path.join(config.cwd, 'node_modules', 'dep-b')),
+    );
+  });
+});
+
 test.concurrent("doesn't write new lockfile if existing one satisfied", (): Promise<void> => {
   return runInstall({}, 'install-dont-write-lockfile-if-satisfied', async (config): Promise<void> => {
     const lockfile = await fs.readFile(path.join(config.cwd, 'yarn.lock'));

__tests__/fixtures/install/install-production-transitive-dep/.npmrc

@@ -0,0 +1 @@
+yarn-offline-mirror=./mirror-for-offline

__tests__/fixtures/install/install-production-transitive-dep/package.json

@@ -0,0 +1,9 @@
+{
+  "dependencies": {
+    "dep-a": "1.0.0"
+  },
+  "devDependencies": {
+    "dep-b": "1.0.0"
+  },
+  "license": "MIT"
+}

__tests__/fixtures/install/install-production-transitive-dep/yarn.lock

@@ -0,0 +1,11 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+[email protected]:
+  version "1.0.0"
+  resolved dep-a-1.0.0.tar
+  dependencies:
+    dep-b "1.0.0"
+
+[email protected]:
+  version "1.0.0"
+  resolved dep-b-1.0.0.tar

src/package-resolver.js

@@ -17,9 +17,8 @@ const semver = require('semver');
 export default class PackageResolver {
   constructor(config: Config, lockfile: Lockfile) {
     this.patternsByPackage = map();
-    this.fetchingPatterns = map();
     this.fetchingQueue = new BlockingQueue('resolver fetching');
-    this.newPatterns = [];
+    this.newPatterns = new Set();
     this.patterns = map();
     this.usedRegistries = new Set();
     this.flat = false;
@@ -41,13 +40,8 @@ export default class PackageResolver {
     end: () => void
   };
 
-  // patterns we've already resolved or are in the process of resolving
-  fetchingPatterns: {
-    [key: string]: true
-  };
-
   // new patterns that didn't exist in the lockfile
-  newPatterns: Array<string>;
+  newPatterns: Set<string>;
 
   // TODO
   fetchingQueue: BlockingQueue;
@@ -83,7 +77,7 @@ export default class PackageResolver {
    */
 
   isNewPattern(pattern: string): boolean {
-    return this.newPatterns.indexOf(pattern) >= 0;
+    return this.newPatterns.has(pattern);
   }
 
   /**
@@ -269,7 +263,8 @@ export default class PackageResolver {
     const ref = pkg._reference;
     invariant(ref, 'expected package reference');
     ref.patterns = [newPattern];
-    this.newPatterns.splice(this.newPatterns.indexOf(pattern), 1, newPattern);
+    this.newPatterns.delete(pattern);
+    this.newPatterns.add(newPattern);
     this.addPattern(newPattern, pkg);
     this.removePattern(pattern);
   }
@@ -423,19 +418,12 @@ export default class PackageResolver {
    */
 
   async find(req: DependencyRequestPattern): Promise<void> {
-    const fetchKey = `${req.registry}:${req.pattern}`;
-    if (this.fetchingPatterns[fetchKey]) {
-      return;
-    } else {
-      this.fetchingPatterns[fetchKey] = true;
-    }
-
     if (this.activity) {
       this.activity.tick(req.pattern);
     }
 
     if (!this.lockfile.getLocked(req.pattern, true)) {
-      this.newPatterns.push(req.pattern);
+      this.newPatterns.add(req.pattern);
     }
 
     const request = new PackageRequest(req, this);