Create lockfile when missing even when integrity hash matches (#1888)

__tests__/commands/install.js

@@ -682,3 +682,9 @@ test.concurrent('install should not rewrite lockfile with no substantial changes
     expect(newLockContent).not.toEqual(lockContent);
   });
 });
+
+test.concurrent('lockfile should be created when missing even if integrity matches', (): Promise<void> => {
+  return runInstall({}, 'lockfile-missing', async (config, reporter) => {
+    expect(await fs.exists(path.join(config.cwd, 'yarn.lock')));
+  });
+});

__tests__/fixtures/install/lockfile-missing/package.json

@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "left-pad": "^1.1.3"
+  }
+}

__tests__/fixtures/request-cache/GET/localhost/.bin

@@ -1,5 +1,5 @@
 HTTP/1.1 200 OK
-Date: Mon, 14 Nov 2016 16:46:07 GMT
+Date: Wed, 16 Nov 2016 15:06:25 GMT
 Connection: close
 Content-Length: 2
 

src/cli/commands/install.js

@@ -290,7 +290,9 @@ export class Install {
     patterns: Array<string>,
   ): Promise<boolean> {
     const match = await this.matchesIntegrityHash(patterns);
-    if (!this.flags.skipIntegrity && !this.flags.force && match.matches) {
+    const haveLockfile = await fs.exists(path.join(this.config.cwd, constants.LOCKFILE_FILENAME));
+
+    if (!this.flags.skipIntegrity && !this.flags.force && match.matches && haveLockfile) {
       this.reporter.success(this.reporter.lang('upToDate'));
       return true;
     }