Fix: Fix numeric versions resolving to local files (#4088)

**Summary**

Fixes #4013. We were blindly priotizing local files (even if they
are not directories) if there's anything on the file system matching
a pattern for a package. This patch ensures that we only do this if
the pattern is not a valid semver range and the matched local entity is a directory.
**Test plan**

Added a new unit test and modified an incorrect old one. Also manually
verified that the issue described in #4013 does not happen anymore.

__tests__/commands/install/__snapshots__/integration.js.snap

@@ -0,0 +1,18 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`install-file-as-default-no-semver 1`] = `
+"{
+  \\"author\\": \\"AJ ONeal <coolaj86@gmail.com> (http://coolaj86.info)\\",
+  \\"name\\": \\"foo\\",
+  \\"description\\": \\"A test module with no \`main\`, \`lib\`, or \`dependencies\` specified\\",
+  \\"version\\": \\"1.0.0\\",
+  \\"repository\\": {
+    \\"type\\": \\"git\\",
+    \\"url\\": \\"git://github.com/coolaj86/node-pakman.git\\"
+  },
+  \\"engines\\": {
+    \\"node\\": \\">= v0.2\\"
+  }
+}
+"
+`;

__tests__/commands/install/integration.js

@@ -385,7 +385,7 @@ test.concurrent('root install with optional deps', (): Promise<void> => {
 });
 
 test.concurrent('install file: protocol with relative paths', (): Promise<void> => {
-  return runInstall({noLockfile: true}, 'install-file-relative', async config => {
+  return runInstall({}, 'install-file-relative', async config => {
     expect(await fs.readFile(path.join(config.cwd, 'node_modules', 'root-a', 'index.js'))).toEqual('foobar;\n');
   });
 });
@@ -459,17 +459,30 @@ test.concurrent('install file: link file dependencies', async (): Promise<void>
 });
 
 test.concurrent('install file: protocol', (): Promise<void> => {
-  return runInstall({noLockfile: true}, 'install-file', async config => {
+  return runInstall({lockfile: false}, 'install-file', async config => {
     expect(await fs.readFile(path.join(config.cwd, 'node_modules', 'foo', 'index.js'))).toEqual('foobar;\n');
   });
 });
 
 test.concurrent('install with file: protocol as default', (): Promise<void> => {
-  return runInstall({noLockfile: true}, 'install-file-as-default', async config => {
+  return runInstall({}, 'install-file-as-default', async config => {
     expect(await fs.readFile(path.join(config.cwd, 'node_modules', 'foo', 'index.js'))).toEqual('foobar;\n');
   });
 });
 
+test.concurrent("don't install with file: protocol as default if target is a file", (): Promise<void> => {
+  // $FlowFixMe
+  return expect(runInstall({lockfile: false}, 'install-file-as-default-no-file')).rejects.toBeDefined();
+});
+
+test.concurrent("don't install with file: protocol as default if target is valid semver", (): Promise<void> => {
+  return runInstall({}, 'install-file-as-default-no-semver', async config => {
+    expect(await fs.readFile(path.join(config.cwd, 'node_modules', 'foo', 'package.json'))).toMatchSnapshot(
+      'install-file-as-default-no-semver',
+    );
+  });
+});
+
 // When local packages are installed, dependencies with different forms of the same relative path
 // should be deduped e.g. 'file:b' and 'file:./b'
 test.concurrent('install file: dedupe dependencies 1', (): Promise<void> => {
@@ -505,7 +518,7 @@ test.concurrent('install file: dedupe dependencies 3', (): Promise<void> => {
 });
 
 test.concurrent('install everything when flat is enabled', (): Promise<void> => {
-  return runInstall({noLockfile: true, flat: true}, 'install-file', async config => {
+  return runInstall({lockfile: false, flat: true}, 'install-file', async config => {
     expect(await fs.readFile(path.join(config.cwd, 'node_modules', 'foo', 'index.js'))).toEqual('foobar;\n');
   });
 });
@@ -587,7 +600,7 @@ test.concurrent('install should run install scripts in the order of dependencies
 });
 
 test.concurrent('install with comments in manifest', (): Promise<void> => {
-  return runInstall({noLockfile: true}, 'install-with-comments', async config => {
+  return runInstall({lockfile: false}, 'install-with-comments', async config => {
     expect(await fs.readFile(path.join(config.cwd, 'node_modules', 'foo', 'index.js'))).toEqual('foobar;\n');
   });
 });
@@ -759,7 +772,7 @@ test.concurrent('offline mirror can be disabled locally', (): Promise<void> => {
 
 // sync test because we need to get all the requests to confirm their validity
 test('install a scoped module from authed private registry', (): Promise<void> => {
-  return runInstall({noLockfile: true}, 'install-from-authed-private-registry', async config => {
+  return runInstall({}, 'install-from-authed-private-registry', async config => {
     const authedRequests = request.__getAuthedRequests();
 
     expect(authedRequests[0].url).toEqual('https://registry.yarnpkg.com/@types%2flodash');
@@ -774,7 +787,7 @@ test('install a scoped module from authed private registry', (): Promise<void> =
 });
 
 test('install a scoped module from authed private registry with a missing trailing slash', (): Promise<void> => {
-  return runInstall({noLockfile: true}, 'install-from-authed-private-registry-no-slash', async config => {
+  return runInstall({}, 'install-from-authed-private-registry-no-slash', async config => {
     const authedRequests = request.__getAuthedRequests();
 
     expect(authedRequests[0].url).toEqual('https://registry.yarnpkg.com/@types%2flodash');

__tests__/fixtures/install/install-file-as-default-no-file/package.json

@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "foo": "bar"
+  }
+}

__tests__/fixtures/install/install-file-as-default-no-semver/1/index.js

@@ -0,0 +1 @@
+foobar;

__tests__/fixtures/install/install-file-as-default-no-semver/1/package.json

@@ -0,0 +1,5 @@
+{
+  "name": "1",
+  "version": "0.0.0",
+  "main": "index.js"
+}

__tests__/fixtures/install/install-file-as-default-no-semver/package.json

@@ -0,0 +1,5 @@
+{
+  "dependencies": {
+    "foo": "1"
+  }
+}

__tests__/fixtures/install/install-file-as-default-no-semver/yarn.lock

@@ -0,0 +1,4 @@
+# THIS IS AN AUTOGENERATED FILE. DO NOT EDIT THIS FILE DIRECTLY.
+# yarn lockfile v1
+"foo@file:bar":
+  version "0.0.0"

src/package-request.js

@@ -134,14 +134,20 @@ export default class PackageRequest {
 
   async normalizeRange(pattern: string): Promise<string> {
     if (pattern.indexOf(':') > -1 || pattern.indexOf('@') > -1 || getExoticResolver(pattern)) {
-      return Promise.resolve(pattern);
+      return pattern;
     }
 
-    if (await fs.exists(path.join(this.config.cwd, pattern))) {
-      return Promise.resolve(`file:${pattern}`);
+    if (!semver.validRange(pattern)) {
+      try {
+        if ((await fs.stat(path.join(this.config.cwd, pattern))).isDirectory()) {
+          return `file:${pattern}`;
+        }
+      } catch (err) {
+        // pass
+      }
     }
 
-    return Promise.resolve(pattern);
+    return pattern;
   }
 
   async normalize(pattern: string): any {