Support UNLICENSE file (#1553)

Author: UnikZ

lib/src/validator/license.dart

@@ -16,7 +16,7 @@ class LicenseValidator extends Validator {
   Future validate() {
     return new Future.sync(() {
       var licenseLike =
-          new RegExp(r"^([a-zA-Z0-9]+[-_])?(LICENSE|COPYING)(\..*)?$");
+          new RegExp(r"^(([a-zA-Z0-9]+[-_])?(LICENSE|COPYING)|UNLICENSE)(\..*)?$");
       if (entrypoint.root
           .listFiles(recursive: false, useGitIgnore: true)
           .map(path.basename)
@@ -25,7 +25,7 @@ class LicenseValidator extends Validator {
       }
 
       errors.add(
-          "You must have a COPYING or LICENSE file in the root directory.\n"
+          "You must have a COPYING, LICENSE or UNLICENSE file in the root directory.\n"
           "An open-source license helps ensure people can legally use your "
           "code.");
     });

test/validator/license_test.dart

@@ -27,6 +27,12 @@ main() {
       expectNoValidationError(license);
     });
 
+    integration('has an UNLICENSE file', () {
+      schedule(() => deleteEntry(path.join(sandboxDir, appPath, 'LICENSE')));
+      d.file(path.join(appPath, 'UNLICENSE'), '').create();
+      expectNoValidationError(license);
+    });
+
     integration('has a prefixed LICENSE file', () {
       schedule(() => deleteEntry(path.join(sandboxDir, appPath, 'LICENSE')));
       d.file(path.join(appPath, 'MIT_LICENSE'), '').create();
@@ -47,6 +53,13 @@ main() {
       expectValidationError(license);
     });
 
+    integration('has a prefixed UNLICENSE file', () {
+      d.validPackage.create();
+      schedule(() => deleteEntry(path.join(sandboxDir, appPath, 'LICENSE')));
+      d.file(path.join(appPath, 'MIT_UNLICENSE'), '').create();
+      expectValidationError(license);
+    });
+
     integration('has a .gitignored LICENSE file', () {
       var repo = d.git(appPath, [d.file(".gitignore", "LICENSE")]);
       d.validPackage.create();