fix slug generation exception

refs VICE-739
flag=none

test plan:
  - tests pass

qa risk: low

Change-Id: I05265f2b28e4c635b96783f27c1ff588c5831162
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/246070
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Caleb Guanzon <cguanzon@instructure.com>
Reviewed-by: Rob Orton <rob@instructure.com>

gems/canvas_slug/canvas_slug.gemspec

@@ -17,5 +17,6 @@ Gem::Specification.new do |spec|
 
   spec.add_development_dependency "bundler", "~> 1.5"
   spec.add_development_dependency "rake"
+  spec.add_development_dependency "rspec", "~> 3.5.0"
   spec.add_dependency "swearjar", "~> 1.4"
 end

gems/canvas_slug/lib/canvas_slug.rb

@@ -28,6 +28,7 @@ class CanvasSlug
       # Ensure we don't get naughties by looping until we get something
       # "clean". Loop count is arbitrary, we use length as shorter strings
       # are less likely to result in problematic strings.
+      uuid = ""
       length.times do
         uuid = Array.new(length) { CHARS[SecureRandom.random_number(CHARS.length)] }.join
         return uuid unless SJ.profane?(uuid)
@@ -35,7 +36,7 @@ class CanvasSlug
 
       # TODO: raise exception to allow consumer to handle
       # raise "CanvasSlug couldn't find valid uuid after #{length} attempts"
-      return uuid
+      uuid
     end
 
     def generate(purpose = nil, length = 4)

gems/canvas_slug/spec/canvas_slug/canvas_slug_spec.rb

@@ -0,0 +1,43 @@
+#
+# Copyright (C) 2020 - present Instructure, Inc.
+#
+# This file is part of Canvas.
+#
+# Canvas is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, version 3 of the License.
+#
+# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
+require 'spec_helper'
+
+describe CanvasSlug do
+  let(:subject) {CanvasSlug}
+
+  describe ".generate_securish_uuid" do
+    it "returns a securish uuid" do
+      expect(subject.generate_securish_uuid).to be_a(String)
+    end
+
+    it "works with length 0" do
+      expect(subject.generate_securish_uuid(0)).to eq ""
+    end
+  end
+
+  describe ".generate" do
+    it "returns a string" do
+      expect(subject.generate).to be_a(String)
+    end
+
+    it "prepends a provided purpose" do
+      expect(subject.generate("foobar")).to match /\Afoobar-\w{4}\z/
+    end
+  end
+end

gems/canvas_slug/spec/spec_helper.rb

@@ -0,0 +1,25 @@
+#
+# Copyright (C) 2020 - present Instructure, Inc.
+#
+# This file is part of Canvas.
+#
+# Canvas is free software: you can redistribute it and/or modify it under
+# the terms of the GNU Affero General Public License as published by the Free
+# Software Foundation, version 3 of the License.
+#
+# Canvas is distributed in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Affero General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Affero General Public License along
+# with this program. If not, see <http://www.gnu.org/licenses/>.
+
+require 'canvas_slug'
+
+RSpec.configure do |config|
+  config.run_all_when_everything_filtered = true
+  config.filter_run :focus
+  config.color = true
+  config.order = 'random'
+end

gems/canvas_slug/test.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+set -e
+
+bundle check || bundle install
+bundle exec rspec spec