Fix XADD maxlen 0 (#192)

* XADD maxlen 0 creates empty stream

* Rubocop

* Ignore emptry streams on cleanup

lib/mock_redis/stream.rb

@@ -37,7 +37,11 @@ def add(id, values)
     def trim(count)
       deleted = @members.size - count
       if deleted > 0
-        @members = @members.to_a[-count..-1].to_set
+        @members = if count == 0
+                     Set.new
+                   else
+                     @members.to_a[-count..-1].to_set
+                   end
         deleted
       else
         0

lib/mock_redis/utility_methods.rb

@@ -18,7 +18,7 @@ def primitive?(value)
     end
 
     def clean_up_empties_at(key)
-      if data[key]&.empty? && data[key] != ''
+      if data[key]&.empty? && data[key] != '' && !data[key].is_a?(Stream)
         del(key)
       end
     end

spec/commands/del_spec.rb

@@ -1,6 +1,14 @@
 require 'spec_helper'
 
 describe '#del(key [, key, ...])' do
+  before :all do
+    sleep 1 - (Time.now.to_f % 1)
+  end
+
+  before :each do
+    @redises._gsub(/\d{3}-\d/, '...-.')
+  end
+
   it 'returns the number of keys deleted' do
     @redises.set('mock-redis-test:1', 1)
     @redises.set('mock-redis-test:2', 1)
@@ -32,4 +40,11 @@
   it 'raises an error if an empty array is given' do
     expect { @redises.del [] }.to raise_error Redis::CommandError
   end
+
+  it 'removes a stream key' do
+    @redises.xadd('mock-redis-stream', { key: 'value' }, maxlen: 0)
+    expect(@redises.exists?('mock-redis-stream')).to eq true
+    @redises.del('mock-redis-stream')
+    expect(@redises.exists?('mock-redis-stream')).to eq false
+  end
 end

spec/commands/xadd_spec.rb

@@ -112,4 +112,11 @@
       ]
     )
   end
+
+  it 'creates an empty stream with maxlen of 0' do
+    @redises.xadd(@key, { key: 'value' }, maxlen: 0)
+    expect(@redises.xlen(@key)).to eq 0
+    expect(@redises.xrange(@key, '-', '+')).to eq([])
+    expect(@redises.exists?(@key)).to eq true
+  end
 end