Add LMPOP (#311)

Currently failing due to needing redis-rb v5 (see also #281 and #293)

Gemfile

@@ -9,5 +9,6 @@ gem 'overcommit', '0.62.0'
 # Pin tool versions (which are executed by Overcommit) for CI builds
 gem 'rubocop', '1.44.1'
 
+gem 'base64', '~> 0.2.0'
 gem 'simplecov', '~> 0.22.0'
 gem 'simplecov-lcov', '~> 0.8.0'

lib/mock_redis/list_methods.rb

@@ -90,6 +90,32 @@ def llen(key)
       with_list_at(key, &:length)
     end
 
+    def lmpop(*keys, **options)
+      keys.each do |key|
+        assert_listy(key)
+      end
+
+      modifier = options.is_a?(Hash) && options[:modifier]&.to_s&.downcase || 'left'
+      count = (options.is_a?(Hash) && options[:count]) || 1
+
+      unless %w[left right].include?(modifier)
+        raise Redis::CommandError, 'ERR syntax error'
+      end
+
+      keys.each do |key|
+        record_count = llen(key)
+        next if record_count.zero?
+
+        values = [count, record_count].min.times.map do
+          modifier == 'left' ? with_list_at(key, &:shift) : with_list_at(key, &:pop)
+        end
+
+        return [key, values]
+      end
+
+      nil
+    end
+
     def lmove(source, destination, wherefrom, whereto)
       assert_listy(source)
       assert_listy(destination)

spec/commands/lmpop_spec.rb

@@ -0,0 +1,75 @@
+require 'spec_helper'
+
+RSpec.describe '#lmpop(*keys)', redis: 7.0 do
+  before do
+    @list1 = 'mock-redis-test:lmpop-list'
+    @list2 = 'mock-redis-test:lmpop-list2'
+
+    @redises.lpush(@list1, 'c')
+    @redises.lpush(@list1, 'b')
+    @redises.lpush(@list1, 'a')
+
+    @redises.lpush(@list2, 'z')
+    @redises.lpush(@list2, 'y')
+    @redises.lpush(@list2, 'x')
+  end
+
+  it 'returns and removes the first element of the first non-empty list' do
+    expect(@redises.lmpop('empty', @list1, @list2)).to eq([@list1, ['a']])
+
+    expect(@redises.lrange(@list1, 0, -1)).to eq(%w[b c])
+    expect(@redises.lrange(@list2, 0, -1)).to eq(%w[x y z])
+  end
+
+  it 'returns and removes the first element of the first non-empty list when modifier is LEFT' do
+    expect(@redises.lmpop('empty', @list1, @list2, modifier: 'LEFT')).to eq([@list1, ['a']])
+
+    expect(@redises.lrange(@list1, 0, -1)).to eq(%w[b c])
+    expect(@redises.lrange(@list2, 0, -1)).to eq(%w[x y z])
+  end
+
+  it 'returns and removes the last element of the first non-empty list when modifier is RIGHT' do
+    expect(@redises.lmpop('empty', @list1, @list2, modifier: 'RIGHT')).to eq([@list1, ['c']])
+
+    expect(@redises.lrange(@list1, 0, -1)).to eq(%w[a b])
+    expect(@redises.lrange(@list2, 0, -1)).to eq(%w[x y z])
+  end
+
+  it 'returns and removes multiple elements from the front when count is given' do
+    expect(@redises.lmpop('empty', @list1, @list2, count: 2)).to eq([@list1, %w[a b]])
+
+    expect(@redises.lrange(@list1, 0, -1)).to eq(%w[c])
+    expect(@redises.lrange(@list2, 0, -1)).to eq(%w[x y z])
+  end
+
+  it 'returns and removes multiple elements from the back when count given and modifier is RIGHT' do
+    expect(@redises.lmpop('empty', @list1, @list2, count: 2, modifier: 'RIGHT')).to(
+      eq([@list1, %w[c b]])
+    )
+
+    expect(@redises.lrange(@list1, 0, -1)).to eq(%w[a])
+    expect(@redises.lrange(@list2, 0, -1)).to eq(%w[x y z])
+  end
+
+  it 'returns falsed if all lists are empty' do
+    expect(@redises.lmpop('empty')).to be_nil
+
+    expect(@redises.lrange(@list1, 0, -1)).to eq(%w[a b c])
+    expect(@redises.lrange(@list2, 0, -1)).to eq(%w[x y z])
+  end
+
+  it 'removes empty lists' do
+    (@redises.llen(@list1) + @redises.llen(@list2)).times { @redises.lmpop(@list1, @list2) }
+    expect(@redises.get(@list1)).to be_nil
+  end
+
+  it 'raises an error for non-list source value' do
+    @redises.set(@list1, 'string value')
+
+    expect do
+      @redises.lmpop(@list1, @list2)
+    end.to raise_error(Redis::CommandError)
+  end
+
+  it_should_behave_like 'a list-only command'
+end