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require "spec_helper"
RSpec.describe BatchLoader do
after do
User.destroy_all
Post.destroy_all
end
context 'lazily' do
it "syncs all BatchLoaders by returning the loaded value" do
user1 = User.save(id: 1)
post1 = Post.new(user_id: user1.id)
user2 = User.save(id: 2)
post2 = Post.new(user_id: user2.id)
result = {user1: post1.user_lazy, user2: post2.user_lazy}
expect(User).to receive(:where).with(id: [1, 2]).once.and_call_original
expect(result).to eq(user1: user1, user2: user2)
end
it 'raises an error if batch was not provided' do
expect {
BatchLoader.for(1).id
}.to raise_error(BatchLoader::NoBatchError, "Please provide a batch block first")
end
it 'caches the result even between different BatchLoader instances' do
user = User.save(id: 1)
post = Post.new(user_id: user.id)
expect(User).to receive(:where).with(id: [1]).once.and_call_original
expect(post.user_lazy.id).to eq(user.id)
expect(post.user_lazy.id).to eq(user.id)
end
it 'caches the result for the same BatchLoader instance' do
user = User.save(id: 1)
post = Post.new(user_id: user.id)
expect(User).to receive(:where).with(id: [1]).once.and_call_original
expect(post.user_lazy).to eq(user)
expect(post.user_lazy).to eq(user)
end
it 'works even if the loaded values is nil' do
post = Post.new(user_id: 1)
expect(User).to receive(:where).with(id: [1]).once.and_call_original
expect(post.user_lazy).to eq(nil)
expect(post.user_lazy).to eq(nil)
end
it 'raises and error if loaded value do not have a method' do
user = User.save(id: 1)
post = Post.new(user_id: user.id)
expect(User).to receive(:where).with(id: [1]).once.and_call_original
expect { post.user_lazy.foo }.to raise_error(NoMethodError, /undefined method `foo' for (#<|an instance of )User/)
end
it 'works with nested BatchLoaders' do
user1 = User.save(id: 1)
Post.new(user_id: user1.id)
user2 = User.save(id: 2)
Post.new(user_id: user2.id)
nested_batch_loader = ->(id) do
BatchLoader.for(id).batch do |user_ids, loader|
User.where(id: user_ids).each { |u| loader.call(u.id, u.id) }
end
end
batch_loader = ->(id) do
BatchLoader.for(id).batch do |user_ids, loader|
user_ids.each { |user_id| loader.call(user_id, nested_batch_loader.call(user_id)) }
end
end
expect(User).to receive(:where).with(id: [1, 2]).once.and_call_original
result = [batch_loader.call(1), batch_loader.call(2)]
expect(result).to eq([1, 2])
end
end
context 'with custom key' do
it 'batches multiple items by key' do
author = Author.save(id: 1)
reader = Reader.save(id: 2)
batch_loader = ->(type, id) do
BatchLoader.for(id).batch(key: type) do |ids, loader, args|
args[:key].where(id: ids).each { |user| loader.call(user.id, user) }
end
end
loader_author = batch_loader.call(Author, 1)
loader_reader = batch_loader.call(Reader, 2)
expect(Author).to receive(:where).with(id: [1]).once.and_call_original
expect(loader_author).to eq(author)
expect(Reader).to receive(:where).with(id: [2]).once.and_call_original
expect(loader_reader).to eq(reader)
end
it 'batches multiple items with hash-identical keys' do
user = Author.new(id: 1)
same_user = Reader.new(id: 1)
other_user = Reader.new(id: 2)
post_1 = Post.save(user_id: 1, title: "First post")
post_2 = Post.save(user_id: 1, title: "Second post")
post_3 = Post.save(user_id: 2, title: "First post")
batch_loader = ->(user, title) do
BatchLoader.for(title).batch(key: user) do |titles, loader, args|
args[:key].posts.select { |p| titles.include?(p.title) }.each { |post| loader.call(post.title, post) }
end
end
loader_1 = batch_loader.call(user, "First post")
loader_2 = batch_loader.call(same_user, "Second post")
loader_3 = batch_loader.call(other_user, "First post")
expect(user).to receive(:posts).once.and_call_original
expect(same_user).not_to receive(:posts)
expect(other_user).to receive(:posts).once.and_call_original
expect(loader_1).to eq(post_1)
expect(loader_2).to eq(post_2)
expect(loader_3).to eq(post_3)
end
end
context 'loader' do
it 'loads the data even in a separate thread' do
lazy = BatchLoader.for(1).batch do |nums, loader|
threads = nums.map do |num|
Thread.new { loader.call(num, num + 1) }
end
threads.each(&:join)
end
expect(lazy).to eq(2)
end
it 'is thread-safe' do
batch_block = Proc.new do |ids, loader|
ids.each do |id|
thread = Thread.new { loader.call(id) { |value| value << id } }
loader.call(id) { |value| value << id + 1 }
thread.join
end
end
slow_executor_proxy = SlowExecutorProxy.new([], nil, &batch_block)
lazy = BatchLoader.new(item: 1, executor_proxy: slow_executor_proxy).batch(default_value: [], &batch_block)
expect(lazy).to match_array([1, 2])
end
it 'supports alternative default values' do
lazy = BatchLoader.for(1).batch(default_value: 123) do |nums, loader|
# No-op, so default is returned
end
expect(lazy).to eq(123)
end
it 'supports memoizing repeated calls to the same item, via a block' do
lazy = BatchLoader.for(1).batch(default_value: []) do |nums, loader|
nums.each do |num|
loader.call(num) { |memo| memo.push(num) }
loader.call(num) { |memo| memo.push(num + 1) }
loader.call(num) { |memo| memo.push(num + 2) }
end
end
expect(lazy).to eq([1,2,3])
end
it 'raises ArgumentError if called with block and value' do
lazy = BatchLoader.for(1).batch do |nums, loader|
nums.each do |num|
loader.call(num, "one value") { "too many values" }
end
end
expect { lazy.sync }.to raise_error(ArgumentError)
end
it 'raises ArgumentError if called without block and value' do
lazy = BatchLoader.for(1).batch do |nums, loader|
nums.each { |num| loader.call(num) }
end
expect { lazy.sync }.to raise_error(ArgumentError)
end
end
context 'instance' do
it 'works for methods with kwargs in Ruby 3' do
user = User.save(id: 1)
post = Post.new(user_id: user.id)
batch_loader = post.user_lazy
expect(batch_loader.method_with_arg_kwarg_and_block(1, b: 2) { |a, b| a + b }).to eq(3)
end
end
describe '#inspect' do
it 'returns BatchLoader without syncing and delegates #inspect after' do
user = User.save(id: 1)
post = Post.new(user_id: user.id)
batch_loader = post.user_lazy
expect(batch_loader.inspect).to match(/#<BatchLoader:0x\w+>/)
expect(batch_loader.to_s).to match(/#<User:0x\w+>/)
expect(batch_loader.inspect).to match(/#<User:0x\w+ @id=1>/)
end
end
describe '#respond_to?' do
let(:user) { User.save(id: 1) }
let(:post) { Post.new(user_id: user.id) }
subject { post.user_lazy }
it 'syncs the object just once' do
loaded_user = post.user_lazy
expect(loaded_user.respond_to?(:id)).to eq(true)
end
it 'returns false for private methods by default' do
expect(subject.respond_to?(:some_private_method)).to eq(false)
end
it 'returns true for private methods if include_private flag is true' do
expect(subject.respond_to?(:some_private_method, true)).to eq(true)
end
it 'does not depend on the loaded value #method_missing' do
expect(user).not_to receive(:method_missing)
expect(subject).to respond_to(:id)
end
context 'when the cache and method replacement is disabled' do
it 'syncs the object on every call' do
loaded_user = post.user_lazy(cache: false, replace_methods: false)
expect(User).to receive(:where).with(id: [1]).twice.and_call_original
loaded_user.respond_to?(:id)
loaded_user.respond_to?(:id)
end
end
end
describe '#batch' do
it 'delegates the second batch call to the loaded value' do
user = User.save(id: 1)
post = Post.new(user_id: user.id)
expect(post.user_lazy.batch).to eq("Batch from User")
end
it 'works without cache between different BatchLoader instances for the same item' do
user1 = User.save(id: 1)
user2 = User.save(id: 2)
post = Post.new(user_id: user1.id)
expect(User).to receive(:where).with(id: [1]).once.and_call_original
expect(post.user_lazy).to eq(user1)
post.user_id = user2.id
expect(User).to receive(:where).with(id: [2]).once.and_call_original
expect(post.user_lazy(cache: false)).to eq(user2)
end
it 'works without cache and method replacement for the same BatchLoader instance' do
user = User.save(id: 1)
post = Post.new(user_id: user.id)
user_lazy = post.user_lazy(cache: false, replace_methods: false)
expect(User).to receive(:where).with(id: [1]).twice.and_call_original
expect(user_lazy).to eq(user)
expect(user_lazy).to eq(user)
end
it 'does not replace methods when replace_methods is false' do
user = User.save(id: 1)
post = Post.new(user_id: user.id)
user_lazy = post.user_lazy(cache: true, replace_methods: false)
expect(user_lazy).to receive(:method_missing).and_call_original
user_lazy.id
end
it 'does not allow mutating a list of items' do
batch_loader = BatchLoader.for(1).batch do |items, loader|
items.map! { |i| i - 1 }
end
expect { batch_loader.to_s }.to raise_error(RuntimeError, /\Acan't modify frozen Array/)
end
it 'raises the error if something went wrong in the batch' do
result = BatchLoader.for(1).batch { |ids, loader| raise "Oops" }
# should work event with Pry which currently shallows errors on #inspect call https://github.com/pry/pry/issues/1642
# require 'pry'; binding.pry
expect { result.to_s }.to raise_error("Oops")
expect { result.to_s }.to raise_error("Oops")
end
end
end
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