Add while enumerator

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 - [437](https://github.com/Shopify/job-iteration/pull/437) - Use minimum between per-class `job_iteration_max_job_runtime` and `JobIteration.max_job_runtime`, instead of enforcing only setting decreasing values.
   Because it is possible to change the global or parent values after setting the value on a class, it is not possible to truly enforce the decreasing value constraint. Instead, we now use the minimum between the global value and per-class value. This is considered a non-breaking change, as it should not break any **existing** code, it only removes the constraint on new classes.
+- [446](https://github.com/Shopify/job-iteration/pull/446) - Support while loop enumerator
 
 ### Bug fixes
 

README.md

@@ -151,6 +151,25 @@ class NestedIterationJob < ApplicationJob
 end
 ```
 
+
+```ruby
+class DeleteXyzJob < ApplicationJob
+  include JobIteration::Iteration
+
+  def build_enumerator(params)
+    enumerator_builder.while query_model_xyz(params).exists?
+  end
+
+  def each_iteration(count, params)
+    query_model_xyz(params).limit(1000).delete_all
+  end
+
+  def query_model_xyz(params)
+    Xyz.where(owner_id: params[:owner_id])
+  end
+end
+```
+
 Iteration hooks into Sidekiq and Resque out of the box to support graceful interruption. No extra configuration is required.
 
 ## Guides

lib/job-iteration/enumerator_builder.rb

@@ -181,6 +181,30 @@ def build_nested_enumerator(enums, cursor:)
       NestedEnumerator.new(enums, cursor: cursor).each
     end
 
+    # Builds Enumerator for while loop iteration.
+    #
+    # @yield Condition to be evaluated before each iteration, the iteration is allowed if a true value is returned.
+    #
+    # @example
+    #   def build_enumerator(params)
+    #     enumerator_builder.while query_model_xyz(params).exists?
+    #   end
+    #
+    #   def each_iteration(count, params)
+    #     query_model_xyz(params).limit(1000).delete_all
+    #   end
+    #
+    #   def query_model_xyz(params)
+    #     Xyz.where(owner_id: params[:owner_id])
+    #   end
+    #
+    def build_while_enumerator(&condition)
+      count = 0
+      Enumerator.new do |yielder|
+        yielder << count += 1 while condition.call
+      end
+    end
+
     alias_method :once, :build_once_enumerator
     alias_method :times, :build_times_enumerator
     alias_method :array, :build_array_enumerator
@@ -190,6 +214,7 @@ def build_nested_enumerator(enums, cursor:)
     alias_method :throttle, :build_throttle_enumerator
     alias_method :csv, :build_csv_enumerator
     alias_method :nested, :build_nested_enumerator
+    alias_method :while, :build_while_enumerator
 
     private
 

test/unit/enumerator_builder_test.rb

@@ -74,6 +74,15 @@ class EnumeratorBuilderTest < ActiveSupport::TestCase
       )
     end
 
+    test_builder_method(:build_while_enumerator) do
+      count = 0
+      enum = enumerator_builder(wraps: 0).build_while_enumerator do
+        count < 3 ? (count += 1) : false
+      end
+
+      assert_equal [1, 2, 3], enum.to_a
+    end
+
     # checks that all the non-alias methods were tested
     raise "methods not tested: #{methods.inspect}" unless methods.empty?