Allow batch_slice_columns to work when batching

Currently the `use_indexes` are set correctly only for the first batch.

Author: doredesign

lib/active_admin_import/importer.rb

@@ -70,7 +70,7 @@ def batch_replace(header_key, options)
       end
     end
 
-    # Use it when CSV file contain redundant columns
+    # Use this method when CSV file contains unnecessary columns
     #
     # Example:
     #
@@ -81,16 +81,22 @@ def batch_replace(header_key, options)
     # end
     #
     def batch_slice_columns(slice_columns)
-      use_indexes = []
-      headers.values.each_with_index do |val, index|
-        use_indexes << index if val.in?(slice_columns)
+      # Only set @use_indexes for the first batch so that @use_indexes are in correct
+      # position for subsequent batches
+      unless defined?(@use_indexes)
+        @use_indexes = []
+        headers.values.each_with_index do |val, index|
+          @use_indexes << index if val.in?(slice_columns)
+        end
+        return csv_lines if @use_indexes.empty?
+
+        # slice CSV headers
+        @headers = headers.to_a.values_at(*@use_indexes).to_h
       end
-      return csv_lines if use_indexes.empty?
-      # slice CSV headers
-      @headers = headers.to_a.values_at(*use_indexes).to_h
+
       # slice CSV values
       csv_lines.map! do |line|
-        line.values_at(*use_indexes)
+        line.values_at(*@use_indexes)
       end
     end
 

spec/fixtures/files/authors.csv

@@ -1,3 +1,3 @@
-Name,Last name,Birthday
-John,Doe,1986-05-01
-Jane,Roe,1988-11-16
+Birthday,Name,Last name
+1986-05-01,John,Doe
+1988-11-16,Jane,Roe

spec/import_spec.rb

@@ -434,25 +434,38 @@ def upload_file!(name, ext = 'csv')
   end
 
   context "with slice_columns option" do
+    let(:batch_size) { 2 }
+
     before do
       add_author_resource template_object: ActiveAdminImport::Model.new,
                           before_batch_import: lambda { |importer|
                             importer.batch_slice_columns(slice_columns)
-                          }
+                          },
+                          batch_size: batch_size
       visit "/admin/authors/import"
       upload_file!(:authors)
     end
 
     context "slice last column and superfluous column" do
       let(:slice_columns) { %w(name last_name not_existing_column) }
 
-      it "should not fill `birthday` column" do
-        expect(Author.pluck(:name, :last_name, :birthday)).to match_array(
-          [
-            ["Jane", "Roe", nil],
-            ["John", "Doe", nil]
-          ]
-        )
+      shared_examples_for "birthday column removed" do
+        it "should not fill `birthday` column" do
+          expect(Author.pluck(:name, :last_name, :birthday)).to match_array(
+            [
+              ["Jane", "Roe", nil],
+              ["John", "Doe", nil]
+            ]
+          )
+        end
+      end
+
+      it_behaves_like "birthday column removed"
+
+      context "when doing more than one batch" do
+        let(:batch_size) { 1 }
+
+        it_behaves_like "birthday column removed"
       end
     end