1 files changed, 34 insertions, 6 deletions
diff --git a/app/services/import_csv/base_service.rb b/app/services/import_csv/base_service.rb
index feb76425fb4..70834b8a85a 100644
--- a/app/services/import_csv/base_service.rb
+++ b/app/services/import_csv/base_service.rb
@@ -2,6 +2,8 @@
 
 module ImportCsv
   class BaseService
+    include Gitlab::Utils::StrongMemoize
+
     def initialize(user, project, csv_io)
       @user = user
       @project = project
@@ -9,6 +11,8 @@ module ImportCsv
       @results = { success: 0, error_lines: [], parse_error: false }
     end
 
+    PreprocessError = Class.new(StandardError)
+
     def execute
       process_csv
       email_results_to_user
@@ -36,7 +40,23 @@ module ImportCsv
       raise NotImplementedError
     end
 
+    def validate_structure!
+      header_line = csv_data.lines.first
+      raise CSV::MalformedCSVError.new('File is empty, no headers found', 1) if header_line.blank?
+
+      validate_headers_presence!(header_line)
+      detect_col_sep
+    end
+
+    def preprocess!
+      # any logic can be added in subclasses if needed
+      # hence just a no-op rather than NotImplementedError
+    end
+
     def process_csv
+      validate_structure!
+      preprocess!
+
       with_csv_lines.each do |row, line_no|
         attributes = attributes_for(row)
 
@@ -46,23 +66,30 @@ module ImportCsv
           results[:error_lines].push(line_no)
         end
       end
-    rescue ArgumentError, CSV::MalformedCSVError
+    rescue ArgumentError, CSV::MalformedCSVError => e
       results[:parse_error] = true
+      results[:error_lines].push(e.line_number) if e.respond_to?(:line_number)
+    rescue PreprocessError
+      results[:parse_error] = false
     end
 
     def with_csv_lines
-      csv_data = @csv_io.open(&:read).force_encoding(Encoding::UTF_8)
-      validate_headers_presence!(csv_data.lines.first)
-
       CSV.new(
         csv_data,
-        col_sep: detect_col_sep(csv_data.lines.first),
+        col_sep: detect_col_sep,
         headers: true,
         header_converters: :symbol
       ).each.with_index(2)
     end
 
-    def detect_col_sep(header)
+    def csv_data
+      @csv_io.open(&:read).force_encoding(Encoding::UTF_8)
+    end
+    strong_memoize_attr :csv_data
+
+    def detect_col_sep
+      header = csv_data.lines.first
+
       if header.include?(",")
         ","
       elsif header.include?(";")
@@ -73,6 +100,7 @@ module ImportCsv
         raise CSV::MalformedCSVError.new('Invalid CSV format', 1)
       end
     end
+    strong_memoize_attr :detect_col_sep
 
     def create_object(attributes)
       # NOTE: CSV imports are performed by workers, so we do not have a request context in order