I created a patch. You get a message when you try to import a file that has only a header row.

<pre><code class="diff">
diff --git a/app/controllers/imports_controller.rb b/app/controllers/imports_controller.rb
index 721d08fa2..2b9edfc31 100644
--- a/app/controllers/imports_controller.rb
+++ b/app/controllers/imports_controller.rb
@@ -50,7 +50,11 @@ class ImportsController < ApplicationController

def settings
if request.post? && @import.parse_file
- redirect_to import_mapping_path(@import)
+ if @import.total_items == 0
+ flash.now[:error] = l(:error_no_data_import_file)
+ else
+ redirect_to import_mapping_path(@import)
+ end
end

rescue CSV::MalformedCSVError, EncodingError => e
diff --git a/config/locales/en.yml b/config/locales/en.yml
index 9d779a2fe..c948d40ff 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -223,6 +223,7 @@ en:
error_invalid_file_encoding: "The file is not a valid %{encoding} encoded file"
error_invalid_csv_file_or_settings: "The file is not a CSV file or does not match the settings below (%{value})"
error_can_not_read_import_file: "An error occurred while reading the file to import"
+ error_no_data_import_file: "There is no data to import into the file"
error_attachment_extension_not_allowed: "Attachment extension %{extension} is not allowed"
error_ldap_bind_credentials: "Invalid LDAP Account/Password"
error_no_tracker_allowed_for_new_issue_in_project: "The project doesn't have any trackers for which you can create an issue"
</code></pre>
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Users can run the import after configuring the field mapping, even if the CSV file contains only a header row.

However, after running the import of the CSV file, only a blank page is displayed (see attachment:Screenshot_2021-06-03.png). I think it is confusing and difficult to troubleshoot for some users.

I think it would be helpful to display an appropriate error message so as not to confuse users.

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Changed the error message in the patch.
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Setting the target version to 5.0.0.
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Committed the patch. Thank you.
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