Add option to ActiveStorage::Blob to set extract_content_type_from_io

This adds a boolean argument called identify to ActiveStorage::Blob
methods #create_after_upload, #build_after_upload and #upload. It
allows a user to bypass the automatic content_type inference from
the io.

2 files changed, 12 insertions, 2 deletions

diff --git a/activestorage/test/models/blob_test.rb b/activestorage/test/models/blob_test.rb
index daa01015f7..17151117db 100644
--- a/activestorage/test/models/blob_test.rb
+++ b/activestorage/test/models/blob_test.rb
@@ -43,6 +43,16 @@ class ActiveStorage::BlobTest < ActiveSupport::TestCase
     assert_equal "text/plain", blob.content_type
   end
 
+  test "create after upload extracts content_type from io when no content_type given and identify: false" do
+    blob = create_blob content_type: nil, identify: false
+    assert_equal "text/plain", blob.content_type
+  end
+
+  test "create after upload uses content_type when identify: false" do
+    blob = create_blob data: "Article,dates,analysis\n1, 2, 3", filename: "table.csv", content_type: "text/csv", identify: false
+    assert_equal "text/csv", blob.content_type
+  end
+
   test "image?" do
     blob = create_file_blob filename: "racecar.jpg"
     assert_predicate blob, :image?
diff --git a/activestorage/test/test_helper.rb b/activestorage/test/test_helper.rb
index 499d955a2f..573a8e0b0b 100644
--- a/activestorage/test/test_helper.rb
+++ b/activestorage/test/test_helper.rb
@@ -50,8 +50,8 @@ class ActiveSupport::TestCase
   end
 
   private
-    def create_blob(data: "Hello world!", filename: "hello.txt", content_type: "text/plain")
-      ActiveStorage::Blob.create_after_upload! io: StringIO.new(data), filename: filename, content_type: content_type
+    def create_blob(data: "Hello world!", filename: "hello.txt", content_type: "text/plain", identify: true)
+      ActiveStorage::Blob.create_after_upload! io: StringIO.new(data), filename: filename, content_type: content_type, identify: identify
     end
 
     def create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg", metadata: nil)