Remove mini_mime usage in favour of marcel

We are using two libraries to do the same job. This commit removes the usage of mini_mime in favour of Marcel instead.

Changes are as follows:
- Replace MiniMime lookup by extension with Marcel Mimetype for lookup with extension
- Replaces usage of MiniMime lookup by content type to fetch extension with usage of Marcel Magic lookup. Marcel has multiple extentions being returned, we pick the first one. MiniMime always returns just one
- Removes specs which we specifically checking failing identification issue of MiniMine on jpeg images
- Removes mini_mime from gemspec

Gemfile.lock

@@ -72,7 +72,6 @@ PATH
       activerecord (= 7.1.0.alpha)
       activesupport (= 7.1.0.alpha)
       marcel (~> 1.0)
-      mini_mime (>= 1.1.0)
     activesupport (7.1.0.alpha)
       concurrent-ruby (~> 1.0, >= 1.0.2)
       connection_pool (>= 2.2.5)

activestorage/CHANGELOG.md

@@ -1,3 +1,10 @@
+*   Remove mini_mime usage in favour of marcel.
+
+    We have two libraries that are have similar usage. This change removes
+    dependency on mini_mime and makes use of similar methods from marcel.
+
+    *Vipul A M*
+
 *   Allow destroying active storage variants
 
     ```ruby

activestorage/activestorage.gemspec

@@ -38,5 +38,4 @@ Gem::Specification.new do |s|
   s.add_dependency "activerecord",  version
 
   s.add_dependency "marcel",    "~> 1.0"
-  s.add_dependency "mini_mime", ">= 1.1.0"
 end

activestorage/app/models/active_storage/blob/representable.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require "mini_mime"
+require "marcel"
 
 module ActiveStorage::Blob::Representable
   extend ActiveSupport::Concern
@@ -112,10 +112,10 @@ module ActiveStorage::Blob::Representable
     end
 
     def format
-      if filename.extension.present? && MiniMime.lookup_by_extension(filename.extension)&.content_type == content_type
+      if filename.extension.present? && Marcel::MimeType.for(extension: filename.extension) == content_type
         filename.extension
       else
-        MiniMime.lookup_by_content_type(content_type)&.extension
+        Marcel::Magic.new(content_type.to_s).extensions.first
       end
     end
 

activestorage/app/models/active_storage/variation.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require "mini_mime"
+require "marcel"
 
 # A set of transformations that can be applied to a blob to create a variant. This class is exposed via
 # the ActiveStorage::Blob#variant method and should rarely be used directly.
@@ -59,14 +59,14 @@ class ActiveStorage::Variation
 
   def format
     transformations.fetch(:format, :png).tap do |format|
-      if MiniMime.lookup_by_extension(format.to_s).nil?
+      if Marcel::Magic.by_extension(format.to_s).nil?
         raise ArgumentError, "Invalid variant format (#{format.inspect})"
       end
     end
   end
 
   def content_type
-    MiniMime.lookup_by_extension(format.to_s).content_type
+    Marcel::MimeType.for(extension: format.to_s)
   end
 
   # Returns a signed key for all the +transformations+ that this variation was instantiated with.

activestorage/test/engine_test.rb

@@ -4,31 +4,21 @@ require "test_helper"
 require "database/setup"
 
 class ActiveStorage::EngineTest < ActiveSupport::TestCase
-  test "all default content types are recognized by mini_mime" do
-    exceptions = ["image/bmp"] # see https://github.com/discourse/mini_mime/pull/45, once mini_mime is updated this can be removed
-
+  test "all default content types are recognized by marcel" do
     ActiveStorage.variable_content_types.each do |content_type|
-      next if exceptions.include?(content_type) # remove this line when there is no exceptions
-
-      assert_equal content_type, MiniMime.lookup_by_content_type(content_type)&.content_type
+      assert_equal content_type, Marcel::Magic.new(content_type).type
     end
 
     ActiveStorage.web_image_content_types.each do |content_type|
-      next if exceptions.include?(content_type) # remove this line when there is no exceptions
-
-      assert_equal content_type, MiniMime.lookup_by_content_type(content_type)&.content_type
+      assert_equal content_type, Marcel::Magic.new(content_type).type
     end
 
     ActiveStorage.content_types_to_serve_as_binary.each do |content_type|
-      next if exceptions.include?(content_type) # remove this line when there is no exceptions
-
-      assert_equal content_type, MiniMime.lookup_by_content_type(content_type)&.content_type
+      assert_equal content_type, Marcel::Magic.new(content_type).type
     end
 
     ActiveStorage.content_types_allowed_inline.each do |content_type|
-      next if exceptions.include?(content_type) # remove this line when there is no exceptions
-
-      assert_equal content_type, MiniMime.lookup_by_content_type(content_type)&.content_type
+      assert_equal content_type, Marcel::Magic.new(content_type).type
     end
   end
 

activestorage/test/models/variant_test.rb

@@ -197,10 +197,10 @@ class ActiveStorage::VariantTest < ActiveSupport::TestCase
     end
   end
 
-  test "content_type not recognized by mini_mime isn't included as variable" do
+  test "content_type not recognized by marcel isn't included as variable" do
     blob = create_file_blob(filename: "racecar.jpg")
 
-    # image/jpg is not recognized by mini_mime (image/jpeg is correct)
+    # image/jpg is not recognized by marcel (image/jpeg is correct)
     blob.update(content_type: "image/jpg")
 
     assert_raises(ActiveStorage::InvariableError) do