Allow providing a custom key per blob

Closes #37315.

activestorage/CHANGELOG.md

@@ -1,3 +1,14 @@
+*   You can optionally provide a custom blob key when attaching a new file:
+
+    ```ruby
+    user.avatar.attach key: "avatars/#{user.id}.jpg",
+      io: io, content_type: "image/jpeg", filename: "avatar.jpg"
+    ```
+
+    Active Storage will store the blob's data on the configured service at the provided key.
+
+    *George Claghorn*
+
 *   Replace `Blob.create_after_upload!` with `Blob.create_and_upload!` and deprecate the former.
 
     `create_after_upload!` has been removed since it could lead to data

activestorage/app/models/active_storage/blob.rb

@@ -58,23 +58,23 @@ def build_after_upload(io:, filename:, content_type: nil, metadata: nil, identif
 
     deprecate :build_after_upload
 
-    def build_after_unfurling(io:, filename:, content_type: nil, metadata: nil, identify: true, record: nil) #:nodoc:
-      new(filename: filename, content_type: content_type, metadata: metadata).tap do |blob|
+    def build_after_unfurling(key: nil, io:, filename:, content_type: nil, metadata: nil, identify: true, record: nil) #:nodoc:
+      new(key: key, filename: filename, content_type: content_type, metadata: metadata).tap do |blob|
         blob.unfurl(io, identify: identify)
       end
     end
 
-    def create_after_unfurling!(io:, filename:, content_type: nil, metadata: nil, identify: true, record: nil) #:nodoc:
-      build_after_unfurling(io: io, filename: filename, content_type: content_type, metadata: metadata, identify: identify).tap(&:save!)
+    def create_after_unfurling!(key: nil, io:, filename:, content_type: nil, metadata: nil, identify: true, record: nil) #:nodoc:
+      build_after_unfurling(key: key, io: io, filename: filename, content_type: content_type, metadata: metadata, identify: identify).tap(&:save!)
     end
 
     # Creates a new blob instance and then uploads the contents of
     # the given <tt>io</tt> to the service. The blob instance is going to
     # be saved before the upload begins to prevent the upload clobbering another due to key collisions.
     # When providing a content type, pass <tt>identify: false</tt> to bypass
     # automatic content type inference.
-    def create_and_upload!(io:, filename:, content_type: nil, metadata: nil, identify: true, record: nil)
-      create_after_unfurling!(io: io, filename: filename, content_type: content_type, metadata: metadata, identify: identify).tap do |blob|
+    def create_and_upload!(key: nil, io:, filename:, content_type: nil, metadata: nil, identify: true, record: nil)
+      create_after_unfurling!(key: key, io: io, filename: filename, content_type: content_type, metadata: metadata, identify: identify).tap do |blob|
         blob.upload_without_unfurling(io)
       end
     end
@@ -87,8 +87,8 @@ def create_and_upload!(io:, filename:, content_type: nil, metadata: nil, identif
     # in order to produce the signed URL for uploading. This signed URL points to the key generated by the blob.
     # Once the form using the direct upload is submitted, the blob can be associated with the right record using
     # the signed ID.
-    def create_before_direct_upload!(filename:, byte_size:, checksum:, content_type: nil, metadata: nil, record: nil)
-      create! filename: filename, byte_size: byte_size, checksum: checksum, content_type: content_type, metadata: metadata
+    def create_before_direct_upload!(key: nil, filename:, byte_size:, checksum:, content_type: nil, metadata: nil, record: nil)
+      create! key: key, filename: filename, byte_size: byte_size, checksum: checksum, content_type: content_type, metadata: metadata
     end
 
     # To prevent problems with case-insensitive filesystems, especially in combination

activestorage/test/models/blob_test.rb

@@ -84,6 +84,15 @@ class ActiveStorage::BlobTest < ActiveSupport::TestCase
     assert_match(/^[a-z0-9]{28}$/, create_blob.key)
   end
 
+  test "create_and_upload accepts a custom key" do
+    key  = SecureRandom.base36(28)
+    data = "Hello world!"
+    blob = create_blob key: key, data: data
+
+    assert_equal key, blob.key
+    assert_equal data, blob.download
+  end
+
   test "create_and_upload accepts a record for overrides" do
     assert_nothing_raised do
       create_blob(record: User.new)

activestorage/test/test_helper.rb

@@ -51,16 +51,16 @@ class ActiveSupport::TestCase
   end
 
   private
-    def create_blob(data: "Hello world!", filename: "hello.txt", content_type: "text/plain", identify: true, record: nil)
-      ActiveStorage::Blob.create_and_upload! io: StringIO.new(data), filename: filename, content_type: content_type, identify: identify, record: record
+    def create_blob(key: nil, data: "Hello world!", filename: "hello.txt", content_type: "text/plain", identify: true, record: nil)
+      ActiveStorage::Blob.create_and_upload! key: key, io: StringIO.new(data), filename: filename, content_type: content_type, identify: identify, record: record
     end
 
-    def create_file_blob(filename: "racecar.jpg", content_type: "image/jpeg", metadata: nil, record: nil)
+    def create_file_blob(key: nil, filename: "racecar.jpg", content_type: "image/jpeg", metadata: nil, record: nil)
       ActiveStorage::Blob.create_and_upload! io: file_fixture(filename).open, filename: filename, content_type: content_type, metadata: metadata, record: record
     end
 
-    def create_blob_before_direct_upload(filename: "hello.txt", byte_size:, checksum:, content_type: "text/plain", record: nil)
-      ActiveStorage::Blob.create_before_direct_upload! filename: filename, byte_size: byte_size, checksum: checksum, content_type: content_type, record: record
+    def create_blob_before_direct_upload(key: nil, filename: "hello.txt", byte_size:, checksum:, content_type: "text/plain", record: nil)
+      ActiveStorage::Blob.create_before_direct_upload! key: key, filename: filename, byte_size: byte_size, checksum: checksum, content_type: content_type, record: record
     end
 
     def directly_upload_file_blob(filename: "racecar.jpg", content_type: "image/jpeg", record: nil)