Creating a table with id: :string on SQLite crashes with duplicated sqlite_autoindex

[pudiva]

Steps to reproduce

Run this:

#!/bin/sh
rails new sqlite_autoindex
cd sqlite_autoindex
bundle exec rails g scaffold broken
patch db/migrate/* <<EOF
--- 20180709003138_create_brokens.rb    2018-07-08 21:32:20.270221417 -0300
+++ db/migrate/20180709003138_create_brokens.rb 2018-07-08 21:32:39.173220733 -0300
@@ -1,6 +1,6 @@
 class CreateBrokens < ActiveRecord::Migration[5.2]
   def change
-    create_table :brokens do |t|
+    create_table :brokens, id: :string do |t|

       t.timestamps
     end
EOF
bundle exec rake db:migrate
bundle exec rake test

Expected behavior

Tests passing

Actual behavior

rails aborted!
ArgumentError: Index name 'sqlite_autoindex_brokens_1' on table 'brokens' already exists

Other considerations

The migrations run correctly and yield the following db/schema.rb:

ActiveRecord::Schema.define(version: 2018_07_09_002932) do

  create_table "brokens", id: :string, force: :cascade do |t|
    t.datetime "created_at", null: false
    t.datetime "updated_at", null: false
    t.index ["id"], name: "sqlite_autoindex_brokens_1", unique: true
  end

end

and running:

RAILS_ENV=test bundle exec rake db:migrate

will get past this error. So teh problem is that this sqlite_autoindex_brokens_1 is automatically created when creating the primary key, but it gets dumped into a separate statement on schema.rb, ending as a duplicate.

I wonder why it doesn't happen with integer keys. Anyway, it shouldn't be dumped to schema.rb.

System configuration

Stuff	Version
Rails version	Rails 5.2.0
Ruby version	ruby 2.5.1p57 (2018-03-29 revision 63029) [x86_64-linux]
SQLite version	sqlite-3.24.0
SQLite gem version	sqlite3 (1.3.13)

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