SQLite3: Implement `add_foreign_key` and `remove_foreign_key`

I implemented Foreign key create in `create_table` for SQLite3 at
#24743. This follows #24743 to implement `add_foreign_key` and
`remove_foreign_key`.
Unfortunately SQLite3 has one limitation that
`PRAGMA foreign_key_list(table-name)` doesn't have constraint name.
So we couldn't implement find/remove foreign key by name for now.

Fixes #35207.
Closes #31343.

actionmailbox/test/dummy/db/schema.rb

@@ -42,4 +42,5 @@ ActiveRecord::Schema.define(version: 2018_02_12_164506) do
     t.index ["key"], name: "index_active_storage_blobs_on_key", unique: true
   end
 
+  add_foreign_key "active_storage_attachments", "active_storage_blobs", column: "blob_id"
 end

actiontext/test/dummy/db/schema.rb

@@ -55,4 +55,5 @@ ActiveRecord::Schema.define(version: 2018_10_03_185713) do
     t.datetime "updated_at", precision: 6, null: false
   end
 
+  add_foreign_key "active_storage_attachments", "active_storage_blobs", column: "blob_id"
 end

activerecord/lib/active_record/connection_adapters/abstract/schema_creation.rb

@@ -15,7 +15,7 @@ module ActiveRecord
         end
 
         delegate :quote_column_name, :quote_table_name, :quote_default_expression, :type_to_sql,
-          :options_include_default?, :supports_indexes_in_create?, :supports_foreign_keys_in_create?, :foreign_key_options,
+          :options_include_default?, :supports_indexes_in_create?, :supports_foreign_keys?, :foreign_key_options,
           to: :@conn, private: true
 
         private
@@ -50,7 +50,7 @@ module ActiveRecord
               statements.concat(o.indexes.map { |column_name, options| index_in_create(o.name, column_name, options) })
             end
 
-            if supports_foreign_keys_in_create?
+            if supports_foreign_keys?
               statements.concat(o.foreign_keys.map { |to_table, options| foreign_key_in_create(o.name, to_table, options) })
             end
 

activerecord/lib/active_record/connection_adapters/abstract/schema_definitions.rb

@@ -102,7 +102,7 @@ module ActiveRecord
       alias validated? validate?
 
       def export_name_on_schema_dump?
-        name !~ ActiveRecord::SchemaDumper.fk_ignore_pattern
+        !ActiveRecord::SchemaDumper.fk_ignore_pattern.match?(name) if name
       end
 
       def defined_for?(to_table_ord = nil, to_table: nil, **options)

activerecord/lib/active_record/connection_adapters/abstract_adapter.rb

@@ -335,6 +335,7 @@ module ActiveRecord
       def supports_foreign_keys_in_create?
         supports_foreign_keys?
       end
+      deprecate :supports_foreign_keys_in_create?
 
       # Does this adapter support views?
       def supports_views?

activerecord/lib/active_record/connection_adapters/sqlite3/schema_statements.rb

@@ -52,6 +52,34 @@ module ActiveRecord
           end.compact
         end
 
+        def add_foreign_key(from_table, to_table, **options)
+          alter_table(from_table) do |definition|
+            to_table = strip_table_name_prefix_and_suffix(to_table)
+            definition.foreign_key(to_table, options)
+          end
+        end
+
+        def remove_foreign_key(from_table, to_table = nil, **options)
+          to_table ||= options[:to_table]
+          options = options.except(:name, :to_table)
+          foreign_keys = foreign_keys(from_table)
+
+          fkey = foreign_keys.detect do |fk|
+            table = to_table || begin
+              table = options[:column].to_s.delete_suffix("_id")
+              Base.pluralize_table_names ? table.pluralize : table
+            end
+            table = strip_table_name_prefix_and_suffix(table)
+            fk_to_table = strip_table_name_prefix_and_suffix(fk.to_table)
+            fk_to_table == table && options.all? { |k, v| fk.options[k].to_s == v.to_s }
+          end || raise(ArgumentError, "Table '#{from_table}' has no foreign key for #{to_table}")
+
+          alter_table(from_table, foreign_keys) do |definition|
+            fk_to_table = strip_table_name_prefix_and_suffix(fkey.to_table)
+            definition.foreign_keys.delete([fk_to_table, fkey.options])
+          end
+        end
+
         def create_schema_dumper(options)
           SQLite3::SchemaDumper.create(self, options)
         end

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -121,7 +121,7 @@ module ActiveRecord
         true
       end
 
-      def supports_foreign_keys_in_create?
+      def supports_foreign_keys?
         true
       end
 
@@ -424,9 +424,8 @@ module ActiveRecord
           type.to_sym == :primary_key || options[:primary_key]
         end
 
-        def alter_table(table_name, options = {})
+        def alter_table(table_name, foreign_keys = foreign_keys(table_name), **options)
           altered_table_name = "a#{table_name}"
-          foreign_keys = foreign_keys(table_name)
 
           caller = lambda do |definition|
             rename = options[:rename] || {}

activerecord/test/cases/adapter_test.rb

@@ -348,6 +348,10 @@ module ActiveRecord
       assert_equal "special_db_type", @connection.type_to_sql(:special_db_type)
     end
 
+    def test_supports_foreign_keys_in_create_is_deprecated
+      assert_deprecated { @connection.supports_foreign_keys_in_create? }
+    end
+
     def test_supports_multi_insert_is_deprecated
       assert_deprecated { @connection.supports_multi_insert? }
     end

activerecord/test/cases/migration/change_schema_test.rb

@@ -462,7 +462,11 @@ module ActiveRecord
         end
 
         def test_create_table_with_force_cascade_drops_dependent_objects
-          skip "MySQL > 5.5 does not drop dependent objects with DROP TABLE CASCADE" if current_adapter?(:Mysql2Adapter)
+          if current_adapter?(:Mysql2Adapter)
+            skip "MySQL > 5.5 does not drop dependent objects with DROP TABLE CASCADE"
+          elsif current_adapter?(:SQLite3Adapter)
+            skip "SQLite3 does not support DROP TABLE CASCADE syntax"
+          end
           # can't re-create table referenced by foreign key
           assert_raises(ActiveRecord::StatementInvalid) do
             @connection.create_table :trains, force: true

activerecord/test/cases/migration/foreign_key_test.rb

@@ -3,7 +3,7 @@
 require "cases/helper"
 require "support/schema_dumping_helper"
 
-if ActiveRecord::Base.connection.supports_foreign_keys_in_create?
+if ActiveRecord::Base.connection.supports_foreign_keys?
   module ActiveRecord
     class Migration
       class ForeignKeyInCreateTest < ActiveRecord::TestCase
@@ -119,6 +119,15 @@ if ActiveRecord::Base.connection.supports_foreign_keys_in_create?
 
           assert_empty @connection.foreign_keys(Astronaut.table_name)
         end
+
+        def test_remove_foreign_key_by_column
+          rocket = Rocket.create!(name: "myrocket")
+          rocket.astronauts << Astronaut.create!
+
+          @connection.remove_foreign_key Astronaut.table_name, column: :rocket_id
+
+          assert_empty @connection.foreign_keys(Astronaut.table_name)
+        end
       end
 
       class ForeignKeyChangeColumnTest < ActiveRecord::TestCase
@@ -156,9 +165,7 @@ if ActiveRecord::Base.connection.supports_foreign_keys_in_create?
       end
     end
   end
-end
 
-if ActiveRecord::Base.connection.supports_foreign_keys?
   module ActiveRecord
     class Migration
       class ForeignKeyTest < ActiveRecord::TestCase
@@ -197,7 +204,7 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
           assert_equal "fk_test_has_pk", fk.to_table
           assert_equal "fk_id", fk.column
           assert_equal "pk_id", fk.primary_key
-          assert_equal "fk_name", fk.name
+          assert_equal "fk_name", fk.name unless current_adapter?(:SQLite3Adapter)
         end
 
         def test_add_foreign_key_inferes_column
@@ -211,7 +218,7 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
           assert_equal "rockets", fk.to_table
           assert_equal "rocket_id", fk.column
           assert_equal "id", fk.primary_key
-          assert_equal("fk_rails_78146ddd2e", fk.name)
+          assert_equal "fk_rails_78146ddd2e", fk.name unless current_adapter?(:SQLite3Adapter)
         end
 
         def test_add_foreign_key_with_column
@@ -225,7 +232,7 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
           assert_equal "rockets", fk.to_table
           assert_equal "rocket_id", fk.column
           assert_equal "id", fk.primary_key
-          assert_equal("fk_rails_78146ddd2e", fk.name)
+          assert_equal "fk_rails_78146ddd2e", fk.name unless current_adapter?(:SQLite3Adapter)
         end
 
         def test_add_foreign_key_with_non_standard_primary_key
@@ -244,7 +251,7 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
           assert_equal "space_shuttles", fk.to_table
           assert_equal "pk", fk.primary_key
         ensure
-          @connection.remove_foreign_key :astronauts, name: "custom_pk"
+          @connection.remove_foreign_key :astronauts, name: "custom_pk", to_table: "space_shuttles"
           @connection.drop_table :space_shuttles
         end
 
@@ -318,6 +325,8 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
         end
 
         def test_foreign_key_exists_by_name
+          skip if current_adapter?(:SQLite3Adapter)
+
           @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", name: "fancy_named_fk"
 
           assert @connection.foreign_key_exists?(:astronauts, name: "fancy_named_fk")
@@ -349,6 +358,8 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
         end
 
         def test_remove_foreign_key_by_name
+          skip if current_adapter?(:SQLite3Adapter)
+
           @connection.add_foreign_key :astronauts, :rockets, column: "rocket_id", name: "fancy_named_fk"
 
           assert_equal 1, @connection.foreign_keys("astronauts").size
@@ -357,9 +368,10 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
         end
 
         def test_remove_foreign_non_existing_foreign_key_raises
-          assert_raises ArgumentError do
+          e = assert_raises ArgumentError do
             @connection.remove_foreign_key :astronauts, :rockets
           end
+          assert_equal "Table 'astronauts' has no foreign key for rockets", e.message
         end
 
         if ActiveRecord::Base.connection.supports_validate_constraints?
@@ -438,7 +450,11 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
 
         def test_schema_dumping_with_options
           output = dump_table_schema "fk_test_has_fk"
-          assert_match %r{\s+add_foreign_key "fk_test_has_fk", "fk_test_has_pk", column: "fk_id", primary_key: "pk_id", name: "fk_name"$}, output
+          if current_adapter?(:SQLite3Adapter)
+            assert_match %r{\s+add_foreign_key "fk_test_has_fk", "fk_test_has_pk", column: "fk_id", primary_key: "pk_id"$}, output
+          else
+            assert_match %r{\s+add_foreign_key "fk_test_has_fk", "fk_test_has_pk", column: "fk_id", primary_key: "pk_id", name: "fk_name"$}, output
+          end
         end
 
         def test_schema_dumping_with_custom_fk_ignore_pattern
@@ -492,7 +508,7 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
         end
 
         class CreateSchoolsAndClassesMigration < ActiveRecord::Migration::Current
-          def change
+          def up
             create_table(:schools)
 
             create_table(:classes) do |t|
@@ -500,6 +516,11 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
             end
             add_foreign_key :classes, :schools
           end
+
+          def down
+            drop_table :classes, if_exists: true
+            drop_table :schools, if_exists: true
+          end
         end
 
         def test_add_foreign_key_with_prefix

activerecord/test/cases/migration/references_foreign_key_test.rb

@@ -2,7 +2,7 @@
 
 require "cases/helper"
 
-if ActiveRecord::Base.connection.supports_foreign_keys_in_create?
+if ActiveRecord::Base.connection.supports_foreign_keys?
   module ActiveRecord
     class Migration
       class ReferencesForeignKeyInCreateTest < ActiveRecord::TestCase
@@ -65,9 +65,7 @@ if ActiveRecord::Base.connection.supports_foreign_keys_in_create?
       end
     end
   end
-end
 
-if ActiveRecord::Base.connection.supports_foreign_keys?
   module ActiveRecord
     class Migration
       class ReferencesForeignKeyTest < ActiveRecord::TestCase
@@ -172,13 +170,18 @@ if ActiveRecord::Base.connection.supports_foreign_keys?
         end
 
         class CreateDogsMigration < ActiveRecord::Migration::Current
-          def change
+          def up
             create_table :dog_owners
 
             create_table :dogs do |t|
               t.references :dog_owner, foreign_key: true
             end
           end
+
+          def down
+            drop_table :dogs, if_exists: true
+            drop_table :dog_owners, if_exists: true
+          end
         end
 
         def test_references_foreign_key_with_prefix