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# Some migrations have been present in glitch-soc for a long time and have then
# been merged in upstream Mastodon, under a different version number.
#
# This puts us in an uneasy situation in which if we remove upstream's
# migration file, people migrating from upstream will end up having a conflict
# with their already-ran migration.
#
# On the other hand, if we keep upstream's migration and remove our own,
# any current glitch-soc user will have a conflict during migration.
#
# For lack of a better solution, as those migrations are indeed identical,
# we decided monkey-patching Rails' Migrator to completely ignore the duplicate,
# keeping only the one that has run, or an arbitrary one.
ALLOWED_DUPLICATES = [20180410220657, 20180831171112].freeze
module ActiveRecord
class Migrator
def self.new(direction, migrations, schema_migration, target_version = nil)
migrated = Set.new(Base.connection.migration_context.get_all_versions)
migrations.group_by(&:name).each do |name, duplicates|
if duplicates.length > 1 && duplicates.all? { |m| ALLOWED_DUPLICATES.include?(m.version) }
# We have a set of allowed duplicates. Keep the migrated one, if any.
non_migrated = duplicates.reject { |m| migrated.include?(m.version.to_i) }
if duplicates.length == non_migrated.length || non_migrated.length == 0
# There weren't any migrated one, so we have to pick one “canonical” migration
migrations = migrations - duplicates[1..-1]
else
# Just reject every duplicate which hasn't been migrated yet
migrations = migrations - non_migrated
end
end
end
super(direction, migrations, schema_migration, target_version)
end
end
class MigrationContext
def needs_migration?
# A set of duplicated migrations is considered migrated if at least one of
# them is migrated.
migrated = get_all_versions
migrations.group_by(&:name).each do |name, duplicates|
return true unless duplicates.any? { |m| migrated.include?(m.version.to_i) }
end
return false
end
end
end
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