Saving diagram failed! Output directory '#{dir}' does not ex

Error message

Saving diagram failed!
Output directory '#{dir}' does not exist.

What it means

Error "Saving diagram failed! Output directory '#{dir}' does not exist." thrown in voormedia/rails-erd.

Source

Thrown at lib/rails_erd/diagram/tbls.rb:42

        next unless entity.model

        table_name = entity.model.table_name
        next if tables_by_name.key?(table_name)

        tables_by_name[table_name] = build_table(entity)
      end

      each_relationship do |relationship|
        next if relationship.indirect?
        next unless relationship.source && relationship.destination
        next if relationship.source.generalized? || relationship.destination.generalized?

        add_foreign_keys(relationship)
      end

      save do
        dir = File.dirname(filename)
        raise "Saving diagram failed!\nOutput directory '#{dir}' does not exist." unless File.directory?(dir)

        File.write(filename, JSON.pretty_generate(schema_payload))
        filename
      end

      def filename
        "#{options.filename}.json"
      end

      private

      def schema_payload
        {
          name: domain.name || "rails-erd",
          tables: tables_by_name.values,
        }
      end

View on GitHub (pinned to dae6e52018)

Solutions

Create the output directory before running the task: `mkdir -p <dir>` (the directory named in the error message).
Pass a filename whose parent directory already exists, e.g. `bundle exec rake erd filename=erd` for the project root, or create the target directory first.

Example fix

mkdir -p doc && bundle exec rake erd filename=doc/erd

When it happens

Trigger: Raised by the tbls generator's save block when the directory portion of the configured output filename (File.dirname(filename)) is not an existing directory, e.g. running `rake erd generator=tbls filename=docs/erd` while the docs/ directory has not been created.

Common situations: See trigger scenarios.

AI-assisted analysis of voormedia/rails-erd@dae6e52018 (2026-08-23). Data as JSON: /api/errors/596c93f0e3b9391a. Report an issue: GitHub.