rebar3_kura

Rebar3 plugin for Kura — auto-generates migration files from schema changes and bootstraps new projects.

Installation

Add the plugin to your rebar.config:

{project_plugins, [
    {rebar3_kura, "~> 0.4"}
]}.

{provider_hooks, [
    {pre, [{compile, {kura, compile}}]}
]}.

Commands

rebar3 kura compile

Runs automatically as a pre-compile hook. Diffs your kura_schema modules against existing migrations and generates new migration files when changes are detected.

$ rebar3 compile
===> kura: generated src/migrations/m20260214120000_create_pets.erl

rebar3 kura setup

Bootstraps Kura in a new project:

$ rebar3 kura setup
$ rebar3 kura setup --name my_db  # custom repo module name

This will:

1. Check that kura is in your deps
2. Generate a repo module (APPNAME_repo.erl) with all kura_repo_worker wrappers
3. Create the src/migrations/ directory
4. Check that the provider hook is configured
5. Print remaining manual setup steps

Auto-migration

The pre-compile hook detects:

• New tables — schema exists, no migration history
• Added columns — field in schema, not in migration history
• Dropped columns — column in migration history, not in schema
• Type changes — same column name, different type

It does not auto-generate:

• drop_table operations (destructive — write manually)
• Nullable-only changes
• Default value changes
• Primary key changes

Enum handling

Enum fields ({enum, [atom()]}) map to VARCHAR(255). Changing the enum value list doesn't trigger a migration since the underlying column type is unchanged.

How it works

1. Change a schema (e.g., add a field to pet.erl)
2. Run rebar3 compile
3. The pre-compile hook diffs schemas against existing migrations
4. If changes are detected, a new migration .erl file is generated in src/migrations/
5. The main compile step compiles everything including the new migration
6. Next rebar3 compile — no diff, no new migration (idempotent)

License

MIT