# `PhoenixMountable.Migrations.Generator`
[🔗](https://github.com/hattoriai/phoenix_mountable/blob/v0.2.1/lib/phoenix_mountable/migrations/generator.ex#L2)

Writes the host's migration for installing or upgrading a library.

Used by `mix phoenix_mountable.gen.migration` and by
`PhoenixMountable.Igniter`. The version the host is at is read from its
existing migrations: the highest `MyLib.Migrations.up(version: n)` among
them. That works before the database is migrated (a new developer, CI),
and keeps the host's history reproducible.

# `pinned_version`

```elixir
@spec pinned_version(module(), Path.t()) ::
  {:ok, non_neg_integer()} | {:unpinned, [Path.t()]}
```

The highest version pinned by `up(version: n)` calls to `migrations` in the
`.exs` files of `dir`.

Returns `{:ok, version}` (`0` when none), or `{:unpinned, files}` when a
file calls `up/0` or `up/1` without a version, which cannot be read
without the database.

# `render`

```elixir
@spec render(
  module(),
  module() | {module(), atom()},
  non_neg_integer(),
  non_neg_integer()
) ::
  {String.t(), String.t()}
```

The name and module body of the migration taking `migrations` from version
`from` to `to` in `repo`.

The body is what goes inside the migration module after `use
Ecto.Migration`. The file itself is written by Ecto's
`mix ecto.gen.migration` (see `write!/5`) or by Igniter's
`Igniter.Libs.Ecto.gen_migration/4`, so its path, timestamp, module name
and `use` line follow the host's Ecto conventions.

# `write!`

```elixir
@spec write!(module(), module(), non_neg_integer(), non_neg_integer(), [String.t()]) ::
  Path.t()
```

Writes the migration with `mix ecto.gen.migration`, then fills in its body.

`args` are passed to Ecto's task: `-r`/`--repo` and `--migrations-path`.
Returns the file written.

---

*Consult [api-reference.md](api-reference.md) for complete listing*