Struct Writer 

pub struct Writer { /* private fields */ }

Available on crate feature std only.

Low-level writer for creating migration files in V3 folder structure.

V3 format creates a folder per migration:

out/
  20231220143052_initial_schema/
    migration.sql
    snapshot.json
  20231221093015_add_users/
    migration.sql
    snapshot.json

Implementations

impl Writer

pub fn new(out: impl Into<PathBuf>, dialect: Dialect) -> Writer

Create a new migration writer with the given settings

pub const fn with_breakpoints(self, enabled: bool) -> Writer

Set whether to use breakpoints in generated SQL

pub const fn with_prefix_mode(self, mode: PrefixMode) -> Writer

Set the prefix mode for migration tags

pub fn with_custom_name(self, name: impl Into<String>) -> Writer

Set a custom name for the next migration

pub fn migrations_dir(&self) -> &Path

Get the migrations directory path

pub const fn dialect(&self) -> Dialect

Get the dialect

pub fn ensure_dirs(&self) -> Result<(), Error>

Ensure the migration directory exists.

Errors

Returns an error if the migrations directory cannot be created (e.g. insufficient permissions or a conflicting non-directory file exists).

pub fn migration_folder_path(&self, tag: &str) -> PathBuf

Get the path to a migration folder

pub fn migration_sql_path(&self, tag: &str) -> PathBuf

Get the path to a migration SQL file (V3 format: folder/migration.sql)

pub fn snapshot_path(&self, tag: &str) -> PathBuf

Get the path to a snapshot file (V3 format: folder/snapshot.json)

pub fn discover_migrations(&self) -> Result<Vec<String>, Error>

Discover all existing migration folders, sorted by name.

Errors

Returns an error if the migrations directory cannot be read.

pub fn load_previous_snapshot(&self) -> Result<Snapshot<SqliteEntity>, Error>

Load the previous snapshot by scanning existing migration folders.

Errors

Returns an error if the migrations directory cannot be read or the found snapshot cannot be parsed.

pub fn write_sqlite_migration( &self, diff: &SchemaDiff, current_snapshot: &Snapshot<SqliteEntity>, ) -> Result<String, MigrationError>

Write a SQLite migration in V3 folder format.

Errors

Returns MigrationError::NoChanges if the diff produces no statements, or MigrationError::IoError if any filesystem operation fails during migration emission.

pub fn generate_migration_from_snapshots( &self, prev: &Snapshot<SqliteEntity>, cur: &Snapshot<SqliteEntity>, ) -> Result<String, MigrationError>

Generate migration from comparing two snapshots.

Errors

Returns MigrationError::NoChanges if the snapshots diff is empty, or any error produced by Self::write_sqlite_migration.

pub fn write_custom_migration(&self) -> Result<String, MigrationError>

Write a custom (empty) migration for user SQL.

Errors

Returns MigrationError::IoError if directory creation or file writes fail while emitting the placeholder migration folder.