Adding barrel feature (#1573)

I've taken the liberty to squash down this epic saga of a pull request. Here is its full list of commit messages for future reference:

* Optionally adding `barrel` crate to diesel_migrations
* Initial support for barrel migrations in diesel cli
* Using the barrel `diesel` feature
* Changing barrel call signature to build Migration on diesel side
* Connecting barrel to diesel migration layouts
* Formatting with rustfmt
* Changing generated migration function signatures
* Cleaning up migration process slightly
* Pointing barrel to github version
* Implementing requested changes in diesel_cli
* Fix git repository link
* Preliminarily commiting refactoring changes
* Moving Migration trait to core diesel library
* Adjusting the module comment formatting to let CI pass
* Moving MigrationName back to migrations_internals
* Adding new import to fix some Migration tests
* Changing the migration generation function signature
* Another clippy change
* Renaming external feature flag. Changing barrel version to non-git
* Changing barrel version to non-git in diesel_cli
* Adjust the diesel feature flag on barrel
* Re-exporting diesel::migration::* to avoid a breaking change
* Cleaning up diesel_migration exports
* Adjusting a few function calls into barrel to the v0.2.0 API
* Re-adding more re-exports to diesel_migrations
* Changing feature and type flag names in diesel_cli
* Making error enums non exhaustive. Only exporting speific error types
* Breaking formatting
* Fixing formatting again
* Touching code to make github see changes
* Changing formatting back to the way it's meant to be
* Handling __NonExaustive options for migration errors
* Not exposing the entire mirations/error module anymore
* Fixing some formatting issues
* Optionally adding `barrel` crate to diesel_migrations
* Initial support for barrel migrations in diesel cli
* Changing barrel call signature to build Migration on diesel side
* Connecting barrel to diesel migration layouts
* Formatting with rustfmt
* Changing generated migration function signatures
* Cleaning up migration process slightly
* Pointing barrel to github version
* Implementing requested changes in diesel_cli
* Preliminarily commiting refactoring changes
* Moving Migration trait to core diesel library
* Adjusting the module comment formatting to let CI pass
* Moving MigrationName back to migrations_internals
* Adding new import to fix some Migration tests
* Changing the migration generation function signature
* Another clippy change
* Renaming external feature flag. Changing barrel version to non-git
* Changing barrel version to non-git in diesel_cli
* Adjust the diesel feature flag on barrel
* Re-exporting diesel::migration::* to avoid a breaking change
* Cleaning up diesel_migration exports
* Adjusting a few function calls into barrel to the v0.2.0 API
* Re-adding more re-exports to diesel_migrations
* Changing feature and type flag names in diesel_cli
* Making error enums non exhaustive. Only exporting speific error types
* Breaking formatting
* Fixing formatting again
* Touching code to make github see changes
* Changing formatting back to the way it's meant to be
* Handling __NonExaustive options for migration errors
* Not exposing the entire mirations/error module anymore
* Fixing some formatting issues
* Cleaning a bad merge artefact
* Fixing a bad rebase

diesel/src/lib.rs

@@ -168,6 +168,7 @@ pub mod serialize;
 pub mod sql_types;
 pub mod types;
 pub mod row;
+pub mod migration;
 
 #[cfg(feature = "mysql")]
 pub mod mysql;

diesel_migrations/migrations_internals/src/migration_error.rs → diesel/src/migration/errors.rs

@@ -1,17 +1,30 @@
-use diesel::result;
+//! Error types that represent migration errors.
+//! These are split into multiple segments, depending on
+//! where in the migration process an error occurs.
 
 use std::convert::From;
 use std::{fmt, io};
 use std::path::PathBuf;
 use std::error::Error;
 
+use result;
+
+/// Errors that occur while preparing to run migrations
 #[derive(Debug)]
 pub enum MigrationError {
+    /// The migration directory wasn't found
     MigrationDirectoryNotFound,
+    /// Provided migration was in an unknown format
     UnknownMigrationFormat(PathBuf),
+    /// General system IO error
     IoError(io::Error),
+    /// Provided migration had an incompatible version number
     UnknownMigrationVersion(String),
+    /// No migrations had to be/ could be run
     NoMigrationRun,
+    ///
+    #[doc(hidden)]
+    __NonExhaustive,
 }
 
 impl Error for MigrationError {
@@ -31,6 +44,7 @@ impl Error for MigrationError {
             MigrationError::NoMigrationRun => {
                 "No migrations have been run. Did you forget `diesel migration run`?"
             }
+            MigrationError::__NonExhaustive => unreachable!(),
         }
     }
 }
@@ -63,12 +77,19 @@ impl From<io::Error> for MigrationError {
     }
 }
 
+/// Errors that occur while running migrations
 #[derive(Debug, PartialEq)]
 #[cfg_attr(feature = "clippy", allow(enum_variant_names))]
 pub enum RunMigrationsError {
+    /// A general migration error occured
     MigrationError(MigrationError),
+    /// The provided migration included an invalid query
     QueryError(result::Error),
+    /// The provided migration was empty
     EmptyMigration,
+    ///
+    #[doc(hidden)]
+    __NonExhaustive,
 }
 
 impl Error for RunMigrationsError {
@@ -77,6 +98,7 @@ impl Error for RunMigrationsError {
             RunMigrationsError::MigrationError(ref error) => error.description(),
             RunMigrationsError::QueryError(ref error) => error.description(),
             RunMigrationsError::EmptyMigration => "Attempted to run an empty migration.",
+            RunMigrationsError::__NonExhaustive => unreachable!(),
         }
     }
 }

diesel/src/migration/mod.rs

@@ -0,0 +1,55 @@
+//! Representation of migrations
+
+mod errors;
+pub use self::errors::{MigrationError, RunMigrationsError};
+
+use connection::SimpleConnection;
+use std::path::Path;
+
+/// Represents a migration that interacts with diesel
+pub trait Migration {
+    /// Get the migration version
+    fn version(&self) -> &str;
+    /// Apply this migration
+    fn run(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError>;
+    /// Revert this migration
+    fn revert(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError>;
+    /// Get the migration file path
+    fn file_path(&self) -> Option<&Path> {
+        None
+    }
+}
+
+impl Migration for Box<Migration> {
+    fn version(&self) -> &str {
+        (&**self).version()
+    }
+
+    fn run(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError> {
+        (&**self).run(conn)
+    }
+
+    fn revert(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError> {
+        (&**self).revert(conn)
+    }
+    fn file_path(&self) -> Option<&Path> {
+        (&**self).file_path()
+    }
+}
+
+impl<'a> Migration for &'a Migration {
+    fn version(&self) -> &str {
+        (&**self).version()
+    }
+
+    fn run(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError> {
+        (&**self).run(conn)
+    }
+
+    fn revert(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError> {
+        (&**self).revert(conn)
+    }
+    fn file_path(&self) -> Option<&Path> {
+        (&**self).file_path()
+    }
+}

diesel_cli/Cargo.toml

@@ -25,6 +25,7 @@ migrations_internals = "~1.2.0"
 serde = { version = "1.0.0", features = ["derive"] }
 toml = "0.4.6"
 url = { version = "1.4.0", optional = true }
+barrel = { version = "<= 0.2.0", optional = true, features = ["diesel-filled"] }
 
 [dev-dependencies]
 difference = "1.0"
@@ -38,6 +39,7 @@ lint = ["clippy"]
 postgres = ["diesel/postgres", "infer_schema_internals/postgres", "url"]
 sqlite = ["diesel/sqlite", "infer_schema_internals/sqlite"]
 mysql = ["diesel/mysql", "infer_schema_internals/mysql", "url"]
+rust-migrations = ["migrations_internals/barrel", "barrel"]
 
 [[test]]
 name = "tests"

diesel_cli/src/cli.rs

@@ -51,6 +51,15 @@ pub fn build_cli() -> App<'static, 'static> {
                              for most use cases.",
                         )
                         .takes_value(true),
+                )
+                .arg(
+                    Arg::with_name("TYPE")
+                        .long("type")
+                        .short("t")
+                        .possible_values(&["sql", "rust"])
+                        .default_value("sql")
+                        .takes_value(true)
+                        .help("Specify the migration type."),
                 ),
         )
         .setting(AppSettings::SubcommandRequiredElseHelp);

diesel_cli/src/main.rs

@@ -24,6 +24,10 @@ extern crate toml;
 extern crate url;
 
 mod config;
+
+#[cfg(feature = "rust-migrations")]
+extern crate barrel;
+
 mod database_error;
 #[macro_use]
 mod database;
@@ -113,39 +117,49 @@ fn run_migration_command(matches: &ArgMatches) -> Result<(), Box<Error>> {
             println!("{:?}", result);
         }
         ("generate", Some(args)) => {
-            use std::io::Write;
-
             let migration_name = args.value_of("MIGRATION_NAME").unwrap();
             let version = migration_version(args);
             let versioned_name = format!("{}_{}", version, migration_name);
             let migration_dir = migrations_dir(matches).join(versioned_name);
-            fs::create_dir(&migration_dir)?;
-
-            let migration_dir_relative =
-                convert_absolute_path_to_relative(&migration_dir, &env::current_dir()?);
-
-            let up_path = migration_dir.join("up.sql");
-            println!(
-                "Creating {}",
-                migration_dir_relative.join("up.sql").display()
-            );
-            let mut up = fs::File::create(up_path).unwrap();
-            up.write_all(b"-- Your SQL goes here").unwrap();
-
-            let down_path = migration_dir.join("down.sql");
-            println!(
-                "Creating {}",
-                migration_dir_relative.join("down.sql").display()
-            );
-            let mut down = fs::File::create(down_path)?;
-            down.write_all(b"-- This file should undo anything in `up.sql`")?;
+            let migration_type: Option<&str> = args.value_of("TYPE");
+            fs::create_dir(&migration_dir).unwrap();
+
+            match migration_type {
+                #[cfg(feature = "rust-migrations")]
+                Some("rust") => ::barrel::integrations::diesel::generate_initial(&migration_dir),
+                _ => generate_sql_migration(&migration_dir),
+            }
         }
         _ => unreachable!("The cli parser should prevent reaching here"),
     };
 
     Ok(())
 }
 
+fn generate_sql_migration(path: &PathBuf) {
+    use std::io::Write;
+
+    let migration_dir_relative =
+        convert_absolute_path_to_relative(path, &env::current_dir().unwrap());
+
+    let up_path = path.join("up.sql");
+    println!(
+        "Creating {}",
+        migration_dir_relative.join("up.sql").display()
+    );
+    let mut up = fs::File::create(up_path).unwrap();
+    up.write_all(b"-- Your SQL goes here").unwrap();
+
+    let down_path = path.join("down.sql");
+    println!(
+        "Creating {}",
+        migration_dir_relative.join("down.sql").display()
+    );
+    let mut down = fs::File::create(down_path).unwrap();
+    down.write_all(b"-- This file should undo anything in `up.sql`")
+        .unwrap();
+}
+
 use std::fmt::Display;
 fn migration_version<'a>(matches: &'a ArgMatches) -> Box<Display + 'a> {
     matches

diesel_migrations/migrations_internals/Cargo.toml

@@ -9,6 +9,7 @@ homepage = "http://diesel.rs"
 [dependencies]
 clippy = { optional = true, version = "=0.0.185" }
 diesel = { version = "~1.2.0", default-features = false }
+barrel = { version = "<= 0.2.0", optional = true, features = ["diesel-filled"] }
 
 [dev-dependencies]
 tempdir = "0.3.4"

diesel_migrations/migrations_internals/src/lib.rs

@@ -77,18 +77,20 @@
 #[macro_use]
 extern crate diesel;
 
-mod migration;
+#[cfg(feature = "barrel")]
+extern crate barrel;
+
+pub mod migration;
 #[doc(hidden)]
 pub mod connection;
-mod migration_error;
 #[doc(hidden)]
 pub mod schema;
 
 #[doc(inline)]
 pub use self::connection::MigrationConnection;
 #[doc(inline)]
 pub use self::migration::*;
-pub use self::migration_error::*;
+pub use diesel::migration::*;
 
 use std::fs::DirEntry;
 use std::io::{stdout, Write};

diesel_migrations/migrations_internals/src/migration.rs

@@ -1,18 +1,9 @@
 use diesel::connection::SimpleConnection;
-use super::{MigrationError, RunMigrationsError};
+use diesel::migration::*;
 
 use std::path::{Path, PathBuf};
 use std::fmt;
 
-pub trait Migration {
-    fn version(&self) -> &str;
-    fn run(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError>;
-    fn revert(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError>;
-    fn file_path(&self) -> Option<&Path> {
-        None
-    }
-}
-
 #[allow(missing_debug_implementations)]
 #[derive(Clone, Copy)]
 pub struct MigrationName<'a> {
@@ -41,6 +32,12 @@ impl<'a> fmt::Display for MigrationName<'a> {
 }
 
 pub fn migration_from(path: PathBuf) -> Result<Box<Migration>, MigrationError> {
+    #[cfg(feature = "barrel")]
+    match ::barrel::integrations::diesel::migration_from(&path) {
+        Some(migration) => return Ok(migration),
+        None => {}
+    }
+
     if valid_sql_migration_directory(&path) {
         let version = try!(version_from_path(&path));
         Ok(Box::new(SqlFileMigration(path, version)))
@@ -49,40 +46,6 @@ pub fn migration_from(path: PathBuf) -> Result<Box<Migration>, MigrationError> {
     }
 }
 
-impl Migration for Box<Migration> {
-    fn version(&self) -> &str {
-        (&**self).version()
-    }
-
-    fn run(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError> {
-        (&**self).run(conn)
-    }
-
-    fn revert(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError> {
-        (&**self).revert(conn)
-    }
-    fn file_path(&self) -> Option<&Path> {
-        (&**self).file_path()
-    }
-}
-
-impl<'a> Migration for &'a Migration {
-    fn version(&self) -> &str {
-        (&**self).version()
-    }
-
-    fn run(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError> {
-        (&**self).run(conn)
-    }
-
-    fn revert(&self, conn: &SimpleConnection) -> Result<(), RunMigrationsError> {
-        (&**self).revert(conn)
-    }
-    fn file_path(&self) -> Option<&Path> {
-        (&**self).file_path()
-    }
-}
-
 fn valid_sql_migration_directory(path: &Path) -> bool {
     file_names(path)
         .map(|files| files.contains(&"down.sql".into()) && files.contains(&"up.sql".into()))

diesel_migrations/migrations_macros/src/embed_migrations.rs

@@ -66,6 +66,7 @@ pub fn derive_embed_migrations(input: &syn::DeriveInput) -> quote::Tokens {
         extern crate diesel_migrations;
 
         use self::diesel_migrations::*;
+        use self::diesel::migration::*;
         use self::diesel::connection::SimpleConnection;
         use std::io;