add: infer migration (#1086)

* add: infer migration

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+* feat: smart migration generator. you can now generate migration based on naming them for creating a table, adding columns, references, join tables and more. [https://github.com/loco-rs/loco/pull/1086](https://github.com/loco-rs/loco/pull/1086)
 * feat: `cargo loco routes` will now pretty-print routes
 * fix: guard jwt error behind feature flag. [https://github.com/loco-rs/loco/pull/1032](https://github.com/loco-rs/loco/pull/1032)
 * fix: logger file_appender not using the seperated format setting. [https://github.com/loco-rs/loco/pull/1036](https://github.com/loco-rs/loco/pull/1036)

docs-site/content/docs/the-app/models.md

@@ -111,9 +111,9 @@ impl super::_entities::users::ActiveModel {
 
 # Crafting models
 
-## Migrations
+## The model generator
 
-To add a new model _you have to use a migration_.
+To add a new model the model generator creates a migration, runs it, and then triggers an entities sync from your database schema which will hydrate and create your model entities.
 
 ```
 $ cargo loco generate model posts title:string! content:text user:references
@@ -181,20 +181,24 @@ You can generate an empty model:
 $ cargo loco generate model posts
 ```
 
-You can generate an empty model **migration only** which means migrations will not run automatically:
+
+Or a data model, without any references:
 
 ```
-$ cargo loco generate model --migration-only posts
+$ cargo loco generate model posts title:string! content:text
 ```
 
-Or a data model, without any references:
+## Migrations
+
+Other than using the model generator, you drive your schema by *creating migrations*.
 
 ```
-$ cargo loco generate model posts title:string! content:text
+$ cargo loco generate migration <name of migration> [name:type, name:type ...]
 ```
 
 This creates a migration in the root of your project in `migration/`.
-You can now apply it:
+
+You can apply it:
 
 ```
 $ cargo loco db migrate
@@ -210,6 +214,63 @@ Loco is a migration-first framework, similar to Rails. Which means that when you
 
 This enforces _everything-as-code_, _reproducibility_ and _atomicity_, where no knowledge of the schema goes missing. 
 
+**Naming the migration is important**, the type of migration that is being generated is inferred from the migration name.
+
+### Create a new table
+
+* Name template: `Create___`
+* Example: `CreatePosts`
+
+```
+$ cargo loco g migration CreatePosts title:string content:string
+```
+
+### Add columns
+
+* Name template: `Add___To___`
+* Example: `AddNameAndAgeToUsers` (the string `NameAndAge` does not matter, you specify columns individually, however `Users` does matter because this will be the name of the table)
+
+```
+$ cargo loco g migration AddNameAndAgeToUsers name:string age:int
+```
+
+### Remove columns
+
+* Name template: `Remove___From___`
+* Example: `RemoveNameAndAgeFromUsers` (same note exists as in _add columns_)
+
+```
+$ cargo logo g migration RemoveNameAndAgeFromUsers name:string age:int
+```
+
+### Add references
+
+* Name template: `Add___RefTo___`
+* Example: `AddUserRefToPosts` (`User` does not matter, as you specify one or many references individually, `Posts` does matter as it will be the table name in the migration)
+
+```
+$ cargo loco g migration AddUserRefToPosts user:references
+```
+
+### Create a join table
+
+* Name template: `CreateJoinTable___And___` (supported between 2 tables)
+* Example: `CreateJoinTableUsersAndGroups`
+
+```
+$ cargo loco g migration CreateJoinTableUsersAndGroups count:int
+```
+
+You can also add some state columns regarding the relationship (such as `count` here).
+
+### Create an empty migration
+
+Use any descriptive name for a migration that does not fall into one of the above patterns to create an empty migration.
+
+```
+$ cargo loco g migration FixUsersTable
+```
+
 ### Down Migrations
 
 If you realize that you made a mistake, you can always undo the migration. This will undo the changes made by the migration (assuming that you added the appropriate code for `down` in the migration).
@@ -247,27 +308,11 @@ $ cargo loco generate model movies long_title:string added_by:references:users d
 * reference added_by is in singular, the referenced model is a model and is plural: `added_by:references:users`
 * column name in snake case: `long_title:string`
 
-### Naming migrations
-
-There are no rules for how to name migrations, but here's a few guidelines to keep your migration stack readable as a list of files:
-
-* `<table>` - create a table, plural, `movies`
-* `add_<table>_<field>` - add a column, `add_users_email`
-* `index_<table>_<field>` - add an index, `index_users_email`
-* `alter_` - change a schema, `alter_users`
-* `delete_<table>_<field>` - remove a column, `delete_users_email`
-* `data_fix_` - fix some data, using entity queries or raw SQL, `data_fix_users_timezone_issue_315`
 
-Example:
-
-```sh
-$ cargo loco generate migration add_users_email
-```
 
+### Migration Definition
 
-### Add or remove a column
-
-Adding a column:
+**Add a column**
 
 ```rust
   manager
@@ -280,7 +325,7 @@ Adding a column:
     .await
 ```
 
-Dropping a column:
+**Drop a column**
 
 ```rust
   manager
@@ -293,8 +338,7 @@ Dropping a column:
     .await
 ```
 
-### Add index
-
+**Add index**
 
 You can copy some of this code for adding an index
 
@@ -310,8 +354,7 @@ You can copy some of this code for adding an index
     .await;
 ```
 
-### Create a data fix
-
+**Create a data fix**
 
 Creating a data fix in a migration is easy - just use SQL statements as you like: