From 03866db9b34b08a9808fc8f4ac87ba0de9cfec6f Mon Sep 17 00:00:00 2001
From: Yaroslav Bolyukin <iam@lach.pw>
Date: Tue, 16 Aug 2022 12:18:25 +0000
Subject: [PATCH] doc(struct-versioning): explain semantics by example


---
--- /dev/null
+++ b/crates/struct-versioning/README.md
@@ -0,0 +1,62 @@
+# struct-versioning
+
+The crate contains procedural macros for versioning data structures.
+Macros [`versioned`] generate versioned variants of a struct.
+
+Example:
+```
+# use struct_versioning::versioned;
+#[versioned(version = 5, first_version = 2)]
+struct Example {}
+
+// versioned macro will generate suffixed versions of example struct,
+// starting from `Version{first_version or 1}` to `Version{version}` inclusive
+let _ver2 = ExampleVersion2 {};
+let _ver3 = ExampleVersion3 {};
+let _ver4 = ExampleVersion4 {};
+let _ver5 = ExampleVersion5 {};
+
+// last version will also be aliased with original struct name
+let _orig: Example = ExampleVersion5 {};
+
+#[versioned(version = 2, upper)]
+#[derive(PartialEq, Debug)]
+struct Upper {
+    #[version(..2)]
+    removed: u32,
+    #[version(2.., upper(10))]
+    added: u32,
+
+    #[version(..2)]
+    retyped: u32,
+    #[version(2.., upper(retyped as u64))]
+    retyped: u64,
+}
+
+// #[version] attribute on field allows to specify, in which versions of structs this field should present
+// versions here works as standard rust ranges, start is inclusive, end is exclusive
+let _up1 = UpperVersion1 {removed: 1, retyped: 0};
+let _up2 = UpperVersion2 {added: 1, retyped: 0};
+
+// and upper() allows to specify, which value should be assigned to this field in `From<OldVersion>` impl
+assert_eq!(
+    UpperVersion2::from(UpperVersion1 {removed: 0, retyped: 6}),
+    UpperVersion2 {added: 10, retyped: 6},
+);
+```
+
+In this case, the upgrade is described in `on_runtime_upgrade` using the `translate_values` substrate feature
+
+```ignore
+#[pallet::hooks]
+impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {
+    fn on_runtime_upgrade() -> Weight {
+        if StorageVersion::get::<Pallet<T>>() < StorageVersion::new(1) {
+            <TokenData<T>>::translate_values::<ItemDataVersion1, _>(|v| {
+                Some(<ItemDataVersion2>::from(v))
+            })
+        }
+        0
+    }
+}
+```
--- a/crates/struct-versioning/src/lib.rs
+++ b/crates/struct-versioning/src/lib.rs
@@ -14,42 +14,8 @@
 // You should have received a copy of the GNU General Public License
 // along with Unique Network. If not, see <http://www.gnu.org/licenses/>.
 
-//! struct-versioning
-//! The crate contains procedural macros for versioning data structures.
-//! Macros `versioned` generate versioned variants of a struct.
-//!
-//! Example:
-//! #[struct_versioning::versioned(version = 2, upper)]
-//! ...
-//! pub struct ItemData {
-//! 	pub const_data: BoundedVec<u8, CustomDataLimit>,
-//!
-//! 	#[version(..2)]
-//! 	pub variable_data: BoundedVec<u8, CustomDataLimit>,
-//! }
-//! ...
-//! `#[version(..2)]` that means that any version before 2 will be upgraded to 2 via the `upper` function.
-//! When version become 3 `#[struct_versioning::versioned(version = 3, upper)]` this field will be removed.
-//! *upper* - generate From impls, which converts old version of structs to new
-//! In this case, the upgrade is described in `on_runtime_upgrade` using the `translate_values` substrate feature
-//!
-//! #[pallet::hooks]
-//! impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {
-//! 	fn on_runtime_upgrade() -> Weight {
-//! 		if StorageVersion::get::<Pallet<T>>() < StorageVersion::new(1) {
-//! 			<TokenData<T>>::translate_values::<ItemDataVersion1, _>(|v| {
-//! 				Some(<ItemDataVersion2>::from(v))
-//! 			})
-//! 		}
-//! 		0
-//! 	}
-//! }
-//!
-//! Another functionality
-///
-/// `#[versioned(version = 1[, first_version = 1][, upper][, versions])]`
-/// - *first_version* - allows to skip generation of structs, which predates first supported version
-/// - *versions* - generate enum, which contains all possible versions of struct
+#![doc = include_str!("../README.md")]
+
 use proc_macro::TokenStream;
 use quote::format_ident;
 use syn::{

-- 
gitstuff