[THRIFT-5314][THRIFT-4101] Generate enums that don't error on unexpected values (#2337)

Client: rs

2 files changed, 50 insertions, 3 deletions

diff --git a/lib/rs/README.md b/lib/rs/README.md
index 555d219d2..1e10e35e3 100644
--- a/lib/rs/README.md
+++ b/lib/rs/README.md
@@ -46,6 +46,51 @@ It does not currently use any Rust 2018 features.
 
 Breaking changes are minimized. When they are made they will be outlined below with transition guidelines.
 
+##### Thrift 0.15.0
+
+* **[THRIFT-5314]** - Generate enums implementations that are forward compatible (i.e. don't error on unknown values)
+
+  As a result of this change the Rust representation of an enum changes from a standard
+  Rust enum into a newtype struct with associated constants.
+  
+  For example:
+
+  ```thrift
+    // THRIFT
+    enum Operation {
+      ADD,
+      SUBTRACT,
+      MULTIPLY,
+      DIVIDE,
+    }
+  ```
+
+  used to generate:
+  
+  ```rust
+    // OLD AUTO-GENERATED RUST
+    pub enum Operation {
+       Add,
+       Subtract,
+       Multiply,
+       Divide,
+     }
+  ```
+
+  It *now* generates:
+  
+  ```rust
+    // NEW AUTO-GENERATED RUST
+    pub struct Operation(pub i32);
+  
+    impl Operation {
+      pub const ADD: Operation = Operation(0);
+      pub const SUBTRACT: Operation = Operation(1);
+      pub const MULTIPLY: Operation = Operation(2);
+      pub const DIVIDE: Operation = Operation(3);
+    }
+  ```
+
 ##### Thrift 0.14.0
 
 * **[THRIFT-5158]** - Rust library and generator now support Rust 2018 only. Required rust 1.40.0 or higher
@@ -91,7 +136,9 @@ Breaking changes are minimized. When they are made they will be outlined below w
        DIVIDE,
      }
     ```
+  
     It *now* generates:
+  
     ```rust
     // NEW AUTO-GENERATED RUST
     pub enum Operation {
diff --git a/lib/rs/test/src/bin/kitchen_sink_server.rs b/lib/rs/test/src/bin/kitchen_sink_server.rs
index 6df39e4bc..8b910b3bf 100644
--- a/lib/rs/test/src/bin/kitchen_sink_server.rs
+++ b/lib/rs/test/src/bin/kitchen_sink_server.rs
@@ -209,12 +209,12 @@ struct FullHandler;
 impl FullMealAndDrinksServiceSyncHandler for FullHandler {
     fn handle_full_meal_and_drinks(&self) -> thrift::Result<FullMealAndDrinks> {
         println!("full_meal_and_drinks: handling full meal and drinks call");
-        Ok(FullMealAndDrinks::new(full_meal(), Drink::CanadianWhisky))
+        Ok(FullMealAndDrinks::new(full_meal(), Drink::CANADIAN_WHISKY))
     }
 
     fn handle_best_pie(&self) -> thrift::Result<Pie> {
         println!("full_meal_and_drinks: handling pie call");
-        Ok(Pie::MississippiMud) // I prefer Pie::Pumpkin, but I have to check that casing works
+        Ok(Pie::MISSISSIPPI_MUD) // I prefer Pie::Pumpkin, but I have to check that casing works
     }
 }
 
@@ -259,7 +259,7 @@ fn noodle() -> Noodle {
 }
 
 fn ramen() -> Ramen {
-    Ramen::new("Mr Ramen".to_owned(), 72, BrothType::Miso)
+    Ramen::new("Mr Ramen".to_owned(), 72, BrothType::MISO)
 }
 
 fn napkin() -> Napkin {