From 8896d740a44ef46a3bad8cbfccedb87ea8e7b0d3 Mon Sep 17 00:00:00 2001
From: John Starks <jostarks@microsoft.com>
Date: Wed, 22 Feb 2023 13:01:41 -0800
Subject: [PATCH] fix: use correct Rust variant name for enum aliases

This change fixes code generation of protobuf enums when aliases are
present.
---
 pbjson-build/src/generator/enumeration.rs | 11 +++++++++--
 pbjson-test/build.rs                      |  1 +
 pbjson-test/protos/enum_alias.proto       | 12 ++++++++++++
 pbjson-test/src/lib.rs                    |  5 +++++
 4 files changed, 27 insertions(+), 2 deletions(-)
 create mode 100644 pbjson-test/protos/enum_alias.proto

diff --git a/pbjson-build/src/generator/enumeration.rs b/pbjson-build/src/generator/enumeration.rs
index 05850af..6aa3105 100644
--- a/pbjson-build/src/generator/enumeration.rs
+++ b/pbjson-build/src/generator/enumeration.rs
@@ -11,6 +11,7 @@ use super::{
 use crate::descriptor::{EnumDescriptor, TypePath};
 use crate::generator::write_fields_array;
 use crate::resolver::Resolver;
+use std::collections::HashMap;
 use std::io::{Result, Write};
 
 pub fn generate_enum<W: Write>(
@@ -22,19 +23,25 @@ pub fn generate_enum<W: Write>(
 ) -> Result<()> {
     let rust_type = resolver.rust_type(path);
 
+    let mut rust_variants = HashMap::new();
     let variants: Vec<_> = descriptor
         .values
         .iter()
         .map(|variant| {
             let variant_name = variant.name.clone().unwrap();
             let variant_number = variant.number();
-            let rust_variant = resolver.rust_variant(path, &variant_name);
-            (variant_name, variant_number, rust_variant)
+            let rust_variant = rust_variants
+                .entry(variant_number)
+                .or_insert_with(|| resolver.rust_variant(path, &variant_name));
+            (variant_name, variant_number, rust_variant.clone())
         })
         .collect();
 
     // Generate Serialize
     write_serialize_start(0, &rust_type, writer)?;
+    // There will be duplicates in the presense of aliases. Let rustc deal with
+    // this.
+    writeln!(writer, "{}#[allow(unreachable_patterns)]", Indent(2))?;
     if use_integers_for_enums {
         writeln!(writer, "{}let variant = match self {{", Indent(2))?;
         for (_, variant_number, rust_variant) in &variants {
diff --git a/pbjson-test/build.rs b/pbjson-test/build.rs
index 02bd410..af66627 100644
--- a/pbjson-test/build.rs
+++ b/pbjson-test/build.rs
@@ -14,6 +14,7 @@ fn main() -> Result<()> {
         root.join("common.proto"),
         root.join("duplicate_name.proto"),
         root.join("escape.proto"),
+        root.join("enum_alias.proto"),
     ];
 
     // Tell cargo to recompile if any of these proto files are changed
diff --git a/pbjson-test/protos/enum_alias.proto b/pbjson-test/protos/enum_alias.proto
new file mode 100644
index 0000000..c857259
--- /dev/null
+++ b/pbjson-test/protos/enum_alias.proto
@@ -0,0 +1,12 @@
+syntax = "proto3";
+package test.enum_alias;
+
+enum Enum {
+    option allow_alias = true;
+    VALUE = 0;
+    OTHER = 1;
+    TWO = 2;
+    DOS = 2;
+    value = 0;
+    alias = 0;
+}
diff --git a/pbjson-test/src/lib.rs b/pbjson-test/src/lib.rs
index a2f604a..0b0fcf8 100644
--- a/pbjson-test/src/lib.rs
+++ b/pbjson-test/src/lib.rs
@@ -49,6 +49,11 @@ pub mod test {
             "/test.r#abstract.r#type.escape.serde.rs"
         ));
     }
+
+    pub mod enum_alias {
+        include!(concat!(env!("OUT_DIR"), "/test.enum_alias.rs"));
+        include!(concat!(env!("OUT_DIR"), "/test.enum_alias.serde.rs"));
+    }
 }
 
 #[cfg(test)]