From 2e0e037e6bd339d9ba715c191013689f815fffd1 Mon Sep 17 00:00:00 2001
From: Russell Cohen <rcoh@amazon.com>
Date: Fri, 15 Mar 2024 17:52:40 -0400
Subject: [PATCH] Fix issue where an empty union was treated as 'None'

---
 build.gradle.kts                                     |  5 ++++-
 buildSrc/build.gradle.kts                            |  1 -
 .../smithy/protocols/parse/JsonParserGenerator.kt    | 12 +++++++++++-
 .../protocols/parse/JsonParserGeneratorTest.kt       |  9 +++++++++
 gradle.properties                                    |  1 +
 5 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/build.gradle.kts b/build.gradle.kts
index 6853712902..20f2d9e400 100644
--- a/build.gradle.kts
+++ b/build.gradle.kts
@@ -15,8 +15,11 @@ buildscript {
 }
 
 allprojects {
+    val allowLocalDeps: String by project
     repositories {
-        mavenLocal()
+        if (allowLocalDeps.toBoolean()) {
+         mavenLocal()
+        }
         mavenCentral()
         google()
     }
diff --git a/buildSrc/build.gradle.kts b/buildSrc/build.gradle.kts
index 104ba2680d..c032bfc8f8 100644
--- a/buildSrc/build.gradle.kts
+++ b/buildSrc/build.gradle.kts
@@ -12,7 +12,6 @@ plugins {
 repositories {
     mavenCentral()
     google()
-    mavenLocal()
 }
 
 // Load properties manually to avoid hard coding smithy version
diff --git a/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/parse/JsonParserGenerator.kt b/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/parse/JsonParserGenerator.kt
index 36b0286e13..4a8b8a1054 100644
--- a/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/parse/JsonParserGenerator.kt
+++ b/codegen-core/src/main/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/parse/JsonParserGenerator.kt
@@ -565,7 +565,7 @@ class JsonParserGenerator(
                                 rustTemplate(
                                     """
                                     if let #{Some}(#{Ok}(#{Token}::ValueNull { .. })) = tokens.peek() {
-                                        #{skip_value}(tokens)?;
+                                        let _ = tokens.next().expect("peek returned a token")?;
                                         continue;
                                     }
                                     """,
@@ -633,6 +633,16 @@ class JsonParserGenerator(
                             *codegenScope,
                         )
                     }
+                    // If we've gotten to the point where the union had a `{ ... }` section, we can't return None
+                    // anymore. If we didn't parse a union at this point, this is an error.
+                    rustTemplate(
+                        """
+                        if variant.is_none() {
+                            return Err(#{Error}::custom("Union did not contain a valid variant."))
+                        }
+                        """,
+                        *codegenScope,
+                    )
                     rust("Ok(variant)")
                 }
             }
diff --git a/codegen-core/src/test/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/parse/JsonParserGeneratorTest.kt b/codegen-core/src/test/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/parse/JsonParserGeneratorTest.kt
index dabc155b75..8e7985a27a 100644
--- a/codegen-core/src/test/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/parse/JsonParserGeneratorTest.kt
+++ b/codegen-core/src/test/kotlin/software/amazon/smithy/rust/codegen/core/smithy/protocols/parse/JsonParserGeneratorTest.kt
@@ -194,6 +194,15 @@ class JsonParserGeneratorTest {
                 """,
             )
 
+            unitTest(
+                "all_variants_null",
+                """
+                // __type field should be ignored during deserialization
+                let input = br#"{ "top": { "choice": { "blob": null, "boolean": null, "int": null, "long": null, "__type": "value-should-be-ignored-anyway" } } }"#;
+                let _err = ${format(operationGenerator)}(input, test_output::OpOutput::builder()).expect_err("invalid union");
+                """,
+            )
+
             unitTest(
                 "empty_error",
                 """
diff --git a/gradle.properties b/gradle.properties
index d5e5184bdb..e198984afd 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -22,6 +22,7 @@ kotlin.code.style=official
 # codegen
 smithyGradlePluginVersion=0.9.0
 smithyVersion=1.45.0
+allowLocalDeps=false
 
 # kotlin
 kotlinVersion=1.9.20