Unique args: Handle embedded field that is *not* a struct (#1088)

Aims to fix #1087.

One thing I hadn't accounted for is that it's actually possible to have
an embedded type that's *not* a struct. e.g.

    type MyStruct struct {
        string // embedded non-struct
    }

The simplified example above is *not* because we short circuit unless
properties are exported (and `string` is not exported because it starts
with a lower case letter), but if we have a similar case with a custom
type (e.g. `type MyString string`) then we can reproduce the error
described in #1087.

Fix the problem by making sure to check that a field is really a struct
before recursing back into `getSortedUniqueFields`. We're able to
simplify the function somewhat by handling all structs (anonymous or
not) in one spot since the logic is so similar.

Fixes #1087.

Author: brandur

CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Unique args: Handle embedded fields that are not structs. [PR #1088](https://github.com/riverqueue/river/pull/1088).
+
 ## [0.27.0] - 2025-11-14
 
 ### Added

internal/dbunique/db_unique_test.go

@@ -200,6 +200,22 @@ func TestUniqueKey(t *testing.T) {
 			uniqueOpts:   UniqueOpts{ByArgs: true},
 			expectedJSON: `&kind=worker_1&args={"recipient":"john@example.com","subject":"Another Test Email"}`,
 		},
+		{
+			name: "ByArgsWithEmbeddedNonStruct",
+			argsFunc: func() rivertype.JobArgs {
+				type MyString string
+				type TaskJobArgs struct {
+					JobArgsStaticKind
+					MyString // anonymous non-struct field; needs to be a custom type because it has to be capitalized to be exported
+				}
+				return TaskJobArgs{
+					JobArgsStaticKind: JobArgsStaticKind{kind: "worker_7"},
+					MyString:          "my_string_in_anonymous_field",
+				}
+			},
+			uniqueOpts:   UniqueOpts{ByArgs: true},
+			expectedJSON: `&kind=worker_7&args={"MyString":"my_string_in_anonymous_field"}`,
+		},
 		{
 			name: "ByArgsWithSubstructTagged",
 			argsFunc: func() rivertype.JobArgs {

internal/dbunique/unique_fields.go

@@ -63,16 +63,6 @@ func getSortedUniqueFields(typ reflect.Type, path []string) ([]string, error) {
 			continue
 		}
 
-		if field.Anonymous {
-			uniqueSubFields, err := getSortedUniqueFields(field.Type, path)
-			if err != nil {
-				return nil, err
-			}
-			uniqueFields = append(uniqueFields, uniqueSubFields...)
-
-			continue
-		}
-
 		var uniqueName string
 		{
 			// Get the corresponding JSON key
@@ -98,11 +88,20 @@ func getSortedUniqueFields(typ reflect.Type, path []string) ([]string, error) {
 			}
 		}
 
-		if field.Type.Kind() == reflect.Struct || field.Type.Kind() == reflect.Ptr && field.Type.Elem().Kind() == reflect.Struct {
-			uniqueSubFields, err := getSortedUniqueFields(field.Type, append(path, uniqueName))
+		if typeStructOrPointerToStruct(field.Type) {
+			// Append the JSON to the path (all path segments sent down
+			// recursively) unless we're looking at an anonymous struct, whose
+			// fields will be let at the top level.
+			fullPath := path
+			if !field.Anonymous {
+				fullPath = append(path, uniqueName) //nolint:gocritic
+			}
+
+			uniqueSubFields, err := getSortedUniqueFields(field.Type, fullPath)
 			if err != nil {
 				return nil, err
 			}
+
 			if len(uniqueSubFields) > 0 {
 				uniqueFields = append(uniqueFields, uniqueSubFields...)
 			} else if hasUniqueTag {
@@ -163,3 +162,15 @@ func parseJSONTag(tag string) string {
 	}
 	return tag
 }
+
+func typeStructOrPointerToStruct(typ reflect.Type) bool {
+	if typ.Kind() == reflect.Struct {
+		return true
+	}
+
+	if typ.Kind() == reflect.Ptr && typ.Elem().Kind() == reflect.Struct {
+		return true
+	}
+
+	return false
+}