handle empty enum values (#842)

Author: ahl

typify-impl/src/convert.rs

@@ -942,10 +942,7 @@ impl TypeSpace {
             if has_null {
                 self.convert_null(metadata)
             } else {
-                Err(Error::InvalidSchema {
-                    type_name: type_name.into_option(),
-                    reason: "empty enum array".to_string(),
-                })
+                self.convert_never(type_name, original_schema)
             }
         } else {
             let mut ty = TypeEntryEnum::from_metadata(
@@ -1948,9 +1945,12 @@ impl TypeSpace {
         metadata: &'a Option<Box<Metadata>>,
         enum_values: &[serde_json::Value],
     ) -> Result<(TypeEntry, &'a Option<Box<Metadata>>)> {
+        if enum_values.is_empty() {
+            return self.convert_never(type_name, original_schema);
+        }
+
         // We're here because the schema didn't have a type; that's a bummer,
         // but we'll do our best to roll with the punches.
-        assert!(!enum_values.is_empty());
 
         // Let's hope all these values are the same type.
         let mut instance_types = enum_values
@@ -1976,10 +1976,14 @@ impl TypeSpace {
                 .cloned()
                 .collect::<Vec<_>>();
 
-            let (type_entry, metadata) =
-                self.convert_unknown_enum(type_name, original_schema, metadata, &enum_values)?;
-            let type_entry = self.type_to_option(type_entry);
-            Ok((type_entry, metadata))
+            if enum_values.is_empty() {
+                self.convert_null(metadata)
+            } else {
+                let (type_entry, metadata) =
+                    self.convert_unknown_enum(type_name, original_schema, metadata, &enum_values)?;
+                let type_entry = self.type_to_option(type_entry);
+                Ok((type_entry, metadata))
+            }
         } else {
             match (instance_types.len(), instance_types.iter().next()) {
                 (1, Some(InstanceType::String)) => self.convert_enum_string(

typify/tests/schemas/various-enums.json

@@ -166,6 +166,13 @@
     "NeverEver": {
       "not": true
     },
+    "AnyOfNothing": {
+      "enum": []
+    },
+    "AnyOfNoStrings": {
+      "type": "string",
+      "enum": []
+    },
     "ShouldBeExclusive": {
       "type": "object",
       "properties": {

typify/tests/schemas/various-enums.rs

@@ -110,6 +110,65 @@ impl ::std::default::Default for AlternativeEnum {
         AlternativeEnum::Choice2
     }
 }
+#[doc = "`AnyOfNoStrings`"]
+#[doc = r""]
+#[doc = r" <details><summary>JSON schema</summary>"]
+#[doc = r""]
+#[doc = r" ```json"]
+#[doc = "{"]
+#[doc = "  \"type\": \"string\","]
+#[doc = "  \"enum\": []"]
+#[doc = "}"]
+#[doc = r" ```"]
+#[doc = r" </details>"]
+#[derive(
+    :: serde :: Deserialize,
+    :: serde :: Serialize,
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    Hash,
+    Ord,
+    PartialEq,
+    PartialOrd,
+)]
+#[serde(deny_unknown_fields)]
+pub enum AnyOfNoStrings {}
+impl ::std::convert::From<&Self> for AnyOfNoStrings {
+    fn from(value: &AnyOfNoStrings) -> Self {
+        value.clone()
+    }
+}
+#[doc = "`AnyOfNothing`"]
+#[doc = r""]
+#[doc = r" <details><summary>JSON schema</summary>"]
+#[doc = r""]
+#[doc = r" ```json"]
+#[doc = "{"]
+#[doc = "  \"enum\": []"]
+#[doc = "}"]
+#[doc = r" ```"]
+#[doc = r" </details>"]
+#[derive(
+    :: serde :: Deserialize,
+    :: serde :: Serialize,
+    Clone,
+    Copy,
+    Debug,
+    Eq,
+    Hash,
+    Ord,
+    PartialEq,
+    PartialOrd,
+)]
+#[serde(deny_unknown_fields)]
+pub enum AnyOfNothing {}
+impl ::std::convert::From<&Self> for AnyOfNothing {
+    fn from(value: &AnyOfNothing) -> Self {
+        value.clone()
+    }
+}
 #[doc = "`CommentedVariants`"]
 #[doc = r""]
 #[doc = r" <details><summary>JSON schema</summary>"]