feat: support custom ids and $defs from draft 2020-12

src/diff_walker.rs

@@ -7,20 +7,27 @@ use schemars::schema::{
 };
 use serde_json::Value;
 
+use crate::resolver::Resolver;
 use crate::{Change, ChangeKind, Error, JsonSchemaType, Range};
 
 pub struct DiffWalker<F: FnMut(Change)> {
     pub cb: F,
     pub lhs_root: RootSchema,
     pub rhs_root: RootSchema,
+    lhs_resolver: Resolver,
+    rhs_resolver: Resolver,
 }
 
 impl<F: FnMut(Change)> DiffWalker<F> {
     pub fn new(cb: F, lhs_root: RootSchema, rhs_root: RootSchema) -> Self {
+        let lhs_resolver = Resolver::for_schema(&lhs_root);
+        let rhs_resolver = Resolver::for_schema(&rhs_root);
         Self {
             cb,
             lhs_root,
             rhs_root,
+            lhs_resolver,
+            rhs_resolver,
         }
     }
 
@@ -143,7 +150,7 @@ impl<F: FnMut(Change)> DiffWalker<F> {
             .object()
             .additional_properties
             .as_ref()
-            .map_or(true, |x| x.clone().into_object().is_true());
+            .is_none_or(|x| x.clone().into_object().is_true());
 
         for removed in lhs_props.difference(&rhs_props) {
             (self.cb)(Change {
@@ -349,28 +356,19 @@ impl<F: FnMut(Change)> DiffWalker<F> {
         Ok(())
     }
 
-    fn resolve_ref<'a>(root_schema: &'a RootSchema, reference: &str) -> Option<&'a Schema> {
-        if let Some(definition_name) = reference.strip_prefix("#/definitions/") {
-            let schema_object = root_schema.definitions.get(definition_name)?;
-            Some(schema_object)
-        } else {
-            None
-        }
-    }
-
     fn resolve_references(
-        &mut self,
+        &self,
         lhs: &mut SchemaObject,
         rhs: &mut SchemaObject,
     ) -> Result<(), Error> {
         if let Some(ref reference) = lhs.reference {
-            if let Some(lhs_inner) = Self::resolve_ref(&self.lhs_root, reference) {
+            if let Some(lhs_inner) = self.lhs_resolver.resolve(&self.lhs_root, reference) {
                 *lhs = lhs_inner.clone().into_object();
             }
         }
 
         if let Some(ref reference) = rhs.reference {
-            if let Some(rhs_inner) = Self::resolve_ref(&self.rhs_root, reference) {
+            if let Some(rhs_inner) = self.rhs_resolver.resolve(&self.rhs_root, reference) {
                 *rhs = rhs_inner.clone().into_object();
             }
         }
@@ -540,7 +538,7 @@ impl JsonSchemaExt for SchemaObject {
             .subschemas()
             .not
             .as_ref()
-            .map_or(false, |x| x.clone().into_object().is_true())
+            .is_some_and(|x| x.clone().into_object().is_true())
         {
             InternalJsonSchemaType::Never
         } else {

src/lib.rs

@@ -6,6 +6,7 @@ use serde_json::Value;
 use thiserror::Error;
 
 mod diff_walker;
+mod resolver;
 mod types;
 
 pub use types::*;

src/resolver.rs

@@ -0,0 +1,147 @@
+use std::collections::BTreeMap;
+
+use schemars::schema::{RootSchema, Schema, SchemaObject};
+
+pub struct Resolver {
+    ref_lookup: BTreeMap<String, String>,
+}
+
+impl Resolver {
+    pub fn for_schema(root: &RootSchema) -> Self {
+        let mut ref_lookup = BTreeMap::new();
+
+        for (key, schema) in &root.definitions {
+            if let Some(id) = schema.get_schema_id() {
+                ref_lookup.insert(id.to_owned(), key.clone());
+            }
+
+            if let Some(root_id) = root.schema.get_schema_id() {
+                ref_lookup.insert(format!("{root_id}#/definitions/{key}"), key.clone());
+                ref_lookup.insert(format!("{root_id}#/$defs/{key}"), key.clone());
+            }
+
+            ref_lookup.insert(format!("#/definitions/{key}"), key.clone());
+            ref_lookup.insert(format!("#/$defs/{key}"), key.clone());
+        }
+
+        Self { ref_lookup }
+    }
+
+    /// Resolves a reference.
+    ///
+    /// `root` must be the same schema that was used to construct the resolver.
+    /// This is not checked.
+    pub fn resolve<'a>(&self, root: &'a RootSchema, reference: &str) -> Option<&'a Schema> {
+        let key = self.ref_lookup.get(reference)?;
+        root.definitions.get(key)
+    }
+}
+
+trait MayHaveSchemaId {
+    fn get_schema_id(&self) -> Option<&str>;
+}
+
+impl MayHaveSchemaId for SchemaObject {
+    fn get_schema_id(&self) -> Option<&str> {
+        self.metadata
+            .as_ref()
+            .and_then(|m| m.id.as_ref())
+            .map(|id| id.as_str())
+    }
+}
+
+impl MayHaveSchemaId for Schema {
+    fn get_schema_id(&self) -> Option<&str> {
+        match self {
+            Schema::Object(schema_obj) => schema_obj.get_schema_id(),
+            Schema::Bool(_) => None,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn draft7_definitions() {
+        let root: RootSchema = serde_json::from_str(
+            r#"{
+                "definitions": {
+                    "A": {}
+                }
+            }"#,
+        )
+        .unwrap();
+        let resolver = Resolver::for_schema(&root);
+
+        let resolved = resolver.resolve(&root, "#/definitions/A");
+        assert!(resolved.is_some());
+
+        let resolved = resolver.resolve(&root, "#/definitions/not-there");
+        assert!(resolved.is_none());
+    }
+
+    #[test]
+    fn draft7_root_has_id() {
+        let root: RootSchema = serde_json::from_str(
+            r#"{
+                "$id": "urn:uuid:e773a2e8-d746-4dc6-9480-0bba5ff33504",
+                "definitions": {
+                    "A": {}
+                }
+            }"#,
+        )
+        .unwrap();
+        let resolver = Resolver::for_schema(&root);
+
+        let resolved = resolver.resolve(&root, "#/definitions/A");
+        assert!(resolved.is_some());
+        let resolved = resolver.resolve(
+            &root,
+            "urn:uuid:e773a2e8-d746-4dc6-9480-0bba5ff33504#/definitions/A",
+        );
+        assert!(resolved.is_some());
+    }
+
+    #[test]
+    fn draft7_definition_has_id() {
+        let root: RootSchema = serde_json::from_str(
+            r#"{
+                "definitions": {
+                    "A": {
+                        "$id": "some-id"
+                    }
+                }
+            }"#,
+        )
+        .unwrap();
+        let resolver = Resolver::for_schema(&root);
+
+        let resolved = resolver.resolve(&root, "some-id");
+        assert!(resolved.is_some());
+        assert_eq!(resolved, resolver.resolve(&root, "#/definitions/A"))
+    }
+
+    #[test]
+    fn draft2020_12_defs() {
+        let root: RootSchema = serde_json::from_str(
+            r#"{
+                "$defs": {
+                    "A": {
+                        "$id": "some-id"
+                    }
+                }
+            }"#,
+        )
+        .unwrap();
+        let resolver = Resolver::for_schema(&root);
+
+        let resolved = resolver.resolve(&root, "#/$defs/A");
+        assert!(resolved.is_some());
+        assert_eq!(resolved, resolver.resolve(&root, "some-id"));
+
+        let resolved = resolver.resolve(&root, "#/$defs/not-there");
+        assert!(resolved.is_none());
+    }
+}