add jsonschema_is_valid function and its tests

README.md

@@ -18,20 +18,26 @@
 
 
 ## API
-Two SQL functions:
+Three SQL functions:
 - json_matches_schema
 - jsonb_matches_schema (note the **jsonb** in front)
+- jsonschema_is_valid
 
 With the following signatures
 ```sql
 -- Validates a json *instance* against a *schema*
 json_matches_schema(schema json, instance json) returns bool
 ```
-and 
+and
 ```sql
 -- Validates a jsonb *instance* against a *schema*
 jsonb_matches_schema(schema json, instance jsonb) returns bool
 ```
+and
+```sql
+-- Validates whether a json *schema* is valid
+jsonschema_is_valid(schema json) returns bool
+```
 
 ## Usage
 Those functions can be used to constrain `json` and `jsonb` columns to conform to a schema.

src/lib.rs

@@ -12,6 +12,23 @@ fn jsonb_matches_schema(schema: Json, instance: JsonB) -> bool {
     jsonschema::is_valid(&schema.0, &instance.0)
 }
 
+#[pg_extern(immutable, strict)]
+fn jsonschema_is_valid(schema: Json) -> bool {
+    match jsonschema::JSONSchema::compile(&schema.0) {
+        Ok(_) => true,
+        Err(e) => {
+            // Only call notice! for a non empty instance_path
+            if e.instance_path.last().is_some() {
+                notice!(
+                    "Invalid JSON schema at path: {}",
+                    e.instance_path.to_string()
+                );
+            }
+            false
+        }
+    }
+}
+
 #[pg_schema]
 #[cfg(any(test, feature = "pg_test"))]
 mod tests {
@@ -101,6 +118,20 @@ mod tests {
         .unwrap();
         assert!(!result);
     }
+
+    #[pg_test]
+    fn test_jsonschema_is_valid() {
+        assert!(crate::jsonschema_is_valid(Json(json!({
+            "type": "object"
+        }))));
+    }
+
+    #[pg_test]
+    fn test_jsonschema_is_not_valid() {
+        assert!(!crate::jsonschema_is_valid(Json(json!({
+            "type": "obj"
+        }))));
+    }
 }
 
 #[cfg(test)]