Fix validate's checking of non-root definitions

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "jtd"
-version = "0.2.0"
+version = "0.2.1"
 description = "A Rust implementation of JSON Type Definition"
 authors = ["JSON Type Definition Contributors"]
 edition = "2018"

src/schema.rs

@@ -110,10 +110,25 @@ impl Schema {
     }
 
     fn validate_with_root(&self, root: Option<&Self>) -> Result<(), ValidateError> {
-        if root.is_none() && !self.definitions.is_empty() {
+        // If root is non-None, then self is not the root schema. We should
+        // therefore not tolerate definitions being placed on this schema.
+        if root.is_some() && !self.definitions.is_empty() {
             return Err(ValidateError::NonRootDefinitions);
         }
 
+        // This root variable is the one we will use for recursive calls to
+        // validate_with_root.
+        //
+        // If we are at the top-level call of validate_with_root (invoked by the
+        // public validate method) wherein root is None, then root will be
+        // Some(self) for the recursive calls, since we ourselves are the root.
+        let root = root.or(Some(self));
+
+        // Validate each definition, if any.
+        for sub_schema in self.definitions.values() {
+            sub_schema.validate_with_root(root)?;
+        }
+
         match &self.form {
             form::Form::Empty | form::Form::Type(_) => {}
             form::Form::Enum(form::Enum { values, .. }) => {
@@ -122,7 +137,9 @@ impl Schema {
                 }
             }
             form::Form::Ref(form::Ref { definition, .. }) => {
-                if !root.unwrap_or(&self).definitions.contains_key(definition) {
+                // This unwrap is safe because the assignment to root above
+                // guarantees root will be non-None.
+                if !root.unwrap().definitions.contains_key(definition) {
                     return Err(ValidateError::NoSuchDefinition(definition.clone()));
                 }
             }

src/validator.rs

@@ -403,11 +403,13 @@ mod tests {
                 .unwrap();
 
         for (name, test_case) in test_cases {
-            let schema = test_case
+            let schema: Schema = test_case
                 .schema
                 .try_into()
                 .expect(&format!("parsing schema: {}", name));
 
+            schema.validate().expect(&format!("validating schema: {}", name));
+
             let validator = Validator {
                 max_depth: None,
                 max_errors: None,