throw an error on non-nullable schema receiving null input

index.js

@@ -560,10 +560,24 @@ function buildObject (context, location) {
   let functionCode = `
   `
 
+  let checkNullableCode = `
+  `
+  const nullable = schema.nullable === true
+  if (!nullable) {
+    // use schemaRef in the hope there's anything useful for which schema is detecting the issue
+    checkNullableCode += `
+    if (obj === null) {
+      throw new Error('schema: ${schemaRef} is not nullable, received null input!')
+    }
+    `
+  }
+
   functionCode += `
     // ${schemaRef}
     function ${functionName} (input) {
       const obj = ${toJSON('input')}
+      ${checkNullableCode}
+
       ${buildInnerObject(context, location)}
     }
   `

test/basic.test.js

@@ -376,6 +376,32 @@ test('render a double quote as JSON /2', (t) => {
   t.ok(validate(JSON.parse(output)), 'valid schema')
 })
 
+test('should error on non-nullable', t => {
+  t.plan(1)
+  const schema = {
+    title: 'non-nullable schema error',
+    type: 'object',
+    properties: {
+      firstName: {
+        type: 'string'
+      },
+      lastName: {
+        type: 'string'
+      }
+    },
+    required: ['firstName', 'lastName']
+  }
+
+  try {
+    const stringify = build(schema)
+    stringify(null)
+    t.fail('stringify should throw for null doc validated on non-nullable schema')
+  } catch (err) {
+    const message = err.message
+    t.equal(message, 'schema: # is not nullable, received null input!')
+  }
+})
+
 test('render a long string', (t) => {
   t.plan(2)