fix side effect on items $ref (#302)

Author: Eomm

index.js

@@ -957,7 +957,7 @@ function buildObject (location, code, name) {
 }
 
 function buildArray (location, code, name, key = null) {
-  const schema = location.schema
+  let schema = location.schema
   code += `
     function ${name} (obj) {
   `
@@ -979,6 +979,10 @@ function buildArray (location, code, name, key = null) {
   }
 
   if (schema.items.$ref) {
+    if (!schema[fjsCloned]) {
+      schema = clone(location.schema)
+      schema[fjsCloned] = true
+    }
     location = refFinder(schema.items.$ref, location)
     schema.items = location.schema
   }
@@ -1215,7 +1219,7 @@ function nested (laterCode, name, key, location, subKey, isArray) {
         `
       } else if ('const' in schema) {
         code += `
-          if(ajv.validate(${require('util').inspect(schema, { depth: null, showHidden: false })}, obj${accessor}))
+          if(ajv.validate(${JSON.stringify(schema)}, obj${accessor}))
             json += '${JSON.stringify(schema.const)}'
           else
             throw new Error(\`Item $\{JSON.stringify(obj${accessor})} does not match schema definition.\`)

test/side-effect.test.js

@@ -121,3 +121,37 @@ test('multiple $ref tree', t => {
   t.is(value, '{"people":{"name":"hello","age":42}}')
   t.deepEqual(schema, clonedSchema)
 })
+
+test('must not mutate items $ref', t => {
+  t.plan(2)
+
+  const referenceSchema = {
+    $id: 'ShowSchema',
+    $schema: 'http://json-schema.org/draft-07/schema#',
+    type: 'object',
+    properties: {
+      name: {
+        type: 'string'
+      }
+    }
+  }
+
+  const schema = {
+    $id: 'ListSchema',
+    $schema: 'http://json-schema.org/draft-07/schema#',
+    type: 'array',
+    items: {
+      $ref: 'ShowSchema#'
+    }
+  }
+  const clonedSchema = clone(schema)
+  const stringify = build(schema, {
+    schema: {
+      [referenceSchema.$id]: referenceSchema
+    }
+  })
+
+  const value = stringify([{ name: 'foo' }])
+  t.is(value, '[{"name":"foo"}]')
+  t.deepEqual(schema, clonedSchema)
+})