Object schema without (#160)

* creating without method on ObjectSchema

* proper documentation

* rollback wrong push

README.md

@@ -295,11 +295,13 @@ const userSchema = S.object()
 console.log(userSchema)
 ```
 
-## Selecting only certain properties of your schema
+## Selecting certain properties of your schema
 
 In addition to extending schemas, it is also possible to reduce them into smaller schemas. This comes in handy
 when you have a large Fluent Schema, and would like to re-use some of its properties.
 
+Select only properties you want to keep.
+
 ```js
 const S = require('fluent-json-schema')
 const userSchema = S.object()
@@ -312,6 +314,20 @@ const userSchema = S.object()
 const loginSchema = userSchema.only(['username', 'password'])
 ```
 
+Or remove properties you dont want to keep.
+
+```js
+const S = require('fluent-json-schema')
+const personSchema = S.object()
+  .prop('name', S.string())
+  .prop('age', S.number())
+  .prop('id', S.string().format('uuid'))
+  .prop('createdAt', S.string().format('time'))
+  .prop('updatedAt', S.string().format('time'))
+
+const bodySchema = personSchema.without(['createdAt', 'updatedAt'])
+```
+
 ### Detect Fluent Schema objects
 
 Every Fluent Schema object contains a boolean `isFluentSchema`. In this way, you can write your own utilities that understands the Fluent Schema API and improve the user experience of your tool.

src/ObjectSchema.js

@@ -344,15 +344,30 @@ const ObjectSchema = ({ schema = initialState, ...options } = {}) => {
       return ObjectSchema({
         schema: {
           ...schema,
-          properties: schema.properties.filter(p =>
-            properties.includes(p.name)
-          ),
+          properties: schema.properties.filter(({ name }) => properties.includes(name)),
           required: schema.required.filter(p => properties.includes(p)),
         },
         ...options,
       })
     },
 
+    /**
+     * Returns an object schema without a subset of keys provided
+     *
+     * @param properties a list of properties you dont want to keep
+     * @returns {ObjectSchema}
+     */
+    without: properties => {
+      return ObjectSchema({
+        schema: {
+          ...schema,
+          properties: schema.properties.filter(p => !properties.includes(p.name)),
+          required: schema.required.filter(p => !properties.includes(p)),
+        },
+        ...options,
+      })
+    },
+
     /**
      * The "definitions" keywords provides a standardized location for schema authors to inline re-usable JSON Schemas into a more general schema.
      * There are no restrictions placed on the values within the array.

src/ObjectSchema.test.js

@@ -945,6 +945,68 @@ describe('ObjectSchema', () => {
     })
   })
 
+  describe('without', () => {
+    it('returns a subset of the object', () => {
+      const base = S.object()
+        .id('base')
+        .title('base')
+        .prop('foo', S.string())
+        .prop('bar', S.string())
+        .prop('baz', S.string())
+        .prop(
+          'children',
+          S.object()
+            .prop('alpha', S.string())
+            .prop('beta', S.string())
+        )
+
+      const without = base.without(['foo', 'children'])
+
+      expect(without.valueOf()).toEqual({
+        $schema: 'http://json-schema.org/draft-07/schema#',
+        $id: 'base',
+        title: 'base',
+        properties: {
+          bar: {
+            type: 'string',
+          },
+          baz: {
+            type: 'string',
+          },
+        },
+        type: 'object',
+      })
+    })
+
+    it('works correctly with required properties', () => {
+      const base = S.object()
+        .id('base')
+        .title('base')
+        .prop('foo', S.string().required())
+        .prop('bar', S.string())
+        .prop('baz', S.string().required())
+        .prop('qux', S.string())
+
+      const without = base.without(['foo', 'bar'])
+
+      expect(without.valueOf()).toEqual({
+        $schema: 'http://json-schema.org/draft-07/schema#',
+        $id: 'base',
+        title: 'base',
+        properties: {
+          baz: {
+            type: 'string',
+          },
+          qux: {
+            type: 'string',
+          },
+        },
+        required: ['baz'],
+        type: 'object',
+      })
+    })
+  })
+
   describe('raw', () => {
     it('allows to add a custom attribute', () => {
       const schema = ObjectSchema()