When removing fields, rename new ones

src/remove.js

@@ -5,7 +5,7 @@ import moveFieldState from './moveFieldState'
 const remove: Mutator<any> = (
   [name, index]: any[],
   state: MutableState<any>,
-  { changeValue }: Tools<any>
+  { changeValue, renameField }: Tools<any>
 ) => {
   let returnValue
   changeValue(state, name, (array: ?(any[])): any[] => {
@@ -30,7 +30,12 @@ const remove: Mutator<any> = (
         // shift all higher ones down
         delete state.fields[key]
         const decrementedKey = `${name}[${fieldIndex - 1}]${tokens[2]}`
-        moveFieldState(state, backup.fields[key], decrementedKey, backup)
+        if (backup.fields[decrementedKey]) {
+          moveFieldState(state, backup.fields[key], decrementedKey, backup)
+        } else {
+          // take care of setting the correct change, blur, focus, validators on new field
+          renameField(state, key, decrementedKey)
+        }
       }
     }
   })

src/remove.test.js

@@ -160,4 +160,63 @@ describe('remove', () => {
       }
     })
   })
+
+  it('should remove value from the specified index, and handle new fields', () => {
+    const array = ['a', { key: 'val' }]
+    const changeValue = jest.fn()
+    const renameField = jest.fn()
+    function blur0() {}
+    function change0() {}
+    function focus0() {}
+    function blur1() {}
+    function change1() {}
+    function focus1() {}
+    function blur2() {}
+    function change2() {}
+    function focus2() {}
+    const state = {
+      formState: {
+        values: {
+          foo: array,
+          anotherField: 42
+        }
+      },
+      fields: {
+        'foo[0]': {
+          name: 'foo[0]',
+          blur: blur0,
+          change: change0,
+          focus: focus0,
+          touched: true,
+          error: 'A Error'
+        },
+        'foo[1]': {
+          name: 'foo[1]',
+          blur: blur1,
+          change: change1,
+          focus: focus1,
+          touched: false,
+          error: 'B Error'
+        },
+        'foo[1].key': {
+          name: 'foo[1].key',
+          blur: blur2,
+          change: change2,
+          focus: focus2,
+          touched: false,
+          error: 'B Error'
+        },
+        anotherField: {
+          name: 'anotherField',
+          touched: false
+        }
+      }
+    }
+    const returnValue = remove(['foo', 0], state, { renameField, changeValue })
+    expect(returnValue).toBeUndefined()
+    expect(renameField).toHaveBeenCalledTimes(1)
+    expect(renameField.mock.calls[0][0]).toEqual(state)
+    expect(renameField.mock.calls[0][1]).toEqual('foo[1].key')
+    expect(renameField.mock.calls[0][2]).toEqual('foo[0].key')
+  })
 })