MM-16821 - Add a KVCompareAndDelete to the plugin API (#11804)

* Implement KVCompareAndDelete and KVCompareAndDeleteJSON

* Add tests for KVCompareAndDelete

* Update minimum server version

* Handle nil value on CompareAndSet so that it deletes it

* Fix comments

* Tweaks from PR comments

* Go back to deleted, err

plugin/api.go

@@ -469,6 +469,14 @@ type API interface {
 	// Minimum server version: 5.12
 	KVCompareAndSet(key string, oldValue, newValue []byte) (bool, *model.AppError)
 
+	// KVCompareAndDelete deletes a key-value pair, unique per plugin, but only if the current value matches the given oldValue.
+	// Returns (false, err) if DB error occurred
+	// Returns (false, nil) if current value != oldValue or key does not exist when deleting
+	// Returns (true, nil) if current value == oldValue and the key was deleted
+	//
+	// Minimum server version: 5.16
+	KVCompareAndDelete(key string, oldValue []byte) (bool, *model.AppError)
+
 	// KVSet stores a key-value pair with an expiry time, unique per plugin.
 	//
 	// Minimum server version: 5.6

plugin/client_rpc_generated.go

@@ -3521,6 +3521,36 @@ func (s *apiRPCServer) KVCompareAndSet(args *Z_KVCompareAndSetArgs, returns *Z_K
 	return nil
 }
 
+type Z_KVCompareAndDeleteArgs struct {
+	A string
+	B []byte
+}
+
+type Z_KVCompareAndDeleteReturns struct {
+	A bool
+	B *model.AppError
+}
+
+func (g *apiRPCClient) KVCompareAndDelete(key string, oldValue []byte) (bool, *model.AppError) {
+	_args := &Z_KVCompareAndDeleteArgs{key, oldValue}
+	_returns := &Z_KVCompareAndDeleteReturns{}
+	if err := g.client.Call("Plugin.KVCompareAndDelete", _args, _returns); err != nil {
+		log.Printf("RPC call to KVCompareAndDelete API failed: %s", err.Error())
+	}
+	return _returns.A, _returns.B
+}
+
+func (s *apiRPCServer) KVCompareAndDelete(args *Z_KVCompareAndDeleteArgs, returns *Z_KVCompareAndDeleteReturns) error {
+	if hook, ok := s.impl.(interface {
+		KVCompareAndDelete(key string, oldValue []byte) (bool, *model.AppError)
+	}); ok {
+		returns.A, returns.B = hook.KVCompareAndDelete(args.A, args.B)
+	} else {
+		return encodableError(fmt.Errorf("API KVCompareAndDelete called but not implemented."))
+	}
+	return nil
+}
+
 type Z_KVSetWithExpiryArgs struct {
 	A string
 	B []byte

plugin/helpers.go

@@ -22,6 +22,14 @@ type Helpers interface {
 	// Minimum server version: 5.12
 	KVCompareAndSetJSON(key string, oldValue interface{}, newValue interface{}) (bool, error)
 
+	// KVCompareAndDeleteJSON deletes a key-value pair, unique per plugin, but only if the current value matches the given oldValue after marshalling as a JSON string.
+	// Returns (false, err) if DB error occurred
+	// Returns (false, nil) if current value != oldValue or the key was already deleted
+	// Returns (true, nil) if current value == oldValue
+	//
+	// Minimum server version: 5.16
+	KVCompareAndDeleteJSON(key string, oldValue interface{}) (bool, error)
+
 	// KVGetJSON retrieves a value based on the key, unique per plugin, unmarshalling the previously set JSON string into the given value. Returns true if the key exists.
 	KVGetJSON(key string, value interface{}) (bool, error)
 

plugin/helpers_kv.go

@@ -59,6 +59,21 @@ func (p *HelpersImpl) KVCompareAndSetJSON(key string, oldValue interface{}, newV
 	return p.API.KVCompareAndSet(key, oldData, newData)
 }
 
+// KVCompareAndDeleteJSON is a wrapper around KVCompareAndDelete to simplify atomically deleting a JSON object from the key value store.
+func (p *HelpersImpl) KVCompareAndDeleteJSON(key string, oldValue interface{}) (bool, error) {
+	var oldData []byte
+	var err error
+
+	if oldValue != nil {
+		oldData, err = json.Marshal(oldValue)
+		if err != nil {
+			return false, errors.Wrap(err, "unable to marshal old value")
+		}
+	}
+
+	return p.API.KVCompareAndDelete(key, oldData)
+}
+
 // KVSetWithExpiryJSON is a wrapper around KVSetWithExpiry to simplify atomically writing a JSON object with expiry to the key value store.
 func (p *HelpersImpl) KVSetWithExpiryJSON(key string, value interface{}, expireInSeconds int64) error {
 	data, err := json.Marshal(value)

plugin/helpers_kv_test.go

@@ -175,6 +175,46 @@ func TestKVCompareAndSetJSON(t *testing.T) {
 	})
 }
 
+func TestKVCompareAndDeleteJSON(t *testing.T) {
+	t.Run("old value JSON marshal error", func(t *testing.T) {
+		api := &plugintest.API{}
+		api.AssertNotCalled(t, "KVCompareAndDelete")
+		p := &plugin.HelpersImpl{API: api}
+
+		ok, err := p.KVCompareAndDeleteJSON("test-key", func() { return })
+
+		api.AssertExpectations(t)
+		assert.Equal(t, false, ok)
+		assert.NotNil(t, err)
+	})
+
+	t.Run("old value nil", func(t *testing.T) {
+		api := &plugintest.API{}
+		api.On("KVCompareAndDelete", "test-key", []byte(nil)).Return(true, nil)
+		p := &plugin.HelpersImpl{API: api}
+
+		ok, err := p.KVCompareAndDeleteJSON("test-key", nil)
+
+		api.AssertExpectations(t)
+		assert.True(t, ok)
+		assert.Nil(t, err)
+	})
+
+	t.Run("old value non-nil", func(t *testing.T) {
+		api := &plugintest.API{}
+		api.On("KVCompareAndDelete", "test-key", []byte(`{"val-a":10}`)).Return(true, nil)
+		p := &plugin.HelpersImpl{API: api}
+
+		ok, err := p.KVCompareAndDeleteJSON("test-key", map[string]interface{}{
+			"val-a": 10,
+		})
+
+		api.AssertExpectations(t)
+		assert.True(t, ok)
+		assert.Nil(t, err)
+	})
+}
+
 func TestKVSetWithExpiryJSON(t *testing.T) {
 	t.Run("JSON marshal error", func(t *testing.T) {
 		api := &plugintest.API{}

plugin/plugintest/api.go

@@ -1903,6 +1903,29 @@ func (_m *API) HasPermissionToTeam(userId string, teamId string, permission *mod
 	return r0
 }
 
+// KVCompareAndDelete provides a mock function with given fields: key, oldValue
+func (_m *API) KVCompareAndDelete(key string, oldValue []byte) (bool, *model.AppError) {
+	ret := _m.Called(key, oldValue)
+
+	var r0 bool
+	if rf, ok := ret.Get(0).(func(string, []byte) bool); ok {
+		r0 = rf(key, oldValue)
+	} else {
+		r0 = ret.Get(0).(bool)
+	}
+
+	var r1 *model.AppError
+	if rf, ok := ret.Get(1).(func(string, []byte) *model.AppError); ok {
+		r1 = rf(key, oldValue)
+	} else {
+		if ret.Get(1) != nil {
+			r1 = ret.Get(1).(*model.AppError)
+		}
+	}
+
+	return r0, r1
+}
+
 // KVCompareAndSet provides a mock function with given fields: key, oldValue, newValue
 func (_m *API) KVCompareAndSet(key string, oldValue []byte, newValue []byte) (bool, *model.AppError) {
 	ret := _m.Called(key, oldValue, newValue)

plugin/plugintest/helpers.go

@@ -33,6 +33,27 @@ func (_m *Helpers) EnsureBot(bot *model.Bot) (string, error) {
 	return r0, r1
 }
 
+// KVCompareAndDeleteJSON provides a mock function with given fields: key, oldValue
+func (_m *Helpers) KVCompareAndDeleteJSON(key string, oldValue interface{}) (bool, error) {
+	ret := _m.Called(key, oldValue)
+
+	var r0 bool
+	if rf, ok := ret.Get(0).(func(string, interface{}) bool); ok {
+		r0 = rf(key, oldValue)
+	} else {
+		r0 = ret.Get(0).(bool)
+	}
+
+	var r1 error
+	if rf, ok := ret.Get(1).(func(string, interface{}) error); ok {
+		r1 = rf(key, oldValue)
+	} else {
+		r1 = ret.Error(1)
+	}
+
+	return r0, r1
+}
+
 // KVCompareAndSetJSON provides a mock function with given fields: key, oldValue, newValue
 func (_m *Helpers) KVCompareAndSetJSON(key string, oldValue interface{}, newValue interface{}) (bool, error) {
 	ret := _m.Called(key, oldValue, newValue)