PLT-7407: Back-end plugin mechanism (#7177)

* begin backend plugin wip

* flesh out rpcplugin. everything done except for minor supervisor stubs

* done with basic plugin infrastructure

* simplify tests

* remove unused test lines

plugin/rpcplugin/hooks_test.go

@@ -0,0 +1,58 @@
+package rpcplugin
+
+import (
+	"io"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/mock"
+
+	"github.com/mattermost/platform/plugin"
+	"github.com/mattermost/platform/plugin/plugintest"
+)
+
+func testHooksRPC(hooks plugin.Hooks, f func(plugin.Hooks)) {
+	r1, w1 := io.Pipe()
+	r2, w2 := io.Pipe()
+
+	c1 := NewMuxer(NewReadWriteCloser(r1, w2), false)
+	defer c1.Close()
+
+	c2 := NewMuxer(NewReadWriteCloser(r2, w1), true)
+	defer c2.Close()
+
+	id, server := c1.Serve()
+	go ServeHooks(hooks, server, c1)
+
+	remote := ConnectHooks(c2.Connect(id), c2)
+	defer remote.Close()
+
+	f(remote)
+}
+
+func TestHooks(t *testing.T) {
+	var api plugintest.API
+	var hooks plugintest.Hooks
+	defer hooks.AssertExpectations(t)
+
+	testHooksRPC(&hooks, func(remote plugin.Hooks) {
+		hooks.On("OnActivate", mock.AnythingOfType("*rpcplugin.RemoteAPI")).Return(nil)
+		assert.NoError(t, remote.OnActivate(&api))
+
+		hooks.On("OnDeactivate").Return(nil)
+		assert.NoError(t, remote.OnDeactivate())
+	})
+}
+
+func BenchmarkOnDeactivate(b *testing.B) {
+	var hooks plugintest.Hooks
+	hooks.On("OnDeactivate").Return(nil)
+
+	testHooksRPC(&hooks, func(remote plugin.Hooks) {
+		b.ResetTimer()
+		for n := 0; n < b.N; n++ {
+			remote.OnDeactivate()
+		}
+		b.StopTimer()
+	})
+}