MM-10702 Moving plugins to use hashicorp go-plugin. (#8978)

* Moving plugins to use hashicorp go-plugin.

* Tweaks from feedback.

app/plugin_test.go

@@ -4,19 +4,14 @@
 package app
 
 import (
-	"errors"
 	"net/http"
 	"net/http/httptest"
 	"testing"
-	"time"
 
 	"github.com/gorilla/mux"
+	"github.com/mattermost/mattermost-server/model"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
-
-	"github.com/mattermost/mattermost-server/model"
-	"github.com/mattermost/mattermost-server/plugin"
-	"github.com/mattermost/mattermost-server/plugin/plugintest"
 )
 
 func TestPluginKeyValueStore(t *testing.T) {
@@ -103,152 +98,6 @@ func TestHandlePluginRequest(t *testing.T) {
 	router.ServeHTTP(nil, r)
 }
 
-type testPlugin struct {
-	plugintest.Hooks
-}
-
-func (p *testPlugin) OnConfigurationChange() error {
-	return nil
-}
-
-func (p *testPlugin) OnDeactivate() error {
-	return nil
-}
-
-type pluginCommandTestPlugin struct {
-	testPlugin
-
-	TeamId string
-}
-
-func (p *pluginCommandTestPlugin) OnActivate(api plugin.API) error {
-	if err := api.RegisterCommand(&model.Command{
-		Trigger: "foo",
-		TeamId:  p.TeamId,
-	}); err != nil {
-		return err
-	}
-	if err := api.RegisterCommand(&model.Command{
-		Trigger: "foo2",
-		TeamId:  p.TeamId,
-	}); err != nil {
-		return err
-	}
-	return api.UnregisterCommand(p.TeamId, "foo2")
-}
-
-func (p *pluginCommandTestPlugin) ExecuteCommand(args *model.CommandArgs) (*model.CommandResponse, *model.AppError) {
-	if args.Command == "/foo" {
-		return &model.CommandResponse{
-			Text: "bar",
-		}, nil
-	}
-	return nil, model.NewAppError("ExecuteCommand", "this is an error", nil, "", http.StatusBadRequest)
-}
-
-func TestPluginCommands(t *testing.T) {
-	th := Setup().InitBasic()
-	defer th.TearDown()
-
-	th.InstallPlugin(&model.Manifest{
-		Id: "foo",
-	}, &pluginCommandTestPlugin{
-		TeamId: th.BasicTeam.Id,
-	})
-
-	require.Nil(t, th.App.EnablePlugin("foo"))
-
-	// Ideally, we would wait for the websocket activation event instead of just sleeping.
-	time.Sleep(500 * time.Millisecond)
-
-	pluginStatuses, err := th.App.GetPluginStatuses()
-	require.Nil(t, err)
-	found := false
-	for _, pluginStatus := range pluginStatuses {
-		if pluginStatus.PluginId == "foo" {
-			require.Equal(t, model.PluginStateRunning, pluginStatus.State)
-			found = true
-		}
-	}
-	require.True(t, found, "failed to find plugin foo in plugin statuses")
-
-	resp, err := th.App.ExecuteCommand(&model.CommandArgs{
-		Command:   "/foo2",
-		TeamId:    th.BasicTeam.Id,
-		UserId:    th.BasicUser.Id,
-		ChannelId: th.BasicChannel.Id,
-	})
-	require.NotNil(t, err)
-	assert.Equal(t, http.StatusNotFound, err.StatusCode)
-
-	resp, err = th.App.ExecuteCommand(&model.CommandArgs{
-		Command:   "/foo",
-		TeamId:    th.BasicTeam.Id,
-		UserId:    th.BasicUser.Id,
-		ChannelId: th.BasicChannel.Id,
-	})
-	require.Nil(t, err)
-	assert.Equal(t, "bar", resp.Text)
-
-	resp, err = th.App.ExecuteCommand(&model.CommandArgs{
-		Command:   "/foo baz",
-		TeamId:    th.BasicTeam.Id,
-		UserId:    th.BasicUser.Id,
-		ChannelId: th.BasicChannel.Id,
-	})
-	require.NotNil(t, err)
-	require.Equal(t, "this is an error", err.Message)
-	assert.Nil(t, resp)
-
-	require.Nil(t, th.App.RemovePlugin("foo"))
-
-	resp, err = th.App.ExecuteCommand(&model.CommandArgs{
-		Command:   "/foo",
-		TeamId:    th.BasicTeam.Id,
-		UserId:    th.BasicUser.Id,
-		ChannelId: th.BasicChannel.Id,
-	})
-	require.NotNil(t, err)
-	assert.Equal(t, http.StatusNotFound, err.StatusCode)
-}
-
-type pluginBadActivation struct {
-	testPlugin
-}
-
-func (p *pluginBadActivation) OnActivate(api plugin.API) error {
-	return errors.New("won't activate for some reason")
-}
-
-func TestPluginBadActivation(t *testing.T) {
-	th := Setup().InitBasic()
-	defer th.TearDown()
-
-	th.InstallPlugin(&model.Manifest{
-		Id: "foo",
-	}, &pluginBadActivation{})
-
-	t.Run("EnablePlugin bad activation", func(t *testing.T) {
-		err := th.App.EnablePlugin("foo")
-		assert.Nil(t, err)
-
-		// Ideally, we would wait for the websocket activation event instead of just
-		// sleeping.
-		time.Sleep(500 * time.Millisecond)
-
-		pluginStatuses, err := th.App.GetPluginStatuses()
-		require.Nil(t, err)
-		found := false
-		for _, pluginStatus := range pluginStatuses {
-			if pluginStatus.PluginId == "foo" {
-				require.Equal(t, model.PluginStateFailedToStart, pluginStatus.State)
-				found = true
-			}
-		}
-		require.True(t, found, "failed to find plugin foo in plugin statuses")
-	})
-}
-
 func TestGetPluginStatusesDisabled(t *testing.T) {
 	th := Setup().InitBasic()
 	defer th.TearDown()