MM-16506: conditionally build go.mod for plugins (#11430)

* MM-16506: conditionally build go.mod for plugins

Unless `GO111MODULE=off`, generate a `go.mod` that points at the local copy of `mattermost-server` to ensure plugin tests that compile source code on demand always test with the local copy of mattermost-server.  This also fixes an issue with early adopters of `GO111MODULE=on` on the server failing to find the right version of go-i18n dependencies.

* plugin: enable testlib resource management

* customize fileutils.Find* for testlib

plugin/main_test.go

@@ -12,7 +12,10 @@ import (
 var mainHelper *testlib.MainHelper
 
 func TestMain(m *testing.M) {
-	mainHelper = testlib.NewMainHelperWithOptions(nil)
+	var options = testlib.HelperOptions{
+		EnableResources: true,
+	}
+	mainHelper = testlib.NewMainHelperWithOptions(&options)
 	defer mainHelper.Close()
 
 	mainHelper.Main(m)

testlib/resources.go

@@ -34,11 +34,38 @@ type testResourceDetails struct {
 	action  int8
 }
 
+// commonBaseSearchPaths is a custom version of what fileutils exposes. At some point, consolidate.
+var commonBaseSearchPaths = []string{
+	".",
+	"..",
+	"../..",
+	"../../..",
+	"../../../..",
+}
+
+func findFile(path string) string {
+	return fileutils.FindPath(path, commonBaseSearchPaths, func(fileInfo os.FileInfo) bool {
+		return !fileInfo.IsDir()
+	})
+}
+
+func findDir(dir string) (string, bool) {
+	found := fileutils.FindPath(dir, commonBaseSearchPaths, func(fileInfo os.FileInfo) bool {
+		return fileInfo.IsDir()
+	})
+	if found == "" {
+		return "./", false
+	}
+
+	return found, true
+}
+
 func getTestResourcesToSetup() []testResourceDetails {
 	var srcPath string
 	var found bool
 
 	var testResourcesToSetup = []testResourceDetails{
+		{"mattermost-server", "mattermost-server", resourceTypeFolder, actionSymlink},
 		{"i18n", "i18n", resourceTypeFolder, actionSymlink},
 		{"templates", "templates", resourceTypeFolder, actionSymlink},
 		{"tests", "tests", resourceTypeFolder, actionSymlink},
@@ -49,14 +76,14 @@ func getTestResourcesToSetup() []testResourceDetails {
 	// Finding resources and setting full path to source to be used for further processing
 	for i, testResource := range testResourcesToSetup {
 		if testResource.resType == resourceTypeFile {
-			srcPath = fileutils.FindFile(testResource.src)
+			srcPath = findFile(testResource.src)
 			if srcPath == "" {
 				panic(fmt.Sprintf("Failed to find file %s", testResource.src))
 			}
 
 			testResourcesToSetup[i].src = srcPath
 		} else if testResource.resType == resourceTypeFolder {
-			srcPath, found = fileutils.FindDir(testResource.src)
+			srcPath, found = findDir(testResource.src)
 			if found == false {
 				panic(fmt.Sprintf("Failed to find folder %s", testResource.src))
 			}

utils/test_files_compiler.go

@@ -4,23 +4,56 @@
 package utils
 
 import (
+	"fmt"
 	"io/ioutil"
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strings"
 	"testing"
 
 	"github.com/stretchr/testify/require"
 )
 
+func goMod(t *testing.T, dir string, args ...string) {
+	cmd := exec.Command("go", append([]string{"mod"}, args...)...)
+	cmd.Dir = dir
+	output, err := cmd.CombinedOutput()
+	if err != nil {
+		t.Fatalf("Failed to %s: %s", strings.Join(args, " "), string(output))
+	}
+}
+
 func CompileGo(t *testing.T, sourceCode, outputPath string) {
 	dir, err := ioutil.TempDir(".", "")
 	require.NoError(t, err)
 	defer os.RemoveAll(dir)
-	require.NoError(t, ioutil.WriteFile(filepath.Join(dir, "main.go"), []byte(sourceCode), 0600))
+
+	dir, err = filepath.Abs(dir)
+	require.NoError(t, err)
+
+	// Write out main.go given the source code.
+	main := filepath.Join(dir, "main.go")
+	err = ioutil.WriteFile(main, []byte(sourceCode), 0600)
+	require.NoError(t, err)
+
+	if os.Getenv("GO111MODULE") != "off" {
+		var mattermostServerPath string
+
+		// Generate a go.mod file relying on the local copy of the mattermost-server.
+		// testlib linked mattermost-server into the general temporary directory for this test.
+		mattermostServerPath, err = filepath.Abs("mattermost-server")
+		require.NoError(t, err)
+
+		goMod(t, dir, "init", "mattermost.com/test")
+		goMod(t, dir, "edit", "-require", "github.com/mattermost/mattermost-server@v0.0.0")
+		goMod(t, dir, "edit", "-replace", fmt.Sprintf("github.com/mattermost/mattermost-server@v0.0.0=%s", mattermostServerPath))
+	}
+
 	cmd := exec.Command("go", "build", "-o", outputPath, "main.go")
 	cmd.Dir = dir
 	cmd.Stdout = os.Stdout
 	cmd.Stderr = os.Stderr
-	require.NoError(t, cmd.Run(), "failed to compile go")
+	err = cmd.Run()
+	require.NoError(t, err, "failed to compile go")
 }