[MM-54730] Don't use old hardcoded rule for validating imported posts (#25823)

* don't use old hardcoded rule for validating imported posts

* fix http verb in doc

* Use client config

* Handle local mode

* E2E tests

* Enforce default if unable to use real limit

* Unit tests

* Fix tests

* Use model.PostMessageMaxRunesV2 as lower default

* Update direct post message length validation

---------

Co-authored-by: Mattermost Build <build@mattermost.com>
Co-authored-by: streamer45 <cstcld91@gmail.com>

server/cmd/mmctl/commands/import.go

@@ -95,7 +95,9 @@ var ImportValidateCmd = &cobra.Command{
 	Example: "  import validate import_file.zip --team myteam --team myotherteam",
 	Short:   "Validate an import file",
 	Args:    cobra.ExactArgs(1),
-	RunE:    importValidateCmdF,
+	RunE: func(command *cobra.Command, args []string) error {
+		return importValidateCmdF(nil, command, args)
+	},
 }
 
 func init() {
@@ -382,7 +384,14 @@ type Statistics struct {
 	Attachments    uint64 `json:"attachments"`
 }
 
-func importValidateCmdF(command *cobra.Command, args []string) error {
+type ImportValidationResult struct {
+	FileName   string                            `json:"file_name"`
+	TotalLines uint64                            `json:"total_lines"`
+	Elapsed    time.Duration                     `json:"elapsed_time_ns"`
+	Errors     []*importer.ImportValidationError `json:"errors"`
+}
+
+func importValidateCmdF(c client.Client, command *cobra.Command, args []string) error {
 	configurePrinter()
 	defer printer.Print("Validation complete\n")
 
@@ -391,9 +400,10 @@ func importValidateCmdF(command *cobra.Command, args []string) error {
 		serverChannels map[importer.ChannelTeam]*model.Channel
 		serverUsers    map[string]*model.User
 		serverEmails   map[string]*model.User
+		maxPostSize    int
 	)
 
-	err := withClient(func(c client.Client, cmd *cobra.Command, args []string) error {
+	preRunWithClient := func(c client.Client, cmd *cobra.Command, args []string) error {
 		users, err := getPages(func(page, numPerPage int, etag string) ([]*model.User, *model.Response, error) {
 			return c.GetUsers(context.TODO(), page, numPerPage, etag)
 		}, DefaultPageSize)
@@ -401,6 +411,16 @@ func importValidateCmdF(command *cobra.Command, args []string) error {
 			return err
 		}
 
+		config, _, err := c.GetOldClientConfig(context.TODO(), "")
+		if err != nil {
+			return err
+		}
+
+		maxPostSize, err = strconv.Atoi(config["MaxPostSize"])
+		if err != nil {
+			return fmt.Errorf("failed to parse MaxPostSize: %w", err)
+		}
+
 		serverUsers = make(map[string]*model.User)
 		serverEmails = make(map[string]*model.User)
 		for _, user := range users {
@@ -442,9 +462,16 @@ func importValidateCmdF(command *cobra.Command, args []string) error {
 		}
 
 		return nil
-	})(command, args)
+	}
+
+	var err error
+	if c != nil {
+		err = preRunWithClient(c, command, args)
+	} else {
+		err = withClient(preRunWithClient)(command, args)
+	}
 	if err != nil {
-		printer.Print("could not initialize client, skipping online checks\n")
+		printer.Print(fmt.Sprintf("could not initialize client (%s), skipping online checks\n", err.Error()))
 	}
 
 	injectedTeams, err := command.Flags().GetStringArray("team")
@@ -476,6 +503,10 @@ func importValidateCmdF(command *cobra.Command, args []string) error {
 		return err
 	}
 
+	if maxPostSize == 0 {
+		maxPostSize = model.PostMessageMaxRunesV2
+	}
+
 	createMissingTeams := !checkMissingTeams && len(injectedTeams) == 0
 	validator := importer.NewValidator(
 		args[0],               // input file
@@ -486,11 +517,14 @@ func importValidateCmdF(command *cobra.Command, args []string) error {
 		serverChannels,        // map of existing channels
 		serverUsers,           // map of users by name
 		serverEmails,          // map of users by email
+		maxPostSize,
 	)
 
+	var errors []*importer.ImportValidationError
 	templateError := template.Must(template.New("").Parse("{{ .Error }}\n"))
 	validator.OnError(func(ive *importer.ImportValidationError) error {
 		printer.PrintPreparedT(templateError, ive)
+		errors = append(errors, ive)
 		return nil
 	})
 
@@ -529,11 +563,7 @@ func importValidateCmdF(command *cobra.Command, args []string) error {
 		}{unusedAttachments})
 	}
 
-	printer.PrintT("It took {{ .Elapsed }} to validate {{ .TotalLines }} lines in {{ .FileName }}\n", struct {
-		FileName   string        `json:"file_name"`
-		TotalLines uint64        `json:"total_lines"`
-		Elapsed    time.Duration `json:"elapsed_time_ns"`
-	}{args[0], validator.Lines(), validator.Duration()})
+	printer.PrintT("It took {{ .Elapsed }} to validate {{ .TotalLines }} lines in {{ .FileName }}\n", ImportValidationResult{args[0], validator.Lines(), validator.Duration(), errors})
 
 	return nil
 }