Increase Channel Purpose length to 250, and add channel field length handling code to the slack importer (#4458)

* Increase Channel Purpose length to 250.

This commit increases the maxmimum length of the channel purpose field
to 250, including the database migration necessary.

It also adds a method to the Slack importer to check the lengths of
channel properties before importing, and truncate them if necessary.

Fixes #4168

* Fix database migration.

1 files changed, 40 insertions, 0 deletions

diff --git a/api/slackimport_test.go b/api/slackimport_test.go
index 81b79b3d1..d78424ac0 100644
--- a/api/slackimport_test.go
+++ b/api/slackimport_test.go
@@ -4,7 +4,9 @@
 package api
 
 import (
+	"github.com/mattermost/platform/model"
 	"os"
+	"strings"
 	"testing"
 )
 
@@ -177,3 +179,41 @@ func TestSlackParsePosts(t *testing.T) {
 		t.Fatalf("Unexpected number of posts: %v", len(posts))
 	}
 }
+
+func TestSlackSanitiseChannelProperties(t *testing.T) {
+	c1 := model.Channel{
+		DisplayName: "display-name",
+		Name:        "name",
+		Purpose:     "The channel purpose",
+		Header:      "The channel header",
+	}
+
+	c1s := SlackSanitiseChannelProperties(c1)
+	if c1.DisplayName != c1s.DisplayName || c1.Name != c1s.Name || c1.Purpose != c1s.Purpose || c1.Header != c1s.Header {
+		t.Fatalf("Unexpected alterations to the channel properties.")
+	}
+
+	c2 := model.Channel{
+		DisplayName: strings.Repeat("abcdefghij", 7),
+		Name:        strings.Repeat("abcdefghij", 7),
+		Purpose:     strings.Repeat("0123456789", 30),
+		Header:      strings.Repeat("0123456789", 120),
+	}
+
+	c2s := SlackSanitiseChannelProperties(c2)
+	if c2s.DisplayName != strings.Repeat("abcdefghij", 6)+"abcd" {
+		t.Fatalf("Unexpected alterations to the channel properties: %v", c2s.DisplayName)
+	}
+
+	if c2s.Name != strings.Repeat("abcdefghij", 6)+"abcd" {
+		t.Fatalf("Unexpected alterations to the channel properties: %v", c2s.Name)
+	}
+
+	if c2s.Purpose != strings.Repeat("0123456789", 25) {
+		t.Fatalf("Unexpected alterations to the channel properties: %v", c2s.Purpose)
+	}
+
+	if c2s.Header != strings.Repeat("0123456789", 102)+"0123" {
+		t.Fatalf("Unexpected alterations to the channel properties: %v", c2s.Header)
+	}
+}