Issue #1256: restrict altering existing SQLite tables, apart from a few things

out/locale/en/LC_MESSAGES/default.po

@@ -7,7 +7,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: HeidiSQL\n"
 "POT-Creation-Date: 2012-11-05 21:40\n"
-"PO-Revision-Date: 2022-02-22 21:16+0100\n"
+"PO-Revision-Date: 2022-04-22 13:06+0200\n"
 "Last-Translator: Ansgar Becker <anse@heidisql.com>\n"
 "Language-Team: English (http://www.transifex.com/projects/p/heidisql/language/en/)\n"
 "MIME-Version: 1.0\n"
@@ -6709,3 +6709,6 @@ msgstr "Connection failed"
 
 msgid "Disable foreign key checks"
 msgstr "Disable foreign key checks"
+
+msgid "Altering tables restricted. For details see %s"
+msgstr "Altering tables restricted. For details see %s"

source/table_editor.pas

@@ -212,6 +212,7 @@ type
     FDeletedKeys,
     FDeletedForeignKeys,
     FDeletedCheckConstraints: TStringList;
+    FAlterRestrictedMessageDisplayed: Boolean;
     procedure ValidateColumnControls;
     procedure ValidateIndexControls;
     procedure MoveFocusedIndexPart(NewIdx: Cardinal);
@@ -253,6 +254,7 @@ begin
   FDeletedCheckConstraints := TStringList.Create;
   FDeletedCheckConstraints.Duplicates := dupIgnore;
   editName.MaxLength := NAME_LEN;
+  FAlterRestrictedMessageDisplayed := False;
 end;
 
 
@@ -1257,6 +1259,20 @@ begin
     9: Result := not chkCharsetConvert.Checked;
     else Result := True;
   end;
+
+  // SQLite does not support altering existing columns, except renaming. See issue #1256
+  if ObjectExists and DBObject.Connection.Parameters.IsAnySQLite then begin
+    if Col.Status in [esUntouched, esModified, esDeleted] then begin
+      Result := Result and (Column = 1);
+      if (not Result) and (not FAlterRestrictedMessageDisplayed) then begin
+        MainForm.LogSQL(
+          f_('Altering tables restricted. For details see %s', ['https://www.sqlite.org/lang_altertable.html#making_other_kinds_of_table_schema_changes']),
+          lcInfo
+          );
+        FAlterRestrictedMessageDisplayed := True;
+      end;
+    end;
+  end;
 end;