Merge 'BTreeTable::to_sql: wrap special column names in brackets' from Nils Koch

Closes #2055

Reviewed-by: Jussi Saurio <jussi.saurio@gmail.com>

Closes #2126

core/schema.rs

@@ -435,7 +435,16 @@ impl BTreeTable {
             if i > 0 {
                 sql.push_str(", ");
             }
-            sql.push_str(column.name.as_ref().expect("column name is None"));
+
+            // we need to wrap the column name in square brackets if it contains special characters
+            let column_name = column.name.as_ref().expect("column name is None");
+            if identifier_contains_special_chars(column_name) {
+                sql.push('[');
+                sql.push_str(column_name);
+                sql.push(']');
+            } else {
+                sql.push_str(column_name);
+            }
 
             if !column.ty_str.is_empty() {
                 sql.push(' ');
@@ -464,6 +473,10 @@ impl BTreeTable {
     }
 }
 
+fn identifier_contains_special_chars(name: &str) -> bool {
+    name.chars().any(|c| !c.is_ascii_alphanumeric() && c != '_')
+}
+
 #[derive(Debug, Default, Clone, Copy)]
 pub struct PseudoCursorType {
     pub column_count: usize,
@@ -1650,6 +1663,25 @@ mod tests {
         assert_eq!(expected, actual);
     }
 
+    #[test]
+    pub fn test_special_column_names() -> Result<()> {
+        let tests = [
+            ("foobar", "CREATE TABLE t (foobar TEXT)"),
+            ("_table_name3", "CREATE TABLE t (_table_name3 TEXT)"),
+            ("special name", "CREATE TABLE t ([special name] TEXT)"),
+            ("foo&bar", "CREATE TABLE t ([foo&bar] TEXT)"),
+            (" name", "CREATE TABLE t ([ name] TEXT)"),
+        ];
+
+        for (input_column_name, expected_sql) in tests {
+            let sql = format!("CREATE TABLE t ([{input_column_name}] TEXT)");
+            let actual = BTreeTable::from_sql(&sql, 0)?.to_sql();
+            assert_eq!(expected_sql, actual);
+        }
+
+        Ok(())
+    }
+
     #[test]
     #[should_panic]
     fn test_automatic_index_single_column() {

testing/alter_table.test

@@ -95,6 +95,18 @@ do_execsql_test_on_specific_db {:memory:} alter-table-drop-column {
   "3"
 }
 
+do_execsql_test_on_specific_db {:memory:} alter-table-drop-column-special-name {
+    CREATE TABLE t(a, b, [c c]);
+    INSERT INTO t VALUES (1, 2, 3);
+    ALTER TABLE t DROP COLUMN b;
+
+    SELECT "c c" FROM t;
+    SELECT sql FROM sqlite_schema;
+} {
+    3
+    "CREATE TABLE t (a, [c c])"
+}
+
 do_execsql_test_in_memory_any_error fail-alter-table-drop-unique-column {
     CREATE TABLE t(a, b UNIQUE);
     ALTER TABLE t DROP b;