[FIX] util.column_type: return the max length of varchar column

This allow the set/drop the max length on existing columns with
`util.alter_column_type()`.

closes #340

Signed-off-by: Christophe Simonis (chs) <[email protected]>

Author: KangOl

src/base/tests/test_util.py

@@ -718,11 +718,31 @@ def test_iter_browse_call_twice(self):
 
 
 class TestPG(UnitTestCase):
+    @parametrize(
+        [
+            ("res_country", "name", "jsonb" if util.version_gte("16.0") else "varchar"),  # translated field
+            ("res_country", "code", "varchar(2)"),
+            ("res_currency", "active", "bool"),
+            ("res_country", "create_date", "timestamp"),
+            ("res_currency", "create_uid", "int4"),
+            ("res_country", "name_position", "varchar"),
+            ("res_country", "address_format", "text"),
+            ("res_partner", "does_not_exists", None),
+        ]
+    )
+    def test_column_type(self, table, column, expected):
+        value = util.column_type(self.env.cr, table, column)
+        if expected is None:
+            self.assertIsNone(value)
+        else:
+            self.assertEqual(value, expected)
+
     def test_alter_column_type(self):
         cr = self.env.cr
         cr.execute(
             """
             ALTER TABLE res_partner_bank ADD COLUMN x bool;
+            ALTER TABLE res_partner_bank ADD COLUMN y varchar(4);
 
             UPDATE res_partner_bank
                SET x = CASE id % 3
@@ -742,6 +762,12 @@ def test_alter_column_type(self):
             "Some values where not casted correctly via USING",
         )
 
+        self.assertEqual(util.column_type(cr, "res_partner_bank", "y"), "varchar(4)")
+        util.alter_column_type(cr, "res_partner_bank", "y", "varchar")
+        self.assertEqual(util.column_type(cr, "res_partner_bank", "y"), "varchar")
+        util.alter_column_type(cr, "res_partner_bank", "y", "varchar(12)")
+        self.assertEqual(util.column_type(cr, "res_partner_bank", "y"), "varchar(12)")
+
     @parametrize(
         [
             ("test", "<p>test</p>"),

src/util/pg.py

@@ -497,9 +497,14 @@ def get_value_or_en_translation(cr, table, column):
 
 def _column_info(cr, table, column):
     _validate_table(table)
+    # NOTE: usage of both `CONCAT` and `||` in the query below is done on purpose to take advantage of their NULL handling.
+    #       NULLS propagate with `||` and are ignored by `CONCAT`.
     cr.execute(
         """
-        SELECT COALESCE(bt.typname, t.typname) AS udt_name,
+        SELECT CONCAT(
+                 COALESCE(bt.typname, t.typname),
+                 '(' || information_schema._pg_char_max_length(information_schema._pg_truetypid(a.*, t.*), information_schema._pg_truetypmod(a.*, t.*)) || ')'
+               ) AS udt_name,
                NOT (a.attnotnull OR t.typtype = 'd' AND t.typnotnull) AS is_nullable,
                (   c.relkind IN ('r','p','v','f')
                AND pg_column_is_updatable(c.oid::regclass, a.attnum, false)