iproto: fix schema with constraints fetch

Before this patch, only schemas with 3-level nesting were expected.
Simple foreign keys schema has 4-level nesting. After this patch,
nesting depth up to 32 is supported. (There are no known schemas with
such nesting, but this should be enough for any future extensions.)

Closes #282

Author: DifferentialOrange

Diff for: CHANGELOG.md

@@ -9,6 +9,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Changed
 - Discovery iproto features only for Tarantools since version 2.10.0 (#283). 
 
+### Fixed
+- Schema fetch for spaces with foreign keys (#282).
+
 ## 0.12.0 - 2023-02-13
 
 ### Added

Diff for: tarantool/schema.py

@@ -12,6 +12,13 @@
 import tarantool.const as const
 
 
+"""
+Max possible known schema depth is 4 if foreign keys are used (since
+Tarantool 2.10), but there are no restrictions in protocol.
+"""
+MAX_RECURSION_DEPTH = 32
+
+
 class RecursionError(Error):
     """
     Report the situation when max recursion depth is reached.
@@ -102,7 +109,7 @@ def __init__(self, index_row, space):
         self.unique = index_row[4]
         self.parts = []
         try:
-            parts_raw = to_unicode_recursive(index_row[5], 3)
+            parts_raw = to_unicode_recursive(index_row[5], MAX_RECURSION_DEPTH)
         except RecursionError as e:
             errmsg = 'Unexpected index parts structure: ' + str(e)
             raise SchemaError(errmsg)
@@ -159,7 +166,7 @@ def __init__(self, space_row, schema):
             self.schema[self.name] = self
         self.format = dict()
         try:
-            format_raw = to_unicode_recursive(space_row[6], 3)
+            format_raw = to_unicode_recursive(space_row[6], MAX_RECURSION_DEPTH)
         except RecursionError as e:
             errmsg = 'Unexpected space format structure: ' + str(e)
             raise SchemaError(errmsg)

Diff for: test/suites/lib/skip.py

@@ -236,3 +236,14 @@ def skip_or_run_auth_type_test_call(self):
 
     return skip_or_run_test_tarantool_call(self, '2.11.0',
                                            'does not support auth type')
+
+def skip_or_run_constraints_test(func):
+    """Decorator to skip or run tests related to spaces with
+    schema constraints.
+
+    Tarantool supports schema constraints only since 2.10.0 version.
+    See https://github.com/tarantool/tarantool/issues/6436
+    """
+
+    return skip_or_run_test_tarantool(func, '2.10.0',
+                                      'does not support schema constraints')

Diff for: test/suites/test_schema.py

@@ -1,7 +1,10 @@
 import sys
 import unittest
 import tarantool
+import pkg_resources
+
 from .lib.tarantool_server import TarantoolServer
+from .lib.skip import skip_or_run_constraints_test
 from tarantool.error import NotSupportedError
 
 
@@ -102,6 +105,33 @@ def setUpClass(self):
             end
         """)
 
+        if self.srv.admin.tnt_version >= pkg_resources.parse_version('2.10.0'):
+            self.srv.admin("""
+            box.schema.create_space(
+                'constr_tester_1', {
+                format = {
+                    { name = 'id', type = 'unsigned' },
+                    { name = 'payload', type = 'number' },
+                }
+            })
+            box.space.constr_tester_1:create_index('I1', { parts = {'id'} })
+
+            box.space.constr_tester_1:replace({1, 999})
+
+            box.schema.create_space(
+                'constr_tester_2', {
+                format = {
+                    { name = 'id', type = 'unsigned' },
+                    { name = 'table1_id', type = 'unsigned', 
+                      foreign_key = { fk_video = { space = 'constr_tester_1', field = 'id' } },
+                    },
+                    { name = 'payload', type = 'number' },
+                }
+            })
+            box.space.constr_tester_2:create_index('I1', { parts = {'id'} })
+            box.space.constr_tester_2:create_index('I2', { parts = {'table1_id'} })
+            """)
+
     def setUp(self):
         # prevent a remote tarantool from clean our session
         if self.srv.is_started():
@@ -541,8 +571,32 @@ def test_08_schema_fetch_disable_via_connection_pool(self):
         self._run_test_schema_fetch_disable(self.pool_con_schema_disable,
                                             mode=tarantool.Mode.ANY)
 
+    @skip_or_run_constraints_test
+    def test_09_foreign_key_info_fetched_to_schema(self):
+        self.assertIn('foreign_key', self.sch.get_space('constr_tester_2').format['table1_id'])
+
+    @skip_or_run_constraints_test
+    def test_10_foreign_key_valid_replace(self):
+        self.assertSequenceEqual(
+            self.con.replace('constr_tester_2', [1, 1, 623]),
+            [[1, 1, 623]])
+
+    @skip_or_run_constraints_test
+    def test_11_foreign_key_invalid_replace(self):
+        with self.assertRaisesRegex(tarantool.DatabaseError,
+                                    'foreign tuple was not found'):
+                self.con.replace('constr_tester_2', [2, 999, 623])
+
     @classmethod
     def tearDownClass(self):
+        # We need to drop spaces with foreign keys with predetermined order,
+        # otherwise remote server clean() will fail to clean up resources.
+        if self.srv.admin.tnt_version >= pkg_resources.parse_version('2.10.0'):
+            self.srv.admin("""
+            box.space.constr_tester_2:drop()
+            box.space.constr_tester_1:drop()
+            """)
+
         self.con.close()
         self.con_schema_disable.close()
         if not sys.platform.startswith("win"):