Fixed #14098 -- Prevented crash for introspection errors in inspectdb

Thanks Tim Graham for the review.

django/core/management/commands/inspectdb.py

@@ -6,6 +6,7 @@ from collections import OrderedDict
 
 from django.core.management.base import BaseCommand, CommandError
 from django.db import DEFAULT_DB_ALIAS, connections
+from django.utils.encoding import force_text
 
 
 class Command(BaseCommand):
@@ -57,25 +58,32 @@ class Command(BaseCommand):
                 if table_name_filter is not None and callable(table_name_filter):
                     if not table_name_filter(table_name):
                         continue
+                try:
+                    try:
+                        relations = connection.introspection.get_relations(cursor, table_name)
+                    except NotImplementedError:
+                        relations = {}
+                    try:
+                        indexes = connection.introspection.get_indexes(cursor, table_name)
+                    except NotImplementedError:
+                        indexes = {}
+                    try:
+                        constraints = connection.introspection.get_constraints(cursor, table_name)
+                    except NotImplementedError:
+                        constraints = {}
+                    table_description = connection.introspection.get_table_description(cursor, table_name)
+                except Exception as e:
+                    yield "# Unable to inspect table '%s'" % table_name
+                    yield "# The error was: %s" % force_text(e)
+                    continue
+
                 yield ''
                 yield ''
                 yield 'class %s(models.Model):' % table2model(table_name)
                 known_models.append(table2model(table_name))
-                try:
-                    relations = connection.introspection.get_relations(cursor, table_name)
-                except NotImplementedError:
-                    relations = {}
-                try:
-                    indexes = connection.introspection.get_indexes(cursor, table_name)
-                except NotImplementedError:
-                    indexes = {}
-                try:
-                    constraints = connection.introspection.get_constraints(cursor, table_name)
-                except NotImplementedError:
-                    constraints = {}
                 used_column_names = []  # Holds column names used in the table so far
                 column_to_field_name = {}  # Maps column names to names of model fields
-                for row in connection.introspection.get_table_description(cursor, table_name):
+                for row in table_description:
                     comment_notes = []  # Holds Field notes, to be displayed in a Python comment.
                     extra_params = OrderedDict()  # Holds Field parameters such as 'db_column'.
                     column_name = row[0]

tests/inspectdb/tests.py

@@ -6,7 +6,8 @@ from unittest import skipUnless
 
 from django.core.management import call_command
 from django.db import connection
-from django.test import TestCase, skipUnlessDBFeature
+from django.test import TestCase, mock, skipUnlessDBFeature
+from django.utils.encoding import force_text
 from django.utils.six import PY3, StringIO
 
 from .models import ColumnTypes
@@ -268,3 +269,17 @@ class InspectDBTestCase(TestCase):
             self.assertIn("big_int_field = models.BigIntegerField()", output)
         finally:
             connection.introspection.data_types_reverse = orig_data_types_reverse
+
+    def test_introspection_errors(self):
+        """
+        Introspection errors should not crash the command, and the error should
+        be visible in the output.
+        """
+        out = StringIO()
+        with mock.patch('django.db.backends.base.introspection.BaseDatabaseIntrospection.table_names',
+                        return_value=['nonexistent']):
+            call_command('inspectdb', stdout=out)
+        output = force_text(out.getvalue())
+        self.assertIn("# Unable to inspect table 'nonexistent'", output)
+        # The error message depends on the backend
+        self.assertIn("# The error was:", output)