From 41b01ca44e8e98d698c2b568757806a57aabbb1e Mon Sep 17 00:00:00 2001
From: Dmitry Tantsur <dtantsur@protonmail.com>
Date: Tue, 30 Aug 2022 12:15:42 +0200
Subject: [PATCH] Improve error message heuristics with jsonschema>=4.8

Before version 4.8, jsonschema did some wild guessing when producing
error messages for schemas with several equivalent subschemas. In
version 4.8 it is no longer done, causing error messages that are more
correct but also more generic.

This change restores guessing the potential root cause without claiming
that it's the only possible root cause. Also the traits schema is
simplified to make it less ambiguous.

See https://github.com/python-jsonschema/jsonschema/issues/991 for details.

Change-Id: Ia75cecd2bfbc602b8b2b85bdda20fdc04c5eadf4
(cherry picked from commit 62f9c61ae6657227fd1f5dbc86c59a22b6bac28f)
---
 ironic/api/controllers/v1/utils.py              | 12 +++++++-----
 ironic/common/args.py                           | 17 +++++++++++------
 .../notes/jsonschema-4.8-1146d103b877cffd.yaml  |  5 +++++
 3 files changed, 23 insertions(+), 11 deletions(-)
 create mode 100644 releasenotes/notes/jsonschema-4.8-1146d103b877cffd.yaml

diff --git a/ironic/api/controllers/v1/utils.py b/ironic/api/controllers/v1/utils.py
index 04525ff651..8de2d156df 100644
--- a/ironic/api/controllers/v1/utils.py
+++ b/ironic/api/controllers/v1/utils.py
@@ -86,11 +86,13 @@
 CUSTOM_TRAIT_PATTERN = "^%s[A-Z0-9_]+$" % os_traits.CUSTOM_NAMESPACE
 CUSTOM_TRAIT_REGEX = re.compile(CUSTOM_TRAIT_PATTERN)
 
-TRAITS_SCHEMA = {'anyOf': [
-    {'type': 'string', 'minLength': 1, 'maxLength': 255,
-     'pattern': CUSTOM_TRAIT_PATTERN},
-    {'type': 'string', 'enum': STANDARD_TRAITS},
-]}
+TRAITS_SCHEMA = {
+    'type': 'string', 'minLength': 1, 'maxLength': 255,
+    'anyOf': [
+        {'pattern': CUSTOM_TRAIT_PATTERN},
+        {'enum': STANDARD_TRAITS},
+    ]
+}
 
 LOCAL_LINK_BASE_SCHEMA = {
     'type': 'object',
diff --git a/ironic/common/args.py b/ironic/common/args.py
index 94cfe8841b..bd13e3eafd 100755
--- a/ironic/common/args.py
+++ b/ironic/common/args.py
@@ -211,12 +211,17 @@ def _validate_schema(name, value, schema):
     try:
         jsonschema.validate(value, schema)
     except jsonschema.exceptions.ValidationError as e:
-
-        # The error message includes the whole schema which can be very
-        # large and unhelpful, so truncate it to be brief and useful
-        error_msg = ' '.join(str(e).split("\n")[:3])[:-1]
-        raise exception.InvalidParameterValue(
-            _('Schema error for %s: %s') % (name, error_msg))
+        error_msg = _('Schema error for %s: %s') % (name, e.message)
+        # Sometimes the root message is too generic, try to find a possible
+        # root cause:
+        cause = None
+        current = e
+        while current.context:
+            current = jsonschema.exceptions.best_match(current.context)
+            cause = current.message
+        if cause is not None:
+            error_msg += _('. Possible root cause: %s') % cause
+        raise exception.InvalidParameterValue(error_msg)
     return value
 
 
diff --git a/releasenotes/notes/jsonschema-4.8-1146d103b877cffd.yaml b/releasenotes/notes/jsonschema-4.8-1146d103b877cffd.yaml
new file mode 100644
index 0000000000..75c0a6c507
--- /dev/null
+++ b/releasenotes/notes/jsonschema-4.8-1146d103b877cffd.yaml
@@ -0,0 +1,5 @@
+---
+fixes:
+  - |
+    Fixes API error messages with jsonschema>=4.8. A possible root cause is
+    now detected for generic schema errors.