chore: clean up validation

quartodoc/autosummary.py

@@ -15,13 +15,14 @@
 from plum import dispatch  # noqa
 from pathlib import Path
 from types import ModuleType
-from pydantic import ValidationError
 
 from .inventory import create_inventory, convert_inventory
 from . import layout
 from .parsers import get_parser_defaults
 from .renderers import Renderer
-from .validation import fmt
+from .validation import fmt_all
+from ._pydantic_compat import ValidationError
+
 
 from typing import Any
 
@@ -485,12 +486,7 @@ def load_layout(self, sections: dict, package: str, options=None):
         try:
             return layout.Layout(sections=sections, package=package, options=options)
         except ValidationError as e:
-            msg = "Configuration error for YAML:\n - "
-            errors = [fmt(err) for err in e.errors() if fmt(err)]
-            first_error = errors[
-                0
-            ]  # we only want to show one error at a time b/c it is confusing otherwise
-            msg += first_error
+            msg = fmt_all(e)
             raise ValueError(msg) from None
 
     # building ----------------------------------------------------------------

quartodoc/tests/__snapshots__/test_validation.ambr

@@ -15,7 +15,7 @@
 
   '''
 # ---
-# name: test_missing_name_contents_2
+# name: test_missing_name_contents
   '''
   Code:
 
@@ -25,7 +25,10 @@
           - title: Section 1
           - title: Section 2
             contents:
+
+              # name missing here ----
               - children: linked
+
               - name: MdRenderer
 
   Error:

quartodoc/validation.py

@@ -1,5 +1,67 @@
+"""User-friendly messages for configuration validation errors.
+
+This module has largely two goals:
+
+* Show the most useful error (pydantic starts with the highest, broadest one).
+* Make the error message very user-friendly.
+
+The key dynamic for understanding formatting is that pydantic is very forgiving.
+It will coerce values to the target type, and by default allows extra fields.
+Critically, if you have a union of types, it will try each type in order until it
+finds a match. In this case, it reports errors for everything it tried.
+
+For example, consider this config:
+
+quartodoc:
+    package: zzz
+    sections:
+    - title: Section 1
+      contents:
+        # name missing here ----
+        - children: linked
+
+In this case, the first element of contents is missing a name field.  Since the
+first type in the union for content elements is _AutoDefault, that is what it
+tries (and logs an error about name). However, it then goes down the list of other
+types in the union and logs errors for those (e.g. Doc). This produce a lot of
+confusing messages, because nowhere does it make clear what type its trying to create.
+
+We don't want error messages for everything it tried, just the first type in the union.
+(For a discriminated union, it uses the `kind:` field to know what the first type to try is).
+"""
+
+
+def fmt_all(e):
+    # if not pydantic.__version__.startswith("1."):
+    #    # error reports are much better in pydantic v2
+    #    # so we just use those.
+    #    return str(e)
+
+    errors = [fmt(err) for err in e.errors() if fmt(err)]
+
+    # the last error is the most specific, while earlier ones can be
+    # for alternative union types that didn't work out.
+    main_error = errors[0]
+
+    msg = f"Configuration error for YAML:\n - {main_error}"
+    return msg
+
+
 def fmt(err: dict):
     "format error messages from pydantic."
+
+    # each entry of loc is a new level in the config tree
+    # 0 is root
+    # 1 is sections
+    # 2 is a section entry
+    # 3 is contents
+    # 4 is a content item
+    # 5 might be Auto.members, etc..
+    # 6 might be an Auto.members item
+
+    # type: value_error.discriminated_union.missing_discriminator
+    # type: value_error.missing
+    # type: value_error.extra
     msg = ""
     if err["msg"].startswith("Discriminator"):
         return msg