squash: more verbose messages from schema validation

tmt/base.py

@@ -16,6 +16,7 @@
 import fmf
 import fmf.base
 import fmf.utils
+import jsonschema
 from click import confirm, echo, style
 from fmf.utils import listed
 from ruamel.yaml.error import MarkedYAMLError
@@ -704,12 +705,72 @@ def _lint_keys(self, additional_keys: List[str]) -> List[str]:
     def lint_validate(self) -> LinterReturn:
         """ C000: fmf node should pass the schema validation """
 
-        errors = tmt.utils.validate_fmf_node(self.node, f'{self.__class__.__name__.lower()}.yaml')
+        schema_name = self.__class__.__name__.lower()
+
+        errors = tmt.utils.validate_fmf_node(self.node, f'{schema_name}.yaml')
 
         if errors:
-            for exc, message in errors:
-                # TODO: one day, this should become FAIL
-                yield LinterOutcome.WARN, f'fmf node failed schema validation, {message}'
+            # A bit of error formatting. It is possible to use str(error), but the result
+            # is a bit too JSON-ish. Let's present an error message in a way that helps
+            # users to point finger on each and every issue.
+
+            def detect_unallowed_properties(error: jsonschema.ValidationError) -> LinterReturn:
+                match = re.search(
+                    r"(?mi)Additional properties are not allowed \(([a-zA-Z0-9', \-]+) (?:was|were) unexpected\)",  # noqa: E501
+                    str(error))
+
+                if not match:
+                    return
+
+                for bad_property in match.group(1).replace("'", '').replace(' ', '').split(','):
+                    yield LinterOutcome.WARN, \
+                        f'key "{bad_property}" not recognized by schema {error.schema["$id"]}'
+
+            # A key value is not recognized. This is often a case with keys whose values are
+            # limited by an enum, like `how`. Unfortunatelly, validator will record every mismatch
+            # between a value and enum even if eventually a match is found. So it might be tempting
+            # to ignore this particular kind of error - it may also indicate a genuine typo in
+            # key name or completely misplaced key, so it's still necessary to report the error.
+            def detect_enum_violations(error: jsonschema.ValidationError) -> LinterReturn:
+                match = re.search(
+                    r"(?mi)'([a-z\-]+)' is not one of \['([a-zA-Z\-]+)'\]",
+                    str(error))
+
+                if not match:
+                    return
+
+                yield LinterOutcome.WARN, \
+                    f'value of "{error.json_path.split(".")[-1]}" is not "{match.group(2)}"'
+
+            for error, _ in errors:
+                # if error.path:
+                #     # Path to a place in tested instance where the error appeared
+                #     error_path = '.'.join(error.path)
+                #
+                #     yield LinterOutcome.WARN, textwrap.dedent(f"""
+                #         At key "{error_path}":
+                #
+                #         -----
+                #         {error_path}:
+                #         {textwrap.indent(tmt.utils.dict_to_yaml(error.instance), '    ')}
+                #         -----
+                #         """)
+                #
+                # else:
+                #     yield LinterOutcome.WARN, textwrap.dedent(f"""
+                #         -----
+                #         {textwrap.indent(tmt.utils.dict_to_yaml(error.instance), '    ')}
+                #         -----
+                #         """)
+
+                yield from detect_unallowed_properties(error)
+                yield from detect_enum_violations(error)
+
+                # Validation errors can have "context", a list of "sub" errors encountered during
+                # validation. Interesting ones are identified &  added to our error message.
+                for suberror in error.context:
+                    yield from detect_unallowed_properties(suberror)
+                    yield from detect_enum_violations(suberror)
 
             return