[PATCH v1 06/10] kconfig-checker: Split schema to support component reuse

["Ahmed S. Darwish" <darwi@linutronix.de>]

Normal rule files require every rule to define both 'expected' and
'severity'.  Overlay files are different: an overlay may update only
selected fields of an existing rule, so a future overlay schema will permit
these fields to be omitted.

Move the common rule definitions into schemas/base.yml and add a strict
schemas/rules.yml wrapper for complete rule files.

Teach the checker to build a Draft7Validator with local file:// URIs so
that rules.yml can resolve base.yml.

Signed-off-by: Ahmed S. Darwish <darwi@linutronix.de>
---
 tools/kconfig-checker/check.py                | 52 ++++++++++++++++---
 .../{schema.yml => schemas/base.yml}          |  3 +-
 tools/kconfig-checker/schemas/rules.yml       | 20 +++++++
 3 files changed, 65 insertions(+), 10 deletions(-)
 rename tools/kconfig-checker/{schema.yml => schemas/base.yml} (97%)
 create mode 100644 tools/kconfig-checker/schemas/rules.yml

diff --git a/tools/kconfig-checker/check.py b/tools/kconfig-checker/check.py
index ef49c28b9dab..4f79ec487da7 100755
--- a/tools/kconfig-checker/check.py
+++ b/tools/kconfig-checker/check.py
@@ -80,6 +80,8 @@ except ModuleNotFoundError as e:
 # Actual script:
 #
 
+from jsonschema import Draft7Validator
+
 class KernelConfig:
     """.config file parser"""
 
@@ -133,9 +135,9 @@ class Helpers:
             error(f'Invalid YAML syntax at {yaml_f}:\n {e}', os.EX_DATAERR)
 
     @staticmethod
-    def validate_yaml(yaml: YamlDict, schema: YamlDict, f_name: str) -> None:
+    def validate_yaml(yaml: YamlDict, validator: Draft7Validator, f_name: str) -> None:
         try:
-            jsonschema.validate(yaml, schema)
+            validator.validate(yaml)
         except jsonschema.exceptions.ValidationError as e:
             error(
                 f'{f_name} does not match its schema\n'
@@ -144,12 +146,45 @@ class Helpers:
             )
 
 class Schema:
-    """Rules file schema, in json-schema.org format"""
+    """Rules file schema, in json-schema.org draft-07 format"""
+
+    # Rules schema refer to definitions from this base schema
+    BASE_SCHEMA = 'base.yml'
 
     def __init__(self, schema_f: Path):
-        self.schema = Helpers.load_yaml(schema_f)
-        # Validate the schema itself against draft-07 metaschema
-        jsonschema.Draft7Validator.check_schema(self.schema)
+        base_schema_f = schema_f.parent / self.BASE_SCHEMA
+
+        # Use file:// URIs so jsonschema can resolve local '$ref' entries
+        base_schema_uri = base_schema_f.resolve().as_uri()
+        schema_uri = schema_f.resolve().as_uri()
+
+        base_schema = self._load(base_schema_f)
+        self.schema = self._load(schema_f)
+
+        self.validator = self._create_validator(
+            base_schema_uri, base_schema,
+            schema_uri, self.schema,
+        )
+
+    @staticmethod
+    def _create_validator(base_schema_uri: str, base_schema: YamlDict,
+                          schema_uri: str, schema: YamlDict) -> Draft7Validator:
+        """Create a schema validator which can resolve local '$ref' URIs"""
+        resolver = jsonschema.RefResolver(
+            base_uri=schema_uri,
+            referrer=schema,
+            store={ base_schema_uri: base_schema },
+        )
+
+        return Draft7Validator(schema, resolver=resolver)
+
+    @staticmethod
+    def _load(path: Path) -> YamlDict:
+        """Load and validate the schema itself against its metaschema"""
+        schema = Helpers.load_yaml(path)
+
+        Draft7Validator.check_schema(schema)
+        return schema
 
     def as_dict(self) -> YamlDict:
         return self.schema
@@ -273,7 +308,7 @@ class RulesFile:
 
     def __init__(self, yaml_f: Path, schema: Schema):
         self.yaml = Helpers.load_yaml(yaml_f)
-        Helpers.validate_yaml(self.yaml, schema.as_dict(), yaml_f.name)
+        Helpers.validate_yaml(self.yaml, schema.validator, yaml_f.name)
 
     def parse(self) -> Rules:
         """Parse the YAML rules into a python Rules object"""
@@ -533,6 +568,7 @@ def parse_args(rules: list[str]) -> argparse.Namespace:
 def main() -> None:
     base_dir = Path(__file__).resolve().parent
     rules_dir = base_dir / 'rules'
+    schema_dir = base_dir / 'schemas'
 
     rules_l = sorted(path.stem for path in rules_dir.glob('*.yml'))
     args = parse_args(rules_l)
@@ -544,7 +580,7 @@ def main() -> None:
     kconfig_f = args.config.resolve()
     kconfig = KernelConfig(kconfig_f)
 
-    schema_f = base_dir / 'schema.yml'
+    schema_f = schema_dir / 'rules.yml'
     schema = Schema(schema_f)
 
     rules_f = rules_dir / f'{args.rules}.yml'
diff --git a/tools/kconfig-checker/schema.yml b/tools/kconfig-checker/schemas/base.yml
similarity index 97%
rename from tools/kconfig-checker/schema.yml
rename to tools/kconfig-checker/schemas/base.yml
index a7f1b0a78cc7..1cc19752ebd6 100644
--- a/tools/kconfig-checker/schema.yml
+++ b/tools/kconfig-checker/schemas/base.yml
@@ -2,7 +2,7 @@
 
 "$schema": "https://json-schema.org/draft-07/schema"
 
-title: Schema for kconfig-checker rule files
+title: Base schema for kconfig-checker rule files
 type: object
 required: [rules]
 additionalProperties: false
@@ -24,7 +24,6 @@ properties:
       oneOf:
         - required: [name]
         - required: [name_pattern]
-      required: [expected, severity]
       additionalProperties: false
 
       properties:
diff --git a/tools/kconfig-checker/schemas/rules.yml b/tools/kconfig-checker/schemas/rules.yml
new file mode 100644
index 000000000000..90f0eeef497f
--- /dev/null
+++ b/tools/kconfig-checker/schemas/rules.yml
@@ -0,0 +1,20 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+"$schema": "https://json-schema.org/draft-07/schema#"
+
+title: Schema for kconfig-checker rule files
+
+allOf:
+  - $ref: "base.yml"
+
+  #
+  # The base schema leaves 'expected' and 'severity' optional so that
+  # overlay files can override only selected fields.  In a full rules
+  # file though, these fields are mandatory for each rule.
+  #
+  - type: object
+    properties:
+      rules:
+        type: array
+        items:
+          required: [expected, severity]
-- 
2.56.0