Considerable headway here

projects/yamlschema/BUILD

@@ -1,12 +1,21 @@
 py_library(
-    name = "yamlschema",
-    srcs = [
+    name="yamlschema",
+    srcs=[
         "yamlschema.py",
     ],
-    imports = [
+    imports=[
         ".",
     ],
-    deps = [
+    deps=[
         py_requirement("PyYAML"),
-    ]
+    ],
+)
+
+py_pytest(
+    name="test_yamlschema",
+    srcs=glob(["test_*.py"]),
+    data=glob(["*.json", "*.yaml"]),
+    deps=[
+        ":yamlschema",
+    ],
 )

projects/yamlschema/test_yamlschema.py

@@ -0,0 +1,19 @@
+"""
+Tests covering the YAML linter.
+"""
+
+from yamlschema import lint_buffer
+
+import pytest
+
+
+@pytest.mark.parametrize('schema, obj', [
+    ({"type": "number"}, "---\n1.0"),
+    ({"type": "integer"}, "---\n3"),
+    ({"type": "string"}, "---\nfoo bar baz"),
+    ({"type": "string", "maxLength": 15}, "---\nfoo bar baz"),
+    ({"type": "string", "minLength": 10}, "---\nfoo bar baz"),
+    ({"type": "string", "pattern": "^foo.*"}, "---\nfoo bar baz"),
+])
+def test_lint_document_ok(schema, obj):
+    assert not list(lint_buffer(schema, obj))

projects/yamlschema/yamlschema.py

@@ -4,94 +4,252 @@ JSONSchema linting for YAML documents.
 
 import logging
 import typing as t
+from enum import Enum
+from io import StringIO
+import re
 
+import yaml
 from yaml.nodes import MappingNode, Node, ScalarNode, SequenceNode
 
 
 log = logging.getLogger(__name__)
 
 
-def lint_mapping(schema, node: Node) -> t.List[str]:
-  lint: t.List[str] = []
+class LintLevel(Enum):
+    """Lint outcome levels."""
+
+    MISSING = 1
+    MISSMATCH = 2
+    UNEXPECTED = 3
+
+
+class LintRecord(t.NamedTuple):
+    """A linting record."""
+
+    level: LintLevel
+    node: Node
+    schema: object
+    message: str
+
+    @property
+    def start_mark(self):
+        return self.node.start_mark
+
+
+class YamlLinter(object):
+    """YAML linting against JSON schemas."""
+
+    def __init__(self, schema):
+        self._schema = schema
+
+    def dereference(self, schema):
+        """Dereference a {"$ref": ""} form."""
+
+        if ref := schema.get("$ref"):
+            assert ref.startswith("#/")
+            path = ref.lstrip("#/").split("/")
+            schema = self._schema
+            for e in path:
+                if not (schema := path.get(e)):
+                    raise ValueError(f"Unable to dereference {ref}")
+
+        return schema
+
+    def lint_mapping(self, schema, node: Node) -> t.Iterable[str]:
+        """FIXME.
+
+        """
+
         if schema["type"] != "object" or not isinstance(node, MappingNode):
-    raise TypeError(
-        f"Expected {schema['type']}, got {node.id} {str(node.start_mark).lstrip()}"
+            yield LintRecord(
+                LintLevel.MISSMATCH,
+                node,
+                schema,
+                f"Expected {schema['type']}, got {node.id} {str(node.start_mark).lstrip()}",
             )
 
-  additional_allowed: bool = schema.get("additionalProperties", False) != False
         additional_type: t.Union[dict, bool] = (
-    schema.get("additionalProperties") if additional_allowed
-    else {}
+            schema.get("additionalProperties", True)
         )
         properties: dict = schema.get("properties", {})
-  required: t.List[str] = schema.get("required", [])
+        required: t.Iterable[str] = schema.get("required", [])
 
         for k in required:
             if k not in [_k.value for _k, _v in node.value]:
-      raise TypeError(
-          f"Required key {k!r} absent from mapping {str(node.start_mark).lstrip()}"
+                yield LintRecord(
+                    LintLevel.MISSING,
+                    node,
+                    schema,
+                    f"Required key {k!r} absent from mapping {str(node.start_mark).lstrip()}",
                 )
 
         for k, v in node.value:
             if k.value in properties:
-      lint.extend(lint_document(properties.get(k.value), v))
+                yield from self.lint_document(properties.get(k.value), v)
+
+            elif additional_type:
+                yield from self.lint_document(additional_type, v)
 
-    elif additional_allowed:
-      # 'true' is a way to encode the any type.
-      if additional_type == True:
-        pass
             else:
-        lint.extend(lint_document(additional_type, v))
-    else:
-      lint.append(
-          f"Key {k.value!r} is not allowed by schema {str(node.start_mark).lstrip()}"
+                yield LintRecord(
+                    LintLevel.UNEXPECTED,
+                    node,
+                    schema,
+                    f"Key {k.value!r} is not allowed by schema {str(node.start_mark).lstrip()}",
                 )
 
-  return lint
-
-
-def lint_sequence(schema, node: Node) -> t.List[str]:
-  """"FIXME.
+    def lint_sequence(self, schema, node: Node) -> t.Iterable[str]:
+        """FIXME.
 
         There aren't sequences we need to lint in the current schema design, punting.
 
         """
 
         if schema["type"] != "array" or not isinstance(node, SequenceNode):
-    raise TypeError(
-      f"Expected {schema['type']}, got {node.id} {str(node.start_mark).lstrip()}"
+            yield LintRecord(
+                LintLevel.MISSMATCH,
+                node,
+                schema,
+                f"Expected {schema['type']}, got {node.id} {str(node.start_mark).lstrip()}",
             )
 
-  lint = []
         subschema = schema.get("items")
         if subschema:
             for item in node.value:
-      lint.extend(lint_document(subschema, item))
-  return lint
+                yield from self.lint_document(subschema, item)
 
-
-def lint_scalar(schema, node: Node) -> t.List[str]:
+    def lint_scalar(self, schema, node: Node) -> t.Iterable[str]:
         """FIXME.
 
         The only terminal we care about linting in the current schema is {"type": "string"}.
 
         """
-  if schema["type"] not in ["string", "number"] or not isinstance(node, ScalarNode):
-    raise TypeError(
-      f"Expected {schema['type']}, got {node.id} {str(node.start_mark).lstrip()}"
+
+        if schema["type"] == "string":
+            yield from self.lint_string(schema, node)
+        elif schema["type"] == "integer":
+            yield from self.lint_integer(schema, node)
+        elif schema["type"] == "number":
+            yield from self.lint_number(schema, node)
+        else:
+            raise NotImplementedError(
+                f"Scalar type {schema['type']} is not supported"
             )
 
-  lint = []
-  if schema["type"] == "string":
-    if not isinstance(node.value, str):
-      lint.append(f"Expected string, got {node.id} {str(node.start_mark).lstrip()}")
+    def lint_string(self, schema, node: Node) -> t.Iterable[str]:
+        """FIXME."""
+
+        if node.tag != "tag:yaml.org,2002:str":
+            yield LintRecord(
+                LintLevel.MISSMATCH,
+                node,
+                schema,
+                f"Expected a string, got a {node}"
+            )
+
+        if maxl := schema.get("maxLength"):
+            if len(node.value) > maxl:
+                yield LintRecord(
+                    LintLevel.MISSMATCH,
+                    node,
+                    schema,
+                    f"Expected a shorter string"
+                )
+
+        if minl := schema.get("minLength"):
+            if len(node.value) < minl:
+                yield LintRecord(
+                    LintLevel.MISSMATCH,
+                    node,
+                    schema,
+                    f"Expected a longer string"
+                )
+
+        if pat := schema.get("pattern"):
+            if not re.fullmatch(pat, node.value):
+                yield LintRecord(
+                    LintLevel.MISSMATCH,
+                    node,
+                    schema,
+                    f"Expected a string matching the pattern"
+                )
+
+    def lint_integer(self, schema, node: Node) -> t.Iterable[str]:
+        if node.tag == "tag:yaml.org,2002:int":
+            value = int(node.value)
+            yield from self._lint_num_range(schema, node, value)
+
         else:
-    log.info(f"Ignoring unlintable scalar, schema {schema!r} {str(node.start_mark).lstrip()}")
+            yield LintRecord(
+                LintLevel.MISSMATCH,
+                node,
+                schema,
+                f"Expected an integer, got a {node}"
+            )
 
-  return lint
+    def lint_number(self, schema, node: Node) -> t.Iterable[str]:
+        if node.tag == "tag:yaml.org,2002:float":
+            value = float(node.value)
+            yield from self._lint_num_range(schema, node, value)
+
+        else:
+            yield LintRecord(
+                LintLevel.MISSMATCH,
+                node,
+                schema,
+                f"Expected an integer, got a {node}"
+            )
 
 
-def lint_document(schema, node):
+    def _lint_num_range(self, schema, node: Node, value) -> t.Iterable[str]:
+        """"FIXME."""
+
+        if base := schema.get("multipleOf"):
+            if value % base != 0:
+                yield LintRecord(
+                    LintLevel.MISSMATCH,
+                    node,
+                    schema,
+                    f"Expected a multiple of {base}, got {value}"
+                )
+
+        if max := schema.get("exclusiveMaximum"):
+            if value >= max:
+                yield LintRecord(
+                    LintLevel.MISSMATCH,
+                    node,
+                    schema,
+                    f"Expected a value less than {max}, got {value}"
+                )
+
+        if max := schema.get("maximum"):
+            if value > max:
+                yield LintRecord(
+                    LintLevel.MISSMATCH,
+                    node,
+                    schema,
+                    f"Expected a value less than or equal to {max}, got {value}"
+                )
+
+        if min := schema.get("exclusiveMinimum"):
+            if value <= min:
+                yield LintRecord(
+                    LintLevel.MISSMATCH,
+                    node,
+                    schema,
+                    f"Expected a value greater than {min}, got {value}"
+                )
+
+        if min := schema.get("minimum"):
+            if value < min:
+                yield LintRecord(
+                    LintLevel.MISSMATCH,
+                    node,
+                    schema,
+                    f"Expected a value greater than or equal to {min}, got {value}"
+                )
+
+    def lint_document(self, node, schema=None) -> t.Iterable[str]:
         """Lint a document.
 
         Given a Node within a document (or the root of a document!), return a
@@ -99,13 +257,40 @@ def lint_document(schema, node):
 
         """
 
+        schema = schema or self._schema  # Fixing up the schema source
+        schema = self.dereference(schema)  # And dereference it if needed
+
         if schema == True or schema == {}:
-    return []
+            yield from []
         elif isinstance(node, MappingNode):
-    return lint_mapping(schema, node)
+            yield from self.lint_mapping(schema, node)
         elif isinstance(node, SequenceNode):
-    return lint_sequence(schema, node)
+            yield from self.lint_sequence(schema, node)
         elif isinstance(node, ScalarNode):
-    return lint_scalar(schema, node)
+            yield from self.lint_scalar(schema, node)
         else:
-    return []
+            yield from []
+
+
+def lint_node(schema, node, cls=YamlLinter):
+    """Lint a document using a schema and linter."""
+
+    print(repr(node))
+    linter = cls(schema)
+    yield from linter.lint_document(node)
+
+
+def lint_buffer(schema, buff: str, cls=YamlLinter):
+    """Lint a buffer (string)."""
+
+    with StringIO(buff) as f:
+        node = yaml.compose(f)
+    yield from lint_node(schema, node, cls=cls)
+
+
+def lint_file(schema, path, cls=YamlLinter):
+    """Lint a file."""
+
+    with open(path) as f:
+        node = yaml.compose(f)
+    yield from lint_node(schema, node, cls=cls)