fix(ack): accept Draft-07 $schema URI and remove dead prefixItems index

docs/guides/json-schema-integration.mdx

@@ -8,16 +8,16 @@ Your Ack [schema](../core-concepts/schemas.mdx) already describes your data's sh
 
 Use strict `Ack.fromJsonSchema()` to turn a decoded JSON Schema document
 (a map or boolean, not a JSON string) into an
-`AckSchema<Object, Object>`. The input dialect is draft 2020-12, including
-when `$schema` is absent. Other explicitly declared dialects are rejected.
+`AckSchema<Object, Object>`. The input dialect is draft 2020-12 or Draft-7
+(`http(s)://json-schema.org/draft-07/schema(#)`), including when `$schema` is
+absent. Other explicitly declared dialects are rejected.
 
 Only the declared `$schema` string is checked — a document is never matched
-against a dialect by shape. Replacing an older draft's `$schema` string does
-not convert its semantics. Tuple-form `items` (a Draft-7 array) is rejected;
-Draft-7 ignores `$ref` siblings that this importer applies. Draft-4 boolean
-`exclusiveMinimum` and `exclusiveMaximum` values are rejected, and Draft-4
-`integer` rejects `1.0` where this importer accepts it. Convert older schemas
-to draft 2020-12 and check their validation results before importing them.
+against a dialect by shape. Draft-7 documents are evaluated under the same
+supported subset: tuple-form `items` (a Draft-7 array) is rejected, and `$ref`
+siblings are applied as in draft 2020-12. Draft-4 boolean `exclusiveMinimum`
+and `exclusiveMaximum` values are rejected, and Draft-4 `integer` rejects `1.0`
+where this importer accepts it.
 
 ```dart
 import 'package:ack/ack.dart';

packages/ack/CHANGELOG.md

@@ -11,6 +11,10 @@
   `double`), and accepts `x-*` vendor extension annotations (such as
   `x-transformed`). Unknown format labels and non-`x-*` extension keywords
   continue to fail import with `unsupported_keyword`.
+* `Ack.fromJsonSchema()` now accepts Draft-07 `$schema` URIs
+  (`http(s)://json-schema.org/draft-07/schema` with or without a trailing `#`),
+  so schemas exported by `.toJsonSchema()` can be re-imported without stripping
+  `$schema`.
 
 ### Changed
 

packages/ack/lib/src/json_schema/json_schema_compiler.dart

@@ -128,7 +128,7 @@ final class _JsonSchemaCompiler {
     'then',
     'else',
   };
-  static const listKeywords = {'anyOf', 'allOf', 'oneOf', 'prefixItems'};
+  static const listKeywords = {'anyOf', 'allOf', 'oneOf'};
 
   // The subsets of the indexing sets above that validation implements.
   static const supportedChildKeywords = {
@@ -166,6 +166,14 @@ final class _JsonSchemaCompiler {
     'exclusiveMinimum',
     'exclusiveMaximum',
   };
+  static const supportedSchemaDialects = {
+    'https://json-schema.org/draft/2020-12/schema',
+    'https://json-schema.org/draft/2020-12/schema#',
+    'http://json-schema.org/draft-07/schema',
+    'http://json-schema.org/draft-07/schema#',
+    'https://json-schema.org/draft-07/schema',
+    'https://json-schema.org/draft-07/schema#',
+  };
   static const supportedFormats = {
     'date-time',
     'date',
@@ -247,12 +255,11 @@ final class _JsonSchemaCompiler {
     if (source.containsKey(r'$schema')) {
       final dialect = source[r'$schema'];
       // An empty fragment identifies the same meta-schema resource.
-      if (dialect != 'https://json-schema.org/draft/2020-12/schema' &&
-          dialect != 'https://json-schema.org/draft/2020-12/schema#') {
+      if (!supportedSchemaDialects.contains(dialect)) {
         _fail(
           node,
           r'$schema',
-          'Only draft 2020-12 input is supported.',
+          'Only draft 2020-12 and draft-07 inputs are supported.',
           code: 'unsupported_dialect',
         );
       }

packages/ack/test/json_schema_import_api_test.dart

@@ -111,7 +111,7 @@ void main() {
       {'minLength': -1},
       {r'$ref': 'missing.json'},
       {r'$ref': '#'},
-      {r'$schema': 'http://json-schema.org/draft-07/schema#'},
+      {r'$schema': 'http://json-schema.org/draft-04/schema#'},
     ]) {
       expect(
         () => Ack.fromJsonSchema(document),

packages/ack/test/json_schema_import_test.dart

@@ -250,13 +250,34 @@ void main() {
         {r'$ref': '#/%FF'},
         {r'$schema': null},
         {r'$anchor': null},
-        {r'$schema': 'http://json-schema.org/draft-07/schema#'},
+        {r'$schema': 'http://json-schema.org/draft-04/schema#'},
       ]) {
         expect(
           () => Ack.fromJsonSchema(document),
           throwsA(isA<JsonSchemaImportException>()),
         );
       }
+
+      for (final draft07Uri in [
+        'http://json-schema.org/draft-07/schema#',
+        'http://json-schema.org/draft-07/schema',
+        'https://json-schema.org/draft-07/schema#',
+        'https://json-schema.org/draft-07/schema',
+      ]) {
+        final draft07Schema = Ack.fromJsonSchema({
+          r'$schema': draft07Uri,
+          'definitions': {
+            'item': {'type': 'string', 'minLength': 2},
+          },
+          'type': 'object',
+          'properties': {
+            'name': {r'$ref': '#/definitions/item'},
+          },
+          'required': ['name'],
+        });
+        expect(draft07Schema.safeParse({'name': 'Ada'}).isOk, isTrue);
+        expect(draft07Schema.safeParse({'name': 'A'}).isFail, isTrue);
+      }
     });
 
     test('attributes duplicate anchors to the second anchor keyword', () {
@@ -1208,6 +1229,31 @@ void main() {
       },
     );
 
+    test('keeps prefixItems unsupported without indexing as a schema list', () {
+      for (final document in [
+        {
+          'type': 'array',
+          'prefixItems': [
+            {'type': 'string'},
+          ],
+        },
+        {'type': 'array', 'prefixItems': 'not-a-list'},
+      ]) {
+        expect(
+          () => Ack.fromJsonSchema(document),
+          throwsA(
+            isA<JsonSchemaImportException>().having(
+              (e) => e.diagnostics.single,
+              'diagnostic',
+              isA<JsonSchemaImportDiagnostic>()
+                  .having((d) => d.code, 'code', 'unsupported_keyword')
+                  .having((d) => d.keyword, 'keyword', 'prefixItems'),
+            ),
+          ),
+        );
+      }
+    });
+
     test('rejects malformed supported keywords', () {
       for (final document in [
         {'type': 'made-up'},