feat(linter): add forbid_empty_enum rule

src/extension/alterschema/CMakeLists.txt

@@ -80,6 +80,7 @@ sourcemeta_library(NAMESPACE sourcemeta PROJECT core NAME alterschema
     linter/duplicate_examples.h
     linter/enum_to_const.h
     linter/equal_numeric_bounds_to_const.h
+    linter/forbid_empty_enum.h
     linter/items_array_default.h
     linter/items_schema_default.h
     linter/multiple_of_default.h

src/extension/alterschema/alterschema.cc

@@ -108,6 +108,7 @@ inline auto APPLIES_TO_POINTERS(std::vector<Pointer> &&keywords)
 #include "linter/duplicate_examples.h"
 #include "linter/enum_to_const.h"
 #include "linter/equal_numeric_bounds_to_const.h"
+#include "linter/forbid_empty_enum.h"
 #include "linter/items_array_default.h"
 #include "linter/items_schema_default.h"
 #include "linter/multiple_of_default.h"
@@ -222,6 +223,7 @@ auto add(SchemaTransformer &bundle, const AlterSchemaMode mode) -> void {
     bundle.add<UnsatisfiableMaxContains>();
     bundle.add<UnsatisfiableMinProperties>();
     bundle.add<EnumToConst>();
+    bundle.add<ForbidEmptyEnum>();
     bundle.add<TopLevelTitle>();
     bundle.add<TopLevelDescription>();
     bundle.add<TopLevelExamples>();

src/extension/alterschema/linter/forbid_empty_enum.h

@@ -0,0 +1,31 @@
+class ForbidEmptyEnum final : public SchemaTransformRule {
+public:
+  using mutates = std::false_type;
+  using reframe_after_transform = std::false_type;
+  ForbidEmptyEnum()
+      : SchemaTransformRule{"forbid_empty_enum",
+                            "enum must contain at least one value"} {};
+
+  [[nodiscard]] auto
+  condition(const sourcemeta::core::JSON &schema,
+            const sourcemeta::core::JSON &,
+            const sourcemeta::core::Vocabularies &vocabularies,
+            const sourcemeta::core::SchemaFrame &,
+            const sourcemeta::core::SchemaFrame::Location &,
+            const sourcemeta::core::SchemaWalker &,
+            const sourcemeta::core::SchemaResolver &) const
+      -> sourcemeta::core::SchemaTransformRule::Result override {
+    ONLY_CONTINUE_IF(vocabularies.contains_any(
+                         {Vocabularies::Known::JSON_Schema_2020_12_Validation,
+                          Vocabularies::Known::JSON_Schema_2019_09_Validation,
+                          Vocabularies::Known::JSON_Schema_Draft_7,
+                          Vocabularies::Known::JSON_Schema_Draft_6,
+                          Vocabularies::Known::JSON_Schema_Draft_4,
+                          Vocabularies::Known::JSON_Schema_Draft_3,
+                          Vocabularies::Known::JSON_Schema_Draft_2,
+                          Vocabularies::Known::JSON_Schema_Draft_1}) &&
+                     schema.is_object() && schema.defines("enum") &&
+                     schema.at("enum").is_array() && schema.at("enum").empty());
+    return APPLIES_TO_KEYWORDS("enum");
+  }
+};

test/alterschema/alterschema_lint_2019_09_test.cc

@@ -4494,3 +4494,71 @@ TEST(AlterSchema_lint_2019_09, empty_object_as_true_1) {
 
   EXPECT_EQ(document, expected);
 }
+
+TEST(AlterSchema_lint_2019_09, forbid_empty_enum_1) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "https://json-schema.org/draft/2019-09/schema",
+    "title": "Example",
+    "description": "Example schema",
+    "examples": [1],
+    "enum": []
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_FALSE(result.first);
+  EXPECT_EQ(traces.size(), 1);
+  EXPECT_LINT_TRACE(traces, 0, "", "forbid_empty_enum",
+                    "enum must contain at least one value", false);
+}
+
+TEST(AlterSchema_lint_2019_09, forbid_empty_enum_2) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "https://json-schema.org/draft/2019-09/schema",
+    "title": "Example",
+    "description": "Example schema",
+    "examples": [1],
+    "enum": [1, 2]
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_TRUE(result.first);
+  EXPECT_EQ(traces.size(), 0);
+}
+
+TEST(AlterSchema_lint_2019_09, forbid_empty_enum_3) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "https://json-schema.org/draft/2019-09/schema",
+    "title": "Example",
+    "description": "Example schema",
+    "examples": [1],
+    "type": "string"
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_TRUE(result.first);
+  EXPECT_EQ(traces.size(), 0);
+}
+
+TEST(AlterSchema_lint_2019_09, forbid_empty_enum_4) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "https://json-schema.org/draft/2019-09/schema",
+    "title": "Example",
+    "description": "Example schema",
+    "examples": [{}],
+    "properties": {
+      "foo": {
+        "enum": []
+      }
+    }
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_FALSE(result.first);
+  EXPECT_EQ(traces.size(), 1);
+  EXPECT_LINT_TRACE(traces, 0, "/properties/foo", "forbid_empty_enum",
+                    "enum must contain at least one value", false);
+}

test/alterschema/alterschema_lint_2020_12_test.cc

@@ -9664,3 +9664,71 @@ TEST(AlterSchema_lint_2020_12, object_oneof_required_not_required_6) {
       "can be elevated",
       true);
 }
+
+TEST(AlterSchema_lint_2020_12, forbid_empty_enum_1) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "https://json-schema.org/draft/2020-12/schema",
+    "title": "Example",
+    "description": "Example schema",
+    "examples": [1],
+    "enum": []
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_FALSE(result.first);
+  EXPECT_EQ(traces.size(), 1);
+  EXPECT_LINT_TRACE(traces, 0, "", "forbid_empty_enum",
+                    "enum must contain at least one value", false);
+}
+
+TEST(AlterSchema_lint_2020_12, forbid_empty_enum_2) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "https://json-schema.org/draft/2020-12/schema",
+    "title": "Example",
+    "description": "Example schema",
+    "examples": [1],
+    "enum": [1, 2]
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_TRUE(result.first);
+  EXPECT_EQ(traces.size(), 0);
+}
+
+TEST(AlterSchema_lint_2020_12, forbid_empty_enum_3) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "https://json-schema.org/draft/2020-12/schema",
+    "title": "Example",
+    "description": "Example schema",
+    "examples": [1],
+    "type": "string"
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_TRUE(result.first);
+  EXPECT_EQ(traces.size(), 0);
+}
+
+TEST(AlterSchema_lint_2020_12, forbid_empty_enum_4) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "https://json-schema.org/draft/2020-12/schema",
+    "title": "Example",
+    "description": "Example schema",
+    "examples": [{}],
+    "properties": {
+      "foo": {
+        "enum": []
+      }
+    }
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_FALSE(result.first);
+  EXPECT_EQ(traces.size(), 1);
+  EXPECT_LINT_TRACE(traces, 0, "/properties/foo", "forbid_empty_enum",
+                    "enum must contain at least one value", false);
+}

test/alterschema/alterschema_lint_draft4_test.cc

@@ -2604,3 +2604,67 @@ TEST(AlterSchema_lint_draft4,
 
   EXPECT_EQ(document, expected);
 }
+
+TEST(AlterSchema_lint_draft4, forbid_empty_enum_1) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "http://json-schema.org/draft-04/schema#",
+    "title": "Example",
+    "description": "Example schema",
+    "enum": []
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_FALSE(result.first);
+  EXPECT_EQ(traces.size(), 1);
+  EXPECT_LINT_TRACE(traces, 0, "", "forbid_empty_enum",
+                    "enum must contain at least one value", false);
+}
+
+TEST(AlterSchema_lint_draft4, forbid_empty_enum_2) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "http://json-schema.org/draft-04/schema#",
+    "title": "Example",
+    "description": "Example schema",
+    "enum": [1, 2]
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_TRUE(result.first);
+  EXPECT_EQ(traces.size(), 0);
+}
+
+TEST(AlterSchema_lint_draft4, forbid_empty_enum_3) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "http://json-schema.org/draft-04/schema#",
+    "title": "Example",
+    "description": "Example schema",
+    "type": "string"
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_TRUE(result.first);
+  EXPECT_EQ(traces.size(), 0);
+}
+
+TEST(AlterSchema_lint_draft4, forbid_empty_enum_4) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "http://json-schema.org/draft-04/schema#",
+    "title": "Example",
+    "description": "Example schema",
+    "properties": {
+      "foo": {
+        "enum": []
+      }
+    }
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_FALSE(result.first);
+  EXPECT_EQ(traces.size(), 1);
+  EXPECT_LINT_TRACE(traces, 0, "/properties/foo", "forbid_empty_enum",
+                    "enum must contain at least one value", false);
+}

test/alterschema/alterschema_lint_draft6_test.cc

@@ -2929,3 +2929,71 @@ TEST(AlterSchema_lint_draft6, empty_object_as_true_1) {
 
   EXPECT_EQ(document, expected);
 }
+
+TEST(AlterSchema_lint_draft6, forbid_empty_enum_1) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "http://json-schema.org/draft-06/schema#",
+    "title": "Example",
+    "description": "Example schema",
+    "examples": [1],
+    "enum": []
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_FALSE(result.first);
+  EXPECT_EQ(traces.size(), 1);
+  EXPECT_LINT_TRACE(traces, 0, "", "forbid_empty_enum",
+                    "enum must contain at least one value", false);
+}
+
+TEST(AlterSchema_lint_draft6, forbid_empty_enum_2) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "http://json-schema.org/draft-06/schema#",
+    "title": "Example",
+    "description": "Example schema",
+    "examples": [1],
+    "enum": [1, 2]
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_TRUE(result.first);
+  EXPECT_EQ(traces.size(), 0);
+}
+
+TEST(AlterSchema_lint_draft6, forbid_empty_enum_3) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "http://json-schema.org/draft-06/schema#",
+    "title": "Example",
+    "description": "Example schema",
+    "examples": [1],
+    "type": "string"
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_TRUE(result.first);
+  EXPECT_EQ(traces.size(), 0);
+}
+
+TEST(AlterSchema_lint_draft6, forbid_empty_enum_4) {
+  const sourcemeta::core::JSON document = sourcemeta::core::parse_json(R"JSON({
+    "$schema": "http://json-schema.org/draft-06/schema#",
+    "title": "Example",
+    "description": "Example schema",
+    "examples": [{}],
+    "properties": {
+      "foo": {
+        "enum": []
+      }
+    }
+  })JSON");
+
+  LINT_WITHOUT_FIX(document, result, traces);
+
+  EXPECT_FALSE(result.first);
+  EXPECT_EQ(traces.size(), 1);
+  EXPECT_LINT_TRACE(traces, 0, "/properties/foo", "forbid_empty_enum",
+                    "enum must contain at least one value", false);
+}