Better distinguish between invalid or missing schema linter titles (#634)

Signed-off-by: Juan Cruz Viotti <jv@jviotti.com>

Author: jviotti

src/linter/include/sourcemeta/blaze/linter_error.h

@@ -18,6 +18,16 @@ namespace sourcemeta::blaze {
 #pragma warning(disable : 4251 4275)
 #endif
 
+/// @ingroup linter
+/// An error that represents a missing rule name
+class SOURCEMETA_BLAZE_LINTER_EXPORT LinterMissingNameError
+    : public std::exception {
+public:
+  [[nodiscard]] auto what() const noexcept -> const char * override {
+    return "The schema rule is missing a title";
+  }
+};
+
 /// @ingroup linter
 /// An error that represents an invalid schema rule name. The name must
 /// consist only of lowercase ASCII letters, digits, underscores, or slashes.

src/linter/schema.cc

@@ -47,9 +47,15 @@ static auto extract_description(const sourcemeta::core::JSON &schema)
 }
 
 static auto extract_title(const sourcemeta::core::JSON &schema) -> std::string {
-  if (!schema.defines("title") || !schema.at("title").is_string()) {
-    throw LinterInvalidNameError(
-        "", "The schema rule title is missing or not a string");
+  if (!schema.defines("title")) {
+    throw LinterMissingNameError{};
+  }
+
+  if (!schema.at("title").is_string()) {
+    std::ostringstream result;
+    sourcemeta::core::stringify(schema.at("title"), result);
+    throw LinterInvalidNameError(std::move(result).str(),
+                                 "The schema rule title is not a string");
   }
 
   auto title{schema.at("title").to_string()};

test/linter/linter_schema_test.cc

@@ -289,7 +289,7 @@ TEST(Linter, schema_rule_missing_title_throws) {
                    rule_schema, sourcemeta::core::schema_walker,
                    sourcemeta::core::schema_resolver,
                    sourcemeta::blaze::default_schema_compiler),
-               sourcemeta::blaze::LinterInvalidNameError);
+               sourcemeta::blaze::LinterMissingNameError);
 }
 
 TEST(Linter, schema_rule_non_string_title_throws) {
@@ -406,7 +406,7 @@ TEST(Linter, schema_rule_invalid_name_error_preserves_name) {
   }
 }
 
-TEST(Linter, schema_rule_missing_title_error_preserves_empty_name) {
+TEST(Linter, schema_rule_missing_title_error_message) {
   const auto rule_schema{sourcemeta::core::parse_json(R"JSON({
     "$schema": "https://json-schema.org/draft/2020-12/schema",
     "type": "object"
@@ -418,11 +418,9 @@ TEST(Linter, schema_rule_missing_title_error_preserves_empty_name) {
         rule_schema, sourcemeta::core::schema_walker,
         sourcemeta::core::schema_resolver,
         sourcemeta::blaze::default_schema_compiler);
-    FAIL() << "Expected LinterInvalidNameError";
-  } catch (const sourcemeta::blaze::LinterInvalidNameError &error) {
-    EXPECT_EQ(error.identifier(), "");
-    EXPECT_STREQ(error.what(),
-                 "The schema rule title is missing or not a string");
+    FAIL() << "Expected LinterMissingNameError";
+  } catch (const sourcemeta::blaze::LinterMissingNameError &error) {
+    EXPECT_STREQ(error.what(), "The schema rule is missing a title");
   }
 }