fix(core): use the default language for a code block typed without one

packages/core/src/blocks/Code/block.test.ts

@@ -82,12 +82,12 @@ describe("Code block input rule", () => {
     expect((block.props as any).language).toBe("ts");
   });
 
-  it("converts ``` + space into a codeBlock with empty language", () => {
+  it("converts ``` + space into a codeBlock with the default language", () => {
     typeString(editor, "``` ");
 
     const block = editor.document[0];
     expect(block.type).toBe("codeBlock");
-    expect((block.props as any).language).toBe("");
+    expect((block.props as any).language).toBe("text");
   });
 
   it("converts ```javascript + space into a codeBlock", () => {
@@ -138,13 +138,13 @@ describe("Code block input rule", () => {
     expect(block.content).toEqual([]);
   });
 
-  it("converts ``` + Enter into a codeBlock with empty language", () => {
+  it("converts ``` + Enter into a codeBlock with the default language", () => {
     typeString(editor, "```");
     pressKey(editor, "Enter");
 
     const block = editor.document[0];
     expect(block.type).toBe("codeBlock");
-    expect((block.props as any).language).toBe("");
+    expect((block.props as any).language).toBe("text");
   });
 
   it("converts ```javascript + Enter into a codeBlock", () => {

packages/core/src/blocks/Code/helpers/extensions/CodeKeyboardShortcutsExtension.ts

@@ -103,8 +103,13 @@ export const CodeKeyboardShortcutsExtension =
           find: /^```(.*?)\s$/,
           replace: ({ match }) => {
             const languageName = match[1].trim();
+            // Without a language suffix there is nothing to resolve, so fall
+            // back to the default rather than storing an empty language that
+            // no highlighter can render.
             const attributes = {
-              language: getLanguageId(options, languageName) ?? languageName,
+              language:
+                getLanguageId(options, languageName) ??
+                (languageName || options.defaultLanguage || "text"),
             };
 
             return {