lib.literalExpression: tag generated code blocks with nix, add usage example and describe function arg; lib.literalCode: init (#467878)

lib/options.nix

@@ -672,11 +672,30 @@ rec {
     is necessary for complex values, e.g. functions, or values that depend on
     other values or packages.
 
+    # Examples
+    :::{.example}
+    ## `literalExpression` usage example
+
+    ```nix
+    llvmPackages = mkOption {
+      type = types.str;
+      description = ''
+        Version of llvm packages to use for
+        this module
+      '';
+      example = literalExpression ''
+        llvmPackages = pkgs.llvmPackages_20;
+      '';
+    };
+    ```
+
+    :::
+
     # Inputs
 
     `text`
 
-    : 1\. Function argument
+    : The text to render as a Nix expression
   */
   literalExpression =
     text:
@@ -688,6 +707,49 @@ rec {
         inherit text;
       };
 
+  /**
+    For use in the `defaultText` and `example` option attributes. Causes the
+    given string to be rendered verbatim in the documentation as a code
+    block with the language bassed on the provided input tag.
+
+    If you wish to render Nix code, please see `literalExpression`.
+
+    # Examples
+    :::{.example}
+    ## `literalCode` usage example
+
+    ```nix
+    myPythonScript = mkOption {
+      type = types.str;
+      description = ''
+        Example python script used by a module
+      '';
+      example = literalCode "python" ''
+        print("Hello world!")
+      '';
+    };
+    ```
+
+    :::
+
+    # Inputs
+
+    `languageTag`
+
+    : The language tag to use when producing the code block (i.e. `js`, `rs`, etc).
+
+    `text`
+
+    : The text to render as a Nix expression
+  */
+  literalCode =
+    languageTag: text:
+    lib.literalMD ''
+      ```${languageTag}
+      ${text}
+      ```
+    '';
+
   /**
     For use in the `defaultText` and `example` option attributes. Causes the
     given MD text to be inserted verbatim in the documentation, for when

pkgs/by-name/ni/nixos-render-docs/src/nixos_render_docs/options.py

@@ -97,7 +97,7 @@ class BaseConverter(Converter[md.TR], Generic[md.TR]):
         if lit := option_is(option, key, 'literalMD'):
             return [ self._render(f"*{key.capitalize()}:*\n{lit['text']}") ]
         elif lit := option_is(option, key, 'literalExpression'):
-            code = md_make_code(lit['text'])
+            code = md_make_code(lit['text'], info="nix")
             return [ self._render(f"*{key.capitalize()}:*\n{code}") ]
         elif key in option:
             raise Exception(f"{key} has unrecognized type", option[key])