derive: document in_doc in doc

book/src/creating_templates.md

@@ -55,6 +55,10 @@ recognized:
       name: &'a str,
   }
   ```
+
+* `in_doc` (as `in_doc = true`):
+  please see the section ["documentation as template code"](#documentation-as-template-code).
+
 * `ext` (as `ext = "txt"`): lets you specify the content type as a file
   extension. This is used to infer an escape mode (see below), and some
   web framework integrations use it to determine the content type.
@@ -66,6 +70,7 @@ recognized:
       name: &'a str,
   }
   ```
+
 * `print` (as `print = "code"`): enable debugging by printing nothing
   (`none`), the parsed syntax tree (`ast`), the generated code (`code`)
   or `all` for both. The requested data will be printed to stdout at
@@ -75,6 +80,7 @@ recognized:
   #[template(path = "hello.html", print = "all")]
   struct HelloTemplate<'a> { ... }
   ```
+
 * `block` (as `block = "block_name"`): renders the block by itself.
   Expressions outside of the block are not required by the struct, and
   inheritance is also supported. This can be useful when you need to
@@ -85,6 +91,7 @@ recognized:
   #[template(path = "hello.html", block = "hello")]
   struct HelloTemplate<'a> { ... }
   ```
+
 * `escape` (as `escape = "none"`): override the template's extension used for
   the purpose of determining the escaper for this template. See the section
   on configuring custom escapers for more information.
@@ -93,6 +100,7 @@ recognized:
   #[template(path = "hello.html", escape = "none")]
   struct HelloTemplate<'a> { ... }
   ```
+
 * `syntax` (as `syntax = "foo"`): set the syntax name for a parser defined
   in the configuration file. The default syntax , "default", is the one
   provided by Rinja.
@@ -101,6 +109,7 @@ recognized:
   #[template(path = "hello.html", syntax = "foo")]
   struct HelloTemplate<'a> { ... }
   ```
+
 * `config` (as `config = "config_file_path"`): set the path for the config file
   to be used. The path is interpreted as relative to your crate root.
   ```rust
@@ -110,6 +119,7 @@ recognized:
   ```
 
 ## Documentation as template code
+[#documentation-as-template-code]: #documentation-as-template-code
 
 As an alternative to supplying the code template code in an external file (as `path` argument),
 or as a string (as `source` argument), you can also enable the `"code-in-doc"` feature.

rinja_derive/src/lib.rs

@@ -63,6 +63,29 @@ use syn::parse_quote_spanned;
 /// web framework integrations use it to determine the content type.
 /// Cannot be used together with `path`.
 ///
+/// ### in_doc
+///
+/// E.g. `in_doc = true`
+///
+/// As an alternative to supplying the code template code in an external file (as `path` argument),
+/// or as a string (as `source` argument), you can also enable the `"code-in-doc"` feature.
+/// With this feature, you can specify the template code directly in the documentation
+/// of the template `struct`.
+///
+/// Instead of `path = "…"` or `source = "…"`, specify `in_doc = true` in the `#[template]`
+/// attribute, and in the struct's documentation add a ```` ```rinja ```` code block:
+///
+/// ```rust,ignore
+/// /// ```rinja
+/// /// <div>{{ lines|linebreaksbr }}</div>
+/// /// ```
+/// #[derive(Template)]
+/// #[template(ext = "html", in_doc = true)]
+/// struct Example<'a> {
+///     lines: &'a str,
+/// }
+/// ```
+///
 /// ### print
 ///
 /// E.g. `print = "code"`