Support hidden lines in languages other than Rust

Co-Authored-By: thecodewarrior <5467669+thecodewarrior@users.noreply.github.com>

guide/book.toml

@@ -17,6 +17,9 @@ edit-url-template = "https://github.com/rust-lang/mdBook/edit/master/guide/{path
 editable = true
 line-numbers = true
 
+[output.html.code.hidelines]
+python = "~"
+
 [output.html.search]
 limit-results = 20
 use-boolean-and = true

guide/src/format/configuration/renderers.md

@@ -223,6 +223,17 @@ runnable = true          # displays a run button for rust code
 
 [Ace]: https://ace.c9.io/
 
+### `[output.html.code]`
+
+The `[output.html.code]` table provides options for controlling code blocks.
+
+```toml
+[output.html.code]
+# A prefix string per language (one or more chars).
+# Any line starting with whitespace+prefix is hidden.
+hidelines = { python = "~" }
+```
+
 ### `[output.html.search]`
 
 The `[output.html.search]` table provides options for controlling the built-in text [search].

guide/src/format/mdbook.md

@@ -4,7 +4,6 @@
 
 There is a feature in mdBook that lets you hide code lines by prepending them
 with a `#` [like you would with Rustdoc][rustdoc-hide].
-This currently only works with Rust language code blocks.
 
 [rustdoc-hide]: https://doc.rust-lang.org/stable/rustdoc/documentation-tests.html#hiding-portions-of-the-example
 
@@ -30,6 +29,46 @@ Will render as
 
 The code block has an eyeball icon (<i class="fa fa-eye"></i>) which will toggle the visibility of the hidden lines.
 
+By default, this only works for code examples that are annotated with `rust`.
+However, you can define custom prefixes for other languages by adding a new line-hiding prefix in your `book.toml` with the language name and prefix character(s):
+
+```toml
+[output.html.code.hidelines]
+python = "~"
+```
+
+The prefix will hide any lines that begin with the given prefix. With the python prefix shown above, this:
+
+```bash
+~hidden()
+nothidden():
+~    hidden()
+    ~hidden()
+    nothidden()
+```
+
+will render as
+
+```python
+~hidden()
+nothidden():
+~    hidden()
+    ~hidden()
+    nothidden()
+```
+
+This behavior can be overridden locally with a different prefix. This has the same effect as above:
+
+~~~bash
+```python,hidelines=!!!
+!!!hidden()
+nothidden():
+!!!    hidden()
+    !!!hidden()
+    nothidden()
+```
+~~~
+
 ## Rust Playground
 
 Rust language code blocks will automatically get a play button (<i class="fa fa-play"></i>) which will execute the code and display the output just below the code block.

guide/src/format/theme/syntax-highlighting.md

@@ -77,38 +77,6 @@ the `theme` folder of your book.
 
 Now your theme will be used instead of the default theme.
 
-## Hiding code lines
-
-There is a feature in mdBook that lets you hide code lines by prepending them
-with a `#`.
-
-
-```bash
-# fn main() {
-    let x = 5;
-    let y = 6;
-
-    println!("{}", x + y);
-# }
-```
-
-Will render as
-
-```rust
-# fn main() {
-    let x = 5;
-    let y = 7;
-
-    println!("{}", x + y);
-# }
-```
-
-**At the moment, this only works for code examples that are annotated with
-`rust`. Because it would collide with semantics of some programming languages.
-In the future, we want to make this configurable through the `book.toml` so that
-everyone can benefit from it.**
-
-
 ## Improve default theme
 
 If you think the default theme doesn't look quite right for a specific language,

src/config.rs

@@ -504,6 +504,8 @@ pub struct HtmlConfig {
     /// Playground settings.
     #[serde(alias = "playpen")]
     pub playground: Playground,
+    /// Code settings.
+    pub code: Code,
     /// Print settings.
     pub print: Print,
     /// Don't render section labels.
@@ -556,6 +558,7 @@ impl Default for HtmlConfig {
             additional_js: Vec::new(),
             fold: Fold::default(),
             playground: Playground::default(),
+            code: Code::default(),
             print: Print::default(),
             no_section_label: false,
             search: None,
@@ -642,6 +645,22 @@ impl Default for Playground {
     }
 }
 
+/// Configuration for tweaking how the the HTML renderer handles code blocks.
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+#[serde(default, rename_all = "kebab-case")]
+pub struct Code {
+    /// A prefix string to hide lines per language (one or more chars).
+    pub hidelines: HashMap<String, String>,
+}
+
+impl Default for Code {
+    fn default() -> Code {
+        Code {
+            hidelines: HashMap::new(),
+        }
+    }
+}
+
 /// Configuration of the search functionality of the HTML renderer.
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 #[serde(default, rename_all = "kebab-case")]