feat: skip-if-optional flag to skip running even if mdbook-pandoc…

… is available

src/lib.rs

@@ -21,14 +21,19 @@ use preprocess::Preprocessor;
 #[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "kebab-case")]
 struct Config {
-    #[serde(rename = "profile")]
+    #[serde(rename = "profile", default = "Default::default")]
     pub profiles: HashMap<String, pandoc::Profile>,
     #[serde(default = "defaults::enabled")]
     pub keep_preprocessed: bool,
     pub hosted_html: Option<String>,
     /// Code block related configuration.
     #[serde(default = "Default::default")]
     pub code: CodeConfig,
+    #[serde(default = "Default::default")]
+    pub optional: bool,
+    /// Never run the renderer if it is marked as optional.
+    #[serde(default = "Default::default")]
+    pub skip_if_optional: bool,
 }
 
 /// Configuration for tweaking how code blocks are rendered.
@@ -97,6 +102,11 @@ impl mdbook::Renderer for Renderer {
             .with_context(|| format!("Unable to deserialize {}", Self::CONFIG_KEY))?
             .ok_or(anyhow!("No {} table found", Self::CONFIG_KEY))?;
 
+        if cfg.skip_if_optional && cfg.optional {
+            log::info!("Skipping rendering since `skip-if-optional` and `optional` are both set");
+            return Ok(());
+        }
+
         let html_cfg: Option<HtmlConfig> = ctx
             .config
             .get_deserialized_opt("output.html")
@@ -1167,6 +1177,23 @@ colorlinks = false
         "###)
     }
 
+    #[test]
+    fn skip_if_optional() {
+        let cfg = r#"
+[output.pandoc]
+optional = true
+skip-if-optional = true
+        "#;
+        let output = MDBook::init()
+            .mdbook_config(mdbook::Config::from_str(cfg).unwrap())
+            .build();
+        insta::assert_snapshot!(output, @r###"
+        ├─ log output
+        │  INFO mdbook::book: Running the pandoc backend    
+        │  INFO mdbook_pandoc: Skipping rendering since `skip-if-optional` and `optional` are both set    
+        "###)
+    }
+
     #[test]
     fn redirects() {
         let cfg = r#"