feat: disabled flag to disable rendering even if mdbook-pandoc is…

… available (#93)

Adds a `disabled` flag to disable rendering even if `mdbook-pandoc` is
available. Since rendering may rely on external dependencies, this can
be used to e.g. disable rendering except in CI where needed dependencies
are known to be installed.

Related to
google/mdbook-i18n-helpers#200 (comment)

src/lib.rs

@@ -21,14 +21,17 @@ 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,
+    /// Skip running the renderer.
+    #[serde(default = "Default::default")]
+    pub disabled: bool,
 }
 
 /// Configuration for tweaking how code blocks are rendered.
@@ -97,6 +100,11 @@ 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.disabled {
+            log::info!("Skipping rendering since `disabled` is set");
+            return Ok(());
+        }
+
         let html_cfg: Option<HtmlConfig> = ctx
             .config
             .get_deserialized_opt("output.html")
@@ -1410,6 +1418,22 @@ colorlinks = false
         "###)
     }
 
+    #[test]
+    fn disabled() {
+        let cfg = r#"
+[output.pandoc]
+disabled = 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 `disabled` is set    
+        "###)
+    }
+
     #[test]
     fn redirects() {
         let cfg = r#"