add more context to errors returned from Renderer::render()

src/lib.rs

@@ -147,7 +147,10 @@ impl mdbook::Renderer for Renderer {
             .with_context(|| format!("Unable to deserialize {}", Self::CONFIG_KEY))?
             .ok_or(anyhow!("No {} table found", Self::CONFIG_KEY))?;
 
-        let source_dir = ctx.source_dir().canonicalize()?;
+        let source_dir = ctx.source_dir();
+        let source_dir = source_dir
+            .canonicalize()
+            .with_context(|| format!("Unable to canonicalize path: {}", source_dir.display()))?;
 
         for (name, profile) in cfg.profiles {
             let destination = ctx.destination.join(name);
@@ -159,26 +162,31 @@ impl mdbook::Renderer for Renderer {
                 destination.join("src").into(),
                 profile.preprocessor_options(),
             );
-            let mut preprocessed = preprocessor.preprocess()?;
+            let mut preprocessed = preprocessor
+                .preprocess()
+                .context("Failed to preprocess book source")?;
 
             // Initialize renderer
             let mut renderer = PandocRenderer::new(profile, &ctx.root, destination.into());
 
             // Add preprocessed book chapters to renderer
             renderer.current_dir(preprocessed.output_dir());
             for input in &mut preprocessed {
-                renderer.input(input?);
+                renderer.input(input.context("Failed to preprocess input file")?);
             }
 
             if let Some(logfile) = &self.logfile {
-                renderer.stderr(logfile.try_clone()?);
+                renderer.stderr(logfile.try_clone().context("Failed to clone logfile")?);
             }
 
             // Render final output
-            renderer.render()?;
+            renderer
+                .render()
+                .context("Failed to render preprocessed source")?;
 
             if !cfg.keep_preprocessed {
-                fs::remove_dir_all(preprocessed.output_dir())?;
+                fs::remove_dir_all(preprocessed.output_dir())
+                    .context("Failed to clear preprocessed source files")?;
             }
         }
 

src/preprocess.rs

@@ -60,10 +60,17 @@ impl<'a> Preprocessor<'a> {
     }
 
     pub fn preprocess(self) -> anyhow::Result<PreprocessedFiles<'a>> {
-        if self.destination.try_exists()? {
-            fs::remove_dir_all(&self.destination)?;
+        let dest_error = || {
+            format!(
+                "Unable to clear destination directory {}",
+                self.destination.display()
+            )
+        };
+        if self.destination.try_exists().with_context(dest_error)? {
+            fs::remove_dir_all(&self.destination).with_context(dest_error)?;
         }
-        fs::create_dir_all(&self.destination)?;
+        fs::create_dir_all(&self.destination).with_context(dest_error)?;
+
         Ok(PreprocessedFiles {
             items: self.book.iter(),
             preprocessor: self,