Added in things from @Phaiax's review

src/config.rs

@@ -32,8 +32,7 @@ impl Config {
     /// Load the configuration file from disk.
     pub fn from_disk<P: AsRef<Path>>(config_file: P) -> Result<Config> {
         let mut buffer = String::new();
-        File::open(config_file)
+        File::open(config_file).chain_err(|| "Unable to open the configuration file")?
-            .chain_err(|| "Unable to open the configuration file")?
                                .read_to_string(&mut buffer)
                                .chain_err(|| "Couldn't read the file")?;
 
@@ -57,25 +56,34 @@ impl Config {
 
     /// Try to get the configuration for a preprocessor, deserializing it as a
     /// `T`.
-    pub fn try_get_preprocessor<'de, T: Deserialize<'de>, S: AsRef<str>>(&self, name: S) -> Result<T> {
+    pub fn try_get_preprocessor<'de, T: Deserialize<'de>, S: AsRef<str>>(&self,
+                                                                         name: S)
+                                                                         -> Result<T> {
         get_deserialized(name, &self.preprocess)
     }
 
     /// Try to get the configuration for a postprocessor, deserializing it as a
     /// `T`.
-    pub fn try_get_postprocessor<'de, T: Deserialize<'de>, S: AsRef<str>>(&self, name: S) -> Result<T> {
+    pub fn try_get_postprocessor<'de, T: Deserialize<'de>, S: AsRef<str>>(&self,
+                                                                          name: S)
+                                                                          -> Result<T> {
         get_deserialized(name, &self.postprocess)
     }
 }
 
 /// Convenience function to load a value from some table then deserialize it.
-fn get_deserialized<'de, T: Deserialize<'de>, S: AsRef<str>>(name: S, table: &BTreeMap<String, Value>) -> Result<T> {
+fn get_deserialized<'de, T: Deserialize<'de>, S: AsRef<str>>(name: S,
-    match table.get(name.as_ref()) {
+                                                             table: &BTreeMap<String, Value>)
-        Some(output) => output
+                                                             -> Result<T> {
-            .clone()
+    let name = name.as_ref();
+
+    match table.get(name) {
+        Some(output) => {
+            output.clone()
                   .try_into()
-            .chain_err(|| "Couldn't deserialize the value"),
+                  .chain_err(|| "Couldn't deserialize the value")
-        None => bail!("Key Not Found"),
+        }
+        None => bail!("Key Not Found, {}", name),
     }
 }
 

src/renderer/html_handlebars/hbs_renderer.rs

@@ -296,7 +296,7 @@ impl Renderer for HtmlHandlebars {
 
         let rendered = self.post_process(rendered,
                                          "print.html",
-                                         &book.config.html_config().unwrap_or_default().playpen);
+                                         &html_config.playpen);
 
         book.write_file(Path::new("print").with_extension("html"),
                         &rendered.into_bytes())?;
@@ -329,7 +329,7 @@ fn make_data(book: &MDBook, config: &Config) -> Result<serde_json::Map<String, s
     }
 
     // Add google analytics tag
-    if let Some(ref ga) = book.config.html_config().and_then(|html| html.google_analytics) {
+    if let Some(ref ga) = config.html_config().and_then(|html| html.google_analytics) {
         data.insert("google_analytics".to_owned(), json!(ga));
     }
 

tests/config.rs

@@ -1,48 +0,0 @@
-extern crate mdbook;
-extern crate tempdir;
-
-use std::fs::File;
-use std::io::Write;
-
-use mdbook::MDBook;
-use tempdir::TempDir;
-
-// Tests that config values unspecified in the configuration file do not
-// overwrite
-// values specified earlier.
-// #[test]
-// fn do_not_overwrite_unspecified_config_values() {
-//     let dir = TempDir::new("mdbook").expect("Could not create a temp dir");
-
-//     let book = MDBook::new(dir.path())
-//         .with_source("bar")
-//         .with_destination("baz")
-//         .with_mathjax_support(true);
-
-//     assert_eq!(book.get_root(), dir.path());
-//     assert_eq!(book.get_source(), dir.path().join("bar"));
-//     assert_eq!(book.get_destination(), dir.path().join("baz"));
-
-//     // Test when trying to read a config file that does not exist
-//     let book = book.read_config().expect("Error reading the config file");
-
-//     assert_eq!(book.get_root(), dir.path());
-//     assert_eq!(book.get_source(), dir.path().join("bar"));
-//     assert_eq!(book.get_destination(), dir.path().join("baz"));
-//     assert_eq!(book.get_mathjax_support(), true);
-
-//     // Try with a partial config file
-//     let file_path = dir.path().join("book.toml");
-// let mut f = File::create(file_path).expect("Could not create config
-// file");
-// f.write_all(br#"source = "barbaz""#).expect("Could not write to config
-// file");
-//     f.sync_all().expect("Could not sync the file");
-
-//     let book = book.read_config().expect("Error reading the config file");
-
-//     assert_eq!(book.get_root(), dir.path());
-//     assert_eq!(book.get_source(), dir.path().join("barbaz"));
-//     assert_eq!(book.get_destination(), dir.path().join("baz"));
-//     assert_eq!(book.get_mathjax_support(), true);
-// }