Fixed the `build.use-default-preprocessors` flag

src/book/mod.rs

@@ -360,16 +360,20 @@ fn determine_preprocessors(config: &Config) -> Result<Vec<Box<Preprocessor>>> {
         .and_then(|value| value.as_table())
         .map(|table| table.keys());
 
+    let mut preprocessors = if config.build.use_default_preprocessors {
+        default_preprocessors()
+    } else {
+        Vec::new()
+    };
+
     let preprocessor_keys = match preprocessor_keys {
         Some(keys) => keys,
         // If no preprocessor field is set, default to the LinkPreprocessor and
         // IndexPreprocessor. This allows you to disable default preprocessors
         // by setting "preprocess" to an empty list.
-        None => return Ok(default_preprocessors()),
+        None => return Ok(preprocessors),
     };
 
-    let mut preprocessors: Vec<Box<Preprocessor>> = Vec::new();
-
     for key in preprocessor_keys {
         match key.as_ref() {
             "links" => preprocessors.push(Box::new(LinkPreprocessor::new())),
@@ -477,6 +481,16 @@ mod tests {
         assert_eq!(got.as_ref().unwrap()[1].name(), "index");
     }
 
+    #[test]
+    fn use_default_preprocessors_works() {
+        let mut cfg = Config::default();
+        cfg.build.use_default_preprocessors = false;
+
+        let got = determine_preprocessors(&cfg).unwrap();
+
+        assert_eq!(got.len(), 0);
+    }
+
     #[test]
     fn config_complains_if_unimplemented_preprocessor() {
         let cfg_str: &'static str = r#"

src/config.rs

@@ -564,7 +564,7 @@ mod tests {
         [build]
         build-dir = "outputs"
         create-missing = false
-        preprocess = ["first_preprocessor", "second_preprocessor"]
+        use-default-preprocessors = true
 
         [output.html]
         theme = "./themedir"
@@ -575,6 +575,10 @@ mod tests {
         [output.html.playpen]
         editable = true
         editor = "ace"
+
+        [preprocess.first]
+
+        [preprocess.second]
         "#;
 
     #[test]