Prohibit 'print.md' files (#524)

* Prohibit 'print.md' files

Fix #258 by emmiting an error whenever an mdBook contains a
"print.md" file in its root.

* Apply suggested changes

* Add tests

src/lib.rs

@@ -129,6 +129,8 @@ pub use renderer::Renderer;
 
 /// The error types used through out this crate.
 pub mod errors {
+    use std::path::PathBuf;
+
     error_chain!{
         foreign_links {
             Io(::std::io::Error);
@@ -147,6 +149,11 @@ pub mod errors {
                 description("A SUMMARY.md parsing error")
                 display("Error at line {}, column {}: {}", line, col, message)
             }
+
+            ReservedFilenameError(filename: PathBuf) {
+                description("Reserved Filename")
+                display("{} is reserved for internal use", filename.display())
+            }
         }
     }
 

src/renderer/html_handlebars/hbs_renderer.rs

@@ -54,6 +54,11 @@ impl HtmlHandlebars {
                                                                            to str")
                                                        })?;
 
+                // "print.html" is used for the print page.
+                if ch.path == Path::new("print.md") {
+                    bail!(ErrorKind::ReservedFilenameError(ch.path.clone()));
+                };
+
                 // Non-lexical lifetimes needed :'(
                 let title: String;
                 {

tests/rendered_output.rs

@@ -2,6 +2,7 @@ extern crate mdbook;
 #[macro_use]
 extern crate pretty_assertions;
 extern crate select;
+extern crate tempdir;
 extern crate walkdir;
 
 mod dummy_book;
@@ -9,11 +10,13 @@ mod dummy_book;
 use dummy_book::{assert_contains_strings, DummyBook};
 
 use std::fs;
+use std::io::Write;
 use std::path::Path;
 use std::ffi::OsStr;
 use walkdir::{DirEntry, WalkDir};
 use select::document::Document;
 use select::predicate::{Class, Name, Predicate};
+use tempdir::TempDir;
 use mdbook::errors::*;
 use mdbook::utils::fs::file_to_string;
 use mdbook::config::Config;
@@ -304,3 +307,21 @@ fn example_book_can_build() {
     let got = md.build();
     assert!(got.is_ok());
 }
+
+#[test]
+fn book_with_a_reserved_filename_does_not_build() {
+    let tmp_dir = TempDir::new("mdBook").unwrap();
+    let src_path = tmp_dir.path().join("src");
+    fs::create_dir(&src_path).unwrap();
+
+    let summary_path = src_path.join("SUMMARY.md");
+    let print_path = src_path.join("print.md");
+
+    fs::File::create(print_path).unwrap();
+    let mut summary_file = fs::File::create(summary_path).unwrap();
+    writeln!(summary_file, "[print](print.md)").unwrap();
+
+    let mut md = MDBook::load(tmp_dir.path()).unwrap();
+    let got = md.build();
+    assert!(got.is_err());
+}