rustdoc: add option to abort the process on markdown differences

src/bootstrap/bin/rustdoc.rs

@@ -57,6 +57,10 @@ fn main() {
         // This "unstable-options" can be removed when `--crate-version` is stabilized
         cmd.arg("-Z").arg("unstable-options")
            .arg("--crate-version").arg(version);
+
+        // While we can assume that `-Z unstable-options` is set, let's also force rustdoc to panic
+        // if pulldown rendering differences are found
+        cmd.arg("--deny-render-differences");
     }
 
     std::process::exit(match cmd.status() {

src/librustdoc/html/render.rs

@@ -495,7 +495,8 @@ pub fn run(mut krate: clean::Crate,
            css_file_extension: Option<PathBuf>,
            renderinfo: RenderInfo,
            render_type: RenderType,
-           sort_modules_alphabetically: bool) -> Result<(), Error> {
+           sort_modules_alphabetically: bool,
+           deny_render_differences: bool) -> Result<(), Error> {
     let src_root = match krate.src {
         FileName::Real(ref p) => match p.parent() {
             Some(p) => p.to_path_buf(),
@@ -659,6 +660,11 @@ pub fn run(mut krate: clean::Crate,
                 render_difference(d, &mut intro_msg, span, text);
             }
         }
+
+        if deny_render_differences {
+            println!("Aborting with {} rendering differences", markdown_warnings.len());
+            ::std::process::exit(1);
+        }
     }
 
     result

src/librustdoc/lib.rs

@@ -257,6 +257,10 @@ pub fn opts() -> Vec<RustcOptGroup> {
             o.optflag("", "sort-modules-by-appearance", "sort modules by where they appear in the \
                                                          program, rather than alphabetically")
         }),
+        unstable("deny-render-differences", |o| {
+            o.optflag("", "deny-render-differences", "abort doc runs when markdown rendering \
+                                                      differences are found")
+        }),
     ]
 }
 
@@ -393,6 +397,7 @@ pub fn main_args(args: &[String]) -> isize {
     }
 
     let output_format = matches.opt_str("w");
+    let deny_render_differences = matches.opt_present("deny-render-differences");
     let res = acquire_input(PathBuf::from(input), externs, &matches, move |out| {
         let Output { krate, passes, renderinfo } = out;
         info!("going to format");
@@ -404,7 +409,8 @@ pub fn main_args(args: &[String]) -> isize {
                                   css_file_extension,
                                   renderinfo,
                                   render_type,
-                                  sort_modules_alphabetically)
+                                  sort_modules_alphabetically,
+                                  deny_render_differences)
                     .expect("failed to generate documentation");
                 0
             }