Auto merge of #79370 - jyn514:tidy-error, r=GuillaumeGomez

Don't abort rustdoc tests if `tidy` isn't installed

Follow-up to #78752.

Before:

```
Check compiletest suite=rustdoc mode=rustdoc (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)

running 396 tests
..................................................2020-11-23T12:12:37.735649Z ERROR compiletest::runtest: fatal error, panic: "failed to run tidy - is it installed? - No such file or directory (os error 2)"
F................................................. 100/396
.................................................................................................... 200/396
.................................................................................................... 300/396
...............................i...............2020-11-23T12:15:00.271271Z ERROR compiletest::runtest: fatal error, panic: "failed to run tidy - is it installed? - No such file or directory (os error 2)"
F................................................
```

After:

```
Check compiletest suite=rustdoc mode=rustdoc (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)

running 4 tests
.FFF
failures:

---- [rustdoc] rustdoc/fn-pointer-arg-name.rs stdout ----

error: htmldocck failed!
status: exit code: 1
command: "/usr/bin/python" "/home/joshua/rustc/src/etc/htmldocck.py" "/home/joshua/rustc/build/x86_64-unknown-linux-gnu/test/rustdoc/fn-pointer-arg-name" "/home/joshua/rustc/src/test/rustdoc/fn-pointer-arg-name.rs"
stdout:
------------------------------------------

------------------------------------------
stderr:
------------------------------------------
4: `@has` check failed
	`XPATH PATTERN` did not match
	// `@has` - '//*[`@class="rust` fn"]' 'pub fn f(callback: fn(len: usize, foo: u32))'

Encountered 1 errors

------------------------------------------

info: generating a diff against nightly rustdoc
failed to run tidy - is it installed? - Permission denied (os error 13)
failed to run tidy - is it installed? - Permission denied (os error 13)
 # a diff without running `tidy`
```

r? `@GuillaumeGomez`

src/tools/compiletest/src/common.rs

@@ -327,6 +327,9 @@ pub struct Config {
     /// created in `/<build_base>/rustfix_missing_coverage.txt`
     pub rustfix_coverage: bool,
 
+    /// whether to run `tidy` when a rustdoc test fails
+    pub has_tidy: bool,
+
     // Configuration for various run-make tests frobbing things like C compilers
     // or querying about various LLVM component information.
     pub cc: String,

src/tools/compiletest/src/main.rs

@@ -14,7 +14,7 @@ use std::ffi::OsString;
 use std::fs;
 use std::io::{self, ErrorKind};
 use std::path::{Path, PathBuf};
-use std::process::Command;
+use std::process::{Command, Stdio};
 use std::time::SystemTime;
 use test::ColorConfig;
 use tracing::*;
@@ -43,6 +43,10 @@ fn main() {
         panic!("Can't find Valgrind to run Valgrind tests");
     }
 
+    if !config.has_tidy && config.mode == Mode::Rustdoc {
+        eprintln!("warning: `tidy` is not installed; generated diffs will be harder to read");
+    }
+
     log_config(&config);
     run_tests(config);
 }
@@ -189,6 +193,11 @@ pub fn parse_config(args: Vec<String>) -> Config {
 
     let src_base = opt_path(matches, "src-base");
     let run_ignored = matches.opt_present("ignored");
+    let has_tidy = Command::new("tidy")
+        .arg("--version")
+        .stdout(Stdio::null())
+        .status()
+        .map_or(false, |status| status.success());
     Config {
         bless: matches.opt_present("bless"),
         compile_lib_path: make_absolute(opt_path(matches, "compile-lib-path")),
@@ -244,6 +253,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
         remote_test_client: matches.opt_str("remote-test-client").map(PathBuf::from),
         compare_mode: matches.opt_str("compare-mode").map(CompareMode::parse),
         rustfix_coverage: matches.opt_present("rustfix-coverage"),
+        has_tidy,
 
         cc: matches.opt_str("cc").unwrap(),
         cxx: matches.opt_str("cxx").unwrap(),

src/tools/compiletest/src/runtest.rs

@@ -2394,7 +2394,8 @@ impl<'test> TestCx<'test> {
 
         let proc_res = new_rustdoc.document(&compare_dir);
         if !proc_res.status.success() {
-            proc_res.fatal(Some("failed to run nightly rustdoc"), || ());
+            eprintln!("failed to run nightly rustdoc");
+            return;
         }
 
         #[rustfmt::skip]
@@ -2408,28 +2409,22 @@ impl<'test> TestCx<'test> {
             "-modify",
         ];
         let tidy_dir = |dir| {
-            let tidy = |file: &_| {
-                Command::new("tidy")
-                    .args(&tidy_args)
-                    .arg(file)
-                    .spawn()
-                    .unwrap_or_else(|err| {
-                        self.fatal(&format!("failed to run tidy - is it installed? - {}", err))
-                    })
-                    .wait()
-                    .unwrap()
-            };
             for entry in walkdir::WalkDir::new(dir) {
                 let entry = entry.expect("failed to read file");
                 if entry.file_type().is_file()
                     && entry.path().extension().and_then(|p| p.to_str()) == Some("html".into())
                 {
-                    tidy(entry.path());
+                    let status =
+                        Command::new("tidy").args(&tidy_args).arg(entry.path()).status().unwrap();
+                    // `tidy` returns 1 if it modified the file.
+                    assert!(status.success() || status.code() == Some(1));
                 }
             }
         };
-        tidy_dir(out_dir);
-        tidy_dir(&compare_dir);
+        if self.config.has_tidy {
+            tidy_dir(out_dir);
+            tidy_dir(&compare_dir);
+        }
 
         let pager = {
             let output = Command::new("git").args(&["config", "--get", "core.pager"]).output().ok();
@@ -2442,7 +2437,8 @@ impl<'test> TestCx<'test> {
             })
         };
         let mut diff = Command::new("diff");
-        diff.args(&["-u", "-r"]).args(&[&compare_dir, out_dir]);
+        // diff recursively, showing context, and excluding .css files
+        diff.args(&["-u", "-r", "-x", "*.css"]).args(&[&compare_dir, out_dir]);
 
         let output = if let Some(pager) = pager {
             let diff_pid = diff.stdout(Stdio::piped()).spawn().expect("failed to run `diff`");