From 341eb6d6f5c636575a42a5d3d75739755c17aade Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Wed, 4 Nov 2020 17:37:46 -0500
Subject: [PATCH 1/8] Give a better error when rustdoc tests fail

- Run the default rustdoc against the current rustdoc
- Diff output recursively
- Colorize diff output
---
 src/tools/compiletest/src/json.rs     | 11 ++--
 src/tools/compiletest/src/runtest.rs  | 72 +++++++++++++++++++++++++--
 src/tools/compiletest/tidy-rustdoc.sh | 38 ++++++++++++++
 3 files changed, 113 insertions(+), 8 deletions(-)
 create mode 100755 src/tools/compiletest/tidy-rustdoc.sh

diff --git a/src/tools/compiletest/src/json.rs b/src/tools/compiletest/src/json.rs
index 19aec0ea598f9..8d23227fdb8b7 100644
--- a/src/tools/compiletest/src/json.rs
+++ b/src/tools/compiletest/src/json.rs
@@ -153,11 +153,14 @@ fn parse_line(file_name: &str, line: &str, output: &str, proc_res: &ProcRes) ->
                 if serde_json::from_str::<FutureIncompatReport>(line).is_ok() {
                     vec![]
                 } else {
-                    proc_res.fatal(Some(&format!(
-                        "failed to decode compiler output as json: \
+                    proc_res.fatal(
+                        Some(&format!(
+                            "failed to decode compiler output as json: \
                          `{}`\nline: {}\noutput: {}",
-                        error, line, output
-                    )));
+                            error, line, output
+                        )),
+                        || (),
+                    );
                 }
             }
         }
diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index d46f905e6cc52..819f7257eee6a 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -287,6 +287,7 @@ pub fn compute_stamp_hash(config: &Config) -> String {
     format!("{:x}", hash.finish())
 }
 
+#[derive(Copy, Clone)]
 struct TestCx<'test> {
     config: &'test Config,
     props: &'test TestProps,
@@ -2208,7 +2209,12 @@ impl<'test> TestCx<'test> {
 
     fn fatal_proc_rec(&self, err: &str, proc_res: &ProcRes) -> ! {
         self.error(err);
-        proc_res.fatal(None);
+        proc_res.fatal(None, || ());
+    }
+
+    fn fatal_proc_rec_with_ctx(&self, err: &str, proc_res: &ProcRes, ctx: impl FnOnce(Self)) -> ! {
+        self.error(err);
+        proc_res.fatal(None, || ctx(*self));
     }
 
     // codegen tests (using FileCheck)
@@ -2325,15 +2331,72 @@ impl<'test> TestCx<'test> {
             let res = self.cmd2procres(
                 Command::new(&self.config.docck_python)
                     .arg(root.join("src/etc/htmldocck.py"))
-                    .arg(out_dir)
+                    .arg(&out_dir)
                     .arg(&self.testpaths.file),
             );
             if !res.status.success() {
-                self.fatal_proc_rec("htmldocck failed!", &res);
+                self.fatal_proc_rec_with_ctx("htmldocck failed!", &res, |mut this| {
+                    this.compare_to_default_rustdoc(&out_dir)
+                });
             }
         }
     }
 
+    fn compare_to_default_rustdoc(&mut self, out_dir: &Path) {
+        println!("info: generating a diff against nightly rustdoc");
+
+        let suffix =
+            self.safe_revision().map_or("nightly".into(), |path| path.to_owned() + "-nightly");
+        let compare_dir = output_base_dir(self.config, self.testpaths, Some(&suffix));
+        let _ = fs::remove_dir_all(&compare_dir);
+        create_dir_all(&compare_dir).unwrap();
+
+        // We need to create a new struct for the lifetimes on `config` to work.
+        let new_rustdoc = TestCx {
+            config: &Config {
+                // FIXME: use beta or a user-specified rustdoc instead of hardcoding
+                // the default toolchain
+                rustdoc_path: Some("rustdoc".into()),
+                ..self.config.clone()
+            },
+            ..*self
+        };
+        let proc_res = new_rustdoc.document(&compare_dir);
+        if !proc_res.status.success() {
+            proc_res.fatal(Some("failed to run nightly rustdoc"), || ());
+        }
+
+        // NOTE: this is fine since compiletest never runs out-of-tree
+        let tidy = concat!(env!("CARGO_MANIFEST_DIR"), "/tidy-rustdoc.sh");
+        // FIXME: this overwrites `out_dir` in place, maybe we should make a copy?
+        let status = Command::new(tidy)
+            .arg(out_dir)
+            .spawn()
+            .expect("tidy-rustdoc not found")
+            .wait()
+            .unwrap();
+        if !status.success() {
+            self.fatal("failed to run tidy - is installed?");
+        }
+        let status = Command::new(tidy).arg(&compare_dir).spawn().unwrap().wait().unwrap();
+        if !status.success() {
+            self.fatal("failed to run tidy");
+        }
+
+        let diff_pid = Command::new("diff")
+            .args(&["-u", "-r"])
+            .args(&[out_dir, &compare_dir])
+            .stdout(Stdio::piped())
+            .spawn()
+            .expect("failed to run `diff`");
+        Command::new("delta")
+            .stdin(diff_pid.stdout.unwrap())
+            .spawn()
+            .expect("delta not found")
+            .wait()
+            .unwrap();
+    }
+
     fn get_lines<P: AsRef<Path>>(
         &self,
         path: &P,
@@ -3590,7 +3653,7 @@ pub struct ProcRes {
 }
 
 impl ProcRes {
-    pub fn fatal(&self, err: Option<&str>) -> ! {
+    pub fn fatal(&self, err: Option<&str>, ctx: impl FnOnce()) -> ! {
         if let Some(e) = err {
             println!("\nerror: {}", e);
         }
@@ -3612,6 +3675,7 @@ impl ProcRes {
             json::extract_rendered(&self.stdout),
             json::extract_rendered(&self.stderr),
         );
+        ctx();
         // Use resume_unwind instead of panic!() to prevent a panic message + backtrace from
         // compiletest, which is unnecessary noise.
         std::panic::resume_unwind(Box::new(()));
diff --git a/src/tools/compiletest/tidy-rustdoc.sh b/src/tools/compiletest/tidy-rustdoc.sh
new file mode 100755
index 0000000000000..ce2c99d94d0c5
--- /dev/null
+++ b/src/tools/compiletest/tidy-rustdoc.sh
@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+indir="${1:?Missing argument 1: input directory}"
+
+tidy () {
+  {
+    # new-inline-tags is workaround for:
+    #   https://github.com/rust-lang/stdarch/issues/945
+    #   https://github.com/rust-lang/mdBook/issues/1372
+    command tidy \
+        --indent yes \
+        --indent-spaces 2 \
+        --wrap 0 \
+        --show-warnings no \
+        --markup yes \
+        --quiet yes \
+        --new-inline-tags 'c t' \
+        "$@" \
+        >/dev/null \
+    || {
+      # tidy exits with code 1 if there were any warnings :facepalm:
+      status=$?
+      if [ $status != 0 ] && [ $status != 1 ]
+      then
+        echo "While tidying $1" >&2
+        exit 1
+      fi
+    }
+  } | sed -E 's/#[0-9]+(-[0-9]+)?/#line/g'
+}
+
+find "$indir" -type f -name '*.html' -print0 \
+| while IFS= read -d '' -r file
+do
+  tidy -modify "$file"
+done

From c0eedc0b6ad30dfa1eb2b225246b4b3debed1cdb Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Fri, 6 Nov 2020 17:37:29 -0500
Subject: [PATCH 2/8] Address review comments

- remove unused args
- Fix formatting
- Improve naming
- Fix typo
---
 src/tools/compiletest/src/runtest.rs  | 15 ++++++++----
 src/tools/compiletest/tidy-rustdoc.sh | 35 +++++++++------------------
 2 files changed, 21 insertions(+), 29 deletions(-)

diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 819f7257eee6a..59c650d94cdcf 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -2212,9 +2212,14 @@ impl<'test> TestCx<'test> {
         proc_res.fatal(None, || ());
     }
 
-    fn fatal_proc_rec_with_ctx(&self, err: &str, proc_res: &ProcRes, ctx: impl FnOnce(Self)) -> ! {
+    fn fatal_proc_rec_with_ctx(
+        &self,
+        err: &str,
+        proc_res: &ProcRes,
+        on_failure: impl FnOnce(Self),
+    ) -> ! {
         self.error(err);
-        proc_res.fatal(None, || ctx(*self));
+        proc_res.fatal(None, || on_failure(*self));
     }
 
     // codegen tests (using FileCheck)
@@ -2376,7 +2381,7 @@ impl<'test> TestCx<'test> {
             .wait()
             .unwrap();
         if !status.success() {
-            self.fatal("failed to run tidy - is installed?");
+            self.fatal("failed to run tidy - is it installed?");
         }
         let status = Command::new(tidy).arg(&compare_dir).spawn().unwrap().wait().unwrap();
         if !status.success() {
@@ -3653,7 +3658,7 @@ pub struct ProcRes {
 }
 
 impl ProcRes {
-    pub fn fatal(&self, err: Option<&str>, ctx: impl FnOnce()) -> ! {
+    pub fn fatal(&self, err: Option<&str>, on_failure: impl FnOnce()) -> ! {
         if let Some(e) = err {
             println!("\nerror: {}", e);
         }
@@ -3675,7 +3680,7 @@ impl ProcRes {
             json::extract_rendered(&self.stdout),
             json::extract_rendered(&self.stderr),
         );
-        ctx();
+        on_failure();
         // Use resume_unwind instead of panic!() to prevent a panic message + backtrace from
         // compiletest, which is unnecessary noise.
         std::panic::resume_unwind(Box::new(()));
diff --git a/src/tools/compiletest/tidy-rustdoc.sh b/src/tools/compiletest/tidy-rustdoc.sh
index ce2c99d94d0c5..b31957058e8c1 100755
--- a/src/tools/compiletest/tidy-rustdoc.sh
+++ b/src/tools/compiletest/tidy-rustdoc.sh
@@ -5,30 +5,17 @@ set -euo pipefail
 indir="${1:?Missing argument 1: input directory}"
 
 tidy () {
-  {
-    # new-inline-tags is workaround for:
-    #   https://github.com/rust-lang/stdarch/issues/945
-    #   https://github.com/rust-lang/mdBook/issues/1372
-    command tidy \
-        --indent yes \
-        --indent-spaces 2 \
-        --wrap 0 \
-        --show-warnings no \
-        --markup yes \
-        --quiet yes \
-        --new-inline-tags 'c t' \
-        "$@" \
-        >/dev/null \
-    || {
-      # tidy exits with code 1 if there were any warnings :facepalm:
-      status=$?
-      if [ $status != 0 ] && [ $status != 1 ]
-      then
-        echo "While tidying $1" >&2
-        exit 1
-      fi
-    }
-  } | sed -E 's/#[0-9]+(-[0-9]+)?/#line/g'
+  command tidy \
+      --indent yes \
+      --indent-spaces 2 \
+      --wrap 0 \
+      --show-warnings no \
+      --markup yes \
+      --quiet yes \
+      "$@" \
+      >/dev/null \
+  # tidy exits with code 1 if there were any warnings
+  || [ $? -eq 1 ]
 }
 
 find "$indir" -type f -name '*.html' -print0 \

From acd6ce2347b80fedfc52df0c2a64127535e186f3 Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Fri, 6 Nov 2020 18:01:50 -0500
Subject: [PATCH 3/8] Fix bugs

---
 src/tools/compiletest/src/main.rs     | 2 +-
 src/tools/compiletest/src/runtest.rs  | 4 +++-
 src/tools/compiletest/tidy-rustdoc.sh | 3 +--
 3 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/src/tools/compiletest/src/main.rs b/src/tools/compiletest/src/main.rs
index 2b167ac8e9fb2..32347db5dbb1c 100644
--- a/src/tools/compiletest/src/main.rs
+++ b/src/tools/compiletest/src/main.rs
@@ -379,7 +379,7 @@ pub fn run_tests(config: Config) {
         }
         Err(e) => {
             // We don't know if tests passed or not, but if there was an error
-            // during testing we don't want to just suceeed (we may not have
+            // during testing we don't want to just succeed (we may not have
             // tested something), so fail.
             //
             // This should realistically "never" happen, so don't try to make
diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 59c650d94cdcf..8a0d671ed559c 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -2394,12 +2394,14 @@ impl<'test> TestCx<'test> {
             .stdout(Stdio::piped())
             .spawn()
             .expect("failed to run `diff`");
-        Command::new("delta")
+        let status = Command::new("delta")
+            .arg("--paging=never")
             .stdin(diff_pid.stdout.unwrap())
             .spawn()
             .expect("delta not found")
             .wait()
             .unwrap();
+        assert!(status.success());
     }
 
     fn get_lines<P: AsRef<Path>>(
diff --git a/src/tools/compiletest/tidy-rustdoc.sh b/src/tools/compiletest/tidy-rustdoc.sh
index b31957058e8c1..407e9169af541 100755
--- a/src/tools/compiletest/tidy-rustdoc.sh
+++ b/src/tools/compiletest/tidy-rustdoc.sh
@@ -14,8 +14,7 @@ tidy () {
       --quiet yes \
       "$@" \
       >/dev/null \
-  # tidy exits with code 1 if there were any warnings
-  || [ $? -eq 1 ]
+  || [ $? -eq 1 ] # tidy exits with code 1 if there were any warnings
 }
 
 find "$indir" -type f -name '*.html' -print0 \

From 975471ca4d5e141c4c885d4715e06671f862eeb7 Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Sat, 7 Nov 2020 12:12:29 -0500
Subject: [PATCH 4/8] Fall back to `diff` if `delta` isn't installed

---
 src/tools/compiletest/src/runtest.rs | 34 ++++++++++++++++------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 8a0d671ed559c..8319b8aba76eb 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -2388,20 +2388,26 @@ impl<'test> TestCx<'test> {
             self.fatal("failed to run tidy");
         }
 
-        let diff_pid = Command::new("diff")
-            .args(&["-u", "-r"])
-            .args(&[out_dir, &compare_dir])
-            .stdout(Stdio::piped())
-            .spawn()
-            .expect("failed to run `diff`");
-        let status = Command::new("delta")
-            .arg("--paging=never")
-            .stdin(diff_pid.stdout.unwrap())
-            .spawn()
-            .expect("delta not found")
-            .wait()
-            .unwrap();
-        assert!(status.success());
+        let has_delta = Command::new("delta")
+            .arg("--version")
+            .status()
+            .map_or(false, |status| status.success());
+        let mut diff = Command::new("diff");
+        diff.args(&["-u", "-r"]).args(&[out_dir, &compare_dir]);
+
+        if has_delta {
+            let diff_pid = diff.stdout(Stdio::piped()).spawn().expect("failed to run `diff`");
+            let status = Command::new("delta")
+                .arg("--paging=never")
+                .stdin(diff_pid.stdout.unwrap())
+                .status()
+                .unwrap();
+            assert!(status.success());
+        } else {
+            eprintln!("warning: `delta` not installed, falling back to `diff --color`");
+            diff.arg("--color").spawn().expect("failed to run `diff`").wait().unwrap();
+            assert!(status.success() || status.code() == Some(1));
+        }
     }
 
     fn get_lines<P: AsRef<Path>>(

From 619880e5546d7a0a5b33ee22b972e4acd6bbcf37 Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Sat, 7 Nov 2020 13:04:52 -0500
Subject: [PATCH 5/8] Fix tests with auxiliary docs

---
 src/tools/compiletest/src/runtest.rs | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 8319b8aba76eb..6eb7edf85aa5f 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -1729,7 +1729,7 @@ impl<'test> TestCx<'test> {
         self.config.target.contains("vxworks") && !self.is_vxworks_pure_static()
     }
 
-    fn compose_and_run_compiler(&self, mut rustc: Command, input: Option<String>) -> ProcRes {
+    fn build_all_auxiliary(&self, rustc: &mut Command) -> PathBuf {
         let aux_dir = self.aux_output_dir_name();
 
         if !self.props.aux_builds.is_empty() {
@@ -1748,6 +1748,11 @@ impl<'test> TestCx<'test> {
             rustc.arg("--extern").arg(format!("{}={}/{}", aux_name, aux_dir.display(), lib_name));
         }
 
+        aux_dir
+    }
+
+    fn compose_and_run_compiler(&self, mut rustc: Command, input: Option<String>) -> ProcRes {
+        let aux_dir = self.build_all_auxiliary(&mut rustc);
         self.props.unset_rustc_env.clone().iter().fold(&mut rustc, |rustc, v| rustc.env_remove(v));
         rustc.envs(self.props.rustc_env.clone());
         self.compose_and_run(
@@ -2359,13 +2364,26 @@ impl<'test> TestCx<'test> {
         // We need to create a new struct for the lifetimes on `config` to work.
         let new_rustdoc = TestCx {
             config: &Config {
-                // FIXME: use beta or a user-specified rustdoc instead of hardcoding
-                // the default toolchain
+                // FIXME: use beta or a user-specified rustdoc instead of
+                // hardcoding the default toolchain
                 rustdoc_path: Some("rustdoc".into()),
+                // Needed for building auxiliary docs below
+                rustc_path: "rustc".into(),
                 ..self.config.clone()
             },
             ..*self
         };
+
+        let output_file = TargetLocation::ThisDirectory(new_rustdoc.aux_output_dir_name());
+        let mut rustc = new_rustdoc.make_compile_args(
+            &new_rustdoc.testpaths.file,
+            output_file,
+            EmitMetadata::No,
+            AllowUnused::Yes,
+        );
+        rustc.arg("-L").arg(&new_rustdoc.aux_output_dir_name());
+        new_rustdoc.build_all_auxiliary(&mut dbg!(rustc));
+
         let proc_res = new_rustdoc.document(&compare_dir);
         if !proc_res.status.success() {
             proc_res.fatal(Some("failed to run nightly rustdoc"), || ());
@@ -2390,6 +2408,7 @@ impl<'test> TestCx<'test> {
 
         let has_delta = Command::new("delta")
             .arg("--version")
+            .stdout(Stdio::null())
             .status()
             .map_or(false, |status| status.success());
         let mut diff = Command::new("diff");

From e6e4a0ab63edb18d28e7de57b10e80f95ffd7666 Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Sat, 7 Nov 2020 13:10:29 -0500
Subject: [PATCH 6/8] Capture stdout and stderr of diff so they'll be printed
 at the end

---
 src/tools/compiletest/src/runtest.rs | 22 ++++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 6eb7edf85aa5f..7e17cac8b83b9 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -2382,7 +2382,7 @@ impl<'test> TestCx<'test> {
             AllowUnused::Yes,
         );
         rustc.arg("-L").arg(&new_rustdoc.aux_output_dir_name());
-        new_rustdoc.build_all_auxiliary(&mut dbg!(rustc));
+        new_rustdoc.build_all_auxiliary(&mut rustc);
 
         let proc_res = new_rustdoc.document(&compare_dir);
         if !proc_res.status.success() {
@@ -2414,19 +2414,25 @@ impl<'test> TestCx<'test> {
         let mut diff = Command::new("diff");
         diff.args(&["-u", "-r"]).args(&[out_dir, &compare_dir]);
 
-        if has_delta {
+        let output = if has_delta {
             let diff_pid = diff.stdout(Stdio::piped()).spawn().expect("failed to run `diff`");
-            let status = Command::new("delta")
+            let output = Command::new("delta")
                 .arg("--paging=never")
                 .stdin(diff_pid.stdout.unwrap())
-                .status()
+                // Capture output and print it explicitly so it will in turn be
+                // captured by libtest.
+                .output()
                 .unwrap();
-            assert!(status.success());
+            assert!(output.status.success());
+            output
         } else {
             eprintln!("warning: `delta` not installed, falling back to `diff --color`");
-            diff.arg("--color").spawn().expect("failed to run `diff`").wait().unwrap();
-            assert!(status.success() || status.code() == Some(1));
-        }
+            let output = diff.arg("--color").output().unwrap();
+            assert!(output.status.success() || output.status.code() == Some(1));
+            output
+        };
+        println!("{}", String::from_utf8_lossy(&output.stdout));
+        eprintln!("{}", String::from_utf8_lossy(&output.stderr));
     }
 
     fn get_lines<P: AsRef<Path>>(

From 4d44d77c4d97f46bbfd184e3995e0278b8c3d096 Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Sat, 14 Nov 2020 02:44:33 -0500
Subject: [PATCH 7/8] Use default git pager instead of hard-coding `delta`

---
 src/tools/compiletest/src/runtest.rs | 32 ++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 9 deletions(-)

diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 7e17cac8b83b9..46bf007c64956 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -2358,6 +2358,7 @@ impl<'test> TestCx<'test> {
         let suffix =
             self.safe_revision().map_or("nightly".into(), |path| path.to_owned() + "-nightly");
         let compare_dir = output_base_dir(self.config, self.testpaths, Some(&suffix));
+        // Don't give an error if the directory didn't already exist
         let _ = fs::remove_dir_all(&compare_dir);
         create_dir_all(&compare_dir).unwrap();
 
@@ -2406,18 +2407,28 @@ impl<'test> TestCx<'test> {
             self.fatal("failed to run tidy");
         }
 
-        let has_delta = Command::new("delta")
-            .arg("--version")
-            .stdout(Stdio::null())
-            .status()
-            .map_or(false, |status| status.success());
+        let pager = {
+            let output = Command::new("git").args(&["config", "--get", "core.pager"]).output().ok();
+            output.and_then(|out| {
+                if out.status.success() {
+                    Some(String::from_utf8(out.stdout).expect("invalid UTF8 in git pager"))
+                } else {
+                    None
+                }
+            })
+        };
         let mut diff = Command::new("diff");
         diff.args(&["-u", "-r"]).args(&[out_dir, &compare_dir]);
 
-        let output = if has_delta {
+        let output = if let Some(pager) = pager {
             let diff_pid = diff.stdout(Stdio::piped()).spawn().expect("failed to run `diff`");
-            let output = Command::new("delta")
-                .arg("--paging=never")
+            let pager = pager.trim();
+            if self.config.verbose {
+                eprintln!("using pager {}", pager);
+            }
+            let output = Command::new(pager)
+                // disable paging; we want this to be non-interactive
+                .env("PAGER", "")
                 .stdin(diff_pid.stdout.unwrap())
                 // Capture output and print it explicitly so it will in turn be
                 // captured by libtest.
@@ -2426,7 +2437,10 @@ impl<'test> TestCx<'test> {
             assert!(output.status.success());
             output
         } else {
-            eprintln!("warning: `delta` not installed, falling back to `diff --color`");
+            eprintln!("warning: no pager configured, falling back to `diff --color`");
+            eprintln!(
+                "help: try configuring a git pager (e.g. `delta`) with `git config --global core.pager delta`"
+            );
             let output = diff.arg("--color").output().unwrap();
             assert!(output.status.success() || output.status.code() == Some(1));
             output

From 25a3ffe5d4768e37fe98c9637db84af4714549d4 Mon Sep 17 00:00:00 2001
From: Joshua Nelson <jyn514@gmail.com>
Date: Fri, 20 Nov 2020 22:58:46 -0500
Subject: [PATCH 8/8] Move from bash to rust

---
 src/tools/compiletest/src/runtest.rs  | 49 ++++++++++++++++++---------
 src/tools/compiletest/tidy-rustdoc.sh | 24 -------------
 2 files changed, 33 insertions(+), 40 deletions(-)
 delete mode 100755 src/tools/compiletest/tidy-rustdoc.sh

diff --git a/src/tools/compiletest/src/runtest.rs b/src/tools/compiletest/src/runtest.rs
index 46bf007c64956..ca9fad41b5624 100644
--- a/src/tools/compiletest/src/runtest.rs
+++ b/src/tools/compiletest/src/runtest.rs
@@ -2390,22 +2390,39 @@ impl<'test> TestCx<'test> {
             proc_res.fatal(Some("failed to run nightly rustdoc"), || ());
         }
 
-        // NOTE: this is fine since compiletest never runs out-of-tree
-        let tidy = concat!(env!("CARGO_MANIFEST_DIR"), "/tidy-rustdoc.sh");
-        // FIXME: this overwrites `out_dir` in place, maybe we should make a copy?
-        let status = Command::new(tidy)
-            .arg(out_dir)
-            .spawn()
-            .expect("tidy-rustdoc not found")
-            .wait()
-            .unwrap();
-        if !status.success() {
-            self.fatal("failed to run tidy - is it installed?");
-        }
-        let status = Command::new(tidy).arg(&compare_dir).spawn().unwrap().wait().unwrap();
-        if !status.success() {
-            self.fatal("failed to run tidy");
-        }
+        #[rustfmt::skip]
+        let tidy_args = [
+            "--indent", "yes",
+            "--indent-spaces", "2",
+            "--wrap", "0",
+            "--show-warnings", "no",
+            "--markup", "yes",
+            "--quiet", "yes",
+            "-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());
+                }
+            }
+        };
+        tidy_dir(out_dir);
+        tidy_dir(&compare_dir);
 
         let pager = {
             let output = Command::new("git").args(&["config", "--get", "core.pager"]).output().ok();
diff --git a/src/tools/compiletest/tidy-rustdoc.sh b/src/tools/compiletest/tidy-rustdoc.sh
deleted file mode 100755
index 407e9169af541..0000000000000
--- a/src/tools/compiletest/tidy-rustdoc.sh
+++ /dev/null
@@ -1,24 +0,0 @@
-#!/usr/bin/env bash
-
-set -euo pipefail
-
-indir="${1:?Missing argument 1: input directory}"
-
-tidy () {
-  command tidy \
-      --indent yes \
-      --indent-spaces 2 \
-      --wrap 0 \
-      --show-warnings no \
-      --markup yes \
-      --quiet yes \
-      "$@" \
-      >/dev/null \
-  || [ $? -eq 1 ] # tidy exits with code 1 if there were any warnings
-}
-
-find "$indir" -type f -name '*.html' -print0 \
-| while IFS= read -d '' -r file
-do
-  tidy -modify "$file"
-done