Add a way to track Rustfix UI test coverage

src/bootstrap/builder.rs

@@ -1856,6 +1856,7 @@ mod __test {
             doc_tests: DocTests::No,
             bless: false,
             compare_mode: None,
+            rustfix_coverage: false,
         };
 
         let build = Build::new(config);
@@ -1897,6 +1898,7 @@ mod __test {
             doc_tests: DocTests::No,
             bless: false,
             compare_mode: None,
+            rustfix_coverage: false,
         };
 
         let build = Build::new(config);

src/bootstrap/flags.rs

@@ -56,6 +56,7 @@ pub enum Subcommand {
         rustc_args: Vec<String>,
         fail_fast: bool,
         doc_tests: DocTests,
+        rustfix_coverage: bool,
     },
     Bench {
         paths: Vec<PathBuf>,
@@ -188,6 +189,12 @@ To learn more about a subcommand, run `./x.py <subcommand> -h`"
                     "mode describing what file the actual ui output will be compared to",
                     "COMPARE MODE",
                 );
+                opts.optflag(
+                    "",
+                    "rustfix-coverage",
+                    "enable this to generate a Rustfix coverage file, which is saved in \
+                        `/<build_base>/rustfix_missing_coverage.txt`",
+                );
             }
             "bench" => {
                 opts.optmulti("", "test-args", "extra arguments", "ARGS");
@@ -363,6 +370,7 @@ Arguments:
                 test_args: matches.opt_strs("test-args"),
                 rustc_args: matches.opt_strs("rustc-args"),
                 fail_fast: !matches.opt_present("no-fail-fast"),
+                rustfix_coverage: matches.opt_present("rustfix-coverage"),
                 doc_tests: if matches.opt_present("doc") {
                     DocTests::Only
                 } else if matches.opt_present("no-doc") {
@@ -467,6 +475,13 @@ impl Subcommand {
         }
     }
 
+    pub fn rustfix_coverage(&self) -> bool {
+        match *self {
+            Subcommand::Test { rustfix_coverage, .. } => rustfix_coverage,
+            _ => false,
+        }
+    }
+
     pub fn compare_mode(&self) -> Option<&str> {
         match *self {
             Subcommand::Test {

src/bootstrap/test.rs

@@ -1284,6 +1284,10 @@ impl Step for Compiletest {
             cmd.arg("--android-cross-path").arg("");
         }
 
+        if builder.config.cmd.rustfix_coverage() {
+            cmd.arg("--rustfix-coverage");
+        }
+
         builder.ci_env.force_coloring_in_ci(&mut cmd);
 
         let _folder = builder.fold_output(|| format!("test_{}", suite));

src/tools/compiletest/src/common.rs

@@ -245,6 +245,11 @@ pub struct Config {
     /// mode describing what file the actual ui output will be compared to
     pub compare_mode: Option<CompareMode>,
 
+    /// If true, this will generate a coverage file with UI test files that run `MachineApplicable`
+    /// diagnostics but are missing `run-rustfix` annotations. The generated coverage file is
+    /// created in `/<build_base>/rustfix_missing_coverage.txt`
+    pub rustfix_coverage: 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

@@ -233,6 +233,12 @@ pub fn parse_config(args: Vec<String>) -> Config {
             "mode describing what file the actual ui output will be compared to",
             "COMPARE MODE",
         )
+        .optflag(
+            "",
+            "rustfix-coverage",
+            "enable this to generate a Rustfix coverage file, which is saved in \
+                `./<build_base>/rustfix_missing_coverage.txt`",
+        )
         .optflag("h", "help", "show this message");
 
     let (argv0, args_) = args.split_first().unwrap();
@@ -336,6 +342,7 @@ pub fn parse_config(args: Vec<String>) -> Config {
         color,
         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"),
 
         cc: matches.opt_str("cc").unwrap(),
         cxx: matches.opt_str("cxx").unwrap(),
@@ -475,6 +482,19 @@ pub fn run_tests(config: &Config) {
         let _ = fs::remove_dir_all("tmp/partitioning-tests");
     }
 
+    // If we want to collect rustfix coverage information,
+    // we first make sure that the coverage file does not exist.
+    // It will be created later on.
+    if config.rustfix_coverage {
+        let mut coverage_file_path = config.build_base.clone();
+        coverage_file_path.push("rustfix_missing_coverage.txt");
+        if coverage_file_path.exists() {
+            if let Err(e) = fs::remove_file(&coverage_file_path) {
+                panic!("Could not delete {} due to {}", coverage_file_path.display(), e)
+            }
+        }
+    }
+
     let opts = test_opts(config);
     let tests = make_tests(config);
     // sadly osx needs some file descriptor limits raised for running tests in

src/tools/compiletest/src/runtest.rs

@@ -19,7 +19,7 @@ use std::collections::{HashMap, HashSet, VecDeque};
 use std::env;
 use std::ffi::{OsStr, OsString};
 use std::fmt;
-use std::fs::{self, create_dir_all, File};
+use std::fs::{self, create_dir_all, File, OpenOptions};
 use std::hash::{Hash, Hasher};
 use std::io::prelude::*;
 use std::io::{self, BufReader};
@@ -2818,6 +2818,31 @@ impl<'test> TestCx<'test> {
 
         if self.config.compare_mode.is_some() {
             // don't test rustfix with nll right now
+        } else if self.config.rustfix_coverage {
+            // Find out which tests have `MachineApplicable` suggestions but are missing
+            // `run-rustfix` or `run-rustfix-only-machine-applicable` headers
+            let suggestions = get_suggestions_from_json(
+                &proc_res.stderr,
+                &HashSet::new(),
+                Filter::MachineApplicableOnly
+            ).unwrap();
+            if suggestions.len() > 0
+                && !self.props.run_rustfix
+                && !self.props.rustfix_only_machine_applicable {
+                    let mut coverage_file_path = self.config.build_base.clone();
+                    coverage_file_path.push("rustfix_missing_coverage.txt");
+                    debug!("coverage_file_path: {}", coverage_file_path.display());
+
+                    let mut file = OpenOptions::new()
+                        .create(true)
+                        .append(true)
+                        .open(coverage_file_path.as_path())
+                        .expect("could not create or open file");
+
+                    if let Err(_) = writeln!(file, "{}", self.testpaths.file.display()) {
+                        panic!("couldn't write to {}", coverage_file_path.display());
+                    }
+            }
         } else if self.props.run_rustfix {
             // Apply suggestions from rustc to the code itself
             let unfixed_code = self