feat(cli): add "--no-clear-screen" flag (#13454)

This commit adds "--no-clear-screen" flag which can be used
with "--watch" flag to disable clearing of terminal screen on
each file change.

8 files changed, 321 insertions, 37 deletions

diff --git a/cli/file_watcher.rs b/cli/file_watcher.rs
index 87531bb77..fd7d4e1a1 100644
--- a/cli/file_watcher.rs
+++ b/cli/file_watcher.rs
@@ -91,18 +91,19 @@ where
         paths_to_watch,
         result,
       } => {
-        // Clear screen first
-        eprint!("{}", CLEAR_SCREEN);
-        info!(
-          "{} File change detected! Restarting!",
-          colors::intense_blue("Watcher"),
-        );
         return (paths_to_watch, result);
       }
     }
   }
 }
 
+pub struct PrintConfig {
+  /// printing watcher status to terminal.
+  pub job_name: String,
+  /// determine whether to clear the terminal screen
+  pub clear_screen: bool,
+}
+
 /// Creates a file watcher, which will call `resolver` with every file change.
 ///
 /// - `resolver` is used for resolving file paths to be watched at every restarting
@@ -113,12 +114,10 @@ where
 /// - `operation` is the actual operation we want to run every time the watcher detects file
 /// changes. For example, in the case where we would like to bundle, then `operation` would
 /// have the logic for it like bundling the code.
-///
-/// - `job_name` is just used for printing watcher status to terminal.
 pub async fn watch_func<R, O, T, F1, F2>(
   mut resolver: R,
   mut operation: O,
-  job_name: &str,
+  print_config: PrintConfig,
 ) -> Result<(), AnyError>
 where
   R: FnMut(Option<Vec<PathBuf>>) -> F1,
@@ -128,11 +127,26 @@ where
 {
   let (sender, mut receiver) = DebouncedReceiver::new_with_sender();
 
+  let PrintConfig {
+    job_name,
+    clear_screen,
+  } = print_config;
+
   // Store previous data. If module resolution fails at some point, the watcher will try to
   // continue watching files using these data.
   let mut paths_to_watch;
   let mut resolution_result;
 
+  let print_after_restart = || {
+    if clear_screen {
+      eprint!("{}", CLEAR_SCREEN);
+    }
+    info!(
+      "{} File change detected! Restarting!",
+      colors::intense_blue("Watcher"),
+    );
+  };
+
   match resolver(None).await {
     ResolutionResult::Ignore => {
       // The only situation where it makes sense to ignore the initial 'change'
@@ -149,6 +163,8 @@ where
       let (paths, result) = next_restart(&mut resolver, &mut receiver).await;
       paths_to_watch = paths;
       resolution_result = result;
+
+      print_after_restart();
     }
     ResolutionResult::Restart {
       paths_to_watch: paths,
@@ -159,8 +175,10 @@ where
     }
   };
 
-  // Clear screen first
-  eprint!("{}", CLEAR_SCREEN);
+  if clear_screen {
+    eprint!("{}", CLEAR_SCREEN);
+  }
+
   info!("{} {} started.", colors::intense_blue("Watcher"), job_name,);
 
   loop {
@@ -175,6 +193,8 @@ where
               paths_to_watch = paths;
             }
             resolution_result = result;
+
+            print_after_restart();
             continue;
           },
           _ = fut => {},
@@ -202,6 +222,8 @@ where
     }
     resolution_result = result;
 
+    print_after_restart();
+
     drop(watcher);
   }
 }
diff --git a/cli/flags.rs b/cli/flags.rs
index 8b308658d..d4ba685fb 100644
--- a/cli/flags.rs
+++ b/cli/flags.rs
@@ -254,6 +254,7 @@ pub struct Flags {
   pub v8_flags: Vec<String>,
   pub version: bool,
   pub watch: Option<Vec<PathBuf>>,
+  pub no_clear_screen: bool,
 }
 
 fn join_paths(allowlist: &[PathBuf], d: &str) -> String {
@@ -561,6 +562,7 @@ fn bundle_subcommand<'a>() -> App<'a> {
     .arg(Arg::new("source_file").takes_value(true).required(true))
     .arg(Arg::new("out_file").takes_value(true).required(false))
     .arg(watch_arg(false))
+    .arg(no_clear_screen_arg())
     .about("Bundle module and dependencies into single file")
     .long_about(
       "Output a single JavaScript file with all dependencies.
@@ -900,6 +902,7 @@ Ignore formatting a file by adding an ignore comment at the top of the file:
         .required(false),
     )
     .arg(watch_arg(false))
+    .arg(no_clear_screen_arg())
     .arg(
       Arg::new("options-use-tabs")
         .long("options-use-tabs")
@@ -1169,6 +1172,7 @@ Ignore linting a file by adding an ignore comment at the top of the file:
         .required(false),
     )
     .arg(watch_arg(false))
+    .arg(no_clear_screen_arg())
 }
 
 fn repl_subcommand<'a>() -> App<'a> {
@@ -1191,6 +1195,7 @@ fn run_subcommand<'a>() -> App<'a> {
         .conflicts_with("inspect")
         .conflicts_with("inspect-brk"),
     )
+    .arg(no_clear_screen_arg())
     .setting(AppSettings::TrailingVarArg)
     .arg(script_arg().required(true))
     .about("Run a JavaScript or TypeScript program")
@@ -1320,6 +1325,7 @@ fn test_subcommand<'a>() -> App<'a> {
         .conflicts_with("no-run")
         .conflicts_with("coverage"),
     )
+    .arg(no_clear_screen_arg())
     .arg(script_arg().last(true))
     .about("Run tests")
     .long_about(
@@ -1672,6 +1678,13 @@ Only local files from entry point module graph are watched.",
   }
 }
 
+fn no_clear_screen_arg<'a>() -> Arg<'a> {
+  Arg::new("no-clear-screen")
+    .requires("watch")
+    .long("no-clear-screen")
+    .help("Do not clear terminal screen when under watch mode")
+}
+
 fn no_check_arg<'a>() -> Arg<'a> {
   Arg::new("no-check")
     .takes_value(true)
@@ -1910,6 +1923,7 @@ fn eval_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
 fn fmt_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
   config_arg_parse(flags, matches);
   watch_arg_parse(flags, matches, false);
+
   let files = match matches.values_of("files") {
     Some(f) => f.map(PathBuf::from).collect(),
     None => vec![],
@@ -2451,6 +2465,10 @@ fn watch_arg_parse(
   } else if matches.is_present("watch") {
     flags.watch = Some(vec![]);
   }
+
+  if matches.is_present("no-clear-screen") {
+    flags.no_clear_screen = true;
+  }
 }
 
 // TODO(ry) move this to utility module and add test.
@@ -2581,6 +2599,30 @@ mod tests {
   }
 
   #[test]
+  fn run_watch_with_no_clear_screen() {
+    let r = flags_from_vec(svec![
+      "deno",
+      "run",
+      "--watch",
+      "--no-clear-screen",
+      "script.ts"
+    ]);
+
+    let flags = r.unwrap();
+    assert_eq!(
+      flags,
+      Flags {
+        subcommand: DenoSubcommand::Run(RunFlags {
+          script: "script.ts".to_string(),
+        }),
+        watch: Some(vec![]),
+        no_clear_screen: true,
+        ..Flags::default()
+      }
+    );
+  }
+
+  #[test]
   fn run_reload_allow_write() {
     let r =
       flags_from_vec(svec!["deno", "run", "-r", "--allow-write", "script.ts"]);
@@ -2813,6 +2855,28 @@ mod tests {
       }
     );
 
+    let r =
+      flags_from_vec(svec!["deno", "fmt", "--watch", "--no-clear-screen"]);
+    assert_eq!(
+      r.unwrap(),
+      Flags {
+        subcommand: DenoSubcommand::Fmt(FmtFlags {
+          ignore: vec![],
+          check: false,
+          files: vec![],
+          ext: "ts".to_string(),
+          use_tabs: None,
+          line_width: None,
+          indent_width: None,
+          single_quote: None,
+          prose_wrap: None,
+        }),
+        watch: Some(vec![]),
+        no_clear_screen: true,
+        ..Flags::default()
+      }
+    );
+
     let r = flags_from_vec(svec![
       "deno",
       "fmt",
@@ -2941,6 +3005,62 @@ mod tests {
       }
     );
 
+    let r = flags_from_vec(svec![
+      "deno",
+      "lint",
+      "--watch",
+      "script_1.ts",
+      "script_2.ts"
+    ]);
+    assert_eq!(
+      r.unwrap(),
+      Flags {
+        subcommand: DenoSubcommand::Lint(LintFlags {
+          files: vec![
+            PathBuf::from("script_1.ts"),
+            PathBuf::from("script_2.ts")
+          ],
+          rules: false,
+          maybe_rules_tags: None,
+          maybe_rules_include: None,
+          maybe_rules_exclude: None,
+          json: false,
+          ignore: vec![],
+        }),
+        watch: Some(vec![]),
+        ..Flags::default()
+      }
+    );
+
+    let r = flags_from_vec(svec![
+      "deno",
+      "lint",
+      "--watch",
+      "--no-clear-screen",
+      "script_1.ts",
+      "script_2.ts"
+    ]);
+    assert_eq!(
+      r.unwrap(),
+      Flags {
+        subcommand: DenoSubcommand::Lint(LintFlags {
+          files: vec![
+            PathBuf::from("script_1.ts"),
+            PathBuf::from("script_2.ts")
+          ],
+          rules: false,
+          maybe_rules_tags: None,
+          maybe_rules_include: None,
+          maybe_rules_exclude: None,
+          json: false,
+          ignore: vec![],
+        }),
+        watch: Some(vec![]),
+        no_clear_screen: true,
+        ..Flags::default()
+      }
+    );
+
     let r =
       flags_from_vec(svec!["deno", "lint", "--ignore=script_1.ts,script_2.ts"]);
     assert_eq!(
@@ -3612,6 +3732,29 @@ mod tests {
   }
 
   #[test]
+  fn bundle_watch_with_no_clear_screen() {
+    let r = flags_from_vec(svec![
+      "deno",
+      "bundle",
+      "--watch",
+      "--no-clear-screen",
+      "source.ts"
+    ]);
+    assert_eq!(
+      r.unwrap(),
+      Flags {
+        subcommand: DenoSubcommand::Bundle(BundleFlags {
+          source_file: "source.ts".to_string(),
+          out_file: None,
+        }),
+        watch: Some(vec![]),
+        no_clear_screen: true,
+        ..Flags::default()
+      }
+    )
+  }
+
+  #[test]
   fn run_import_map() {
     let r = flags_from_vec(svec![
       "deno",
@@ -4372,6 +4515,31 @@ mod tests {
   }
 
   #[test]
+  fn test_watch_with_no_clear_screen() {
+    let r =
+      flags_from_vec(svec!["deno", "test", "--watch", "--no-clear-screen"]);
+    assert_eq!(
+      r.unwrap(),
+      Flags {
+        subcommand: DenoSubcommand::Test(TestFlags {
+          no_run: false,
+          doc: false,
+          fail_fast: None,
+          filter: None,
+          allow_none: false,
+          shuffle: None,
+          include: None,
+          ignore: vec![],
+          concurrent_jobs: NonZeroUsize::new(1).unwrap(),
+        }),
+        watch: Some(vec![]),
+        no_clear_screen: true,
+        ..Flags::default()
+      }
+    );
+  }
+
+  #[test]
   fn bundle_with_cafile() {
     let r = flags_from_vec(svec![
       "deno",
@@ -4676,4 +4844,14 @@ mod tests {
       vec![PathBuf::from("dir/a.js"), PathBuf::from("dir/b.js")]
     );
   }
+
+  #[test]
+  fn test_no_clear_watch_flag_without_watch_flag() {
+    let r = flags_from_vec(svec!["deno", "run", "--no-clear-screen", "foo.js"]);
+    assert!(r.is_err());
+    let error_message = r.unwrap_err().to_string();
+    assert!(&error_message
+      .contains("error: The following required arguments were not provided:"));
+    assert!(&error_message.contains("--watch=<FILES>..."));
+  }
 }
diff --git a/cli/main.rs b/cli/main.rs
index c996425c7..b6bc0c7ad 100644
--- a/cli/main.rs
+++ b/cli/main.rs
@@ -529,15 +529,7 @@ async fn lint_command(
     return Ok(0);
   }
 
-  let ps = ProcState::build(flags.clone()).await?;
-  let maybe_lint_config = if let Some(config_file) = &ps.maybe_config_file {
-    config_file.to_lint_config()?
-  } else {
-    None
-  };
-
-  tools::lint::lint(maybe_lint_config, lint_flags, flags.watch.is_some())
-    .await?;
+  tools::lint::lint(flags, lint_flags).await?;
   Ok(0)
 }
 
@@ -853,7 +845,15 @@ async fn bundle_command(
   };
 
   if flags.watch.is_some() {
-    file_watcher::watch_func(resolver, operation, "Bundle").await?;
+    file_watcher::watch_func(
+      resolver,
+      operation,
+      file_watcher::PrintConfig {
+        job_name: "Bundle".to_string(),
+        clear_screen: !flags.no_clear_screen,
+      },
+    )
+    .await?;
   } else {
     let module_graph =
       if let ResolutionResult::Restart { result, .. } = resolver(None).await {
@@ -894,8 +894,7 @@ async fn format_command(
     return Ok(0);
   }
 
-  tools::fmt::format(fmt_flags, flags.watch.is_some(), maybe_fmt_config)
-    .await?;
+  tools::fmt::format(flags, fmt_flags, maybe_fmt_config).await?;
   Ok(0)
 }
 
@@ -1118,7 +1117,15 @@ async fn run_with_watch(flags: Flags, script: String) -> Result<i32, AnyError> {
     }
   };
 
-  file_watcher::watch_func(resolver, operation, "Process").await?;
+  file_watcher::watch_func(
+    resolver,
+    operation,
+    file_watcher::PrintConfig {
+      job_name: "Process".to_string(),
+      clear_screen: !flags.no_clear_screen,
+    },
+  )
+  .await?;
   Ok(0)
 }
 
diff --git a/cli/tests/integration/watcher_tests.rs b/cli/tests/integration/watcher_tests.rs
index 89d4bf3f7..cdc7a2c98 100644
--- a/cli/tests/integration/watcher_tests.rs
+++ b/cli/tests/integration/watcher_tests.rs
@@ -997,3 +997,51 @@ fn test_watch_module_graph_error_referrer() {
   wait_for("Process failed", &mut stderr_lines);
   check_alive_then_kill(child);
 }
+
+#[test]
+fn watch_with_no_clear_screen_flag() {
+  let t = TempDir::new().unwrap();
+  let file_to_watch = t.path().join("file_to_watch.js");
+  write(&file_to_watch, "export const foo = 0;").unwrap();
+
+  // choose deno run subcommand to test --no-clear-screen flag
+  let mut child = util::deno_cmd()
+    .current_dir(util::testdata_path())
+    .arg("run")
+    .arg("--watch")
+    .arg("--no-clear-screen")
+    .arg("--unstable")
+    .arg(&file_to_watch)
+    .env("NO_COLOR", "1")
+    .stdout(std::process::Stdio::piped())
+    .stderr(std::process::Stdio::piped())
+    .spawn()
+    .unwrap();
+  let (_, mut stderr_lines) = child_lines(&mut child);
+
+  let next_line = stderr_lines.next().unwrap();
+
+  // no clear screen
+  assert!(!&next_line.contains(CLEAR_SCREEN));
+  assert_contains!(&next_line, "Process started");
+  assert_contains!(
+    stderr_lines.next().unwrap(),
+    "Process finished. Restarting on file change..."
+  );
+
+  // Change content of the file
+  write(&file_to_watch, "export const bar = 0;").unwrap();
+
+  let next_line = stderr_lines.next().unwrap();
+
+  // no clear screen
+  assert!(!&next_line.contains(CLEAR_SCREEN));
+
+  assert_contains!(&next_line, "Watcher File change detected! Restarting!");
+  assert_contains!(
+    stderr_lines.next().unwrap(),
+    "Process finished. Restarting on file change..."
+  );
+
+  check_alive_then_kill(child);
+}
diff --git a/cli/tools/fmt.rs b/cli/tools/fmt.rs
index 3044f13d5..a0ab3ea56 100644
--- a/cli/tools/fmt.rs
+++ b/cli/tools/fmt.rs
@@ -14,7 +14,7 @@ use crate::config_file::ProseWrap;
 use crate::diff::diff;
 use crate::file_watcher;
 use crate::file_watcher::ResolutionResult;
-use crate::flags::FmtFlags;
+use crate::flags::{Flags, FmtFlags};
 use crate::fs_util::specifier_to_file_path;
 use crate::fs_util::{collect_files, get_extension};
 use crate::text_encoding;
@@ -39,8 +39,8 @@ use std::sync::{Arc, Mutex};
 
 /// Format JavaScript/TypeScript files.
 pub async fn format(
+  flags: Flags,
   fmt_flags: FmtFlags,
-  watch: bool,
   maybe_fmt_config: Option<FmtConfig>,
 ) -> Result<(), AnyError> {
   let FmtFlags {
@@ -136,8 +136,16 @@ pub async fn format(
     Ok(())
   };
 
-  if watch {
-    file_watcher::watch_func(resolver, operation, "Fmt").await?;
+  if flags.watch.is_some() {
+    file_watcher::watch_func(
+      resolver,
+      operation,
+      file_watcher::PrintConfig {
+        job_name: "Fmt".to_string(),
+        clear_screen: !flags.no_clear_screen,
+      },
+    )
+    .await?;
   } else {
     let files =
       collect_files(&include_files, &exclude_files, is_supported_ext_fmt)
diff --git a/cli/tools/lint.rs b/cli/tools/lint.rs
index b103550e2..74c5540fc 100644
--- a/cli/tools/lint.rs
+++ b/cli/tools/lint.rs
@@ -8,9 +8,10 @@
 //! the same functions as ops available in JS runtime.
 use crate::config_file::LintConfig;
 use crate::file_watcher::ResolutionResult;
-use crate::flags::LintFlags;
+use crate::flags::{Flags, LintFlags};
 use crate::fmt_errors;
 use crate::fs_util::{collect_files, is_supported_ext, specifier_to_file_path};
+use crate::proc_state::ProcState;
 use crate::tools::fmt::run_parallelized;
 use crate::{colors, file_watcher};
 use deno_ast::MediaType;
@@ -48,11 +49,7 @@ fn create_reporter(kind: LintReporterKind) -> Box<dyn LintReporter + Send> {
   }
 }
 
-pub async fn lint(
-  maybe_lint_config: Option<LintConfig>,
-  lint_flags: LintFlags,
-  watch: bool,
-) -> Result<(), AnyError> {
+pub async fn lint(flags: Flags, lint_flags: LintFlags) -> Result<(), AnyError> {
   let LintFlags {
     maybe_rules_tags,
     maybe_rules_include,
@@ -69,6 +66,13 @@ pub async fn lint(
   let mut include_files = args.clone();
   let mut exclude_files = ignore.clone();
 
+  let ps = ProcState::build(flags.clone()).await?;
+  let maybe_lint_config = if let Some(config_file) = &ps.maybe_config_file {
+    config_file.to_lint_config()?
+  } else {
+    None
+  };
+
   if let Some(lint_config) = maybe_lint_config.as_ref() {
     if include_files.is_empty() {
       include_files = lint_config
@@ -166,13 +170,21 @@ pub async fn lint(
 
     Ok(())
   };
-  if watch {
+  if flags.watch.is_some() {
     if args.len() == 1 && args[0].to_string_lossy() == "-" {
       return Err(generic_error(
         "Lint watch on standard input is not supported.",
       ));
     }
-    file_watcher::watch_func(resolver, operation, "Lint").await?;
+    file_watcher::watch_func(
+      resolver,
+      operation,
+      file_watcher::PrintConfig {
+        job_name: "Lint".to_string(),
+        clear_screen: !flags.no_clear_screen,
+      },
+    )
+    .await?;
   } else {
     if args.len() == 1 && args[0].to_string_lossy() == "-" {
       let reporter_lock =
diff --git a/cli/tools/standalone.rs b/cli/tools/standalone.rs
index a0960d051..ec957e195 100644
--- a/cli/tools/standalone.rs
+++ b/cli/tools/standalone.rs
@@ -248,5 +248,6 @@ pub fn compile_to_runtime_flags(
     v8_flags: flags.v8_flags,
     version: false,
     watch: None,
+    no_clear_screen: false,
   })
 }
diff --git a/cli/tools/test.rs b/cli/tools/test.rs
index 5e2d74ecf..daae61d7f 100644
--- a/cli/tools/test.rs
+++ b/cli/tools/test.rs
@@ -1279,7 +1279,15 @@ pub async fn run_tests_with_watch(
     }
   };
 
-  file_watcher::watch_func(resolver, operation, "Test").await?;
+  file_watcher::watch_func(
+    resolver,
+    operation,
+    file_watcher::PrintConfig {
+      job_name: "Test".to_string(),
+      clear_screen: !flags.no_clear_screen,
+    },
+  )
+  .await?;
 
   Ok(())
 }