feat: deno run with no arguments prints list of available tasks

cli/args/flags.rs

@@ -339,6 +339,7 @@ pub struct RunFlags {
   pub watch: Option<WatchFlagsWithPaths>,
   pub bare: bool,
   pub coverage_dir: Option<String>,
+  pub print_task_list: bool,
 }
 
 impl RunFlags {
@@ -349,6 +350,7 @@ impl RunFlags {
       watch: None,
       bare: false,
       coverage_dir: None,
+      print_task_list: false,
     }
   }
 
@@ -5763,7 +5765,7 @@ fn repl_parse(
 fn run_parse(
   flags: &mut Flags,
   matches: &mut ArgMatches,
-  mut app: Command,
+  app: Command,
   bare: bool,
 ) -> clap::error::Result<()> {
   runtime_args_parse(flags, matches, true, true, true)?;
@@ -5782,6 +5784,7 @@ fn run_parse(
         watch: watch_arg_parse_with_paths(matches)?,
         bare,
         coverage_dir,
+        print_task_list: false,
       });
     }
     _ => {
@@ -5791,10 +5794,14 @@ fn run_parse(
       "[SCRIPT_ARG] may only be omitted with --v8-flags=--help, else to use the repl with arguments, please use the `deno repl` subcommand",
     ));
       } else {
-        return Err(app.find_subcommand_mut("run").unwrap().error(
-          clap::error::ErrorKind::MissingRequiredArgument,
-          "[SCRIPT_ARG] may only be omitted with --v8-flags=--help",
-        ));
+        // When no script argument is provided, show available tasks like `deno task`
+        flags.subcommand = DenoSubcommand::Run(RunFlags {
+          script: "".to_string(),
+          watch: None,
+          bare: false,
+          coverage_dir: None,
+          print_task_list: true,
+        });
       }
     }
   }
@@ -6764,6 +6771,7 @@ mod tests {
           }),
           bare: false,
           coverage_dir: None,
+          print_task_list: false,
         }),
         code_cache_enabled: true,
         ..Flags::default()
@@ -6790,6 +6798,7 @@ mod tests {
           }),
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         code_cache_enabled: true,
         ..Flags::default()
@@ -6817,6 +6826,7 @@ mod tests {
           }),
           bare: false,
           coverage_dir: None,
+          print_task_list: false,
         }),
         code_cache_enabled: true,
         ..Flags::default()
@@ -6844,6 +6854,7 @@ mod tests {
           }),
           bare: false,
           coverage_dir: None,
+          print_task_list: false,
         }),
         code_cache_enabled: true,
         ..Flags::default()
@@ -6871,6 +6882,7 @@ mod tests {
           }),
           bare: false,
           coverage_dir: None,
+          print_task_list: false,
         }),
         code_cache_enabled: true,
         ..Flags::default()
@@ -6899,6 +6911,7 @@ mod tests {
           }),
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         code_cache_enabled: true,
         ..Flags::default()
@@ -6930,6 +6943,7 @@ mod tests {
           }),
           bare: false,
           coverage_dir: None,
+          print_task_list: false,
         }),
         code_cache_enabled: true,
         ..Flags::default()
@@ -6960,6 +6974,7 @@ mod tests {
           }),
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         code_cache_enabled: true,
         ..Flags::default()
@@ -6987,6 +7002,7 @@ mod tests {
           }),
           bare: false,
           coverage_dir: None,
+          print_task_list: false,
         }),
         code_cache_enabled: true,
         ..Flags::default()
@@ -7015,6 +7031,7 @@ mod tests {
           }),
           bare: false,
           coverage_dir: None,
+          print_task_list: false,
         }),
         code_cache_enabled: true,
         ..Flags::default()
@@ -7042,6 +7059,7 @@ mod tests {
           }),
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         code_cache_enabled: true,
         ..Flags::default()
@@ -7081,6 +7099,7 @@ mod tests {
           watch: None,
           bare: false,
           coverage_dir: Some("foo".to_string()),
+          print_task_list: false,
         }),
         code_cache_enabled: true,
         ..Flags::default()
@@ -7120,7 +7139,7 @@ mod tests {
     );
 
     let r = flags_from_vec(svec!["deno", "run", "--v8-flags=--expose-gc"]);
-    assert!(r.is_err());
+    assert!(r.is_ok());
   }
 
   #[test]
@@ -7397,6 +7416,7 @@ mod tests {
           watch: None,
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         permissions: PermissionFlags {
           deny_read: Some(vec![]),
@@ -8687,6 +8707,7 @@ mod tests {
           watch: None,
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         permissions: PermissionFlags {
           deny_net: Some(svec!["127.0.0.1"]),
@@ -8875,6 +8896,7 @@ mod tests {
           watch: None,
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         permissions: PermissionFlags {
           deny_sys: Some(svec!["hostname"]),
@@ -9175,6 +9197,7 @@ mod tests {
           watch: None,
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         ..Flags::default()
       }
@@ -9486,6 +9509,7 @@ mod tests {
           watch: None,
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         log_level: Some(Level::Error),
         code_cache_enabled: true,
@@ -9607,6 +9631,7 @@ mod tests {
           watch: None,
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         type_check_mode: TypeCheckMode::None,
         code_cache_enabled: true,
@@ -9779,6 +9804,7 @@ mod tests {
           watch: None,
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         node_modules_dir: Some(NodeModulesDirMode::Auto),
         code_cache_enabled: true,
@@ -11003,6 +11029,7 @@ mod tests {
           watch: None,
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         inspect_wait: Some("127.0.0.1:9229".parse().unwrap()),
         code_cache_enabled: true,
@@ -11697,6 +11724,7 @@ mod tests {
           watch: None,
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         type_check_mode: TypeCheckMode::None,
         code_cache_enabled: true,
@@ -12251,6 +12279,7 @@ mod tests {
           watch: None,
           bare: true,
           coverage_dir: None,
+          print_task_list: false,
         }),
         config_flag: ConfigFlag::Disabled,
         code_cache_enabled: true,

cli/main.rs

@@ -33,6 +33,7 @@ use std::collections::HashMap;
 use std::env;
 use std::future::Future;
 use std::io::IsTerminal;
+use std::io::Write as _;
 use std::ops::Deref;
 use std::path::PathBuf;
 use std::sync::Arc;
@@ -241,7 +242,28 @@ async fn run_subcommand(
       spawn_subcommand(async move { tools::repl::run(flags, repl_flags).await })
     }
     DenoSubcommand::Run(run_flags) => spawn_subcommand(async move {
-      if run_flags.is_stdin() {
+      if run_flags.print_task_list {
+        let task_flags = TaskFlags {
+          cwd: None,
+          task: None,
+          is_run: true,
+          recursive: false,
+          filter: None,
+          eval: false,
+        };
+        let mut flags = flags.deref().clone();
+        flags.subcommand = DenoSubcommand::Task(task_flags.clone());
+        writeln!(
+          &mut std::io::stdout(),
+          "Please specify a {} or a {}.\n",
+          colors::bold("[SCRIPT_ARG]"),
+          colors::bold("task name")
+        )?;
+        std::io::stdout().flush()?;
+        tools::task::execute_script(Arc::new(flags), task_flags)
+          .await
+          .map(|_| 1)
+      } else if run_flags.is_stdin() {
         // these futures are boxed to prevent stack overflows on Windows
         tools::run::run_from_stdin(flags.clone(), unconfigured_runtime, roots)
           .boxed_local()

cli/tools/task.rs

@@ -63,7 +63,7 @@ pub async fn execute_script(
   let start_dir = &cli_options.start_dir;
   if !start_dir.has_deno_or_pkg_json() && !task_flags.eval {
     bail!(
-      "deno task couldn't find deno.json(c). See https://docs.deno.com/go/config"
+      "deno task couldn't find deno.json(c) or package.json. See https://docs.deno.com/go/config"
     )
   }
   let force_use_pkg_json =

tests/specs/run/run_task/empty.out

@@ -1,4 +1,7 @@
-error: [SCRIPT_ARG] may only be omitted with --v8-flags=--help
-
-Usage: deno run [OPTIONS] [SCRIPT_ARG]...
+Please specify a [SCRIPT_ARG] or a task name.
 
+Available tasks:
+- main
+    deno run main.ts
+- main:foo
+    deno run main.ts