feat(repl): add --eval flag for evaluating code when the repl starts (#11590)

cli/flags.rs

@@ -91,7 +91,9 @@ pub enum DenoSubcommand {
     rules: bool,
     json: bool,
   },
-  Repl,
+  Repl {
+    eval: Option<String>,
+  },
   Run {
     script: String,
   },
@@ -119,7 +121,7 @@ pub enum DenoSubcommand {
 
 impl Default for DenoSubcommand {
   fn default() -> DenoSubcommand {
-    DenoSubcommand::Repl
+    DenoSubcommand::Repl { eval: None }
   }
 }
 
@@ -955,6 +957,13 @@ Ignore linting a file by adding an ignore comment at the top of the file:
 fn repl_subcommand<'a, 'b>() -> App<'a, 'b> {
   runtime_args(SubCommand::with_name("repl"), false, true)
     .about("Read Eval Print Loop")
+    .arg(
+      Arg::with_name("eval")
+        .long("eval")
+        .help("Evaluates the provided code when the REPL starts.")
+        .takes_value(true)
+        .value_name("code"),
+    )
 }
 
 fn run_subcommand<'a, 'b>() -> App<'a, 'b> {
@@ -1701,7 +1710,9 @@ fn lint_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
 fn repl_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
   runtime_args_parse(flags, matches, false, true);
   flags.repl = true;
-  flags.subcommand = DenoSubcommand::Repl;
+  flags.subcommand = DenoSubcommand::Repl {
+    eval: matches.value_of("eval").map(ToOwned::to_owned),
+  };
   flags.allow_net = Some(vec![]);
   flags.allow_env = Some(vec![]);
   flags.allow_run = Some(vec![]);
@@ -2706,7 +2717,7 @@ mod tests {
       r.unwrap(),
       Flags {
         repl: true,
-        subcommand: DenoSubcommand::Repl,
+        subcommand: DenoSubcommand::Repl { eval: None },
         allow_net: Some(vec![]),
         allow_env: Some(vec![]),
         allow_run: Some(vec![]),
@@ -2727,7 +2738,7 @@ mod tests {
       r.unwrap(),
       Flags {
         repl: true,
-        subcommand: DenoSubcommand::Repl,
+        subcommand: DenoSubcommand::Repl { eval: None },
         import_map_path: Some("import_map.json".to_string()),
         no_remote: true,
         config_path: Some("tsconfig.json".to_string()),
@@ -2753,6 +2764,29 @@ mod tests {
     );
   }
 
+  #[test]
+  fn repl_with_eval_flag() {
+    #[rustfmt::skip]
+    let r = flags_from_vec(svec!["deno", "repl", "--eval", "console.log('hello');"]);
+    assert_eq!(
+      r.unwrap(),
+      Flags {
+        repl: true,
+        subcommand: DenoSubcommand::Repl {
+          eval: Some("console.log('hello');".to_string()),
+        },
+        allow_net: Some(vec![]),
+        allow_env: Some(vec![]),
+        allow_run: Some(vec![]),
+        allow_read: Some(vec![]),
+        allow_write: Some(vec![]),
+        allow_plugin: true,
+        allow_hrtime: true,
+        ..Flags::default()
+      }
+    );
+  }
+
   #[test]
   fn allow_read_allowlist() {
     use tempfile::TempDir;

cli/main.rs

@@ -774,7 +774,10 @@ async fn format_command(
   Ok(())
 }
 
-async fn run_repl(flags: Flags) -> Result<(), AnyError> {
+async fn run_repl(
+  flags: Flags,
+  maybe_eval: Option<String>,
+) -> Result<(), AnyError> {
   let main_module = resolve_url_or_path("./$deno$repl.ts").unwrap();
   let permissions = Permissions::from_options(&flags.clone().into());
   let program_state = ProgramState::build(flags).await?;
@@ -782,7 +785,7 @@ async fn run_repl(flags: Flags) -> Result<(), AnyError> {
     create_main_worker(&program_state, main_module.clone(), permissions, false);
   worker.run_event_loop(false).await?;
 
-  tools::repl::run(&program_state, worker).await
+  tools::repl::run(&program_state, worker, maybe_eval).await
 }
 
 async fn run_from_stdin(flags: Flags) -> Result<(), AnyError> {
@@ -1341,7 +1344,7 @@ fn get_subcommand(
       ignore,
       json,
     } => lint_command(flags, files, rules, ignore, json).boxed_local(),
-    DenoSubcommand::Repl => run_repl(flags).boxed_local(),
+    DenoSubcommand::Repl { eval } => run_repl(flags, eval).boxed_local(),
     DenoSubcommand::Run { script } => run_command(flags, script).boxed_local(),
     DenoSubcommand::Test {
       no_run,

cli/tests/integration/repl_tests.rs

@@ -436,7 +436,7 @@ fn exports_stripped() {
 }
 
 #[test]
-fn eval_unterminated() {
+fn call_eval_unterminated() {
   let (out, err) = util::run_and_collect_output(
     true,
     "repl",
@@ -644,3 +644,45 @@ fn custom_inspect() {
   assert!(out.contains("Oops custom inspect error"));
   assert!(err.is_empty());
 }
+
+#[test]
+fn eval_flag_valid_input() {
+  let (out, err) = util::run_and_collect_output_with_args(
+    true,
+    vec!["repl", "--eval", "const t = 10;"],
+    Some(vec!["t * 500;"]),
+    None,
+    false,
+  );
+  assert!(out.contains("5000"));
+  assert!(err.is_empty());
+}
+
+#[test]
+fn eval_flag_parse_error() {
+  let (out, err) = util::run_and_collect_output_with_args(
+    true,
+    vec!["repl", "--eval", "const %"],
+    Some(vec!["250 * 10"]),
+    None,
+    false,
+  );
+  assert!(test_util::strip_ansi_codes(&out)
+    .contains("error in --eval flag. parse error: Unexpected token `%`."));
+  assert!(out.contains("2500")); // should not prevent input
+  assert!(err.is_empty());
+}
+
+#[test]
+fn eval_flag_runtime_error() {
+  let (out, err) = util::run_and_collect_output_with_args(
+    true,
+    vec!["repl", "--eval", "throw new Error('Testing')"],
+    Some(vec!["250 * 10"]),
+    None,
+    false,
+  );
+  assert!(out.contains("error in --eval flag. Uncaught Error: Testing"));
+  assert!(out.contains("2500")); // should not prevent input
+  assert!(err.is_empty());
+}

cli/tools/repl.rs

@@ -418,6 +418,20 @@ Object.defineProperty(globalThis, "_error", {
 });
 "#;
 
+enum EvaluationOutput {
+  Value(String),
+  Error(String),
+}
+
+impl std::fmt::Display for EvaluationOutput {
+  fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+    match self {
+      EvaluationOutput::Value(value) => f.write_str(value),
+      EvaluationOutput::Error(value) => f.write_str(value),
+    }
+  }
+}
+
 struct ReplSession {
   worker: MainWorker,
   session: LocalInspectorSession,
@@ -497,7 +511,7 @@ impl ReplSession {
   pub async fn evaluate_line_and_get_output(
     &mut self,
     line: &str,
-  ) -> Result<String, AnyError> {
+  ) -> Result<EvaluationOutput, AnyError> {
     match self.evaluate_line_with_object_wrapping(line).await {
       Ok(evaluate_response) => {
         let evaluate_result = evaluate_response.get("result").unwrap();
@@ -512,20 +526,20 @@ impl ReplSession {
 
         let value = self.get_eval_value(evaluate_result).await?;
         Ok(match evaluate_exception_details {
-          Some(_) => format!("Uncaught {}", value),
-          None => value,
+          Some(_) => EvaluationOutput::Error(format!("Uncaught {}", value)),
+          None => EvaluationOutput::Value(value),
         })
       }
       Err(err) => {
         // handle a parsing diagnostic
         match err.downcast_ref::<Diagnostic>() {
-          Some(diagnostic) => Ok(format!(
+          Some(diagnostic) => Ok(EvaluationOutput::Error(format!(
             "{}: {} at {}:{}",
             colors::red("parse error"),
             diagnostic.message,
             diagnostic.location.line,
             diagnostic.location.col
-          )),
+          ))),
           None => Err(err),
         }
       }
@@ -707,6 +721,7 @@ async fn read_line_and_poll(
 pub async fn run(
   program_state: &ProgramState,
   worker: MainWorker,
+  maybe_eval: Option<String>,
 ) -> Result<(), AnyError> {
   let mut repl_session = ReplSession::initialize(worker).await?;
   let (message_tx, mut message_rx) = channel(1);
@@ -721,6 +736,14 @@ pub async fn run(
   let history_file_path = program_state.dir.root.join("deno_history.txt");
   let editor = ReplEditor::new(helper, history_file_path);
 
+  if let Some(eval) = maybe_eval {
+    let output = repl_session.evaluate_line_and_get_output(&eval).await?;
+    // only output errors
+    if let EvaluationOutput::Error(error_text) = output {
+      println!("error in --eval flag. {}", error_text);
+    }
+  }
+
   println!("Deno {}", crate::version::deno());
   println!("exit using ctrl+d or close()");
 

test_util/src/lib.rs

@@ -1142,10 +1142,26 @@ pub fn run_and_collect_output(
   input: Option<Vec<&str>>,
   envs: Option<Vec<(String, String)>>,
   need_http_server: bool,
+) -> (String, String) {
+  run_and_collect_output_with_args(
+    expect_success,
+    args.split_whitespace().collect(),
+    input,
+    envs,
+    need_http_server,
+  )
+}
+
+pub fn run_and_collect_output_with_args(
+  expect_success: bool,
+  args: Vec<&str>,
+  input: Option<Vec<&str>>,
+  envs: Option<Vec<(String, String)>>,
+  need_http_server: bool,
 ) -> (String, String) {
   let mut deno_process_builder = deno_cmd();
   deno_process_builder
-    .args(args.split_whitespace())
+    .args(args)
     .current_dir(&tests_path())
     .stdin(Stdio::piped())
     .stdout(Stdio::piped())