feat: Add "deno ast" subcommand

cli/flags.rs

@@ -15,6 +15,9 @@ macro_rules! svec {
 
 #[derive(Clone, Debug, PartialEq)]
 pub enum DenoSubcommand {
+  Ast {
+    source_file: String,
+  },
   Bundle {
     source_file: String,
     out_file: Option<PathBuf>,
@@ -273,6 +276,8 @@ pub fn flags_from_vec_safe(args: Vec<String>) -> clap::Result<Flags> {
     doc_parse(&mut flags, m);
   } else if let Some(m) = matches.subcommand_matches("lint") {
     lint_parse(&mut flags, m);
+  } else if let Some(m) = matches.subcommand_matches("ast") {
+    ast_parse(&mut flags, m);
   } else {
     repl_parse(&mut flags, &matches);
   }
@@ -314,6 +319,7 @@ If the flag is set, restrict these messages to errors.",
         )
         .global(true),
     )
+    .subcommand(ast_subcommand())
     .subcommand(bundle_subcommand())
     .subcommand(cache_subcommand())
     .subcommand(completions_subcommand())
@@ -337,6 +343,13 @@ fn types_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
   flags.subcommand = DenoSubcommand::Types;
 }
 
+fn ast_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
+  unstable_arg_parse(flags, matches);
+
+  let source_file = matches.value_of("source_file").unwrap().to_string();
+  flags.subcommand = DenoSubcommand::Ast { source_file };
+}
+
 fn fmt_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
   let files = match matches.values_of("files") {
     Some(f) => f.map(String::from).collect(),
@@ -755,6 +768,21 @@ If no output file is given, the output is written to standard output:
     )
 }
 
+fn ast_subcommand<'a, 'b>() -> App<'a, 'b> {
+  SubCommand::with_name("ast")
+    .arg(
+      Arg::with_name("source_file")
+        .takes_value(true)
+        .required(true),
+    )
+    .arg(unstable_arg())
+    .about("Print the AST of a particular source file.")
+    .long_about(
+      "Prints the AST of a single JavaScript/TypeScript file.
+  deno ast https://deno.land/std/examples/colors.ts",
+    )
+}
+
 fn completions_subcommand<'a, 'b>() -> App<'a, 'b> {
   SubCommand::with_name("completions")
     .setting(AppSettings::DisableHelpSubcommand)
@@ -3027,7 +3055,25 @@ mod tests {
       }
     );
   }
-
+  #[test]
+  fn ast() {
+    let r = flags_from_vec_safe(svec![
+      "deno",
+      "ast",
+      "--unstable",
+      "https://deno.land/std/http/file_server.ts"
+    ]);
+    assert_eq!(
+      r.unwrap(),
+      Flags {
+        subcommand: DenoSubcommand::Ast {
+          source_file: "https://deno.land/std/http/file_server.ts".to_string(),
+        },
+        unstable: true,
+        ..Flags::default()
+      }
+    );
+  }
   #[test]
   fn inspect_default_host() {
     let r = flags_from_vec_safe(svec!["deno", "run", "--inspect", "foo.js"]);

cli/main.rs

@@ -81,6 +81,7 @@ use crate::global_state::GlobalState;
 use crate::msg::MediaType;
 use crate::op_error::OpError;
 use crate::permissions::Permissions;
+use crate::swc_util::AstParser;
 use crate::tsc::TargetLib;
 use crate::worker::MainWorker;
 use deno_core::v8_set_flags;
@@ -436,6 +437,38 @@ async fn eval_command(
   Ok(())
 }
 
+async fn ast_command(flags: Flags, source_file: String) -> Result<(), ErrBox> {
+  let module_specifier = ModuleSpecifier::resolve_url_or_path(&source_file)?;
+
+  debug!(">>>>> ast START");
+
+  if !flags.unstable {
+    exit_unstable("ast");
+  }
+
+  let global_state = GlobalState::new(flags)?;
+
+  let out = global_state
+    .file_fetcher
+    .fetch_source_file(&module_specifier, None, Permissions::allow_all())
+    .await?;
+  let src = std::str::from_utf8(&out.source_code)?;
+  let parser = AstParser::new();
+  let ast = parser.parse_module::<_, Result<swc_ecma_ast::Module, ErrBox>>(
+    &module_specifier.to_string(),
+    out.media_type,
+    src,
+    |parse_result| {
+      let module = parse_result.unwrap();
+      Ok(module)
+    },
+  )?;
+
+  debug!(">>>>> ast END");
+  write_to_stdout_ignore_sigpipe(serde_json::to_string_pretty(&ast)?.as_bytes())
+    .map_err(ErrBox::from)
+}
+
 async fn bundle_command(
   flags: Flags,
   source_file: String,
@@ -701,6 +734,9 @@ pub fn main() {
   log::set_max_level(log_level.to_level_filter());
 
   let fut = match flags.clone().subcommand {
+    DenoSubcommand::Ast { source_file } => {
+      ast_command(flags, source_file).boxed_local()
+    }
     DenoSubcommand::Bundle {
       source_file,
       out_file,