feat: add mvp language server (#8515)

Resolves #8400

1 files changed, 35 insertions, 3 deletions

diff --git a/cli/flags.rs b/cli/flags.rs
index 5ff21971d..2210d7565 100644
--- a/cli/flags.rs
+++ b/cli/flags.rs
@@ -17,6 +17,9 @@ pub enum DenoSubcommand {
     source_file: String,
     out_file: Option<PathBuf>,
   },
+  Cache {
+    files: Vec<String>,
+  },
   Compile {
     source_file: String,
     output: Option<PathBuf>,
@@ -35,9 +38,6 @@ pub enum DenoSubcommand {
     code: String,
     as_typescript: bool,
   },
-  Cache {
-    files: Vec<String>,
-  },
   Fmt {
     check: bool,
     files: Vec<PathBuf>,
@@ -54,6 +54,7 @@ pub enum DenoSubcommand {
     root: Option<PathBuf>,
     force: bool,
   },
+  LanguageServer,
   Lint {
     files: Vec<PathBuf>,
     ignore: Vec<PathBuf>,
@@ -293,6 +294,8 @@ pub fn flags_from_vec_safe(args: Vec<String>) -> clap::Result<Flags> {
     lint_parse(&mut flags, m);
   } else if let Some(m) = matches.subcommand_matches("compile") {
     compile_parse(&mut flags, m);
+  } else if let Some(m) = matches.subcommand_matches("lsp") {
+    language_server_parse(&mut flags, m);
   } else {
     repl_parse(&mut flags, &matches);
   }
@@ -349,6 +352,7 @@ If the flag is set, restrict these messages to errors.",
     .subcommand(fmt_subcommand())
     .subcommand(info_subcommand())
     .subcommand(install_subcommand())
+    .subcommand(language_server_subcommand())
     .subcommand(lint_subcommand())
     .subcommand(repl_subcommand())
     .subcommand(run_subcommand())
@@ -685,6 +689,10 @@ fn doc_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
   };
 }
 
+fn language_server_parse(flags: &mut Flags, _matches: &clap::ArgMatches) {
+  flags.subcommand = DenoSubcommand::LanguageServer;
+}
+
 fn lint_parse(flags: &mut Flags, matches: &clap::ArgMatches) {
   let files = match matches.values_of("files") {
     Some(f) => f.map(PathBuf::from).collect(),
@@ -1076,6 +1084,18 @@ Show documentation for runtime built-ins:
     )
 }
 
+fn language_server_subcommand<'a, 'b>() -> App<'a, 'b> {
+  SubCommand::with_name("lsp")
+    .setting(AppSettings::Hidden)
+    .about("Start the language server")
+    .long_about(
+      r#"Start the Deno language server which will take input
+from stdin and provide output to stdout.
+  deno lsp
+"#,
+    )
+}
+
 fn lint_subcommand<'a, 'b>() -> App<'a, 'b> {
   SubCommand::with_name("lint")
     .about("Lint source files")
@@ -1953,6 +1973,18 @@ mod tests {
   }
 
   #[test]
+  fn language_server() {
+    let r = flags_from_vec_safe(svec!["deno", "lsp"]);
+    assert_eq!(
+      r.unwrap(),
+      Flags {
+        subcommand: DenoSubcommand::LanguageServer,
+        ..Flags::default()
+      }
+    );
+  }
+
+  #[test]
   fn lint() {
     let r = flags_from_vec_safe(svec![
       "deno",