add dump subcommand

# Conflicts:
#	rescript
#	scripts/rescript_arg.js

Author: bobzhang

rescript

@@ -125,6 +125,7 @@ Subcommands:
     clean
     format
     convert
+    dump
     help
 Run rescript subcommand -h for more details,
 For example:
@@ -153,6 +154,13 @@ if (
         bsc_exe
       );
       break;
+    case "dump":
+      require("./scripts/rescript_dump.js").main(
+        process.argv.slice(3),
+        bsb_exe,
+        bsc_exe
+      );
+      break;
     case "convert":
       // Todo
       require("./scripts/rescript_convert.js").main(

scripts/rescript_arg.js

@@ -36,17 +36,18 @@ function bad_arg(s) {
  */
 function usage_b(b, usage, specs) {
   b.add(usage);
-  b.add(`\nOptions:\n`);
-  if(specs.length === 0){
-    return 
+  if (specs.length === 0) {
+    return;
   }
+  b.add(`\nOptions:\n`);
   var max_col = 0;
   for (let [key] of specs) {
     if (key.length > max_col) {
       max_col = key.length;
     }
   }
-  for (let [key, _, doc] of specs) {
+  for (let i = 0; i < specs.length; i++) {
+    let [key, _, doc] = specs[i];
     if (!doc.startsWith("*internal*")) {
       b.add("  ")
         .add(key)
@@ -83,7 +84,7 @@ function stop_raise(usage, error, specs) {
     case "Unknown":
       if (["-help", "--help", "-h"].includes(error.data)) {
         usage_b(b, usage, specs);
-        console.error(b.val);
+        process.stderr.write(b.val);
         process.exit(0);
       } else {
         b.add("unknown option: '").add(error.data).add("'.\n");
@@ -160,6 +161,6 @@ function parse_exn(
   }
   annofun(list);
 }
-
+exports.bad_arg = bad_arg;
 exports.parse_exn = parse_exn;
 exports.ArgError = ArgError;

scripts/rescript_dump.js

@@ -0,0 +1,57 @@
+//@ts-check
+var arg = require("./rescript_arg.js");
+var dump_usage = `Usage: rescript dump <options> [target]
+\`rescript dump\` dumps the information for the target
+`;
+var child_process = require("child_process");
+var path = require("path");
+var specs = [];
+
+/**
+ * @param {string[]} argv
+ * @param {string} bsb_exe
+ * @param {string} bsc_exe
+ */
+function main(argv, bsb_exe, bsc_exe) {
+  var target;
+  arg.parse_exn(dump_usage, argv, specs, (xs) => {
+    if (xs.length !== 1) {
+      arg.bad_arg(`Expect only one target, ${xs.length} found` );
+    }
+    target = xs[0];
+  });
+
+  var { ext } = path.parse(target);
+  if (ext !== ".cmi") {
+    console.error("Only .cmi target allowed");
+    process.exit(2);
+  }
+
+
+  var output = child_process.spawnSync(
+    bsb_exe,
+    ["build", "--", target],
+    {
+      encoding: "utf-8",
+    }
+  );
+  if (output.status !== 0) {
+    console.log(output.stdout);
+    console.error(output.stderr);
+    process.exit(2);
+  }
+  output = child_process.spawnSync(
+    bsc_exe,
+    [path.join("lib", "bs", target)],
+    {
+      encoding: "utf-8",
+    }
+  );
+  console.log(output.stdout.trimEnd());
+  if (output.status !== 0) {
+    console.error(output.stderr);
+    process.exit(2);
+  }
+}
+
+exports.main = main;