support dumping AST (#1879)

Re-order `AST_Binary` properties to make dump more readable.

closes #769

4 files changed, 45 insertions, 6 deletions

diff --git a/README.md b/README.md
index 3ad072cf..d2343728 100644
--- a/README.md
+++ b/README.md
@@ -95,8 +95,9 @@ The available options are:
                                 `wrap_iife`  Wrap IIFEs in parenthesis. Note: you may
                                              want to disable `negate_iife` under
                                              compressor options.
-    -o, --output <file>         Output file (default STDOUT). Specify "spidermonkey"
-                                to dump SpiderMonkey AST format (as JSON) to STDOUT.
+    -o, --output <file>         Output file path (default STDOUT). Specify `ast` or
+                                `spidermonkey` to write UglifyJS or SpiderMonkey AST
+                                as JSON to STDOUT respectively.
     --comments [filter]         Preserve copyright comments in the output. By
                                 default this works like Google Closure, keeping
                                 JSDoc-style comments that contain "@license" or
diff --git a/bin/uglifyjs b/bin/uglifyjs
index b67eb6ba..5fa81f3b 100755
--- a/bin/uglifyjs
+++ b/bin/uglifyjs
@@ -15,6 +15,7 @@ var path = require("path");
 var program = require("commander");
 var UglifyJS = require("../tools/node");
 
+var skip_keys = [ "cname", "enclosed", "parent_scope", "scope", "thedef", "uses_eval", "uses_with" ];
 var files = {};
 var options = {
     compress: false,
@@ -107,6 +108,12 @@ if (program.nameCache) {
         }
     }
 }
+if (program.output == "ast") {
+    options.output = {
+        ast: true,
+        code: false
+    };
+}
 if (program.parse) {
     if (program.parse.acorn || program.parse.spidermonkey) {
         if (program.sourceMap) fatal("ERROR: inline source map only works with built-in parser");
@@ -211,7 +218,23 @@ function run() {
         }
         fatal("ERROR: " + ex.message);
     }
-    if (program.output == "spidermonkey") {
+    if (program.output == "ast") {
+        console.log(JSON.stringify(result.ast, function(key, value) {
+            if (skip_key(key)) return;
+            if (value instanceof UglifyJS.AST_Token) return;
+            if (value instanceof UglifyJS.Dictionary) return;
+            if (value instanceof UglifyJS.AST_Node) {
+                var result = {
+                    _class: "AST_" + value.TYPE
+                };
+                value.CTOR.PROPS.forEach(function(prop) {
+                    result[prop] = value[prop];
+                });
+                return result;
+            }
+            return value;
+        }, 2));
+    } else if (program.output == "spidermonkey") {
         console.log(JSON.stringify(UglifyJS.minify(result.code, {
             compress: false,
             mangle: false,
@@ -237,8 +260,8 @@ function run() {
 }
 
 function fatal(message) {
-  console.error(message);
-  process.exit(1);
+    console.error(message);
+    process.exit(1);
 }
 
 // A file glob function that only supports "*" and "?" wildcards in the basename.
@@ -352,3 +375,7 @@ function to_cache(key) {
     }
     return cache[key];
 }
+
+function skip_key(key) {
+    return skip_keys.indexOf(key) >= 0;
+}
diff --git a/lib/ast.js b/lib/ast.js
index e61a31e5..962c8f7b 100644
--- a/lib/ast.js
+++ b/lib/ast.js
@@ -619,7 +619,7 @@ var AST_UnaryPostfix = DEFNODE("UnaryPostfix", null, {
     $documentation: "Unary postfix expression, i.e. `i++`"
 }, AST_Unary);
 
-var AST_Binary = DEFNODE("Binary", "left operator right", {
+var AST_Binary = DEFNODE("Binary", "operator left right", {
     $documentation: "Binary expression, i.e. `a + b`",
     $propdoc: {
         left: "[AST_Node] left-hand side expression",
diff --git a/test/mocha/cli.js b/test/mocha/cli.js
index cac920d3..8c7964ac 100644
--- a/test/mocha/cli.js
+++ b/test/mocha/cli.js
@@ -509,4 +509,15 @@ describe("bin/uglifyjs", function () {
             return JSON.stringify(map).replace(/"/g, '\\"');
         }
     });
+    it("Should dump AST as JSON", function(done) {
+        var command = uglifyjscmd + " test/input/global_defs/simple.js -mco ast";
+        exec(command, function (err, stdout) {
+            if (err) throw err;
+
+            var ast = JSON.parse(stdout);
+            assert.strictEqual(ast._class, "AST_Toplevel");
+            assert.ok(Array.isArray(ast.body));
+            done();
+        });
+    });
 });