3 files changed, 36 insertions, 18 deletions

diff --git a/bin/uglifyjs2 b/bin/uglifyjs2
index 0ed873a9..aa302044 100755
--- a/bin/uglifyjs2
+++ b/bin/uglifyjs2
@@ -12,6 +12,7 @@ Use a single dash to read input from the standard input.\
 ")
     .describe("source-map", "Specify an output file where to generate source map.")
     .describe("source-map-root", "The path to the original source to be included in the source map.")
+    .describe("in-source-map", "Input source map, useful if you're compressing JS that was generated from some other original code.")
     .describe("p", "Skip prefix for original filenames that appear in source maps. For example -p 3 will drop 3 directories from file names and ensure they are relative paths.")
     .describe("o", "Output file (default STDOUT)")
     .describe("b", "Beautify output")
@@ -60,12 +61,27 @@ if (ARGS.c && ARGS.c !== true) {
         var a = opt.split(/\s*=\s*/);
         COMPRESSOR_OPTIONS[a[0]] = new Function("return(" + a[1] + ")")();
     });
+    normalize(COMPRESSOR_OPTIONS);
 }
 
 var files = ARGS._.slice();
 
-if (files.length == 0)
+var ORIG_MAP = ARGS.in_source_map;
+
+if (ORIG_MAP) {
+    ORIG_MAP = JSON.parse(fs.readFileSync(ORIG_MAP));
+    if (files.length == 0) {
+        sys.error("INFO: Using file from the input source map: " + ORIG_MAP.file);
+        files = [ ORIG_MAP.file ];
+    }
+    if (ARGS.source_map_root == null) {
+        ARGS.source_map_root = ORIG_MAP.sourceRoot;
+    }
+}
+
+if (files.length == 0) {
     files = [ "-" ];
+}
 
 if (files.indexOf("-") >= 0 && ARGS.source_map) {
     sys.error("ERROR: Source map doesn't work with input from STDIN");
@@ -83,7 +99,8 @@ var TOPLEVEL = null;
 
 var SOURCE_MAP = ARGS.source_map ? UglifyJS.SourceMap({
     file: OUTPUT_FILE,
-    root: ARGS.source_map_root
+    root: ARGS.source_map_root,
+    orig: ORIG_MAP,
 }) : null;
 
 var output = UglifyJS.OutputStream({
diff --git a/lib/output.js b/lib/output.js
index a7a580c9..69401d0d 100644
--- a/lib/output.js
+++ b/lib/output.js
@@ -55,7 +55,6 @@ function OutputStream(options) {
         ie_proof      : true,
         beautify      : true,
         source_map    : null,
-        in_source_map : null
     });
 
     var indentation = 0;
diff --git a/lib/sourcemap.js b/lib/sourcemap.js
index 6cbce5e1..da4ab4fe 100644
--- a/lib/sourcemap.js
+++ b/lib/sourcemap.js
@@ -45,16 +45,30 @@
 function SourceMap(options) {
     options = defaults(options, {
         file : null,
-        root : null
+        root : null,
+        orig : null,
     });
     var generator = new MOZ_SourceMap.SourceMapGenerator({
         file       : options.file,
         sourceRoot : options.root
     });
+    var orig_map = options.orig && new MOZ_SourceMap.SourceMapConsumer(options.orig);
     function add(source, gen_line, gen_col, orig_line, orig_col, name) {
+        orig_line++;
+        gen_line++;
+        if (orig_map) {
+            var info = orig_map.originalPositionFor({
+                line: orig_line,
+                column: orig_col
+            });
+            source = info.source;
+            orig_line = info.line;
+            orig_col = info.column;
+            name = info.name;
+        }
         generator.addMapping({
-            generated : { line: gen_line + 1, column: gen_col },
-            original  : { line: orig_line + 1, column: orig_col },
+            generated : { line: gen_line, column: gen_col },
+            original  : { line: orig_line, column: orig_col },
             source    : source,
             name      : name
         });
@@ -65,15 +79,3 @@ function SourceMap(options) {
         toString   : function() { return generator.toString() }
     };
 };
-
-function SourceMapInput(map) {
-    map = new MOZ_SourceMap.SourceMapConsumer(map);
-    return {
-        info: function(line, col) {
-            return map.originalPositionFor({
-                line: line,
-                column: col
-            });
-        }
-    };
-};