add support-ie7 option

when true, catch vars are considered in the global scope.
https://github.com/mishoo/UglifyJS2/issues/1039

README.md

@@ -74,6 +74,9 @@ The available options are:
                                 for `compress`, `mangle` and `output` options.
                                 Note: `--support-ie8` may generate incorrect code
                                 for `try`/`catch` in ES5 compliant browsers.
+  --support-ie7                 Use this flag to support Internet Explorer 6/7
+                                Note: `--support-ie7` may generate incorrect code
+                                for `try`/`catch` in ES5 compliant browsers.
   --expr                        Parse a single expression, rather than a
                                 program (for parsing JSON)
   -p, --prefix                  Skip prefix for original filenames that appear

bin/uglifyjs

@@ -11,6 +11,7 @@ var path = require("path");
 var async = require("async");
 var acorn;
 var screw_ie8 = true;
+var support_ie7 = false;
 var ARGS = yargs
     .usage("$0 input1.js [input2.js ...] [options]\n\
 Use a single dash to read input from the standard input.\
@@ -28,6 +29,7 @@ mangling you need to use `-c` and `-m`.\
     .describe("in-source-map", "Input source map, useful if you're compressing JS that was generated from some other original code.")
     .describe("screw-ie8", "Do not support Internet Explorer 6/7/8. This flag is enabled by default.")
     .describe("support-ie8", "Support non-standard Internet Explorer 6/7/8 javascript. Note: may generate incorrect code for try/catch in ES5 compliant browsers.")
+    .describe("support-ie7", "Support non-standard Internet Explorer 6/7 javascript. Note: may generate incorrect code for try/catch in ES5 compliant browsers.")
     .describe("expr", "Parse a single expression, rather than a program (for parsing JSON)")
     .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. \
@@ -119,6 +121,7 @@ You need to pass an argument to this option to specify the name that your module
     .boolean("source-map-include-sources")
     .boolean("screw-ie8")
     .boolean("support-ie8")
+    .boolean("support-ie7")
     .boolean("export-all")
     .boolean("self")
     .boolean("v")
@@ -242,7 +245,10 @@ if (ARGS.mangle_props == 2) {
 if (ARGS.support_ie8 === true && ARGS.screw_ie8 !== true) {
     screw_ie8 = false;
 }
-
+if (ARGS.support_ie7 === true) {
+    support_ie7 = true;
+    screw_ie8 = false;
+}
 if (COMPRESS) COMPRESS.screw_ie8 = screw_ie8;
 if (MANGLE) MANGLE.screw_ie8 = screw_ie8;
 OUTPUT_OPTIONS.screw_ie8 = screw_ie8;
@@ -432,7 +438,7 @@ async.eachLimit(files, 1, function (file, cb) {
 
     if (SCOPE_IS_NEEDED) {
         time_it("scope", function(){
-            TOPLEVEL.figure_out_scope(MANGLE || { screw_ie8: screw_ie8, cache: TL_CACHE });
+            TOPLEVEL.figure_out_scope(MANGLE || { screw_ie8: screw_ie8, support_ie7: support_ie7, cache: TL_CACHE });
             if (ARGS.lint) {
                 TOPLEVEL.scope_warnings();
             }
@@ -447,7 +453,7 @@ async.eachLimit(files, 1, function (file, cb) {
 
     if (SCOPE_IS_NEEDED) {
         time_it("scope", function(){
-            TOPLEVEL.figure_out_scope(MANGLE || { screw_ie8: screw_ie8, cache: TL_CACHE });
+            TOPLEVEL.figure_out_scope(MANGLE || { screw_ie8: screw_ie8, support_ie7: support_ie7, cache: TL_CACHE });
             if (MANGLE && !TL_CACHE) {
                 TOPLEVEL.compute_char_frequency(MANGLE);
             }

lib/scope.js

@@ -89,6 +89,7 @@ SymbolDef.prototype = {
 AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
     options = defaults(options, {
         screw_ie8: true,
+        support_ie7: false,
         cache: null
     });
 
@@ -99,6 +100,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
     var defun = null;
     var last_var_had_const_pragma = false;
     var nesting = 0;
+    var global_scope = this;
     var tw = new TreeWalker(function(node, descend){
         if (options.screw_ie8 && node instanceof AST_Catch) {
             var save_scope = scope;
@@ -165,7 +167,7 @@ AST_Toplevel.DEFMETHOD("figure_out_scope", function(options){
             def.init = tw.parent().value;
         }
         else if (node instanceof AST_SymbolCatch) {
-            (options.screw_ie8 ? scope : defun)
+            (options.support_ie7 ? global_scope : options.screw_ie8 ? scope : defun)
                 .def_variable(node);
         }
         else if (node instanceof AST_LabelRef) {

test/mocha/support-ie7.js

@@ -0,0 +1,19 @@
+var assert = require("assert");
+var uglify = require("../../");
+
+describe("support_ie7", function (){
+    //solves issue https://github.com/mishoo/UglifyJS2/issues/1039
+    it ("When support_ie7 is true, should treat the catch parameter as a global parameter", function() {
+        var ast = uglify.parse(                "function a(b){\
+                    try {\
+                        throw 'Stuff';\
+                    } catch (e) {\
+                        console.log('caught: ' + undefined);\
+                    }\
+                    console.log('undefined is ' + undefined);\
+                    return b === undefined;\
+                };");
+        ast.figure_out_scope({support_ie7: true});
+        assert.equal(ast.variables.has("e"), true);
+    });
+});