From 43ff5ed37fd95c2f5f3c06634abd8afda7902ab0 Mon Sep 17 00:00:00 2001
From: pborunda <pborunda@gmail.com>
Date: Fri, 24 Feb 2017 16:01:59 -0700
Subject: [PATCH] Add option discard_error: Error('foo') -> Error()

Add option discard_error:
Error('foo') -> Error()

Applies to built in error types Error, EvalError, InternalError,
RangeError, ReferenceError, SyntaxError, TypeError, URIError
---
 README.md                   |  3 ++
 lib/compress.js             | 23 +++++++++++
 test/compress/drop-error.js | 80 +++++++++++++++++++++++++++++++++++++
 3 files changed, 106 insertions(+)
 create mode 100644 test/compress/drop-error.js

diff --git a/README.md b/README.md
index 490f178c..d1e9ca09 100644
--- a/README.md
+++ b/README.md
@@ -420,6 +420,9 @@ to set `true`; it's effectively a shortcut for `foo=true`).
   such as `console.info` and/or retain side effects from function arguments
   after dropping the function call then use `pure_funcs` instead.
 
+- `drop_error` -- default `false`.  Pass `true` to discard description
+  of Error() calls.
+
 - `keep_fargs` -- default `true`.  Prevents the
   compressor from discarding unused function arguments.  You need this
   for code which relies on `Function.length`.
diff --git a/lib/compress.js b/lib/compress.js
index 2bc1c5a5..9e07e724 100644
--- a/lib/compress.js
+++ b/lib/compress.js
@@ -78,6 +78,7 @@ function Compressor(options, false_by_default) {
         negate_iife   : !false_by_default,
         screw_ie8     : true,
         drop_console  : false,
+        drop_error    : false,
         angular       : false,
         warnings      : true,
         global_defs   : {},
@@ -2581,6 +2582,22 @@ merge(Compressor.prototype, {
                 return best_of(self, node);
             }
         }
+        if (compressor.option("drop_error")) {
+            var exp = self.expression;
+            if (exp instanceof AST_SymbolRef
+                && (exp.name == "Error" || 
+                    exp.name == "EvalError" || 
+                    exp.name == "InternalError" || 
+                    exp.name == "RangeError" || 
+                    exp.name == "ReferenceError" || 
+                    exp.name == "SyntaxError" || 
+                    exp.name == "TypeError" || 
+                    exp.name == "URIError")
+                && exp.undeclared()) {
+                   // drop error description(s)
+                   self.args = [];
+                }
+        }
         if (compressor.option("side_effects")) {
             if (self.expression instanceof AST_Function
                 && self.args.length == 0
@@ -2618,6 +2635,12 @@ merge(Compressor.prototype, {
                   case "RegExp":
                   case "Function":
                   case "Error":
+                  case "EvalError":
+                  case "InternalError":
+                  case "RangeError":
+                  case "ReferenceError":
+                  case "SyntaxError":
+                  case "URIError":
                   case "Array":
                     return make_node(AST_Call, self, self).transform(compressor);
                 }
diff --git a/test/compress/drop-error.js b/test/compress/drop-error.js
new file mode 100644
index 00000000..8bcc5f9f
--- /dev/null
+++ b/test/compress/drop-error.js
@@ -0,0 +1,80 @@
+drop_error_1: {
+    options = {};
+    input: {
+        Error('foo');
+        Error('foo', arguments);
+        EvalError('foo');
+        EvalError('foo', arguments);
+        InternalError('foo');
+        InternalError('foo', arguments);
+        RangeError('foo');
+        RangeError('foo', arguments);
+        ReferenceError('foo');
+        ReferenceError('foo', arguments);
+        SyntaxError('foo');
+        SyntaxError('foo', arguments);
+        TypeError('foo');
+        TypeError('foo', arguments);
+        URIError('foo');
+        URIError('foo', arguments);
+
+    }
+    expect: {
+        Error('foo');
+        Error('foo', arguments);
+        EvalError('foo');
+        EvalError('foo', arguments);
+        InternalError('foo');
+        InternalError('foo', arguments);
+        RangeError('foo');
+        RangeError('foo', arguments);
+        ReferenceError('foo');
+        ReferenceError('foo', arguments);
+        SyntaxError('foo');
+        SyntaxError('foo', arguments);
+        TypeError('foo');
+        TypeError('foo', arguments);
+        URIError('foo');
+        URIError('foo', arguments);
+    }
+}
+
+drop_error_2: {
+    options = { drop_error: true };
+    input: {
+        Error('foo');
+        Error('foo', arguments);
+        EvalError('foo');
+        EvalError('foo', arguments);
+        InternalError('foo');
+        InternalError('foo', arguments);
+        RangeError('foo');
+        RangeError('foo', arguments);
+        ReferenceError('foo');
+        ReferenceError('foo', arguments);
+        SyntaxError('foo');
+        SyntaxError('foo', arguments);
+        TypeError('foo');
+        TypeError('foo', arguments);
+        URIError('foo');
+        URIError('foo', arguments);
+    }
+    expect: {
+        Error();
+        Error();
+        EvalError();
+        EvalError();
+        InternalError();
+        InternalError();
+        RangeError();
+        RangeError();
+        ReferenceError();
+        ReferenceError();
+        SyntaxError();
+        SyntaxError();
+        TypeError();
+        TypeError();
+        URIError();
+        URIError();
+    }
+}