Without this fix, the following source:
x = {"\u200c": 42};
would incorrectly be converted into a quoteless key. But while \u200c is allowed
to be in identifiers, it cannot be at the beginning, as per ES5.
(For example, the SockJS client library doesn't work under uglify starting with
d9ad3c7c.)
Previously:
Without `--screw-ie`, UglifyJS would always leak names of function
expressions into the containing scope, as if they were function
declarations. That was to emulate IE<9 behavior. Code relying on this
IE bug would continue to work properly after mangling, although it would
only work in IE (since other engines don't share the bug). Sometimes
this broke legitimage code (see #153 and #155).
With `--screw-ie` the names would not be leaked into the current scope,
working properly in legit cases; but still it broke legit code when
running in IE<9 (see #24).
Currently:
Regardless of the `--screw-ie` setting, the names will not be leaked.
Code relying on the IE bug will not work properly after mangling.
<evil laughter here>
Without `--screw-ie`: a hack has been added to the mangler to avoid
using the same name for a function expression and some other variable in
the same scope. This keeps legit code working, at the (negligible,
indeed) cost of one more identifier.
With `--screw-ie` you allow the mangler to name function expressions
with the same identifier as another variable in scope. After mangling
code might break in IE<9.
Oh man, the commit message is longer than the patch.
Fix#153, #155
1b6bcca7 was a first attempt at this. That commit made Uglify stop replacing
holes with undefined, but instead it started replacing undefined with
holes. This is slightly problematic, because there is a difference between a
hole and an undefined value. More problematically, it changed [1,undefined] to
[1,] which generally doesn't even parse as a hole (just as a trailing comma), so
it didn't even preserve the length of the array!
Instead, parse holes as their own special AST node which prints invisibly.
AST_Accessor will represent the function for a setter or getter. Since they
are not mangleable, and they should not introduce a name in scope, we have a
new node for their name (AST_SymbolAccessor) which doesn't inherit from
AST_SymbolDeclaration.
fix#37
- a = a + x ==> a+=x
- joining consecutive var statements (hoisting is not always desirable)
- x == false ==> x == 0, x != true ==> x != 1
- x, x ==> x; x = exp(), x ==> x = exp()
- discarding useless break-s
The following nodes were instances of AST_BlockStatement: AST_Scope,
AST_SwitchBlock, AST_SwitchBranch. Also, AST_Try, AST_Catch, AST_Finally
were having a body instanceof AST_BlockStatement.
Overloading the meaning of AST_BlockStatement this way turned out to be a
mess; we now have an AST_Block class that is the base class for things
having a block of statements (might or might not be bracketed). The
`this.body` of AST_Scope, AST_Try, AST_Catch, AST_Finally is now an array of
statements (as they inherit from AST_Block).
Avoiding calling superclass's _walk function in walkers (turns out we walked
a node multiple times).
