How to use screw-ie8 from programmatic API?

[qyoz]

After this change, I'm trying the disable it, using this example from issue #409 :

var code = 'bad = function(e){return function(error){try {e();}catch(e){error(e);}};};';
var options = {
    fromString: true,
    warnings: false,
    mangle: true,
    screw_ie8: false, // <== doesn't work
    support_ie8: true, // <== doesn't work
    compress: {
        hoist_funs: false,
        if_return: false,
        screw_ie8: false, // <== doesn't work
    },
    output: {
        comments: /^!/,
        beautify: true
    }       

};

UglifyJs.minify(code, options).code;

(In 2.7.0) Toggling the screw_ie8 option produces this output on both occasions:

bad = function(n) {
    return function(t) {
        try {
            n();
        } catch (n) {
            t(n);
        }
    };
};

What I'm expecting is (2.6.4):

bad = function(n) {
    return function(n) {
        try {
            t();
        } catch (t) {
            n(t);
        }
    };
};

Maybe I'm misusing the API, but this option does not work in the current configuration.

[kzc]

Adapted from: #1201 (comment)

cat ug.js

function ug(src, screw_ie8) {
    console.log("\n// screw_ie8 =", screw_ie8);
    console.log(U.minify(src, {
        fromString: true,
        compress: { screw_ie8: screw_ie8 },
        mangle:   { screw_ie8: screw_ie8 },
        output:   { screw_ie8: screw_ie8, beautify: true },
    }).code);
}
var U = require('uglify-js');
var src = "bad=function(e){return function(error){try{e()}catch(e){error(e)}}};";
ug(src, true);
ug(src, false);

node ug.js

// screw_ie8 = true
bad = function(n) {
    return function(t) {
        try {
            n();
        } catch (n) {
            t(n);
        }
    };
};

// screw_ie8 = false
bad = function(n) {
    return function(n) {
        try {
            t();    // Edit: note incorrect code generated with screw_ie8 = false
        } catch (t) {
            n(t);
        }
    };
};

[qyoz]

@kzc so I'm not the only one who was confused by this.
I don't mind updating the docs again (in this PR) but this API is just ugly. Is there a reason why its not merged into one option?

[kzc]

It's not a great API. You have to look at the bin/uglifyjs source code to find out what needs to be set. An additional top level screw_ie8 option for minify() that sets the options in compress, mangle and output would be good. Only set the lower level options if typeof top level screw_ie8 is "boolean" and the lower level options are not set (i.e., undefined). The old options must remain for backwards compatibility. keep_fnames has the exact same problem for compress and mangle. Might be other options with similar issues. Pull requests welcome.

[kzc]

@qyoz for keep_fnames - see: #1187 (comment) and #1210