[Feature Request] Verbose log mangled and skipped props due to regex mismatch

[mirfatif]

Please consider if it makes sense. Excuse my ignorance if this can already be done in a better way.

~$ uglifyjs source.js -o uglified.js --verbose --warn -c -m --mangle-props regex=/_$/
...
INFO: Skipping expiry
INFO: Mangling connected_
INFO: Skipping track
INFO: Mangling afterHtmlSet_
INFO: Mangling rootElement_
INFO: Mangling url_
...

--- lib/propmangle.js
+++ lib/propmangle.js
@@ -175,6 +175,9 @@
         cache = new Dictionary();
     }
 
+    // --name-cache doesn't log skipped names
+    var verbose_cache = new Dictionary();
+
     var regex = options.regex;
 
     // note debug is either false (disabled), or a string of the debug suffix to use (enabled).
@@ -261,8 +264,15 @@
 
     function should_mangle(name) {
         if (reserved.has(name)) return false;
-        if (regex && !regex.test(name)) return false;
-        return cache.has(name) || names_to_mangle.has(name);
+        const logged = verbose_cache.has(name);
+        verbose_cache.set(name);
+        if (regex && !regex.test(name)) {
+            logged || AST_Node.info('Skipping ' + name);
+            return false;
+        }
+        const ret = cache.has(name) || names_to_mangle.has(name);
+        ret && !logged && AST_Node.info('Mangling ' + name);
+        return ret;
     }
 
     function add(name) {

[alexlamsl]

Please try #5621 and see if it works for you.

As for your proposed patch − for starters there's no need for verbose_cache since AST_Node.info() already has built-in de-duplication:

UglifyJS/lib/ast.js

Lines 188 to 206 in 8602d1b

	(AST_Node.log_function = function(fn, verbose) {
	if (typeof fn != "function") {
	AST_Node.info = AST_Node.warn = noop;
	return;
	}
	var printed = Object.create(null);
	AST_Node.info = verbose ? function(text, props) {
	log("INFO: " + string_template(text, props));
	} : noop;
	AST_Node.warn = function(text, props) {
	log("WARN: " + string_template(text, props));
	};
	function log(msg) {
	if (printed[msg]) return;
	printed[msg] = true;
	fn(msg);
	}
	})();

[mirfatif]

Thank you for looking into it.

Actually this gives excessive verbosity. I don't think one would be interested in mangling window.location:

INFO: Preserving property location

I was after getting a list of properties and variables which shows if regex was applied or not (with mangle: { properties: { regex: /_$/ } } and compress: { top_retain: /[^_]$/ }). This could help in fixing bad variable/prop names quickly.

But I think it's not possible at the moment.

[alexlamsl]

I don't think one would be interested in mangling window.location

window.location will be preserved if you specify domprops, since builtins refers to JavaScript runtime rather than DOM environment.

I was after getting a list of properties and variables which shows if regex was applied or not

Since mangle.properties.regex applies to all properties under consideration, you will be able to see what gets mangled/preserved to determine if you need to tweak your regex.

For the record, compress.top_retain has nothing to do with name mangling.

[mirfatif]

window.location will be preserved if you specify domprops, since builtins refers to JavaScript runtime rather than DOM environment.

DOM props are preserved. My point is that they are unnecessarily logged:

INFO: Preserving property classList
INFO: Preserving property contains
INFO: Preserving property display
INFO: Preserving property fontWeight
INFO: Preserving property getElementsByClassName
INFO: Preserving property href
INFO: Preserving property location
INFO: Preserving property parentElement
INFO: Preserving property scrollIntoView
INFO: Preserving property style
INFO: Preserving property tagName

There's no way to prevent logging of preserved builtins and domprops, right?

For the record, compress.top_retain has nothing to do with name mangling.

Correct. I was referring to the regex part i.e. get a list of top-level variables which have or have not been gone through "unused removal" due to regex (mis)match.

[alexlamsl]

IMHO there are merits in reporting properties which are affected by builtins etc. − however we can improve readability by differentiating the messages between those and regex.

Please take a look at #5622 which also logs actions related to compress.top_retain

[alexlamsl]

Patches released in [email protected]