rewrite: stop prepending semicolon to this. special property access (…

…#850)

The prepended semicolon breaks code (such as jQuery) that looks like:

    foo = foo ? foo :
                this.location;

I think the reason we started inserting the semicolon was because in situations like:

    x = 1 + 2
    this.location = "foo"

we used to rewrite to:

    x = 1 + 2
    (this && this._WB_wombat_obj_proxy || this).location = "foo"

which the browser would interpret as a bogus function call like `2(this && ... )`.
But nowadays prepending the semicolon should be unnecessary as we currently rewrite to:

    x = 2 + 3
    _____WB$wombat$check$this$function_____(this).location = "foo"

which will trigger JavaScript's automatic semicolon insertion rules like the original code does.

pywb/rewrite/regex_rewriters.py

@@ -124,9 +124,7 @@ def __init__(self):
             (r'(?<![$.])\s*\blocation\b\s*[=]\s*(?![=])', self.add_suffix(check_loc), 0),
             # rewriting 'return this'
             (r'\breturn\s+this\b\s*(?![.$])', self.replace_str(this_rw), 0),
-            # rewriting 'this.' special properties access on new line, with ; prepended
-            (r'\n\s*this\b(?=(?:\.(?:{0})\b))'.format(prop_str), self.replace_str(';' + this_rw), 0),
-            # rewriting 'this.' special properties access, not on new line (no ;)
+            # rewriting 'this.' special properties access
             (r'(?<![$.])\s*this\b(?=(?:\.(?:{0})\b))'.format(prop_str), self.replace_str(this_rw), 0),
             # rewrite '= this' or ', this'
             (r'(?<=[=,])\s*this\b\s*(?![:.$])', self.replace_str(this_rw), 0),

pywb/rewrite/test/test_regex_rewriters.py

@@ -143,7 +143,7 @@
 'var foo = _____WB$wombat$check$this$function_____(this).location'
 
 >>> _test_js_obj_proxy('A = B\nthis.location = "foo"')
-'A = B\n;_____WB$wombat$check$this$function_____(this).location = "foo"'
+'A = B\n_____WB$wombat$check$this$function_____(this).location = "foo"'
 
 >>> _test_js_obj_proxy('var foo = this.location2')
 'var foo = this.location2'