Auto merge of #8854 - KiChjang:undefined-as-missing, r=frewsxcv

Treat 'undefined' passed to optional JS arguments as missing

@frewsxcv please don't hurt me for this.

I've added an AND condition to check whether the value being passed is undefined while checking whether the argument exists at all. Essentially, this is now treating undefined arguments the same as missing arguments.

Fixes #8813.
Fixes #6558.

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1 files changed, 5 insertions, 5 deletions

diff --git a/components/script/dom/bindings/codegen/CodegenRust.py b/components/script/dom/bindings/codegen/CodegenRust.py
index c714bddb983..f947b0b2f80 100644
--- a/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/components/script/dom/bindings/codegen/CodegenRust.py
@@ -1142,7 +1142,6 @@ class CGArgumentConverter(CGThing):
             "argc": argc,
             "args": args
         }
-        condition = string.Template("${index} < ${argc}").substitute(replacer)
 
         replacementVariables = {
             "val": string.Template("${args}.get(${index})").substitute(replacer),
@@ -1164,17 +1163,18 @@ class CGArgumentConverter(CGThing):
 
         if not argument.variadic:
             if argument.optional:
+                condition = "{args}.get({index}).is_undefined()".format(**replacer)
                 if argument.defaultValue:
                     assert default
                     template = CGIfElseWrapper(condition,
-                                               CGGeneric(template),
-                                               CGGeneric(default)).define()
+                                               CGGeneric(default),
+                                               CGGeneric(template)).define()
                 else:
                     assert not default
                     declType = CGWrapper(declType, pre="Option<", post=">")
                     template = CGIfElseWrapper(condition,
-                                               CGGeneric("Some(%s)" % template),
-                                               CGGeneric("None")).define()
+                                               CGGeneric("None"),
+                                               CGGeneric("Some(%s)" % template)).define()
             else:
                 assert not default