From 22652ae92cd3779827d35eb8e470101a6ca96502 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sat, 19 Sep 2026 00:57:28 +0000
Subject: [PATCH 1/2] Initial plan


From 09f82b6fd962e23e1706ded14c1ae8dc84cccd03 Mon Sep 17 00:00:00 2001
From: "copilot-swe-agent[bot]" <198982749+Copilot@users.noreply.github.com>
Date: Sat, 19 Sep 2026 01:09:02 +0000
Subject: [PATCH 2/2] Update MutationObserverInit.attributeFilter to accept
 Iterable<string>

Co-authored-by: RyanCavanaugh <6685088+RyanCavanaugh@users.noreply.github.com>
---
 tsc/internal/bundled/libs/lib.dom.d.ts        |  2 +-
 ...tionObserverInitAttributeFilterIterable.js | 16 ++++++++++
 ...bserverInitAttributeFilterIterable.symbols | 26 ++++++++++++++++
 ...nObserverInitAttributeFilterIterable.types | 31 +++++++++++++++++++
 ...tionObserverInitAttributeFilterIterable.ts |  8 +++++
 5 files changed, 82 insertions(+), 1 deletion(-)
 create mode 100644 tsc/testdata/baselines/reference/compiler/mutationObserverInitAttributeFilterIterable.js
 create mode 100644 tsc/testdata/baselines/reference/compiler/mutationObserverInitAttributeFilterIterable.symbols
 create mode 100644 tsc/testdata/baselines/reference/compiler/mutationObserverInitAttributeFilterIterable.types
 create mode 100644 tsc/testdata/tests/cases/compiler/mutationObserverInitAttributeFilterIterable.ts

diff --git a/tsc/internal/bundled/libs/lib.dom.d.ts b/tsc/internal/bundled/libs/lib.dom.d.ts
index 9e127c3f5a524..7ffa528860919 100644
--- a/tsc/internal/bundled/libs/lib.dom.d.ts
+++ b/tsc/internal/bundled/libs/lib.dom.d.ts
@@ -1671,7 +1671,7 @@ interface MultiCacheQueryOptions extends CacheQueryOptions {
 
 interface MutationObserverInit {
     /** Set to a list of attribute local names (without namespace) if not all attribute mutations need to be observed and attributes is true or omitted. */
-    attributeFilter?: string[];
+    attributeFilter?: string[] | Iterable<string>;
     /** Set to true if attributes is true or omitted and target's attribute value before the mutation needs to be recorded. */
     attributeOldValue?: boolean;
     /** Set to true if mutations to target's attributes are to be observed. Can be omitted if attributeOldValue or attributeFilter is specified. */
diff --git a/tsc/testdata/baselines/reference/compiler/mutationObserverInitAttributeFilterIterable.js b/tsc/testdata/baselines/reference/compiler/mutationObserverInitAttributeFilterIterable.js
new file mode 100644
index 0000000000000..d5b15bc48b2cd
--- /dev/null
+++ b/tsc/testdata/baselines/reference/compiler/mutationObserverInitAttributeFilterIterable.js
@@ -0,0 +1,16 @@
+//// [tests/cases/compiler/mutationObserverInitAttributeFilterIterable.ts] ////
+
+//// [mutationObserverInitAttributeFilterIterable.ts]
+const names = new Set<string>();
+
+const options1: MutationObserverInit = { attributeFilter: names.keys() };
+const options2: MutationObserverInit = { attributeFilter: ["foo", "bar"] };
+const options3: MutationObserverInit = { attributeFilter: names };
+
+
+//// [mutationObserverInitAttributeFilterIterable.js]
+"use strict";
+const names = new Set();
+const options1 = { attributeFilter: names.keys() };
+const options2 = { attributeFilter: ["foo", "bar"] };
+const options3 = { attributeFilter: names };
diff --git a/tsc/testdata/baselines/reference/compiler/mutationObserverInitAttributeFilterIterable.symbols b/tsc/testdata/baselines/reference/compiler/mutationObserverInitAttributeFilterIterable.symbols
new file mode 100644
index 0000000000000..199da748ffdb9
--- /dev/null
+++ b/tsc/testdata/baselines/reference/compiler/mutationObserverInitAttributeFilterIterable.symbols
@@ -0,0 +1,26 @@
+//// [tests/cases/compiler/mutationObserverInitAttributeFilterIterable.ts] ////
+
+=== mutationObserverInitAttributeFilterIterable.ts ===
+const names = new Set<string>();
+>names : Symbol(names, Decl(mutationObserverInitAttributeFilterIterable.ts, 0, 5))
+>Set : Symbol(Set, Decl(lib.es2015.collection.d.ts, --, --), Decl(lib.es2015.collection.d.ts, --, --), Decl(lib.es2015.iterable.d.ts, --, --), Decl(lib.es2015.symbol.wellknown.d.ts, --, --), Decl(lib.es2025.collection.d.ts, --, --))
+
+const options1: MutationObserverInit = { attributeFilter: names.keys() };
+>options1 : Symbol(options1, Decl(mutationObserverInitAttributeFilterIterable.ts, 2, 5))
+>MutationObserverInit : Symbol(MutationObserverInit, Decl(lib.dom.d.ts, --, --))
+>attributeFilter : Symbol(attributeFilter, Decl(mutationObserverInitAttributeFilterIterable.ts, 2, 40))
+>names.keys : Symbol(Set.keys, Decl(lib.es2015.iterable.d.ts, --, --))
+>names : Symbol(names, Decl(mutationObserverInitAttributeFilterIterable.ts, 0, 5))
+>keys : Symbol(Set.keys, Decl(lib.es2015.iterable.d.ts, --, --))
+
+const options2: MutationObserverInit = { attributeFilter: ["foo", "bar"] };
+>options2 : Symbol(options2, Decl(mutationObserverInitAttributeFilterIterable.ts, 3, 5))
+>MutationObserverInit : Symbol(MutationObserverInit, Decl(lib.dom.d.ts, --, --))
+>attributeFilter : Symbol(attributeFilter, Decl(mutationObserverInitAttributeFilterIterable.ts, 3, 40))
+
+const options3: MutationObserverInit = { attributeFilter: names };
+>options3 : Symbol(options3, Decl(mutationObserverInitAttributeFilterIterable.ts, 4, 5))
+>MutationObserverInit : Symbol(MutationObserverInit, Decl(lib.dom.d.ts, --, --))
+>attributeFilter : Symbol(attributeFilter, Decl(mutationObserverInitAttributeFilterIterable.ts, 4, 40))
+>names : Symbol(names, Decl(mutationObserverInitAttributeFilterIterable.ts, 0, 5))
+
diff --git a/tsc/testdata/baselines/reference/compiler/mutationObserverInitAttributeFilterIterable.types b/tsc/testdata/baselines/reference/compiler/mutationObserverInitAttributeFilterIterable.types
new file mode 100644
index 0000000000000..bc1d6158fd41e
--- /dev/null
+++ b/tsc/testdata/baselines/reference/compiler/mutationObserverInitAttributeFilterIterable.types
@@ -0,0 +1,31 @@
+//// [tests/cases/compiler/mutationObserverInitAttributeFilterIterable.ts] ////
+
+=== mutationObserverInitAttributeFilterIterable.ts ===
+const names = new Set<string>();
+>names : Set<string>
+>new Set<string>() : Set<string>
+>Set : SetConstructor
+
+const options1: MutationObserverInit = { attributeFilter: names.keys() };
+>options1 : MutationObserverInit
+>{ attributeFilter: names.keys() } : { attributeFilter: SetIterator<string>; }
+>attributeFilter : SetIterator<string>
+>names.keys() : SetIterator<string>
+>names.keys : () => SetIterator<string>
+>names : Set<string>
+>keys : () => SetIterator<string>
+
+const options2: MutationObserverInit = { attributeFilter: ["foo", "bar"] };
+>options2 : MutationObserverInit
+>{ attributeFilter: ["foo", "bar"] } : { attributeFilter: string[]; }
+>attributeFilter : string[]
+>["foo", "bar"] : string[]
+>"foo" : "foo"
+>"bar" : "bar"
+
+const options3: MutationObserverInit = { attributeFilter: names };
+>options3 : MutationObserverInit
+>{ attributeFilter: names } : { attributeFilter: Set<string>; }
+>attributeFilter : Set<string>
+>names : Set<string>
+
diff --git a/tsc/testdata/tests/cases/compiler/mutationObserverInitAttributeFilterIterable.ts b/tsc/testdata/tests/cases/compiler/mutationObserverInitAttributeFilterIterable.ts
new file mode 100644
index 0000000000000..1c6681e6b91e5
--- /dev/null
+++ b/tsc/testdata/tests/cases/compiler/mutationObserverInitAttributeFilterIterable.ts
@@ -0,0 +1,8 @@
+// @target: esnext
+// @lib: dom,esnext
+
+const names = new Set<string>();
+
+const options1: MutationObserverInit = { attributeFilter: names.keys() };
+const options2: MutationObserverInit = { attributeFilter: ["foo", "bar"] };
+const options3: MutationObserverInit = { attributeFilter: names };