servo / servo/servo

`--unminify-js` causes `called Option::unwrap() on a None value (thread Script#1, at components/script/dom/document/document.rs:2371)`

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C-needs-investigation C-triggered-by-web-page I-panic
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Rust
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Description

To reproduce: /mach run https://reddit.com --unminify-js

Backtrace 
[2026-05-14T23:10:24Z ERROR script::script_module] Fetching module script failed CORS check failed
[2026-05-14T23:10:24Z ERROR script::script_module] Fetching module script failed CORS check failed
(new TypeError("Module fetching failed", "https://www.reddit.com/?solution=4f5eda6bb95f83934f5eda6bb95f8393&js_challenge=1&token=bbbe4bf1c9a2b5160829c4be34da5861a60ca96269ac28ea3a45f1b4cc79fb19&jsc_orig_r=", 123))
[2026-05-14T23:10:26Z ERROR servoshell::desktop::headed_window] (new TypeError("Module fetching failed", "https://www.reddit.com/?solution=4f5eda6bb95f83934f5eda6bb95f8393&js_challenge=1&token=bbbe4bf1c9a2b5160829c4be34da5861a60ca96269ac28ea3a45f1b4cc79fb19&jsc_orig_r=", 123))
(new TypeError("Module fetching failed", "https://www.reddit.com/?solution=4f5eda6bb95f83934f5eda6bb95f8393&js_challenge=1&token=bbbe4bf1c9a2b5160829c4be34da5861a60ca96269ac28ea3a45f1b4cc79fb19&jsc_orig_r=", 123))
[2026-05-14T23:10:26Z ERROR servoshell::desktop::headed_window] (new TypeError("Module fetching failed", "https://www.reddit.com/?solution=4f5eda6bb95f83934f5eda6bb95f8393&js_challenge=1&token=bbbe4bf1c9a2b5160829c4be34da5861a60ca96269ac28ea3a45f1b4cc79fb19&jsc_orig_r=", 123))
called `Option::unwrap()` on a `None` value (thread Script#1, at components/script/dom/document/document.rs:2371)
   0: servoshell::backtrace::print
             at /home/alaska/servo/ports/servoshell/backtrace.rs:18:5
   1: servoshell::panic_hook::panic_hook
             at /home/alaska/servo/ports/servoshell/panic_hook.rs:40:17
   2: core::ops::function::Fn::call
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:79:5
   3: <alloc::boxed::Box<dyn for<'a, 'b> core::ops::function::Fn<(&'a std::panic::PanicHookInfo<'b>,), Output = ()> + core::marker::Sync + core::marker::Send> as core::ops::function::Fn<(&std::panic::PanicHookInfo,)>>::call
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/alloc/src/boxed.rs:2254:9
      std::panicking::panic_with_hook
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:833:13
   4: std::panicking::panic_handler::{closure#0}
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:691:13
   5: std::sys::backtrace::__rust_end_short_backtrace::<std::panicking::panic_handler::{closure#0}, !>
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/sys/backtrace.rs:182:18
   6: __rustc::rust_begin_unwind
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/panicking.rs:689:5
   7: core::panicking::panic_fmt
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/panicking.rs:80:14
   8: core::panicking::panic
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/panicking.rs:150:5
   9: core::option::unwrap_failed
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/core/src/option.rs:2236:5
  10: <core::option::Option<usize>>::unwrap
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/option.rs:1016:21
      <script::dom::document::document::Document>::asap_script_loaded
             at /home/alaska/servo/components/script/dom/document/document.rs:2371:18
  11: script::dom::html::htmlscriptelement::finish_fetching_a_script
             at /home/alaska/servo/components/script/dom/html/htmlscriptelement.rs:327:22
  12: <script::dom::html::htmlscriptelement::HTMLScriptElement>::prepare::{closure#3}
             at /home/alaska/servo/components/script/dom/html/htmlscriptelement.rs:928:29
  13: script::script_module::fetch_the_descendants_and_link_module_script::<<script::dom::html::htmlscriptelement::HTMLScriptElement>::prepare::{closure#3}>
             at /home/alaska/servo/components/script/script_module.rs:1386:9
  14: script::script_module::fetch_an_external_module_script::<<script::dom::html::htmlscriptelement::HTMLScriptElement>::prepare::{closure#3}>::{closure#0}
             at /home/alaska/servo/components/script/script_module.rs:1260:13
  15: script::script_module::fetch_a_single_module_script::<script::script_module::fetch_an_external_module_script<<script::dom::html::htmlscriptelement::HTMLScriptElement>::prepare::{closure#3}>::{closure#0}>
             at /home/alaska/servo/components/script/script_module.rs:1495:20
  16: script::script_module::fetch_an_external_module_script::<<script::dom::html::htmlscriptelement::HTMLScriptElement>::prepare::{closure#3}>
             at /home/alaska/servo/components/script/script_module.rs:1242:5
  17: <script::dom::html::htmlscriptelement::HTMLScriptElement>::prepare
             at /home/alaska/servo/components/script/dom/html/htmlscriptelement.rs:919:21
  18: <script::dom::html::htmlscriptelement::HTMLScriptElement as script::dom::virtualmethods::VirtualMethods>::post_connection_steps
             at /home/alaska/servo/components/script/dom/html/htmlscriptelement.rs:1291:18
  19: <script::dom::node::node::Node>::insert::{closure#4}
             at /home/alaska/servo/components/script/dom/node/node.rs:3252:39
  20: <<script::dom::node::node::Node>::insert::{closure#4} as core::ops::function::FnOnce<(&mut mozjs::context::JSContext, smallvec::SmallVec<[script_bindings::root::Root<script_bindings::root::Dom<script::dom::node::node::Node>>; 4]>)>>::call_once
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
  21: <<script::dom::node::node::Node>::insert::PostConnectionSteps<<script::dom::node::node::Node>::insert::{closure#4}> as script::task::NonSendTaskOnce>::run_once
             at /home/alaska/servo/components/script/task.rs:81:17
  22: <<script::dom::node::node::Node>::insert::PostConnectionSteps<<script::dom::node::node::Node>::insert::{closure#4}> as script::task::NonSendTaskBox>::run_box
             at /home/alaska/servo/components/script/task.rs:141:14
  23: <script::dom::document::document::Document>::remove_script_and_layout_blocker
             at /home/alaska/servo/components/script/dom/document/document.rs:3750:18
  24: <script::dom::node::node::Node>::insert
             at /home/alaska/servo/components/script/dom/node/node.rs:3258:23
  25: <script::dom::node::node::Node>::pre_insert
             at /home/alaska/servo/components/script/dom/node/node.rs:3060:9
  26: <script::dom::node::node::Node as script_bindings::codegen::GenericBindings::NodeBinding::Node_Binding::NodeMethods<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>>::AppendChild
             at /home/alaska/servo/components/script/dom/node/node.rs:4134:9
  27: script_bindings::codegen::GenericBindings::NodeBinding::Node_Binding::appendChild::<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>::{closure#0}::{closure#0}
             at /home/alaska/servo/target/debug/build/servo-script-bindings-dbadbfe1b1efd54b/out/Bindings/NodeBinding.rs:1707:60
  28: script_bindings::codegen::GenericBindings::NodeBinding::Node_Binding::appendChild::<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>::{closure#0}
             at /home/alaska/servo/target/debug/build/servo-script-bindings-dbadbfe1b1efd54b/out/Bindings/NodeBinding.rs:1679:33
  29: <&mut dyn core::ops::function::FnMut<(), Output = ()> as core::ops::function::FnOnce<()>>::call_once
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:310:21
  30: <core::panic::unwind_safe::AssertUnwindSafe<&mut dyn core::ops::function::FnMut<(), Output = ()>> as core::ops::function::FnOnce<()>>::call_once
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panic/unwind_safe.rs:274:9
  31: std::panicking::catch_unwind::do_call::<core::panic::unwind_safe::AssertUnwindSafe<&mut dyn core::ops::function::FnMut<(), Output = ()>>, ()>
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:581:40
  32: __rust_try
  33: std::panicking::catch_unwind::<(), core::panic::unwind_safe::AssertUnwindSafe<&mut dyn core::ops::function::FnMut<(), Output = ()>>>
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:544:19
      std::panic::catch_unwind::<core::panic::unwind_safe::AssertUnwindSafe<&mut dyn core::ops::function::FnMut<(), Output = ()>>, ()>
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:359:14
  34: mozjs::panic::wrap_panic
             at /home/alaska/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/mozjs-0.15.14/src/panic.rs:22:11
  35: script_bindings::codegen::GenericBindings::NodeBinding::Node_Binding::appendChild::<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>
             at /home/alaska/servo/target/debug/build/servo-script-bindings-dbadbfe1b1efd54b/out/Bindings/NodeBinding.rs:1679:5
  36: CallJitMethodOp
             at /home/runner/work/mozjs/mozjs/mozjs-sys/./src/jsglue.cpp:717:22
  37: script_bindings::utils::generic_call::<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder, false>
             at /home/alaska/servo/components/script_bindings/utils.rs:647:5
  38: script_bindings::utils::generic_method::<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder, script_bindings::utils::call_policies::Normal, false>
             at /home/alaska/servo/components/script_bindings/utils.rs:671:5
  39: _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructENS_10CallReasonE
  40: _ZN2js9InterpretEP9JSContextRNS_8RunStateE
  41: _ZN2js9RunScriptEP9JSContextRNS_8RunStateE
  42: _ZN2js23InternalCallOrConstructEP9JSContextRKN2JS8CallArgsENS_14MaybeConstructENS_10CallReasonE
  43: _ZN2js4CallEP9JSContextN2JS6HandleINS2_5ValueEEES5_RKNS_13AnyInvokeArgsENS2_13MutableHandleIS4_EENS_10CallReasonE
  44: _ZN2JS4CallEP9JSContextNS_6HandleINS_5ValueEEES4_RKNS_16HandleValueArrayENS_13MutableHandleIS3_EE
  45: mozjs::rust::wrappers::Call
             at /home/alaska/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/mozjs-0.15.14/src/rust.rs:1439:51
  46: <script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>>::HandleEvent
             at /home/alaska/servo/target/debug/build/servo-script-bindings-dbadbfe1b1efd54b/out/Bindings/EventListenerBinding.rs:61:18
  47: <script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>>::HandleEvent_::<script::dom::event::eventtarget::EventTarget>::{closure#0}
             at /home/alaska/servo/target/debug/build/servo-script-bindings-dbadbfe1b1efd54b/out/Bindings/EventListenerBinding.rs:35:27
  48: script_bindings::callback::call_setup::<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder, script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>, core::result::Result<(), script_bindings::error::Error>, <script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>>::HandleEvent_<script::dom::event::eventtarget::EventTarget>::{closure#0}>::{closure#0}::{closure#0}
             at /home/alaska/servo/components/script_bindings/callback.rs:279:26
  49: script_bindings::settings_stack::run_a_callback::<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder, core::result::Result<(), script_bindings::error::Error>, script_bindings::callback::call_setup<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder, script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>, core::result::Result<(), script_bindings::error::Error>, <script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>>::HandleEvent_<script::dom::event::eventtarget::EventTarget>::{closure#0}>::{closure#0}::{closure#0}>
             at /home/alaska/servo/components/script_bindings/settings_stack.rs:85:18
  50: script_bindings::callback::call_setup::<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder, script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>, core::result::Result<(), script_bindings::error::Error>, <script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>>::HandleEvent_<script::dom::event::eventtarget::EventTarget>::{closure#0}>::{closure#0}
             at /home/alaska/servo/components/script_bindings/callback.rs:300:13
  51: script_bindings::settings_stack::run_a_script::<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder, core::result::Result<(), script_bindings::error::Error>, script_bindings::callback::call_setup<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder, script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>, core::result::Result<(), script_bindings::error::Error>, <script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>>::HandleEvent_<script::dom::event::eventtarget::EventTarget>::{closure#0}>::{closure#0}>
             at /home/alaska/servo/components/script_bindings/settings_stack.rs:43:18
  52: script_bindings::callback::call_setup::<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder, script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>, core::result::Result<(), script_bindings::error::Error>, <script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>>::HandleEvent_<script::dom::event::eventtarget::EventTarget>::{closure#0}>
             at /home/alaska/servo/components/script_bindings/callback.rs:276:5
  53: <script_bindings::codegen::GenericBindings::EventListenerBinding::EventListener<script::dom::bindings::codegen::DomTypeHolder::DomTypeHolder>>::HandleEvent_::<script::dom::event::eventtarget::EventTarget>
             at /home/alaska/servo/target/debug/build/servo-script-bindings-dbadbfe1b1efd54b/out/Bindings/EventListenerBinding.rs:29:9
  54: <script::dom::event::eventtarget::CompiledEventListener>::call_or_handle_event
             at /home/alaska/servo/components/script/dom/event/eventtarget.rs:217:26
  55: script::dom::event::event::inner_invoke
             at /home/alaska/servo/components/script/dom/event/event.rs:1442:14
  56: script::dom::event::event::invoke
             at /home/alaska/servo/components/script/dom/event/event.rs:1321:17
  57: <script::dom::event::event::Event>::dispatch_inner
             at /home/alaska/servo/components/script/dom/event/event.rs:619:17
  58: <script::dom::event::event::Event>::dispatch
             at /home/alaska/servo/components/script/dom/event/event.rs:295:14
  59: <script::dom::event::eventtarget::EventTarget>::dispatch_event
             at /home/alaska/servo/components/script/dom/event/eventtarget.rs:477:15
  60: <script::dom::event::event::Event>::fire
             at /home/alaska/servo/components/script/dom/event/event.rs:777:16
  61: <script::dom::event::eventtarget::EventTarget>::fire_event_with_params
             at /home/alaska/servo/components/script/dom/event/eventtarget.rs:877:15
  62: <script::dom::event::eventtarget::EventTarget>::fire_bubbling_event
             at /home/alaska/servo/components/script/dom/event/eventtarget.rs:821:14
  63: <script::dom::document::document::Document>::maybe_dispatch_dom_content_loaded::{closure#0}
             at /home/alaska/servo/components/script/dom/document/document.rs:2466:46
  64: <<script::dom::document::document::Document>::maybe_dispatch_dom_content_loaded::{closure#0} as core::ops::function::FnOnce<(&mut mozjs::context::JSContext,)>>::call_once
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
  65: <<script::dom::document::document::Document>::maybe_dispatch_dom_content_loaded::fire_dom_content_loaded_event<<script::dom::document::document::Document>::maybe_dispatch_dom_content_loaded::{closure#0}> as script::task::TaskOnce>::run_once
             at /home/alaska/servo/components/script/task.rs:102:17
  66: <script::task::CancellableTask<<script::dom::document::document::Document>::maybe_dispatch_dom_content_loaded::fire_dom_content_loaded_event<<script::dom::document::document::Document>::maybe_dispatch_dom_content_loaded::{closure#0}>> as script::task::TaskOnce>::run_once
             at /home/alaska/servo/components/script/task.rs:203:24
  67: <script::task::CancellableTask<<script::dom::document::document::Document>::maybe_dispatch_dom_content_loaded::fire_dom_content_loaded_event<<script::dom::document::document::Document>::maybe_dispatch_dom_content_loaded::{closure#0}>> as script::task::TaskBox>::run_box
             at /home/alaska/servo/components/script/task.rs:154:14
  68: <script::script_thread::ScriptThread>::handle_msg_from_script
             at /home/alaska/servo/components/script/script_thread.rs:2106:22
  69: <script::script_thread::ScriptThread>::handle_msgs::{closure#2}
             at /home/alaska/servo/components/script/script_thread.rs:1518:30
  70: <script::script_thread::ScriptThread>::profile_event::<<script::script_thread::ScriptThread>::handle_msgs::{closure#2}, bool>
             at /home/alaska/servo/components/script/script_thread.rs:1758:13
  71: <script::script_thread::ScriptThread>::handle_msgs
             at /home/alaska/servo/components/script/script_thread.rs:1508:32
  72: <script::script_thread::ScriptThread>::start
             at /home/alaska/servo/components/script/script_thread.rs:1096:20
  73: <script::script_thread::ScriptThread as layout_api::ScriptThreadFactory>::create::{closure#0}::{closure#1}
             at /home/alaska/servo/components/script/script_thread.rs:514:38
  74: <profile_traits::mem::ProfilerChan>::run_with_memory_reporting::<<script::script_thread::ScriptThread as layout_api::ScriptThreadFactory>::create::{closure#0}::{closure#1}, script::messaging::CommonScriptMsg::CollectReports, script::messaging::CommonScriptMsg, script::messaging::ScriptEventLoopSender>
             at /home/alaska/servo/components/shared/profile/mem.rs:143:9
  75: <script::script_thread::ScriptThread as layout_api::ScriptThreadFactory>::create::{closure#0}
             at /home/alaska/servo/components/script/script_thread.rs:513:40
  76: std::sys::backtrace::__rust_begin_short_backtrace::<<script::script_thread::ScriptThread as layout_api::ScriptThreadFactory>::create::{closure#0}, ()>
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/sys/backtrace.rs:166:18
  77: std::thread::lifecycle::spawn_unchecked::<<script::script_thread::ScriptThread as layout_api::ScriptThreadFactory>::create::{closure#0}, ()>::{closure#1}::{closure#0}
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/lifecycle.rs:91:13
  78: <core::panic::unwind_safe::AssertUnwindSafe<std::thread::lifecycle::spawn_unchecked<<script::script_thread::ScriptThread as layout_api::ScriptThreadFactory>::create::{closure#0}, ()>::{closure#1}::{closure#0}> as core::ops::function::FnOnce<()>>::call_once
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/panic/unwind_safe.rs:274:9
  79: std::panicking::catch_unwind::do_call::<core::panic::unwind_safe::AssertUnwindSafe<std::thread::lifecycle::spawn_unchecked<<script::script_thread::ScriptThread as layout_api::ScriptThreadFactory>::create::{closure#0}, ()>::{closure#1}::{closure#0}>, ()>
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:581:40
  80: __rust_try
  81: std::panicking::catch_unwind::<(), core::panic::unwind_safe::AssertUnwindSafe<std::thread::lifecycle::spawn_unchecked<<script::script_thread::ScriptThread as layout_api::ScriptThreadFactory>::create::{closure#0}, ()>::{closure#1}::{closure#0}>>
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panicking.rs:544:19
      std::panic::catch_unwind::<core::panic::unwind_safe::AssertUnwindSafe<std::thread::lifecycle::spawn_unchecked<<script::script_thread::ScriptThread as layout_api::ScriptThreadFactory>::create::{closure#0}, ()>::{closure#1}::{closure#0}>, ()>
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:359:14
      std::thread::lifecycle::spawn_unchecked::<<script::script_thread::ScriptThread as layout_api::ScriptThreadFactory>::create::{closure#0}, ()>::{closure#1}
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/thread/lifecycle.rs:89:26
  82: <std::thread::lifecycle::spawn_unchecked<<script::script_thread::ScriptThread as layout_api::ScriptThreadFactory>::create::{closure#0}, ()>::{closure#1} as core::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
             at /home/alaska/.rustup/toolchains/1.95.0-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ops/function.rs:250:5
  83: <alloc::boxed::Box<dyn core::ops::function::FnOnce<(), Output = ()> + core::marker::Send> as core::ops::function::FnOnce<()>>::call_once
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/alloc/src/boxed.rs:2240:9
      <std::sys::thread::unix::Thread>::new::thread_start
             at /rustc/59807616e1fa2540724bfbac14d7976d7e4a3860/library/std/src/sys/thread/unix.rs:118:17
  84: start_thread
  85: __GI___clone3
[2026-05-14T23:10:33Z ERROR servoshell::panic_hook] called `Option::unwrap()` on a `None` value
[2026-05-14T23:10:33Z ERROR servo_constellation::constellation] Error sending message to (1,2): Disconnected
[2026-05-14T23:10:33Z ERROR servo_constellation::constellation] crash page crashed

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Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Reproduce the crash with /mach run https://reddit.com --unminify-js, then inspect components/script/dom/document/document.rs:2371 and the stack's related paths in htmlscriptelement.rs and script_module.rs. Trace the failed module-fetch flow and ensure the reproduction no longer panics with Option::unwrap().

Written by the indexing model from the issue text.

Assessment

Tech stack
javascript, rust
Domain
frontend, web-dev
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
52/100

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