Two defects: the position keyword was matched case-sensitively with no default
(so 'BeforeEnd' inserted nothing and an invalid position silently no-oped
instead of throwing SyntaxError), and fragments were parsed inside a throwaway
<div>, so context-sensitive children (<tr>, <td>, <option>, …) were dropped.
Lowercase the position and throw SyntaxError on an unknown value; parse via a
table/select-aware wrapMap (chosen from the fragment's leading tag, falling back
to the insertion context) so rows/cells/options survive.
Fixes#495
resolveOrFallback(undefined) returned undefined, so applyVirtual set
__virtualUrl to null and location reverted to the document URL. Per the HTML
spec a missing url keeps the current document URL; return __currentUrl() so the
new history entry captures the current location instead of clearing it.
Fixes#496
before(), after() and replaceWith() only converted string arguments to Text
nodes; other primitives (numbers, booleans, null) were passed straight to
insert_before with no _nid, corrupting the call. Route them through the shared
_convertNodes helper (the same path append/prepend use), so every non-node
argument becomes document.createTextNode(String(n)).
Fixes#498
The old sub-millisecond bump (_sub += 0.1) was uncapped, so after >10 calls in
one millisecond it exceeded 1.0; when the wall clock then ticked over and the
bump reset to 0, now() returned a value below the previous call. Track the last
returned value and never go below it (advance by a tiny epsilon when the clock
has not moved past it).
Fixes#497
The three NS methods ignored the namespace: setAttributeNS stored the qualified
name against the non-namespaced store and getAttributeNS/removeAttributeNS
looked up by local name only, so a namespaced attribute was not addressable by
(namespace, localName) — getAttributeNS(xlink, 'href') returned null.
Record the namespace on the attribute and add namespace-aware DOM ops that match
by (namespace, localName), where the local name is the attribute name after any
prefix (so both setAttributeNS-created 'xlink:href' and parser-created 'href'
resolve). The non-namespaced getAttribute/serialization paths are untouched, and
getAttributeNS(null, name) still reads plain attributes.
Fixes#503
cloneNode(true) round-tripped through a throwaway <div>'s innerHTML, so the
HTML fragment parser discarded elements that are not valid children of <div>
(<tr>, <td>, <option>, <tbody>, …) — createElement('tr').cloneNode(true)
returned null — and JS-set inline styles were lost. The shallow path also
re-derived attributes by regex-scraping serialized HTML.
Clone structurally with real DOM APIs: shallow-clone each node via
createElement/createElementNS plus a getAttributeNames() attribute copy (no
parsing context, every attribute preserved), then descend into children with an
explicit stack so a deep subtree cannot overflow the JS stack. Text, Comment,
DocumentFragment and <template> contents are handled.
Fixes#490
CSSStyleDeclaration was backed by an in-memory _props map that was never
bridged to the element's style content attribute. Parsed inline styles were
invisible to el.style.*, setAttribute('style', …) did not update el.style, and
el.style.x = … never reached the attribute or serialization; getComputedStyle
read the same disconnected declaration.
Give the declaration its owner element: lazily pull the style attribute into
_props on read (skipping the reparse when unchanged) and push _props back to the
attribute on every mutation. Owner-less declarations (getComputedStyle fallback,
stylesheet rules) stay purely in-memory, so their behavior is unchanged.
Fixes#488
get namespaceURI() derived the namespace from the tag name and only ever
recognised the <svg> root, so every element parsed inside an <svg> subtree
reported the XHTML namespace. get href() gates the SVGAnimatedString
reflection on the SVG namespace, so for parsed content the gate never
opened: href returned a plain string and .animVal/.baseVal were undefined,
making new URL(el.href.animVal) throw. Only createElementNS-built elements
worked, because createElementNS records _ns explicitly.
The tree builder already applies the HTML5 foreign-content rules, so
QualName.ns is correct for parsed SVG; it just was not exposed to JS. Add a
namespace_uri DOM op and read it in get namespaceURI(), keeping _ns as the
override and the old tag-name heuristic as the fallback when no element name
is recorded. Namespaces are immutable, so the result is cached like _lname.
Fixes#484
Keep pumping the event loop past the general 500ms settle limit only while the dynamic-script queue remains pending, with a 3s hard cap.
Add a deterministic CDP regression for direct and nested external scripts whose fetch crosses the original settle deadline.
parentNode() inspected only the immediate parent, which caused three
spec deviations:
- With currentNode at root, the `parent !== this.root` guard did not
fire (parent is root's OWN parent), so a node OUTSIDE the walker's
subtree was returned — createTreeWalker(root).parentNode() yielded
<body>. A TreeWalker must never surface a node above its root.
- The same guard excluded root as a *result*, so when currentNode's
accepted ancestor was root itself, parentNode() returned null instead
of root.
- A skipped (or otherwise non-accepted) immediate parent ended the
search rather than continuing up to the first accepted ancestor.
Replaced with the DOM 6.1 algorithm: climb from currentNode, returning
the first ancestor that filters to FILTER_ACCEPT, with the loop's
`node !== this.root` guard keeping the walk inside root while still
letting root be returned. Reuses the three-valued `_filter` from #461.
Last of the TreeWalker mover deviations, after nextNode (#461),
previousNode (#462) and the child/sibling movers (#469).
createNodeIterator returned a TreeWalker with a flag on it. The two are
different interfaces, and the alias got two things wrong.
An iterator's pointer starts *before* its root, so the first nextNode()
returns the root itself; a TreeWalker starts *at* its root and never
returns it. So createNodeIterator(el, SHOW_ELEMENT) silently skipped
exactly the element it was rooted at:
<div id=root><a></a></div> -> ["A"] (Chrome: ["DIV","A"])
It also exposed the wrong surface: no referenceNode,
pointerBeforeReferenceNode or detach (older library code still calls
detach and hit "not a function"), while leaking currentNode, firstChild,
parentNode and the rest of TreeWalker's movers.
Implemented DOM 6.2 "traverse" directly. Keeping the pointer as
(referenceNode, pointerBeforeReferenceNode) rather than a single cursor
is what makes a direction change re-yield the current node instead of
stepping over it, and a failed traversal leaves both untouched so the
iterator stays resumable either way.
The backward step is a new `DomTree::prev_in_subtree`, mirroring
`next_in_subtree`. It can live entirely in the DOM layer because a
NodeIterator prunes nothing -- unlike the TreeWalker's backward walk
(#462), where FILTER_REJECT forces the filter to be consulted at every
step of the descent.
FILTER_REJECT still behaves as FILTER_SKIP here, which the existing test
keeps covering; its expectation gains the root node the alias used to
drop. The TreeWalker's now-dead `_rejectIsSkip` branch is removed.
firstChild/lastChild/nextSibling/previousSibling stepped straight to the
next sibling whenever a node was not accepted, so a FILTER_SKIP node hid
its children instead of exposing them:
<div id=root><section><a></a></section></div>, SECTION -> FILTER_SKIP
w.firstChild() // null (Chrome: <a>)
They also used the boolean `_accept`, so FILTER_REJECT (which must not
descend) and FILTER_SKIP (which must) were indistinguishable — the same
root cause #461 fixed for nextNode().
Replaced all four with the spec's "traverse children" and "traverse
siblings" algorithms, parameterised by direction so forward and backward
share one implementation and cannot drift: `edge` is first/last child and
`step` is next/previous sibling. Both consult the three-valued `_filter`
from #461, so SKIP descends, REJECT prunes, and the climb back out stops
at root or the node the walk started from.
parentNode() is left alone here: its deviations are different (it checks
only the immediate parent, and excludes root, which the spec permits it
to return), so it belongs in its own change.
The parser already put template children in a separate contents document
per the HTML spec (tree_sink.rs), but nothing exposed that node, so
`get content()` fabricated an empty DocumentFragment and the parsed
markup was unreachable:
document.body.innerHTML = '<template id=t><p>a</p></template>';
t.content.childNodes.length // 0 (Chrome: 1)
t.innerHTML // "" (Chrome: '<p>a</p>')
Every <template>-driven UI — custom elements cloning
`template.content`, lit, Vue runtime templates, htmx fragments, Alpine
x-if/x-for — stamped nothing, with no error raised.
Three layers were involved:
- `DomTree::template_contents` returns the contents node, allocating one
on demand so templates built via `createElement` work too. Exposed as
the `template_contents` op; `get content()` wraps it as a
DocumentFragment cached by node id, so `.content` keeps a stable
identity across reads.
- `import_node_from` cloned the element data verbatim, carrying the
*source* tree's contents NodeId into the destination tree, where it
indexed whatever unrelated node occupied that slot. That is why a
template injected via innerHTML resolved `.content` to a bogus node
rather than merely an empty one. The contents are now imported into a
fresh node and the reference remapped, queued onto the existing
worklist so nested templates stay iterative.
- The serializer emitted a template's own (always empty) children, so
contents vanished from outerHTML/innerHTML and `cloneNode(true)` —
which round-trips through outer_html — produced an empty template.
`content_source` resolves a template to its contents document for both
inner_html and outer_html.
With serialization fixed on the Rust side, the `set innerHTML` template
branch that routed to `.content` now has a matching getter for free, so
no template special case is needed on the JS hot path.
window.scrollTo/scrollBy/scroll were empty stubs, scrollX/scrollY and
pageXOffset/pageYOffset were hard-coded 0 data properties, no scroll
event was ever fired at the window, and document.scrollingElement did
not exist.
that "scroll-driven lazy loaders advance instead of throwing". But the
dominant infinite-scroll idiom is window-level:
window.scrollTo(0, document.body.scrollHeight);
if (window.scrollY + innerHeight >= body.scrollHeight) loadMore();
all of which was inert -- the call succeeded, the offset never moved, the
sentinel never tripped -- so automation that scrolls a page to trigger
loading silently got one screenful.
The offset is stored on the scrolling element rather than in separate
window state, so window.scrollY and document.scrollingElement.scrollTop
are two views of one value in both directions, which is what pages
assume when they mix the two. scrollX/scrollY/pageXOffset/pageYOffset
become read-only accessors over it, matching a real Window, and
document.scrollingElement returns documentElement (standards mode; we
never parse in quirks mode).
The scroll event is dispatched at both the document and the window.
Chrome propagates a page scroll to both, but Document.dispatchEvent here
runs only its own listeners and does not propagate, so firing once would
strand half the listeners.
As with #431 there is no layout, so the offset still cannot be clamped to
a real maximum; negative values clamp to 0 exactly as they do for
elements.
previousNode() considered exactly one candidate — the previous sibling's
deepest last child — and returned null as soon as the filter rejected it,
so a backward walk died mid-tree. This is the backward mirror of #432,
which was fixed forward-only in #447.
<div id=root><a><b></b></a><c></c></div>, SHOW_ELEMENT, B -> FILTER_SKIP
forward: ["A","C"] backward: [] (Chrome: ["A"])
Replaced with the DOM 6.1 algorithm verbatim: scan previous siblings,
descend to the deepest last descendant of each, then step up to the
parent, continuing until a node is accepted or root is reached. The
descent stops on FILTER_REJECT, which is what makes rejection prune
subtrees in the backward direction too.
Unlike nextNode this stays in JS rather than adding a DOM traversal op:
the descent has to consult the filter at every step to honour REJECT, so
there is no run of JS/native crossings for a native helper to collapse.
Depends on the three-valued `_filter` from #461.
`_accept` collapsed every non-ACCEPT filter result into a single boolean,
so FILTER_REJECT behaved exactly like FILTER_SKIP: the node was not
returned, but the walk still descended into its subtree. Per DOM 6.1,
FILTER_REJECT rejects a node *and* its descendants.
This was unreachable until #440 exposed the real NodeFilter constants,
which made the canonical prune idiom
if (node.tagName === 'SCRIPT') return NodeFilter.FILTER_REJECT;
start yielding nodes from inside the pruned subtree instead of failing
loudly — sanitizers and text extractors built on TreeWalker silently got
extra content.
Split the filter into a three-valued `_filter` (keeping `_accept` as the
boolean wrapper the sibling/child movers use) and give nextNode a second
traversal step for the reject case. That step lives in the DOM layer as
`DomTree::next_after_subtree`, mirroring how #447 put `next_in_subtree`
there: both share the ancestor climb, and REJECT costs no more JS/native
crossings than SKIP.
NodeIterator shares this walker but has no subtree pruning (DOM 6.2:
FILTER_REJECT behaves as FILTER_SKIP), so `createNodeIterator` marks the
walker `_rejectIsSkip` and keeps the plain step. Covered by its own test
so the shared implementation cannot drift.
Move fragment children into the target for appendChild, insertBefore, and replaceChild while preserving their order and emptying the fragment.
Add runtime regression coverage for the DOM attachment portion of #452.
The premise was wrong. deno_core 0.350's run_event_loop is:
pub async fn run_event_loop(&mut self, opts) -> Result<(), CoreError> {
poll_fn(|cx| self.poll_event_loop(cx, opts)).await
}
so replacing `timeout(budget, run_event_loop())` with a hand-rolled
`poll_fn(poll_event_loop)` loop is the same code with the same cancellation
semantics, not safer ones. The mechanism I described cannot happen either:
`poll` is a synchronous `&mut self` call, a future can only be dropped between
polls, and the HandleScope/ContextScope live inside poll_event_loop as stack
locals that are destroyed before it returns. The isolate is exited between
polls both before and after that change.
What actually fixes#430 is confining each connection's isolates to their own
OS thread, which the next commits do. The regression test still reproduces the
abort on the pre-thread-per-connection tree and still passes here without this
commit, so nothing depended on it.
It was not merely a no-op. Two regressions it introduced:
- resolve_promises_until inverted the meaning of tick_ms. It was "pump the
event loop for up to tick_ms, returning early on idle"; it became one single
poll followed by an unconditional sleep(tick_ms). With the 1->50ms backoff
that settles at 20 event-loop turns per second, so an awaited promise chain
needing many turns crawls, and past the budget the caller silently reads a
stale __obscura_await_meta.
- drive_module_eval replaced `e?` with `let _ = poll_event_loop(...)`,
discarding event-loop errors. A module stalled on a top-level await used to
exit immediately with a logged error; it instead spun for the whole budget
logging nothing -- the exact #374 starvation the surrounding comment claims
to prevent.
Keep the drive_module_eval extraction (it genuinely dedupes load_module and
load_inline_module) but restore the original select!-based body.
Refs #430.
- Delete the now-unused CdpContext::new_full (its only caller switched to
new_with_shared_context); have _new_inner build the shared BrowserContext and
delegate, so the struct's field list lives in one place.
- Extract drive_module_eval, shared verbatim by load_module and
load_inline_module.
- Update comments that still described the deleted process-wide V8 lock and the
single-LocalSet model to the per-connection reality, drop the dangling
reference to the removed obscura-js/src/v8_lock.rs, and soften the
ISOLATE_CREATE_LOCK note now that the main-thread warmup is the real guard
against the InitializeBuiltinJSDispatchTable segfault.
Refs #430.
The per-command V8 watchdog kept a single global slot whose correctness relied
on the old process-wide lock (at most one command armed at a time). With
thread-per-connection several connections arm concurrently, so a second arm
overwrote the first's slot and left that command's isolate unbounded. Key the
armed slots by generation so each connection's command has its own; the worker
fires whichever have overrun and terminates each via its IsolateHandle.
Refs #430.
With every connection on its own thread (previous commit), the process-wide V8
lock served no safety purpose across connections yet forced all of them to
serialize on one mutex, so throughput did not scale with concurrency. Move the
lock into CdpContext so each connection has its own: a connection's nav task and
command dispatch still coordinate on one page's isolate at a time on its thread,
but different connections no longer block each other. Delete the now-unused
process-wide obscura_js::v8_lock.
Measured on a local CPU-bound fixture, page throughput stays flat (~75/s from
concurrency 1 to 8) with the global lock and scales to about 2.5x at concurrency
8 with the per-connection lock, with no crash at any concurrency. Obstacle
course 33/33, obscura-cdp 76/76.
Refs #430.
The CDP server ran every connection's pages on one LocalSet thread, so two
pages' V8 isolates shared an OS thread. Under concurrent navigation a cancelled
event-loop future could leave one isolate entered while another page's
execute_script ran, tripping V8's heap->isolate() == Isolate::TryGetCurrent()
check and aborting the process (#430). No single-thread serialization fixes
this reliably: the cancellation-leak pattern is pervasive and partly inside
deno_core.
Give each WebSocket connection its own OS thread with its own current_thread
runtime, LocalSet, and CdpContext, so every page's isolate is confined to one
thread. V8's invariant is per-thread, so two connections' isolates can never
collide. This is the "Option 2" fix named in obscura-js/src/v8_lock.rs, and it
also lets connections run in parallel instead of serializing on one thread.
- CdpContext::new_with_shared_context reuses one Arc<BrowserContext> across all
connections, so they share one cookie jar and one HTTP client.
- A single signal watcher flips the accept flag and wakes every connection's
processor via notify_waiters(); the accept side persists cookies once on
shutdown.
- Serialize isolate construction with a process-wide lock: the leaptiering
JSDispatchTable setup is not safe to run from several threads at once.
- Warm up V8 once on the main thread before any connection thread creates an
isolate; creating the first isolate off the main thread segfaults in
InitializeBuiltinJSDispatchTable.
obstacle course 33/33, obscura-cdp 75/75 including the concurrent-navigation and
control-plane tests. Concurrency 2 and 4 against heavy pages no longer abort.
Fixes#430.
Several event-loop operations bounded their runtime with
tokio::time::timeout(budget, run_event_loop()) or a select! against a
timer. When the timer wins, tokio drops the run_event_loop future
mid-poll; deno_core enters the isolate while polling, so the drop leaves
the isolate entered on the OS thread. Under concurrent CDP work a second
page's execute_script then trips heap->isolate() == TryGetCurrent() and
aborts the process (#430).
Drive the loop with poll_event_loop inside a poll_fn instead. It creates
and drops its own isolate scope per call, so stopping between ticks never
leaves the isolate entered. Convert resolve_promises_until,
run_event_loop_bounded, resolve_promises, the mod_evaluate settle in
load_module and load_inline_module, and the two navigation settle loops
in page.rs. Add poll_event_loop_once as the cancellation-safe single-tick
primitive the settle loops use.
Keeps the obstacle course at 33/33. This is hardening toward #430; the
residual concurrency abort still needs the thread-per-runtime refactor
that v8_lock.rs calls the "Option 2" fix.
Refs #430.
The on_request/on_response Vec lived on the ObscuraHttpClient shared by
every page in the context, so a callback registered on one page fired for
all pages (#408 cross-page bleed) and outlived its page.
Callbacks now live in a per-page CallbackRegistry (Arc shared with the
page's JS runtime state). Page-driven fetch paths (navigation, POST,
scripts, stylesheets, robots.txt, module loads, JS fetch/XHR in both
plain and stealth modes) pass the registry through; the HTTP client
itself is callback-free.
Adds callbacks_do_not_bleed_across_pages: page A's callback stays silent
for page B's requests and stops firing after page A is dropped.
on_request/on_response stored callbacks in append-only Vecs with no way
to remove one, so a crawler that installed a response-body capture hook
for one phase could never detach it: it fired for the shared client's
whole lifetime, re-registering across navigations piled up duplicates,
and (because the client is shared per context) it saw sibling pages'
requests too.
Tag each callback with a stable id. on_request/on_response now return
the id and off_request/off_response (remove_on_request/remove_on_response
on the client) detach a specific one. Storage is Vec<(u64, Callback)>;
all fire sites destructure the tuple. Closes#408.
Requests made by page JS (fetch/XHR/dynamic script and stylesheet loads)
run in the V8 op layer and never produced a NetworkEvent, so CDP emitted
Network.requestWillBeSent / responseReceived only for the static
navigation subresources. Puppeteer/Playwright page.on('request') and
on('response') therefore missed every XHR/JSON response, which breaks
response capture (and is the root cause of the Aviasales half of #394).
op_fetch_url now records a JsNetworkEvent keyed by the same fetch-{N} id
under which it already stores the response body. The Page drains these
into its network_events before the CDP layer emits, so they flow through
emit_navigation_events as requestWillBeSent / responseReceived /
loadingFinished alongside the document subresources, and
Network.getResponseBody resolves for them via the shared id. Applied to
both navigation paths (server process_navigation and in-process
do_navigate). The queue is capped at 4096 events per page.
Closes#406.
load_module and load_inline_module drove run_event_loop to full idle
before reading the module's mod_evaluate result. A page timer keeps the
loop busy forever (Vite's HMR / React-Refresh client installs a
setInterval), so the preamble inline module burned the entire budget
waiting for an idle that never came, and the later module that mounts the
app was skipped, leaving #root empty while the production preview rendered
fine (issue #374).
Drive the event loop and the mod_evaluate result together and return as
soon as the module finishes evaluating, so a busy background timer no
longer starves the remaining modules. Post-eval async work is still
drained by the normal post-load settle.
Fixes#374.
Regression test for #355: an uncaught `throw` in one inline <script> must
not prevent later independent <script>s from running. This was fixed by
the #147 poison-guard (present on main) but reported again against 0.1.9
with an explicit throw; this pins the exact scenario so it cannot regress.
Closes#355.
el.style (CSSStyleDeclaration) and el.dataset (DOMStringMap) were plain
Proxies with only get/set traps, so `'color' in el.style`, `Object.keys
(el.style)`, `'foo' in el.dataset`, and `Object.keys(el.dataset)` all
failed, and Object.keys(el.style) leaked the internal `_props` (issue
#356). cssText also serialized camelCase names without a trailing
semicolon.
Add has / ownKeys / getOwnPropertyDescriptor traps to both proxies so the
`in` operator and enumeration behave like real CSSOM. CSSStyleDeclaration
now stores properties by their dashed name (matching the spec), so
el.style.fontSize and getPropertyValue('font-size') stay in sync, and
cssText serializes dashed names with a trailing semicolon. A known CSS
property list backs `in`/enumeration so feature detection ('object-fit'
in el.style) works for unset properties.
Closes#356.
Typing over CDP into a React controlled input never fired onChange, so
the value never reached component state (issue #324). Two root causes,
both needed:
1. Value tracker. React/Preact/Vue install a value tracker by redefining
`value` on the element instance to record the last value they wrote.
obscura's CDP typing assigned `el.value = ...` directly, which runs
that wrapper and keeps the tracker in sync, so React saw no change on
the input event. Synthetic value/backspace writes now go through a new
__obscura_setFieldValue helper that writes via the element's prototype
setter, bypassing the tracker. The tracker stays stale, so the input
event reads as a real edit.
2. Event handler feature detection. React decides whether to use the
modern `input` event via `("oninput" in document)`. obscura exposed the
GlobalEventHandlers on* attributes only on window, so that check failed
and React fell back to a legacy change-detection path that ignores
input events. The on* attributes are now also present on Document and
Element, matching the HTML spec (GlobalEventHandlers is mixed into
Window, Document, and HTMLElement).
Verified end to end over CDP against the real React 18 UMD build: typing
into controlled inputs updates state, the component re-renders, and a
submit handler reads the captured values.
Closes#324.
crypto.subtle only implemented digest. sign returned a fixed 32-byte
buffer, verify always returned true, encrypt and decrypt threw, and
generateKey, importKey and deriveBits handed back placeholder data.
Pages that use WebCrypto (anti-bot probes, PKCE and other auth flows,
client-side crypto) silently got wrong results.
Implement the secret-key half of WebCrypto on RustCrypto, following the
existing op_subtle_digest pattern:
- HMAC sign and verify (SHA-1/256/384/512)
- AES-GCM, AES-CBC and AES-CTR encrypt and decrypt
- PBKDF2 and HKDF deriveBits and deriveKey
- raw and symmetric JWK (oct) importKey and exportKey, generateKey,
wrapKey and unwrapKey
- getRandomValues and randomUUID now draw from the OS CSPRNG instead of
Math.random, so they are uniform across typed-array widths and no
longer a fingerprinting tell
Unsupported algorithms (RSA, ECDSA, ECDH) and key formats (pkcs8, spki)
throw NotSupportedError instead of returning fake data. The crypto runs
in stateless Rust ops; the bootstrap.js shim only marshals bytes and
normalizes algorithm parameters, so the native fast paths are untouched
and there is no cost unless a page calls crypto.
Verified against RFC 4231 (HMAC), the NIST GCM vectors, NIST SP800-38A
(AES-CTR), RFC 6070 (PBKDF2) and RFC 5869 (HKDF), plus roundtrip and
tag/padding tamper-rejection checks.
A Continue resolution that rewrites the request URL applied the new URL
after validate_fetch_url had already run on the original, so a rewrite
could reach a private or internal address the original request was
blocked from. Run the overridden URL back through validate_fetch_url,
matching how redirects are re-validated, and return a blocked response
if it fails.
Also fix a doc comment that ended up attached to the new fetch_response
helper instead of stealth_fetch_all.
op_fetch_url ignored the url/method/headers/body fields on
InterceptResolution::Continue, so the interception channel could pass, mock, or
block a request but not rewrite it. Apply them: shadow url/method/body and
derive custom_headers from the override after the channel resolves Continue.
Also fix enable_interception() called before the first navigation: init_js
propagated intercept_tx to the new runtime but not intercept_enabled, so the
runtime started with interception disabled and op_fetch_url never intercepted.
Propagate intercept_enabled in init_js as well.
Add a test that rewrites a fetch's url via Continue and asserts the rewritten
response is captured.
SGavrl