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feat(jco): add future lower tests #1422

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967d690
feat(jco): add future lower tests, refactor existing
vados-cosmonic Apr 20, 2026
4fbc3e3
wip(jco): add stub for stream + future lower test
vados-cosmonic Apr 20, 2026
e187473
test(jco): fill out sync passthrough test
vados-cosmonic Apr 20, 2026
18dcd65
feat(bindgen): fill out future lower impl
vados-cosmonic Apr 20, 2026
fbf794c
chore(bindgen): exclude host from same-component numeric type check
vados-cosmonic Apr 20, 2026
fa37e81
fix(bindgen): fix future lower impl
vados-cosmonic Apr 21, 2026
784fe49
test(jco): refactor, enable more future lower tests
vados-cosmonic Apr 21, 2026
b265b2f
refactor(bindgen): more consistency around passing reallocfn
vados-cosmonic Apr 21, 2026
101b126
test(jco): uncomment more tests
vados-cosmonic Apr 21, 2026
98f8e75
fix(bindgen): restore coin flip determinism
vados-cosmonic Apr 22, 2026
cafa44b
wip(bindgen): fix check for waiting
vados-cosmonic Apr 23, 2026
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205 changes: 190 additions & 15 deletions crates/js-component-bindgen/src/function_bindgen.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -4,8 +4,9 @@ use std::mem;

use heck::{ToLowerCamelCase, ToUpperCamelCase};
use wasmtime_environ::component::{
CanonicalOptions, InterfaceType, ResourceIndex, TypeComponentLocalErrorContextTableIndex,
TypeFutureTableIndex, TypeResourceTableIndex, TypeStreamTableIndex,
CanonicalOptions, CanonicalOptionsDataModel, InterfaceType, LinearMemoryOptions, ResourceIndex,
TypeComponentLocalErrorContextTableIndex, TypeFutureTableIndex, TypeResourceTableIndex,
TypeStreamTableIndex,
};
use wit_bindgen_core::abi::{Bindgen, Bitcast, Instruction};
use wit_component::StringEncoding;
Expand Down Expand Up @@ -396,12 +397,16 @@ impl FunctionBindgen<'_> {
));
let component_instance_idx = self.canon_opts.instance.as_u32();

// If we're within an async function, wait for all top level previous tasks to finish before running
// If we're within a true async function, or one that has simply been lowered as async,
// wait for all top level previous tasks to finish before running
// to ensure that guests do not try to run two tasks at the same time.
if is_async && self.requires_async_porcelain {
if is_async || self.requires_async_porcelain {
uwriteln!(
self.src,
r#"
// TODO(fix): this logic should be in the async task.enter() and be backpressure driven
// (note, we may need specific handlers for backpressure changes)
//
// All other tasks must finish before we can start this one
const taskMetas = {global_task_map}.get({component_instance_idx});
if (taskMetas) {{
Expand Down Expand Up @@ -2596,19 +2601,172 @@ impl Bindgen for FunctionBindgen<'_> {
results.push(item.clone());
}

Instruction::FutureLower { .. } => {
// TODO: convert this return of the lifted Future:
//
// ```
// return BigInt(writeEndWaitableIdx) << 32n | BigInt(readEndWaitableIdx);
// ```
//
// Into a component-local Future instance
//
Instruction::FutureLower { ty, .. } => {
let debug_log_fn = self.intrinsic(Intrinsic::DebugLog);
let get_or_create_async_state_fn = self.intrinsic(Intrinsic::Component(
ComponentIntrinsic::GetOrCreateAsyncState,
));
let gen_future_host_inject_fn = self.intrinsic(Intrinsic::AsyncFuture(
AsyncFutureIntrinsic::GenFutureHostInjectFn,
));
let is_future_lowerable_object_fn = self.intrinsic(Intrinsic::AsyncFuture(
AsyncFutureIntrinsic::IsFutureLowerableObject,
));

let component_idx = self.canon_opts.instance.as_u32();

let future_arg = operands
.first()
.expect("unexpectedly missing ErrorContextLower arg");
results.push(future_arg.clone());

// Build the lowering function for the type produced by the future
let type_id = &crate::dealias(self.resolve, *ty);
let ResourceTable {
imported: true,
data:
ResourceData::Guest {
extra:
Some(ResourceExtraData::Future {
table_idx: future_table_idx_ty,
elem_ty,
}),
..
},
} = self
.resource_map
.get(type_id)
.expect("missing resource mapping for future lower")
else {
unreachable!("invalid resource table observed during future lower");
};
let future_table_idx = future_table_idx_ty.as_u32();

// Generate payload metadata ('elemMeta')
let (
payload_type_name_js,
lift_fn_js,
lower_fn_js,
payload_is_none,
payload_is_numeric,
payload_is_borrow,
payload_is_async_value,
payload_size32_js,
payload_align32_js,
payload_flat_count_js,
) = match elem_ty {
Some(PayloadTypeMetadata {
ty: _,
iface_ty,
lift_js_expr,
lower_js_expr,
size32,
align32,
flat_count,
}) => (
format!("'{iface_ty:?}'"),
lift_js_expr.as_str(),
lower_js_expr.as_str(),
"false",
format!(
"{}",
matches!(
iface_ty,
InterfaceType::U8
| InterfaceType::U16
| InterfaceType::U32
| InterfaceType::U64
| InterfaceType::S8
| InterfaceType::S16
| InterfaceType::S32
| InterfaceType::S64
| InterfaceType::Float32
| InterfaceType::Float64
)
),
format!("{}", matches!(iface_ty, InterfaceType::Borrow(_))),
format!(
"{}",
matches!(
iface_ty,
InterfaceType::Stream(_) | InterfaceType::Future(_)
)
),
size32.to_string(),
align32.to_string(),
flat_count.unwrap_or(0).to_string(),
),
None => (
"null".into(),
"() => {{ throw new Error('no lift fn'); }}",
"() => {{ throw new Error('no lower fn'); }}",
"true",
"false".into(),
"false".into(),
"false".into(),
"null".into(),
"null".into(),
"0".into(),
),
};

// Retrieve the realloc fn if present, in case lowering fns need to allocate
//
// The realloc fn is saved on the element metadata which is passed through to
// stream end and underlying buffer
let get_realloc_fn_js = match self.canon_opts.data_model {
CanonicalOptionsDataModel::LinearMemory(LinearMemoryOptions {
realloc: Some(realloc_idx),
..
}) => format!("() => realloc{}", realloc_idx.as_u32()),
_ => "undefined".into(),
};

let tmp = self.tmp();
let lowered_future_waitable_idx = format!("futureWaitableIdx{tmp}");
uwriteln!(
self.src,
r#"
if (!{is_future_lowerable_object_fn}({future_arg})) {{
{debug_log_fn}('[Instruction::FutureLower] object is not a Promise/Thenable', {{ {future_arg} }});
throw new Error('unrecognized future object (not Promise/Thenable)');
}}

const cstate{tmp} = {get_or_create_async_state_fn}({component_idx});
if (!cstate{tmp}) {{ throw new Error(`missing component state for component [{component_idx}]`); }}

// TODO(feat): facilitate non utf8 string encoding for lowered futures
const stringEncoding = 'utf8';

const {{ writeEnd: hostWriteEnd{tmp}, readEnd: readEnd{tmp} }} = cstate{tmp}.createFuture({{
tableIdx: {future_table_idx},
elemMeta: {{
liftFn: {lift_fn_js},
lowerFn: {lower_fn_js},
payloadTypeName: {payload_type_name_js},
isNone: {payload_is_none},
isNumeric: {payload_is_numeric},
isBorrowed: {payload_is_borrow},
isAsyncValue: {payload_is_async_value},
flatCount: {payload_flat_count_js},
align32: {payload_align32_js},
size32: {payload_size32_js},
stringEncoding,
getReallocFn: {get_realloc_fn_js},
}},
}});

const hostInjectFn = {gen_future_host_inject_fn}({{
promise: {future_arg},
stringEncoding,
hostWriteEnd: hostWriteEnd{tmp},
}});
readEnd{tmp}.setHostInjectFn(hostInjectFn);

const {lowered_future_waitable_idx} = readEnd{tmp}.waitableIdx();
"#
);

results.push(lowered_future_waitable_idx);
}

Instruction::FutureLift { payload, ty } => {
Expand Down Expand Up @@ -2713,9 +2871,12 @@ impl Bindgen for FunctionBindgen<'_> {
ComponentIntrinsic::GetOrCreateAsyncState,
));
let gen_host_inject_fn = self.intrinsic(Intrinsic::AsyncStream(
AsyncStreamIntrinsic::GenHostInjectFn,
AsyncStreamIntrinsic::GenStreamHostInjectFn,
));

// TODO(???): A component could end up receiving a stream that it outputted,
// and the below would fail (imported: false)?

// Build the lowering function for the type produced by the stream
let type_id = &crate::dealias(self.resolve, *ty);
let ResourceTable {
Expand Down Expand Up @@ -2807,6 +2968,18 @@ impl Bindgen for FunctionBindgen<'_> {
),
};

// Retrieve the realloc fn if present, in case lowering fns need to allocate
//
// The realloc fn is saved on the element metadata which is passed through to
// stream end and underlying buffer
let get_realloc_fn_js = match self.canon_opts.data_model {
CanonicalOptionsDataModel::LinearMemory(LinearMemoryOptions {
realloc: Some(realloc_idx),
..
}) => format!("() => realloc{}", realloc_idx.as_u32()),
_ => "undefined".into(),
};

let tmp = self.tmp();
let lowered_stream_waitable_idx = format!("streamWaitableIdx{tmp}");
uwriteln!(
Expand Down Expand Up @@ -2837,6 +3010,7 @@ impl Bindgen for FunctionBindgen<'_> {
size32: {payload_size32_js},
// TODO(feat): facilitate non utf8 string encoding for lowered streams
stringEncoding: 'utf8',
geReallocFn: {get_realloc_fn_js},
}},
}});

Expand All @@ -2863,6 +3037,7 @@ impl Bindgen for FunctionBindgen<'_> {
const {lowered_stream_waitable_idx} = readEnd{tmp}.waitableIdx();
"#
);

results.push(lowered_stream_waitable_idx);
}

Expand Down
20 changes: 7 additions & 13 deletions crates/js-component-bindgen/src/intrinsics/lift.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -393,7 +393,7 @@ impl LiftIntrinsic {
let val;

if (ctx.useDirectParams) {{
if (params.length === 0) {{ throw new Error('expected at least a single i32 argument'); }}
if (ctx.params.length === 0) {{ throw new Error('expected at least a single i32 argument'); }}
val = ctx.params[0];
ctx.params = ctx.params.slice(1);
return [val, ctx];
Expand Down Expand Up @@ -734,11 +734,6 @@ impl LiftIntrinsic {
return function {lift_flat_record_fn}Inner(ctx) {{
{debug_log_fn}('[{lift_flat_record_fn}()] args', {{ ctx }});

if (ctx.useDirectParams) {{
ctx.storagePtr = ctx.params[0];
ctx.params = ctx.params.slice(1);
}}

const res = {{}};
for (const [key, liftFn, _size32, _align32] of keysAndLiftFns) {{
let [val, newCtx] = liftFn(ctx);
Expand Down Expand Up @@ -1233,28 +1228,27 @@ impl LiftIntrinsic {
output.push_str(&format!(r#"
function {lift_flat_error_fn}(errCtxTableIdx, ctx) {{
{debug_log_fn}('[{lift_flat_error_fn}()] ctx', ctx);
const {{ useDirectParams, params, componentIdx }} = ctx;

let val;
let table;
if (useDirectParams) {{
if (params.length === 0) {{ throw new Error('expected at least one single i32 argument'); }}
if (ctx.useDirectParams) {{
if (ctx.params.length === 0) {{ throw new Error('expected at least one single i32 argument'); }}
val = ctx.params[0];
ctx.params = ctx.params.slice(1);
table = {get_err_ctx_local_table_fn}(componentIdx, errCtxTableIdx);
table = {get_err_ctx_local_table_fn}(ctx.componentIdx, errCtxTableIdx);
}} else {{
throw new Error('indirect flat lift for error-contexts not yet implemented!');
}}

let handle = table.get(val);
if (handle === undefined) {{
throw new Error(`missing error ctx (handle [${{val}}], component [${{componentIdx}}], error context table [${{errCtxTableIdx}}])`);
throw new Error(`missing error ctx (handle [${{val}}], component [${{ctx.componentIdx}}], error context table [${{errCtxTableIdx}}])`);
}}

const cstate = {get_or_create_async_state_fn}(componentIdx);
const cstate = {get_or_create_async_state_fn}(ctx.componentIdx);
const errCtx = cstate.handles.get(handle);
if (!errCtx || errCtx.globalRep === undefined || errCtx.refCount === undefined) {{
throw new Error(`malformed error context (handle [${{handle}}], component [${{componentIdx}}])`);
throw new Error(`malformed error context (handle [${{handle}}], component [${{ctx.componentIdx}}])`);
}}

errCtx.refCount -= 1;
Expand Down
4 changes: 2 additions & 2 deletions crates/js-component-bindgen/src/intrinsics/lower.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -498,7 +498,7 @@ impl LowerIntrinsic {
function {lower_flat_f64_fn}(ctx) {{
{debug_log_fn}('[{lower_flat_f64_fn}()] args', {{ ctx }});

if (vals.length !== 1) {{ throw new Error('unexpected number of vals'); }}
if (ctx.vals.length !== 1) {{ throw new Error('unexpected number of vals'); }}

const rem = ctx.storagePtr % 8;
if (rem !== 0) {{ ctx.storagePtr += (8 - rem); }}
Expand Down Expand Up @@ -994,7 +994,7 @@ impl LowerIntrinsic {
Intrinsic::AsyncStream(AsyncStreamIntrinsic::GenReadFnFromLowerableStream)
.name();
let gen_host_inject_fn =
Intrinsic::AsyncStream(AsyncStreamIntrinsic::GenHostInjectFn).name();
Intrinsic::AsyncStream(AsyncStreamIntrinsic::GenStreamHostInjectFn).name();
let lower_u32_fn = Self::LowerFlatU32.name();

output.push_str(&format!(
Expand Down
29 changes: 27 additions & 2 deletions crates/js-component-bindgen/src/intrinsics/mod.rs
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -614,7 +614,8 @@ impl Intrinsic {
storagePtr: startPtr,
componentIdx: this.#componentIdx,
stringEncoding: this.#elemMeta.stringEncoding,
realloc: this.#elemMeta.reallocFn,
realloc: this.#elemMeta.getReallocFn?.(),
getReallocFn: this.#elemMeta.getReallocFn,
}}
for (const v of values) {{
lowerCtx.vals = [v];
Expand Down Expand Up @@ -1367,7 +1368,22 @@ pub fn render_intrinsics(args: RenderIntrinsicsArgs) -> Source {
&Intrinsic::SymbolResourceRep,
&Intrinsic::Component(ComponentIntrinsic::GetOrCreateAsyncState),
&Intrinsic::AsyncStream(AsyncStreamIntrinsic::GenReadFnFromLowerableStream),
&Intrinsic::AsyncStream(AsyncStreamIntrinsic::GenHostInjectFn),
&Intrinsic::AsyncStream(AsyncStreamIntrinsic::GenStreamHostInjectFn),
&Intrinsic::Lower(LowerIntrinsic::LowerFlatU32),
])
}

if args
.intrinsics
.contains(&Intrinsic::Lower(LowerIntrinsic::LowerFlatFuture))
{
args.intrinsics.extend([
&Intrinsic::AsyncFuture(AsyncFutureIntrinsic::GlobalFutureMap),
&Intrinsic::AsyncFuture(AsyncFutureIntrinsic::InternalFutureClass),
&Intrinsic::AsyncFuture(AsyncFutureIntrinsic::IsFutureLowerableObject),
&Intrinsic::SymbolResourceRep,
&Intrinsic::Component(ComponentIntrinsic::GetOrCreateAsyncState),
&Intrinsic::AsyncFuture(AsyncFutureIntrinsic::GenFutureHostInjectFn),
&Intrinsic::Lower(LowerIntrinsic::LowerFlatU32),
])
}
Expand Down Expand Up @@ -1501,6 +1517,15 @@ pub fn render_intrinsics(args: RenderIntrinsicsArgs) -> Source {
]);
}

if args.intrinsics.contains(&Intrinsic::AsyncFuture(
AsyncFutureIntrinsic::FutureNewFromLift,
)) {
args.intrinsics.extend([
&Intrinsic::AsyncFuture(AsyncFutureIntrinsic::GlobalFutureMap),
&Intrinsic::AsyncFuture(AsyncFutureIntrinsic::HostFutureClass),
]);
}

if args.intrinsics.contains(&Intrinsic::AsyncFuture(
AsyncFutureIntrinsic::FutureWritableEndClass,
)) || args.intrinsics.contains(&Intrinsic::AsyncFuture(
Expand Down
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